Age, gender and normalization covariates for spinal cord gray matter and total cross-sectional areas at cervical and thoracic levels: A 2D phase sensitive inversion recovery imaging study

Establishing Normative Values for Entire Spinal Cord Morphometrics in East Asian Young Adults

OBJECTIVE

The quantitative assessment of spinal cord volume is still in the early stages of development. Recently, normative morphometric values of the cervical spinal cord have been reported. This study aimed to establish normative values for spinal cord morphometry, extending beyond the cervical region to include the thoracic and lumbar spinal cord, and to examine the influence of sex and ethnicity on these measurements.

MATERIALS AND METHODS

This prospective study included 28 young, healthy, East Asian volunteers (14 males and 14 females; mean age, 30.14 ± 4.07 years) who underwent spinal cord MRI using a 3T scanner. The cross-sectional areas (CSAs), anteroposterior (AP) and transverse diameters, and compression ratios of the entire spinal cord were calculated. Additionally, the effects of sex and ethnicity on spinal cord volumetry were evaluated, with the influence of ethnicity assessed by comparing the findings with a Caucasian dataset from the PAM50 study.

RESULTS

The CSAs demonstrated two enlargements at the cervical and lumbar levels. The cervical enlargement at C4-5 exhibited an elliptical shape, while the lumbar enlargement at T12 appeared more circular. The CSAs and AP and transverse diameters of the spinal cords in males were significantly larger than that of females (P < 0.001). The spinal cord compression ratios in East Asians were significantly lower than those in Caucasians (P < 0.001).

CONCLUSION

This study revealed that the two spinal cord enlargements exhibit different patterns and suggest significant differences in spinal cord morphometric values according to sex and ethnicity.

Association of the Cervical Canal Area With Disability and Progression in People With Multiple Sclerosis

BACKGROUND AND OBJECTIVES

In multiple sclerosis (MS), brain reserve serves as a protective factor against cognitive impairment. Previous research has suggested a structural counterpart in the spine-spinal cord reserve-seemed to be associated with physical disability. This study aimed to investigate the potential of the cervical canal area (CCaA) as a proxy for spinal cord reserve in a multicentric cohort of people with MS (PwMS).

METHODS

This retrospective, multicentric, longitudinal study included PwMS and healthy controls (HCs) from 9 European MAGNIMS sites. Baseline cervical 3D T1-weighted images were acquired, excluding poor-quality images. CCaA was estimated independently at the C2/C3 and C3/C4 levels. The Expanded Disability Status Scale (EDSS) score was assessed at baseline and 5-year follow-up. We analyzed mean CCaA differences between groups and the association of CCaA with baseline EDSS scores and disability progression using multivariable regression models adjusted for age, sex, spinal cord parenchymal fraction, and cervical cord lesions.

RESULTS

After quality check, the cohort included 177 HCs (mean age 39.8 years, 57.6% women) and 428 PwMS (mean age 46.5 years, 60.8% women), comprising 289 people with relapsing MS (PwRMS) and 139 people with progressive MS (PwPMS). No significant differences in CCaA were found between HCs and PwRMS at C2/C3 or C3/C4 levels. Conversely, PwPMS showed a smaller CCaA at the C2/C3 level (210.51 mm2) than HCs (214.62 mm2, estimated mean difference [EMD] -4.11, 95% CI -6.28 to -1.00, p = 0.007) and PwRMS (213.68 mm2, EMD -3.17, 95% CI -5.22 to -0.34, p = 0.026). PwPMS also had a smaller CCaA at C3/C4 (165.16 mm2) than HCs (169.67 mm2, EMD -4.51, 95% CI -5.50 to -1.60, p < 0.001) and PwRMS (169.44 mm2, EMD -3.81, 95% CI -5.22 to -0.34, p < 0.001). At the C3/C4 level, CCaA and baseline EDSS scores were significantly associated (β = -0.13, p < 0.001); in addition, PwMS with clinical worsening at 5-year follow-up displayed a smaller baseline CCaA (worsened vs stable: 167.03 mm2 vs 169.13 mm2, EMD -2.10, 95% CI -3.98 to -023, p = 0.028).

DISCUSSION

CCaA was associated with baseline EDSS scores and clinical worsening in a multicentric MS cohort, suggesting the existence of spinal cord reserve. PwPMS had a smaller CCaA, indicating that reduced spinal cord reserve might be characteristic of progressive MS. Therefore, spinal cord reserve may represent a novel radiologic marker for better understanding physical disability in MS.

Spinal cord gray matter atrophy is associated with disability in spinal muscular atrophy

BACKGROUND

With the approval of disease-modifying treatments for 5q-spinal muscular atrophy (SMA), there is an increasing need for biomarkers for disease course and therapeutic response monitoring. Radially sampled Averaged Magnetization Inversion Recovery Acquisitions (rAMIRA) MR-imaging enables spinal cord (SC) gray matter (GM) delineation and quantification in vivo. This study aims to assess SC GM atrophy in patients with 5q-SMA and its associations with clinical disability.

METHODS

Twenty-one patients with 5q-SMA and twenty-one age- and sex-matched healthy controls (HCs) prospectively underwent 3 T axial 2D-rAMIRA MR-imaging at the intervertebral disc levels C2/C3-C5/C6 and Tmax (lumbar enlargement level). Associations between SC GM areas with muscle strength tested by dynamometry, Motor Function Measure (MFM), revised upper limb module (RULM), Revised Hammersmith Scale (RHS), and SMA-Functional Rating Scale (SMA-FRS) were assessed by Spearman Rank correlations and linear regression analysis.

RESULTS

Compared to HCs, patients had significantly reduced SC GM areas at levels C3/C4 (relative reduction (RR) = 13.6%, p < 0.0001); C4/C5 (RR = 16.7%, p < 0.0001), C5/C6 (RR = 17.1%, p < 0.0001), and Tmax (RR = 17.4%, p < 0.0001). Significant correlations were found between cervical SC GM areas and muscle strength, RULM, MFM, RHS, and SMA-FRS. In linear regression analysis, GM area C3/C4 explained 33% of RHS variance.

CONCLUSION

SC GM atrophy is detectable in patients with 5q-SMA and is consistently associated with clinical measures of upper limb function, physiotherapeutic assessments, and SMA-FRS indicating the clinical relevance of the observed atrophy. Further longitudinal investigations are necessary next steps to evaluate this novel and easily applicable imaging marker as a potential disease course and therapeutic response marker.

Feasibility of interleaved multislice averaged magnetization inversion-recovery acquisitions of the spinal cord

PURPOSE

To establish an interleaved multislice variant of the averaged magnetization inversion-recovery acquisitions (AMIRA) approach for 2D spinal cord imaging with increased acquisition efficiency compared with the conventional 2D single-slice approach(es), and to determine essential prerequisites for a working interleaved multislice AMIRA approach in practice.

METHODS

The general AMIRA concept is based on an inversion recovery-prepared, segmented, and time-limited cine balanced SSFP sequence, generating images of different contrast. For AMIRA imaging of multiple, independent slices in a 2D interleaved fashion, a slice loop within the acquisition loops was programmed. The former non-selective inversions were replaced with slice-selective inversions with user-definable slice thickness.

RESULTS

The thickness of the slice-selective inversion in 2D interleaved multislice AMIRA should be doubled compared with the manufacturer's standard setting to avoid an increased sensitivity to flow and pulsation effects particularly in the CSF. However, this solution also limits its practical applicability, as slices located at directly adjacent vertebrae cannot be imaged together. Successful interleaved two-slice AMIRA imaging for a "reference" in vivo protocol with 0.50 × 0.50 mm2 in-plane resolution and 8-mm slice thickness is demonstrated, therefore halving its acquisition time per slice from 3 min down to 1.5 min.

CONCLUSION

The investigated 2D interleaved two-slice AMIRA variant facilitates spinal cord imaging that maintains similar contrast and the same resolution as the conventional 2D single-slice AMIRA approach, but does so with a halved acquisition time.

Thoracic canal morphology on preoperative magnetic resonance imaging in spinal cord stimulation patients

INTRODUCTION

In high-frequency spinal cord stimulation anatomic placement targeting of the T9-10 disc space is based on "empiric" results that are best replicated with coverage broadly from T8 to T10. This study contains the largest cohort of patients evaluating low thoracic morphology and seeks to address the lack of MRI morphological analysis in literature.

METHODS

This study was a retrospective review of a database of 101 consecutive patients undergoing permanent implant of thoracic SCS for chronic pain. Measurements were carried out on preoperative MRI imaging. Anteroposterior (AP) and lateral dimensions of the spinal cord as well as dural sac were measured. In addition, dorsal cerebrospinal fluid thickness and paddle depression distance were also measured.

RESULTS

When comparing morphological dimensions by level, dorsal CSF thickness was smaller at T9-10 than T7-8 (p = 0.018). In addition, lateral dural and spinal cord diameters were larger at T10-11 than T9-10, contributing to larger dural surface area at T10-11 (p = 0.028). While trends of dorsal CSF thickness tend to decrease with lower thoracic levels, the ratio of surface area of spinal cord to dural sac appeared to remain relatively constant.

CONCLUSIONS

Dorsal CSF thickness is smaller at T9-10 than T7-8 in chronic pain patients in this cohort. More ellipsoid, cord, and spinal canal diameter measurements were noted at lower levels of the thoracic spinal cord, particularly at T10-11. This may correlate with anatomical SCS placement. Future studies should evaluate efficacy of SCS therapy for pain based on these anatomical considerations.

Cervical spinal cord morphometrics in degenerative cervical myelopathy: quantification using semi-automated normalized technique and correlation with neurological dysfunctions

BACKGROUND CONTEXT

Degenerative cervical myelopathy (DCM) is characterized by spinal cord atrophy. Accurate estimation of spinal cord atrophy is key to the understanding of neurological diseases, including DCM. However, its clinical application is hampered by difficulties in its precise and consistent estimation due to significant variability in spinal cord morphometry along the cervical spine, both within and between individuals.

PURPOSE

To characterize morphometrics of the compressed spinal cord in DCM patients. We employed our semiautomated analysis framework that incorporates the Spinal Cord Toolbox (SCT) and a normalization approach to effectively address the challenges posed by cord compression in these patients. Additionally, we examined the clinical relevance of these morphometric measures to enhance our understanding of DCM pathophysiology.

STUDY DESIGN

Prospective study.

PATIENT SAMPLE

This study investigated 36 DCM patients and 31 healthy controls (HCs).

OUTCOME MEASURES

Clinical scores including 9-hole peg test for hand dexterity, hand grip strength, balance, gait speed, modified Japanese Orthopaedic Association (mJOA) score, and imaging-based spinal cord morphometrics.

METHOD

Using the generic spine acquisition protocol and our semiautomated analysis pipeline, spinal cord morphometrics, including cross-sectional area (CSA), anterior-posterior (AP) and transverse (RL) diameters, eccentricity, and solidity, were estimated from sagittal T2w magnetic resonance imaging (MRI) images using the Spinal Cord Toolbox (SCT). Normalized metrics were extracted from the C1 to C7 vertebral levels and compared between DCM patients and HC. Morphometric data at regions of maximum spinal cord compression (MSCC) were correlated with the clinical scores. A subset of participants underwent follow-up scans at 6 months to monitor longitudinal changes in spinal cord atrophy.

RESULTS

Spinal cord morphometric data were normalized against the healthy population morphometry (PAM50 database) and extracted for all participants. DCM patients showed a notable reduction in CSA, AP, and RL diameter across all vertebral levels compared to HC. MSCC metrics correlated significantly with clinical scores like dexterity, grip strength, and mJOA scores. Longitudinal analysis indicated a decrease in CSA and worsening clinical scores in DCM patients.

CONCLUSION

Our processing pipeline offers a reliable method for assessing spinal cord compression in DCM patients. Normalized spinal cord morphometrics, particularly the CSA could have potential for monitoring DCM disease severity and progression, guiding treatment decisions. Furthermore, to our knowledge our study is the first to apply the generic spinal cord acquisition protocol, ensuring consistent imaging across different MRI scanners and settings. Coupled with our semiautomated analysis pipeline, this protocol is key for the detailed morphometric characterization of compressed spinal cords in patients with DCM, a disease that is both complex and heterogenous. This study was funded by the National Institute of Neurological Disorders and Stroke (NINDS) (K23:NS091430) and (R01: NS129852-01A1).

Biological variation in cervical spinal cord MRI morphometry in healthy individuals and people with multiple sclerosis

BACKGROUND AND PURPOSE

Conclusions from prior literature regarding the impact of sex, age, and height on spinal cord (SC) MRI morphometrics are conflicting, while the effect of body weight on SC morphometrics has been found to be nonsignificant. The purpose of this case-control study is to assess the associations between cervical SC MRI morphometric parameters and age, sex, height, and weight to establish their potential role as confounding variables in a clinical study of people with multiple sclerosis (MS) compared to a cohort of healthy volunteers.

METHODS

Sixty-nine healthy volunteers and 31 people with MS underwent cervical SC MRI at 3 Tesla field strength. Images were centered at the C3/C4 intervertebral disc and processed using Spinal Cord Toolbox v.4.0.2. Mixed-effects linear regression models were used to evaluate the effects of biological variables and disease status on morphometric parameters.

RESULTS

Sex, age, and height had significant effects on cord and gray matter (GM) cross-sectional area (CSA) as well as the GM:cord CSA ratio. There were no significant effects of body weight on morphometric parameters. The effect of MS disease duration on cord CSA in the C4 level was significant when controlling for all other variables.

CONCLUSIONS

Studies of disease-related changes in SC morphometry should control for sex, age, and height to account for physiological variation.

Body size interacts with the structure of the central nervous system: A multi-center in vivo neuroimaging study

Clinical research emphasizes the implementation of rigorous and reproducible study designs that rely on between-group matching or controlling for sources of biological variation such as subject's sex and age. However, corrections for body size (i.e. height and weight) are mostly lacking in clinical neuroimaging designs. This study investigates the importance of body size parameters in their relationship with spinal cord (SC) and brain magnetic resonance imaging (MRI) metrics. Data were derived from a cosmopolitan population of 267 healthy human adults (age 30.1±6.6 years old, 125 females). We show that body height correlated strongly or moderately with brain gray matter (GM) volume, cortical GM volume, total cerebellar volume, brainstem volume, and cross-sectional area (CSA) of cervical SC white matter (CSA-WM; 0.44≤r≤0.62). In comparison, age correlated weakly with cortical GM volume, precentral GM volume, and cortical thickness (-0.21≥r≥-0.27). Body weight correlated weakly with magnetization transfer ratio in the SC WM, dorsal columns, and lateral corticospinal tracts (-0.20≥r≥-0.23). Body weight further correlated weakly with the mean diffusivity derived from diffusion tensor imaging (DTI) in SC WM (r=-0.20) and dorsal columns (-0.21), but only in males. CSA-WM correlated strongly or moderately with brain volumes (0.39≤r≤0.64), and weakly with precentral gyrus thickness and DTI-based fractional anisotropy in SC dorsal columns and SC lateral corticospinal tracts (-0.22≥r≥-0.25). Linear mixture of sex and age explained 26±10% of data variance in brain volumetry and SC CSA. The amount of explained variance increased at 33±11% when body height was added into the mixture model. Age itself explained only 2±2% of such variance. In conclusion, body size is a significant biological variable. Along with sex and age, body size should therefore be included as a mandatory variable in the design of clinical neuroimaging studies examining SC and brain structure.

Predictors of Skip Laminotomy for Placement of Paddle Leads for Spinal Cord Stimulation

OBJECTIVES

Placement of a standard paddle lead for spinal cord stimulation (SCS) requires a laminotomy for positioning of the lead within the epidural space. During initial placement, an additional laminotomy or laminectomy, termed a "skip" laminotomy, may be necessary at a higher level to pass the lead to the appropriate midline position. Patient and radiographic factors that predict the need for a skip laminotomy have yet to be identified.

MATERIALS AND METHODS

Participants who underwent SCS paddle placement at Albany Medical Center between 2016 and 2017 were identified. Operative reports were reviewed to identify the paddle type, level of initial laminotomy, target level, and skip laminotomy level. Preoperative thoracic magnetic resonance images (MRIs) were reviewed, and spinal canal diameter, interpedicular distance, and dorsal cerebral spinal fluid thickness were measured for each participant when available.

RESULTS

A total of 106 participants underwent thoracic SCS placement. Of these, 97 had thoracic MRIs available for review. Thirty-eight participants required a skip laminotomy for placement of the paddle compared with 68 participants who did not. There was no significant difference in demographic features including age, sex, body mass index, and surgical history. Univariate analyses that suggested trends were selected for further analysis using binary logistic regression. Level of initial laminotomy (odds ratio [OR] = 1.51, p = 0.028), spinal canal diameter (OR = 0.71, p = 0.015), and dorsal cerebrospinal fluid thickness (OR = 0.61, p = 0.011) were correlated with skip laminotomy. Target level (OR = 1.27, p = 0.138) and time from trial (1.01, p = 0.117) suggested potential association. The multivariate regression was statistically significant, X2(10) = 28.02, p = 0.002. The model explained 38.3% of the variance (Nagelkerke R2) and predicted skip laminectomy correctly in 73.3% of cases. However, for the multivariate regression, only a decrease in spinal canal diameter (OR = 0.59, p = 0.041) was associated with a greater odds of skip laminotomy.

CONCLUSIONS

This study aims to characterize the patient and radiographic factors that may predict the need to perform a skip laminotomy during the initial placement of SCS paddles. Here, we show that radiographic and anatomic variables, primarily spinal canal diameter, play an important role in predicting the need for a skip laminotomy. Furthermore, we suggest that target level for placement and level of initial laminotomy also may contribute. Further investigation of the predictive factors for performing a skip laminotomy would help optimize surgical planning and preoperative patient selection and counseling.

Validation of a New Semiautomated Segmentation Pipeline Based on the Spinal Cord Toolbox DeepSeg Algorithm to Estimate the Cervical Canal Area

BACKGROUND AND PURPOSE

As in the brain reserve concept, a larger cervical canal area may also protect against disability. In this context, a semiautomated pipeline has been developed to obtain quantitative estimations of the cervical canal area. The aim of the study was to validate the pipeline, to evaluate the consistency of the cervical canal area measurements during a 1-year period, and to compare cervical canal area estimations obtained from brain and cervical MRI acquisitions.

MATERIALS AND METHODS

Eight healthy controls and 18 patients with MS underwent baseline and follow-up 3T brain and cervical spine sagittal 3D MPRAGE. The cervical canal area was measured in all acquisitions, and estimations obtained with the proposed pipeline were compared with manual segmentations performed by 1 evaluator using the Dice similarity coefficient. The cervical canal area estimations obtained on baseline and follow-up T1WI were compared; brain and cervical cord acquisitions were also compared using the individual and average intraclass correlation coefficients.

RESULTS

The agreement between the manual cervical canal area masks and the masks provided by the proposed pipeline was excellent, with a mean Dice similarity coefficient mean of 0.90 (range, 0.73-0.97). The cervical canal area estimations obtained from baseline and follow-up scans showed a good level of concordance (intraclass correlation coefficient = 0.76; 95% CI, 0.44-0.88); estimations obtained from brain and cervical MRIs also had good agreement (intraclass correlation coefficient = 0.77; 95% CI, 0.45-0.90).

CONCLUSIONS

The proposed pipeline is a reliable tool to estimate the cervical canal area. The cervical canal area is a stable measure across time; moreover, when cervical sequences are not available, the cervical canal area could be estimated using brain T1WI.

Reliability of spinal cord measures based on synthetic T1-weighted MRI derived from multiparametric mapping (MPM)

Short MRI acquisition time, high signal-to-noise ratio, and high reliability are crucial for image quality when scanning healthy volunteers and patients. Cross-sectional cervical cord area (CSA) has been suggested as a marker of neurodegeneration and potential outcome measure in clinical trials and is conventionally measured on T₁-weigthed 3D Magnetization Prepared Rapid Acquisition Gradient-Echo (MPRAGE) images. This study aims to reduce the acquisition time for the comprehensive assessment of the spinal cord, which is typically based on MPRAGE for morphometry and multi-parameter mapping (MPM) for microstructure. The MPRAGE is replaced by a synthetic T₁-w MRI (synT₁-w) estimated from the MPM, in order to measure CSA. SynT₁-w images were reconstructed using the MPRAGE signal equation based on quantitative maps of proton density (PD), longitudinal (R₁) and effective transverse (R₂*) relaxation rates. The reliability of CSA measurements from synT₁-w images was determined within a multi-center test-retest study format and validated against acquired MPRAGE scans by assessing the agreement between both methods. The response to pathological changes was tested by longitudinally measuring spinal cord atrophy following spinal cord injury (SCI) for synT₁-w and MPRAGE using linear mixed effect models. CSA measurements based on the synT₁-w MRI showed high intra-site (Coefficient of variation [CoV]: 1.43% to 2.71%) and inter-site repeatability (CoV: 2.90% to 5.76%), and only a minor deviation of -1.65 mm² compared to MPRAGE. Crucially, by assessing atrophy rates and by comparing SCI patients with healthy controls longitudinally, differences between synT₁-w and MPRAGE were negligible. These results demonstrate that reliable estimates of CSA can be obtained from synT₁-w images, thereby reducing scan time significantly.

Spinal cord atrophy after spinal cord injury - A systematic review and meta-analysis

Cervical spinal cord atrophy occurs after spinal cord injury. The atrophy and how level of injury affects atrophy differs between studies. A systematic review and metaanalysis were done after systematic searches of PubMed, CINAHL, APA PsycInfo and Web of Science. English language original studies analyzing MRI cervical spinal cord cross-sectional area in adults with spinal cord injury were included. Atrophy and correlation between injury level and atrophy were estimated with random-effects models, standardized mean differences, and 95% confidence intervals. 24 studies were identified. 13/24 studies had low risk of bias. Cord atrophy meta-analysis of 18 articles corresponded to a standardized mean difference of -1.48 (95% CI -1.78 to -1.19) with moderate to large interstudy heterogeneity. Logarithmic time since injury influenced heterogeneity. Longitudinal atrophy was best described by a logarithmic model, indicating that rate of spinal atrophy decreases over time. Meta-correlation of eight studies indicated more severe atrophy in more rostral injuries (0.41, 95% CI 0.20-0.59). Larger and preferably longitudinal studies, data sharing, and standardized protocols are warranted.

Association of daily physical activity with brain volumes and cervical spinal cord areas in multiple sclerosis

BACKGROUND

Remote activity monitoring has the potential to evaluate real-world, motor function, and disability at home. The relationships of daily physical activity with spinal cord white matter and gray matter (GM) areas, multiple sclerosis (MS) disability and leg function, are unknown.

OBJECTIVE

Evaluate the association of structural central nervous system pathology with ambulatory disability.

METHODS

Fifty adults with progressive or relapsing MS with motor disability who could walk >2 minutes were assessed using clinician-evaluated, patient-reported outcomes, and quantitative brain and spinal cord magnetic resonance imaging (MRI) measures. Fitbit Flex2, worn on the non-dominant wrist, remotely assessed activity over 30 days. Univariate and multivariate analyses were performed to assess correlations between physical activity and other disability metrics.

RESULTS

Mean age was 53.3 years and median Expanded Disability Status Scale (EDSS) was 4.0. Average daily step counts (STEPS) were highly correlated with EDSS and walking measures. Greater STEPS were significantly correlated with greater C2-C3 spinal cord GM areas (ρ = 0.39, p = 0.04), total cord area (TCA; ρ = 0.35, p = 0.04), and cortical GM volume (ρ = 0.32, p = 0.04).

CONCLUSION

These results provide preliminary evidence that spinal cord GM area is a neuroanatomical substrate associated with STEPS. STEPS could serve as a proxy to alert clinicians and researchers to possible changes in structural nervous system pathology.

Longitudinal assessment of cervical spinal cord compartments in multiple sclerosis

BACKGROUND

Although cervical spinal cord (cSC) area is an established biomarker in MS, there is currently a lack of longitudinal assessments of cSC gray and white matter areas.

OBJECTIVE

We conducted an explorative analysis of longitudinal changes of cSC gray and white matter areas in MS patients.

METHODS

65 MS patients (33 relapsing-remitting; 20 secondary progressive and 12 primary progressive) and 20 healthy controls (HC) received clinical and upper cSC MRI assessments over 1.10±0.28 years. cSC compartments were quantified on MRI using the novel averaged magnetization inversion recovery acquisitions sequence (in-plane resolution=0.67 × 0.67mm²), and in-house developed post-processing methods. Patients were stratified regarding clinical progression.

RESULTS

Patients with clinical progression showed faster reduction of cSC areas over time at the level of cSC enlargement (approximate vertebral level C4-C5) compared to stable patients (p<0.05). In addition, when compared to the rostral-cSC (approximate vertebral level C2-C3), a preferential reduction of cSC and white matter areas over time at the level of cSC enlargement (p<0.05 and p<0.01, respectively) was demonstrated only in patients with clinical progression, but not in stable MS patients and HC. Compared to HC, MS patients showed comparable changes over time in all cSC compartments.

CONCLUSIONS

MS patients with clinical disease progression demonstrate subtle signs of a more pronounced tissue loss at the level of cSC enlargement. Future studies should consider larger sample sizes and more extended observation periods.

Fully Automatic Method for Reliable Spinal Cord Compartment Segmentation in Multiple Sclerosis

BACKGROUND AND PURPOSE

Fully automatic quantification methods of spinal cord compartments are needed to study pathologic changes of the spinal cord GM and WM in MS in vivo. We propose a novel method for automatic spinal cord compartment segmentation (SCORE) in patients with MS.

MATERIALS AND METHODS

The cervical spinal cords of 24 patients with MS and 24 sex- and age-matched healthy controls were scanned on a 3T MR imaging system, including an averaged magnetization inversion recovery acquisition sequence. Three experienced raters manually segmented the spinal cord GM and WM, anterior and posterior horns, gray commissure, and MS lesions. Subsequently, manual segmentations were used to train neural segmentation networks of spinal cord compartments with multidimensional gated recurrent units in a 3-fold cross-validation fashion. Total intracranial volumes were quantified using FreeSurfer.

RESULTS

The intra- and intersession reproducibility of SCORE was high in all spinal cord compartments (eg, mean relative SD of GM and WM: ≤ 3.50% and ≤1.47%, respectively) and was better than manual segmentations (all P < .001). The accuracy of SCORE compared with manual segmentations was excellent, both in healthy controls and in patients with MS (Dice similarity coefficients of GM and WM: ≥ 0.84 and ≥0.92, respectively). Patients with MS had lower total WM areas (P < .05), and total anterior horn areas (P < .01 respectively), as measured with SCORE.

CONCLUSIONS

We demonstrate a novel, reliable quantification method for spinal cord tissue segmentation in healthy controls and patients with MS and other neurologic disorders affecting the spinal cord. Patients with MS have reduced areas in specific spinal cord tissue compartments, which may be used as MS biomarkers.

Automatic measure and normalization of spinal cord cross-sectional area using the pontomedullary junction

Spinal cord cross-sectional area (CSA) is a relevant biomarker to assess spinal cord atrophy in neurodegenerative diseases. However, the considerable inter-subject variability among healthy participants currently limits its usage. Previous studies explored factors contributing to the variability, yet the normalization models required manual intervention and used vertebral levels as a reference, which is an imprecise prediction of the spinal levels. In this study we implemented a method to measure CSA automatically from a spatial reference based on the central nervous system (the pontomedullary junction, PMJ), we investigated factors to explain variability, and developed normalization strategies on a large cohort (N = 804). Following automatic spinal cord segmentation, vertebral labeling and PMJ labeling, the spinal cord CSA was computed on T1w MRI scans from the UK Biobank database. The CSA was computed using two methods. For the first method, the CSA was computed at the level of the C2-C3 intervertebral disc. For the second method, the CSA was computed at 64 mm caudally from the PMJ, this distance corresponding to the average distance between the PMJ and the C2-C3 disc across all participants. The effect of various demographic and anatomical factors was explored, and a stepwise regression found significant predictors; the coefficients of the best fit model were used to normalize CSA. CSA measured at C2-C3 disc and using the PMJ differed significantly (paired t-test, p-value = 0.0002). The best normalization model included thalamus, brain volume, sex and the interaction between brain volume and sex. The coefficient of variation went down for PMJ CSA from 10.09 (without normalization) to 8.59%, a reduction of 14.85%. For CSA at C2-C3, it went down from 9.96 to 8.42%, a reduction of 15.13 %. This study introduces an end-to-end automatic pipeline to measure and normalize cord CSA from a neurological reference. This approach requires further validation to assess atrophy in longitudinal studies. The inter-subject variability of CSA can be partly accounted for by demographics and anatomical factors.

Advanced spinal cord MRI in multiple sclerosis: Current techniques and future directions

Spinal cord magnetic resonance imaging (MRI) has a central role in multiple sclerosis (MS) clinical practice for diagnosis and disease monitoring. Advanced MRI sequences capable of visualizing and quantifying tissue macro- and microstructure and reflecting different pathological disease processes have been used in MS research; however, the spinal cord remains under-explored, partly due to technical obstacles inherent to imaging this structure. We propose that the study of the spinal cord merits equal ambition in overcoming technical challenges, and that there is much information to be exploited to make valuable contributions to our understanding of MS. We present a narrative review on the latest progress in advanced spinal cord MRI in MS, covering in the first part structural, functional, metabolic and vascular imaging methods. We focus on recent studies of MS and those making significant technical steps, noting the challenges that remain to be addressed and what stands to be gained from such advances. Throughout we also refer to other works that presend more in-depth review on specific themes. In the second part, we present several topics that, in our view, hold particular potential. The need for better imaging of gray matter is discussed. We stress the importance of developing imaging beyond the cervical spinal cord, and explore the use of ultra-high field MRI. Finally, some recommendations are given for future research, from study design to newer developments in analysis, and the need for harmonization of sequences and methods within the field. This review is aimed at researchers and clinicians with an interest in gaining an overview of the current state of advanced MRI research in this field and what is primed to be the future of spinal cord imaging in MS research.

Structural MRI Reveals Cervical Spinal Cord Atrophy in the P301L Mouse Model of Tauopathy: Gender and Transgene-Dosing Effects

In primary tauopathies, the deposition of tau neurofibrillary tangles and threads as well as neurodegenerative changes have been found within the brain and spinal cord. While degenerative changes have been intensively studied in the brain using structural magnetic resonance imaging (MRI), MRI studies investigating the spinal cord are still scarce. In the present study, we acquired ex vivo high resolution structural MRI of the cervical spinal cord of 8.5–9 month old hemizygous and homozygous P301L mice and non-transgenic littermates of both genders. We assessed the total cross-sectional area, and the gray and white matter anterior-posterior width and left-right width that are established imaging marker of spinal cord degeneration. We observed significant tissue-specific reductions in these parameters in female P301L mice that were stronger in homozygous than in hemizygous P301L mice, indicating both an effect of gender and transgene expression on cervical spinal cord atrophy. Moreover, atrophy was stronger in the gray matter than in the white matter. Immunohistochemical analysis revealed neurodegenerative and neuroinflammatory changes in the cervical spinal cord in both the gray and white matter of P301L mice. Collectively, our results provide evidence for cervical spinal cord atrophy that may directly contribute to the motor signs associated with tauopathy.

Spinal Cord Gray Matter Atrophy is associated with functional decline in Post-Polio Syndrome

Objective

To determine if patients with post‐polio syndrome (PPS) show spinal cord gray matter (SCGM) atrophy and to assess associations between SCGM atrophy, muscle strength and patient‐reported functional decline.

Methods

Twenty patients diagnosed with PPS (March of Dimes criteria) and 20 age‐ and sex‐matched healthy controls (HC) underwent 3T axial 2D‐rAMIRA magnetic resonance imaging at the intervertebral disc levels C2/C3–C6/C7, T9/T10 and the lumbar enlargement level (T_max) (0.5 × 0.5 mm² in‐plane resolution). SCGM areas were segmented manually by two independent raters. Muscle strength, self‐reported fatigue, depression and pain measures were assessed.

Results

Post‐polio syndrome patients showed significantly and preferentially reduced SCGM areas at C2/C3 (p = 0.048), C3/C4 (p = 0.001), C4/C5 (p < 0.001), C5/C6 (p = 0.004) and T_max (p = 0.041) compared to HC. SCGM areas were significantly associated with muscle strength in corresponding myotomes even after adjustment for fatigue, pain and depression. SCGM area_Tmax together with age and sex explained 68% of ankle dorsiflexion strength variance. No associations were found with age at or time since infection. Patients reporting PPS‐related decline in arm function showed significant cervical SCGM atrophy compared to stable patients adjusted for initial disease severity.

Conclusions

Patients with PPS show significant SCGM atrophy that correlates with muscle strength and is associated with PPS‐related functional decline. Our findings suggest a secondary neurodegenerative process underlying SCGM atrophy in PPS that is not explained by aging or residua of the initial infection alone. Confirmation by longitudinal studies is needed. The described imaging methodology is promising for developing novel imaging surrogates for SCGM diseases.

A New Framework for Investigating the Biological Basis of Degenerative Cervical Myelopathy [AO Spine RECODE-DCM Research Priority Number 5]: Mechanical Stress, Vulnerability and Time

STUDY DESIGN

Literature Review (Narrative).

OBJECTIVE

To propose a new framework, to support the investigation and understanding of the pathobiology of DCM, AO Spine RECODE-DCM research priority number 5.

METHODS

Degenerative cervical myelopathy is a common and disabling spinal cord disorder. In this perspective, we review key knowledge gaps between the clinical phenotype and our biological models. We then propose a reappraisal of the key driving forces behind DCM and an individual's susceptibility, including the proposal of a new framework.

RESULTS

Present pathobiological and mechanistic knowledge does not adequately explain the disease phenotype; why only a subset of patients with visualized cord compression show clinical myelopathy, and the amount of cord compression only weakly correlates with disability. We propose that DCM is better represented as a function of several interacting mechanical forces, such as shear, tension and compression, alongside an individual's vulnerability to spinal cord injury, influenced by factors such as age, genetics, their cardiovascular, gastrointestinal and nervous system status, and time.

CONCLUSION

Understanding the disease pathobiology is a fundamental research priority. We believe a framework of mechanical stress, vulnerability, and time may better represent the disease as a whole. Whilst this remains theoretical, we hope that at the very least it will inspire new avenues of research that better encapsulate the full spectrum of disease.

Lumbar Thecal Sac Dimensions and Axial Spinal Cord Areas on Magnetic Resosnace Imaging in 626 Healthy Subjects

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

The aim of this study was to investigate the lumbar thecal sac dimensions and spinal cord area on magnetic resonance (MR) imaging in healthy volunteers.

SUMMARY OF BACKGROUND DATA

There are few reports regarding lumbar spine MRI in healthy subjects, and the difference in spinal canal dimensions by age remains unclear.

METHODS

A total of 629 healthy volunteers were enrolled, including ≥50 males, females, and subjects in each of the 20s to 70s age decades. The anteroposterior and transverse diameters of the thecal sac and axial areas of the thecal sac and spinal cord were measured at the disc levels on T2-weighted axial MR images. The anteroposterior-to-transverse ratio of the thecal sac (APTR) was calculated.

RESULTS

The thecal sac area from T12/L1 to L4/5 was reduced in older age group, but there was no significant difference in L5/S1. The thecal sac area was significantly reduced in older age group: 89.9%, 86.0%, 84.6%, 80.3% at T12/L1, L1/2, L2/3, and L3/4, respectively, and 79.9% at L4/5 in subjects in their 70 s relative to that in subjects in their 20 s. The APTR was significantly reduced in older age group from T11/12 to L2/L3 in males and at T10/11, L3/4 and from T11/12 to L2/3 in females. Narrow thecal sac areas <80 mm2 were found in 10 subjects. The spinal cord area was significantly reduced in older age group at T10/11 in males and at T9/10, T10/11, and T11/12 in females. The area was 92.0% at T10/11 in subjects in their 70s relative to the area of subjects in their 20s.

CONCLUSION

The thecal sac area was reduced in older age group from T12/L1 to L4/5, and the thecal sac area was reduced in the anteroposterior and all directions in the upper and lower lumbar area in age group, respectively. Approximately, 3.0% of healthy population in their 50s or older will have severe asymptomatic stenosis.Level of Evidence: 2.

Open-access quantitative MRI data of the spinal cord and reproducibility across participants, sites and manufacturers

In a companion paper by Cohen-Adad et al. we introduce the spine generic quantitative MRI protocol that provides valuable metrics for assessing spinal cord macrostructural and microstructural integrity. This protocol was used to acquire a single subject dataset across 19 centers and a multi-subject dataset across 42 centers (for a total of 260 participants), spanning the three main MRI manufacturers: GE, Philips and Siemens. Both datasets are publicly available via git-annex. Data were analysed using the Spinal Cord Toolbox to produce normative values as well as inter/intra-site and inter/intra-manufacturer statistics. Reproducibility for the spine generic protocol was high across sites and manufacturers, with an average inter-site coefficient of variation of less than 5% for all the metrics. Full documentation and results can be found at https://spine-generic.rtfd.io/ . The datasets and analysis pipeline will help pave the way towards accessible and reproducible quantitative MRI in the spinal cord.

Normalization of Spinal Cord Total Cross-Sectional and Gray Matter Areas as Quantified With Radially Sampled Averaged Magnetization Inversion Recovery Acquisitions

Background: MR imaging of the spinal cord (SC) gray matter (GM) at the cervical and lumbar enlargements' level may be particularly informative in lower motor neuron disorders, e. g., spinal muscular atrophy, but also in other neurodegenerative or autoimmune diseases affecting the SC. Radially sampled averaged magnetization inversion recovery acquisition (rAMIRA) is a novel approach to perform SC imaging in clinical settings with favorable contrast and is well-suited for SC GM quantitation. However, before applying rAMIRA in clinical studies, it is important to understand (i) the sources of inter-subject variability of total SC cross-sectional areas (TCA) and GM area (GMA) measurements in healthy subjects and (ii) their relation to age and sex to facilitate the detection of pathology-associated changes. In this study, we aimed to develop normalization strategies for rAMIRA-derived SC metrics using skull and spine-based metrics to reduce anatomical variability.

Methods: Sixty-one healthy subjects (age range 11–93 years, 37.7% women) were investigated with axial two-dimensional rAMIRA imaging at 3T MRI. Cervical and thoracic levels including the level of the cervical (C4/C5) and lumbar enlargements (T_max) were examined. SC T2-weighted sagittal images and high-resolution 3D whole-brain T1-weighted images were acquired. TCA and GMAs were quantified. Anatomical variables with associations of |r| > 0.30 in univariate association with SC areas, and age and sex were used to construct normalization models using backward selection with TCA_C4/C5 as outcome. The effect of the normalization was assessed by % relative standard deviation (RSD) reductions.

Results: Mean inter-individual variability and the SD of the SC area metrics were considerable: TCA_C4/5: 8.1%/9.0; TCA_Tmax: 8.9%/6.5; GMA_C4/C5: 8.6%/2.2; GMA_Tmax: 12.2%/3.8. Normalization based on sex, brain WM volume, and spinal canal area resulted in RSD reductions of 23.7% for TCAs and 12.0% for GM areas at C4/C5. Normalizations based on the area of spinal canal alone resulted in RSD reductions of 10.2% for TCAs and 9.6% for GM areas at C4/C5, respectively.

Discussion: Anatomic inter-individual variability of SC areas is substantial. This study identified effective normalization models for inter-subject variability reduction in TCA and SC GMA in healthy subjects based on rAMIRA imaging.

Comparative neuroanatomy of the lumbosacral spinal cord of the rat, cat, pig, monkey, and human

The overall goal of this work was to create a high-resolution MRI atlas of the lumbosacral enlargement of the spinal cord of the rat (Sprague-Dawley), cat, domestic pig, rhesus monkey, and human. These species were chosen because they are commonly used in basic and translational research in spinal cord injuries and diseases. Six spinal cord specimens from each of the studied species (total of 30 specimens) were fixed, extracted, and imaged. Sizes of the spinal cord segments, cross-sectional dimensions, and locations of the spinal cord gray and white matter were quantified and compared across species. The lumbar enlargement spans spinal cord levels L3-S1 in rats, L4-S1 in cats, L3-S1 in pigs, L2/L3-L7/S1 in monkeys, and T12/L1-S1/S2 in humans. The enlargements in pigs and humans are largest and most similar in size (length and cross-sectional area); followed by monkeys and cats; and followed by rats. The obtained atlas establishes a neuroanatomical reference for the intact lumbosacral spinal cord in these species. It can also be used to guide the planning of surgical procedures of the spinal cord and technology design and development of spinal cord neuroprostheses, as well as precise delivery of cells/drugs into target regions within the spinal cord parenchyma.

MRI Measurement of Upper Cervical Spinal Cord Cross-Sectional Area in Children

BACKGROUND AND PURPOSE

Neurological and neurodegenerative diseases can affect the spinal cord (SC) of pediatric patients. Magnetic resonance imaging (MRI) allows for in vivo quantification of SC atrophy via cross-sectional area (CSA). The study of CSA values in the general population is important to disentangle disease-related changes from intersubject variability. This study aimed at providing normative values for cervical CSA in children, extending our previous work performed with adults.

METHODS

Seventy-eight children (age 7-17 years) were selected from a Developmental Dyslexia study. All subjects underwent a 3T brain MRI session and any incidental findings were reported on the scans. A sagittal 1 mm³ 3-dimensional T₁ -weighted brain acquisition extended to the upper cervical cord was used to measure CSA at C2-C3, as well as spinal canal area and skull volume (V-scale). These three metrics were linearly fitted as a function of age to extract trends and percentage annual changes. Sex differences of CSA were assessed using least squares regression analyses, adjusting for age. We tested normalization strategies proven to be effective in reducing the intersubject variability of adults' CSA.

RESULTS

CSA changed as a function of age at a faster rate when compared with skull volume (CSA: 1.82% increase, V-scale: .60% reduction). Sex had a statistically significant effect on CSA. Normalization methods based on canal area and skull volume reduced the CSA intersubject variability up to 16.84%.

CONCLUSIONS

We present CSA normative values in a large cohort of children, reporting on sources of intersubject variability and how to reduce them applying normalization methods previously developed.

Imaging of the thoracic spinal cord using radially sampled averaged magnetization inversion recovery acquisitions

BACKGROUND

Spinal cord (SC) gray and white matter atrophy quantification by advanced morphometric MRI can help to better characterize the course of neurodegenerative diseases in vivo, such as e.g. lower motor neuron disorders. Imaging the lower thoracic cord - containing those motor neurons that control leg function - could be particularly informative, however, is challenging due to tissue composition, physiological motion and large field of views.

NEW METHOD

An "averaged magnetization inversion recovery acquisitions" (AMIRA) approach with a radial k-space acquisition scheme was developed. The method is designed for morphometric SC imaging with a focus on the thoracic SC.

RESULTS

In a typical setting, radial AMIRA acquires transverse slices with a high 0.50 × 0.50mm² in-plane resolution and a pronounced positive contrast between thoracic gray and white matter, within typically 2:39 min. Additional proof-of-concept measurements in patients demonstrate that such contrast and resolving capability is indeed necessary to assess potential atrophy of the anterior horns.

COMPARISON WITH EXISTING METHOD(S)

Radial AMIRA utilizes two benefits of radial MRI techniques: being generally less prone to motion effects and that fold over artifacts can manifest less intrusively. These benefits are united with the original AMIRA approach which allows the contrast to be 'tuned' and improved based on the combination of five simultaneously acquired images of different tissue contrast.

CONCLUSIONS

Radial AMIRA is a promising approach for in vivo SC gray and white matter atrophy visualization and quantification in lower motor neuron diseases and other autoimmune or genetic diseases involving the entire (not only cervical) spinal cord.

Heritability of cervical spinal cord structure

OBJECTIVE

Measures of spinal cord structure can be a useful phenotype to track disease severity and development; this observational study measures the hereditability of cervical spinal cord anatomy and its correlates in healthy human beings.

METHODS

Twin data from the Human Connectome Project were analyzed with semiautomated spinal cord segmentation, evaluating test-retest reliability and broad-sense heritability with an AE model. Relationships between spinal cord metrics, general physical measures, regional brain structural measures, and motor function were assessed.

RESULTS

We found that the spinal cord C2 cross-sectional area (CSA), left-right width (LRW), and anterior-posterior width (APW) are highly heritable (85%-91%). All measures were highly correlated with the brain volume, and CSA only was positively correlated with thalamic volumes (p = 0.005) but negatively correlated with the occipital cortex area (p = 0.001). LRW was correlated with the participant's height (p = 0.00027). The subjects' sex significantly influenced these metrics. Analyses of a test-retest data set confirmed validity of the approach.

CONCLUSIONS

This study provides the evidence of genetic influence on spinal cord structure. MRI metrics of cervical spinal cord anatomy are robust and not easily influenced by nonpathological environmental factors, providing a useful metric for monitoring normal development and progression of neurodegenerative disorders affecting the spinal cord, including-but not limited to-spinal cord injury and MS.

Intersubject Variability and Normalization Strategies for Spinal Cord Total Cross-Sectional and Gray Matter Areas

BACKGROUND AND PURPOSE

The quantification of spinal cord (SC) atrophy by MRI has assumed an important role in assessment of neuroinflammatory/neurodegenerative diseases and traumatic SC injury. Recent technical advances make possible the quantification of gray matter (GM) and white matter tissues in clinical settings. However, the goal of a reliable diagnostic, prognostic or predictive marker is still elusive, in part due to large intersubject variability of SC areas. Here, we investigated the sources of this variability and explored effective strategies to reduce it.

METHODS

One hundred twenty-nine healthy subjects (mean age: 41.0 ± 15.9) underwent MRI on a Siemens 3T Skyra scanner. Two-dimensional PSIR at the C2-C3 vertebral level and a sagittal 1 mm³ 3D T1-weighted brain acquisition extended to the upper cervical cord were acquired. Total cross-sectional area and GM area were measured at C2-C3, as well as measures of the vertebra, spinal canal and the skull. Correlations between the different metrics were explored using Pearson product-moment coefficients. The most promising metrics were used to normalize cord areas using multiple regression analyses.

RESULTS

The most effective normalization metrics were the V-scale (from SienaX) and the product of the C2-C3 spinal canal diameters. Normalization methods based on these metrics reduced the intersubject variability of cord areas of up to 17.74%. The measured cord areas had a statistically significant sex difference, while the effect of age was moderate.

CONCLUSIONS

The present work explored in a large cohort of healthy subjects the source of intersubject variability of SC areas and proposes effective normalization methods for its reduction.

Evaluation of Intra- and Interscanner Reliability of MRI Protocols for Spinal Cord Gray Matter and Total Cross-Sectional Area Measurements

BACKGROUND

In vivo quantification of spinal cord atrophy in neurological diseases using MRI has attracted increasing attention.

PURPOSE

To compare across different platforms the most promising imaging techniques to assess human spinal cord atrophy.

STUDY TYPE

Test/retest multiscanner study.

SUBJECTS

Twelve healthy volunteers.

FIELD STRENGTH/SEQUENCE

Three different 3T scanner platforms (Siemens, Philips, and GE) / optimized phase sensitive inversion recovery (PSIR), T1 -weighted (T1 -w), and T2 *-weighted (T2 *-w) protocols.

ASSESSMENT

On all images acquired, two operators assessed contrast-to-noise ratio (CNR) between gray matter (GM) and white matter (WM), and between WM and cerebrospinal fluid (CSF); one experienced operator measured total cross-sectional area (TCA) and GM area using JIM and the Spinal Cord Toolbox (SCT).

STATISTICAL TESTS

Coefficient of variation (COV); intraclass correlation coefficient (ICC); mixed effect models; analysis of variance (t-tests).

RESULTS

For all the scanners, GM/WM CNR was higher for PSIR than T2 *-w (P < 0.0001) and WM/CSF CNR for T1 -w was the highest (P < 0.0001). For TCA, using JIM, median COVs were smaller than 1.5% and ICC >0.95, while using SCT, median COVs were in the range 2.2-2.75% and ICC 0.79-0.95. For GM, despite some failures of the automatic segmentation, median COVs using SCT on T2 *-w were smaller than using JIM manual PSIR segmentations. In the mixed effect models, the subject was always the main contributor to the variance of area measurements and scanner often contributed to TCA variance (P < 0.05). Using JIM, TCA measurements on T2 *-w were different than on PSIR (P = 0.0021) and T1 -w (P = 0.0018), while using SCT, no notable differences were found between T1 -w and T2 *-w (P = 0.18). JIM and SCT-derived TCA were not different on T1 -w (P = 0.66), while they were different for T2 *-w (P < 0.0001). GM area derived using SCT/T2 *-w versus JIM/PSIR were different (P < 0.0001).

DATA CONCLUSION

The present work sets reference values for the magnitude of the contribution of different effects to cord area measurement intra- and interscanner variability.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2019;49:1078-1090.

Spinal myoclonus following neuraxial anesthesia: a literature review

Spinal myoclonus (SM) is a rare neurologic movement disorder following neuraxial anesthesia (NA). SM following NA (SM-NA) has insufficient clinical information and its pathogenesis remains to be elucidated. The aim of this review article was to summarize the past cases and consider SM-NA pathophysiology. Based on our PubMed search, it was revealed that SM-NA develops within several hours after neuraxial local anesthetic (LA) administration and resolves in a day without leaving neurologic compilations. It occurs primarily in the lower extremities, but can sometimes spread upward and affect the upper extremities and trunk. Although statistical adjustments are indispensable, analysis of the previous cases provided important facts that seem to be related with the mechanism of SM-NA. The frequently used LAs for spinal anesthesia were hyperbaric. SM-NA occurrence was more frequent in women. After initiation of spinal anesthesia, intrathecal hyperbaric LA distributes cephalad. In the LA elimination process, the large concentration differences in intrathecal LA may induce the partially functioning spinal neurons, resulting in myoclonus generation. The morphological features of the lumbar spine in women can predispose to a higher LA concentration difference. SM-NA is an unpredictable and rare neural complication following NA and should be confirmed by basic experiments and large-scale researches.

Automatic segmentation of the spinal cord and intramedullary multiple sclerosis lesions with convolutional neural networks

The spinal cord is frequently affected by atrophy and/or lesions in multiple sclerosis (MS) patients. Segmentation of the spinal cord and lesions from MRI data provides measures of damage, which are key criteria for the diagnosis, prognosis, and longitudinal monitoring in MS. Automating this operation eliminates inter-rater variability and increases the efficiency of large-throughput analysis pipelines. Robust and reliable segmentation across multi-site spinal cord data is challenging because of the large variability related to acquisition parameters and image artifacts. In particular, a precise delineation of lesions is hindered by a broad heterogeneity of lesion contrast, size, location, and shape. The goal of this study was to develop a fully-automatic framework - robust to variability in both image parameters and clinical condition - for segmentation of the spinal cord and intramedullary MS lesions from conventional MRI data of MS and non-MS cases. Scans of 1042 subjects (459 healthy controls, 471 MS patients, and 112 with other spinal pathologies) were included in this multi-site study (n = 30). Data spanned three contrasts (T1-, T2-, and T2∗-weighted) for a total of 1943 vol and featured large heterogeneity in terms of resolution, orientation, coverage, and clinical conditions. The proposed cord and lesion automatic segmentation approach is based on a sequence of two Convolutional Neural Networks (CNNs). To deal with the very small proportion of spinal cord and/or lesion voxels compared to the rest of the volume, a first CNN with 2D dilated convolutions detects the spinal cord centerline, followed by a second CNN with 3D convolutions that segments the spinal cord and/or lesions. CNNs were trained independently with the Dice loss. When compared against manual segmentation, our CNN-based approach showed a median Dice of 95% vs. 88% for PropSeg (p ≤ 0.05), a state-of-the-art spinal cord segmentation method. Regarding lesion segmentation on MS data, our framework provided a Dice of 60%, a relative volume difference of -15%, and a lesion-wise detection sensitivity and precision of 83% and 77%, respectively. In this study, we introduce a robust method to segment the spinal cord and intramedullary MS lesions on a variety of MRI contrasts. The proposed framework is open-source and readily available in the Spinal Cord Toolbox.

Gray vs. White Matter Segmentation of the Conus Medullaris: Reliability and Variability in Healthy Volunteers

BACKGROUND AND PURPOSE

Magnetic resonance imaging (MRI)-derived spinal cord (SC) gray and white matter (GM/WM) volume are useful indirect measures of atrophy and neurodegeneration over time, typically obtained in the upper SC. Neuropathological evidence suggests that in certain neurological conditions, early degeneration may occur as low as the sacral SC. In this study, the feasibility of GM/WM segmentation of the conus medullaris (CM) was assessed in vivo.

METHODS

Twenty-three healthy volunteers (11 female, mean age 47 years) underwent high-resolution 3T MRI of the CM using a 3-dimensional fast field echo sequence. Reproducibility of the volume measurements was assessed in 5 subjects (2 female, 25-37 years) by one rater who repeated the analysis 3 times and also with 2 additional raters working independently in order to calculate the intra- and interrater coefficient of variation (COV), respectively. Furthermore, the influence of age, gender, spine and SC metrics on tissue-specific measures of the CM was investigated.

RESULTS

Volumetric CM analyses (N = 23) for the SC, GM, and WM revealed a mean (SD) total volume of CM-TV = 1746.9 (296.7) mm³ , CM-GM-TV = 731.2 (106.0) mm³ , and CM-WM-TV = 1014.6 (211.3) mm³ , respectively. The intra-rater COV for measuring the CM-TV and CM-GM-TV was 3.38% and 7.42%, respectively; the interrater COV was 3.43% and 10.80%, respectively. Using age, gender, spine and SC metrics in regression models substantially reduced group variability for CM-TV, CM-WM-TV, and CM-GM-TV by up to 39.2%, 42.7%, and 21.2%, respectively.

CONCLUSIONS

The results from this study demonstrate the feasibility of obtaining tissue-specific volume measurements in the CM by means of MRI with good reproducibility and provide normative data for future applications in neurological diseases affecting the lower SC.

Correlations between cervical spinal cord magnetic resonance diffusion tensor and diffusion kurtosis imaging metrics and motor performance in patients with chronic ischemic brain lesions of the corticospinal tract

PURPOSE

To investigate modifications of Magnetic Resonance Diffusion Tensor Imaging (DTI) and Diffusion Kurtosis Imaging (DKI) metrics in lateral white matter (WM) bundles of the cervical spinal cord in patients with previous stroke in the vascular territory of the middle cerebral artery (MCA).

METHODS

Twenty consecutive patients with a previous ischemic stroke of the MCA territory and a varying degree of upper motor impairment were enrolled. DKI was centered at the C3C4 and C5C6 intervertebral level.

RESULTS

The fractional anisotropy (FA) values in C3C4 and C5C6 were found to be significantly lower in the lateral WM bundles contralateral to the ischemic lesion and thus, in the WM bundle including the affected corticospinal tract (CST) (p = 0.005 and p = 0.008, respectively), as well as mean kurtosis (MK) and axonal water fraction (AWF) values (p = 0.004 and p = 0.04. respectively). FA values correlated significantly with the Global Motor Index (GMI) both for C3C4 (ρ = 0.61, p = 0.004) and C5C6 (ρ = 0.69, p = 0.002). At C3C4, AWF correlated significantly with GMI (ρ = 0.54, p = 0.03). No correlations were found between lateral WM bundle volumes and GMI.

CONCLUSION

A reduction of anisotropy and microstructural complexity in the affected lateral WM bundle of the cervical spinal cord was observed in patients with previous ischemic stroke involving the CST. The correlations between these metrics and motor performance were statistically significant.

Measurement of spinal cord atrophy using phase sensitive inversion recovery (PSIR) imaging in motor neuron disease

BACKGROUND

The spectrum of motor neuron disease (MND) includes numerous phenotypes with various life expectancies. The degree of upper and lower motor neuron involvement can impact prognosis. Phase sensitive inversion recovery (PSIR) imaging has been shown to detect in vivo gray matter (GM) and white matter (WM) atrophy in the spinal cord of other patient populations but has not been explored in MND.

METHODS

In this study, total cord, WM and GM areas of ten patients with a diagnosis within the MND spectrum were compared to those of ten healthy controls (HC). Patients' diagnosis included amyotrophic lateral sclerosis (ALS), primary lateral sclerosis, primary muscular atrophy, facial onset sensory and motor neuronopathy and ALS-Frontotemporal dementia. Axial 2D PSIR images were acquired at four cervical disc levels (C2-C3, C3-C4, C5-C6 and C7-T1) with a short acquisition time (2 minutes) protocol. Total cross-sectional areas (TCA), GM and WM areas were measured using a combination of highly reliable manual and semi-automated methods. Cord areas in MND patients were compared with HC using linear regression analyses adjusted for age and sex. Correlation of WM and GM areas in MND patients was explored to gain insights into underlying atrophy patterns.

RESULTS

MND patients as a group had significantly smaller cervical cord GM area compared to HC at all four levels (C2-C3: p = .009; C3-C4: p = .001; C5-C6: p = .006; C7-T1: p = .002). WM area at C5-C6 level was significantly smaller (p = .001). TCA was significantly smaller at C3-C4 (p = .018) and C5-C6 (p = .002). No significant GM and WM atrophy was detected in the two patients with predominantly bulbar phenotype. Concomitant GM and WM atrophy was detected in solely upper or lower motor neuron level phenotypes. There was a significant correlation between GM and WM areas at all four levels in this diverse population of MND.

CONCLUSION

Spinal cord GM and WM atrophy can be detected in vivo in patients within the MND spectrum using a short acquisition time 2D PSIR imaging protocol. PSIR imaging shows promise as a method for quantifying spinal cord involvement and thus may be useful for diagnosis, prognosis and for monitoring disease progression.

Spinal cord lesions and atrophy in NMOSD with AQP4-IgG and MOG-IgG associated autoimmunity

BACKGROUND

Spinal cord (SC) affection is a hallmark symptom of neuromyelitis optica spectrum disorders (NMOSD). Patients with aquaporin-4 (AQP4-IgG+) or myelin oligodendrocyte glycoprotein (MOG-IgG+) antibody seropositivity show this overlapping clinical phenotype.

OBJECTIVE

Quantitative comparison of SC lesions and atrophy in AQP4-IgG+ and MOG-IgG+ NMOSD.

METHODS

AQP4-IgG+ (n = 38), MOG-IgG+ (n = 15) NMOSD patients and healthy controls (HC, n = 24) were analysed for SC lesion (prevalence, length, location), atrophy as mean upper cervical cord area (MUCCA), Expanded Disability Status Scale (EDSS), timed 25-foot walk speed (T25FWS) and 9-hole peg test (9HPT) measures.

RESULTS

In total, 92% (35/38) of AQP4-IgG+ and 53% (8/15) of MOG-IgG+ patients had myelitis attacks (χ² = 6.47, p = 0.011). 65.8%/26.7% of AQP4-/MOG-IgG+ patients had chronic SC lesions (χ² = 5.16, p = 0.023), with similar proportions in cervical, upper thoracic and lower thoracic cord, and no length differences. MUCCA was decreased in AQP4-IgG+ (t = -2.27, p = 0.028), but not MOG-IgG+ patients (t = 0.58, p = 0.57) compared to HC. MUCCA associated with myelitis attacks (rho = -0.33, p = 0.016), EDSS (rho = -0.31, p = 0.030), pyramidal functional score (rho = -0.42, p = 0.003), T25FWS (r = 0.43, p = 0.010) and 9HPT Z-score (r = 0.32, p = 0.037), regardless of antibody status.

CONCLUSION

AQP4-IgG+ patients had more myelitis attacks, SC lesions and SC atrophy was more pronounced than in MOG-IgG+ patients. MUCCA is associated with clinical myelitis attacks and disability in all NMOSD patients.

SUMMIT (Serially Unified Multicenter Multiple Sclerosis Investigation): creating a repository of deeply phenotyped contemporary multiple sclerosis cohorts

BACKGROUND

There is a pressing need for robust longitudinal cohort studies in the modern treatment era of multiple sclerosis.

OBJECTIVE

Build a multiple sclerosis (MS) cohort repository to capture the variability of disability accumulation, as well as provide the depth of characterization (clinical, radiologic, genetic, biospecimens) required to adequately model and ultimately predict a patient's course.

METHODS

Serially Unified Multicenter Multiple Sclerosis Investigation (SUMMIT) is an international multi-center, prospectively enrolled cohort with over a decade of comprehensive follow-up on more than 1000 patients from two large North American academic MS Centers (Brigham and Women's Hospital (Comprehensive Longitudinal Investigation of Multiple Sclerosis at the Brigham and Women's Hospital (CLIMB; BWH)) and University of California, San Francisco (Expression/genomics, Proteomics, Imaging, and Clinical (EPIC))). It is bringing online more than 2500 patients from additional international MS Centers (Basel (Universitätsspital Basel (UHB)), VU University Medical Center MS Center Amsterdam (MSCA), Multiple Sclerosis Center of Catalonia-Vall d'Hebron Hospital (Barcelona clinically isolated syndrome (CIS) cohort), and American University of Beirut Medical Center (AUBMC-Multiple Sclerosis Interdisciplinary Research (AMIR)).

RESULTS AND CONCLUSION

We provide evidence for harmonization of two of the initial cohorts in terms of the characterization of demographics, disease, and treatment-related variables; demonstrate several proof-of-principle analyses examining genetic and radiologic predictors of disease progression; and discuss the steps involved in expanding SUMMIT into a repository accessible to the broader scientific community.

Spinal cord volume loss: A marker of disease progression in multiple sclerosis

OBJECTIVE

Cross-sectional studies have shown that spinal cord volume (SCV) loss is related to disease severity in multiple sclerosis (MS). However, long-term data are lacking. Our aim was to evaluate SCV loss as a biomarker of disease progression in comparison to other MRI measurements in a large cohort of patients with relapse-onset MS with 6-year follow-up.

METHODS

The upper cervical SCV, the total brain volume, and the brain T2 lesion volume were measured annually in 231 patients with MS (180 relapsing-remitting [RRMS] and 51 secondary progressive [SPMS]) over 6 years on 3-dimensional, T1-weighted, magnetization-prepared rapid-acquisition gradient echo images. Expanded Disability Status Scale (EDSS) score and relapses were recorded at every follow-up.

RESULTS

Patients with SPMS had lower baseline SCV (p < 0.01) but no accelerated SCV loss compared to those with RRMS. Clinical relapses were found to predict SCV loss over time (p < 0.05) in RRMS. Furthermore, SCV loss, but not total brain volume and T2 lesion volume, was a strong predictor of EDSS score worsening over time (p < 0.05). The mean annual rate of SCV loss was the strongest MRI predictor for the mean annual EDSS score change of both RRMS and SPMS separately, while correlating stronger in SPMS. Every 1% increase of the annual SCV loss rate was associated with an extra 28% risk increase of disease progression in the following year in both groups.

CONCLUSION

SCV loss over time relates to the number of clinical relapses in RRMS, but overall does not differ between RRMS and SPMS. SCV proved to be a strong predictor of physical disability and disease progression, indicating that SCV may be a suitable marker for monitoring disease activity and severity.

Preferential spinal cord volume loss in primary progressive multiple sclerosis

BACKGROUND

Little is known on longer term changes of spinal cord volume (SCV) in primary progressive multiple sclerosis (PPMS).

OBJECTIVE

Longitudinal evaluation of SCV loss in PPMS and its correlation to clinical outcomes, compared to relapse-onset multiple sclerosis (MS) subtypes.

METHODS

A total of 60 MS age-, sex- and disease duration-matched patients (12 PPMS, each 24 relapsing-remitting (RRMS) and secondary progressive MS (SPMS)) were analysed annually over 6 years of follow-up. The upper cervical SCV was measured on 3D T1-weighted magnetization-prepared rapid gradient-echo (MPRAGE) images using a semi-automatic software (CORDIAL), along with the total brain volume (TBV), brain T2 lesion volume (T2LV) and Expanded Disability Status Scale (EDSS).

RESULTS

PPMS showed faster SCV loss over time than RRMS ( p < 0.01) and by trend ( p = 0.066) compared with SPMS. In contrast to relapse-onset MS, in PPMS SCV loss progressed independent of TBV and T2LV changes. Moreover, in PPMS, SCV was the only magnetic resonance imaging (MRI) measurement associated with EDSS increase over time ( p < 0.01), as opposed to RRMS and SPMS.

CONCLUSION

SCV loss is a strong predictor of clinical outcomes in PPMS and has shown to be faster and independent of brain MRI metrics compared to relapse-onset MS.

MRI-Based Methods for Spinal Cord Atrophy Evaluation: A Comparison of Cervical Cord Cross-Sectional Area, Cervical Cord Volume, and Full Spinal Cord Volume in Patients with Aquaporin-4 Antibody Seropositive Neuromyelitis Optica Spectrum Disorders

BACKGROUND AND PURPOSE

Measures for spinal cord atrophy have become increasingly important as imaging biomarkers in the assessment of neuroinflammatory diseases, especially in neuromyelitis optica spectrum disorders. The most commonly used method, mean upper cervical cord area, is relatively easy to measure and can be performed on brain MRIs that capture cervical myelon. Measures of spinal cord volume (eg, cervical cord volume or total cord volume) require longer scanning and more complex analysis but are potentially better suited as spinal cord atrophy measures. This study investigated spinal cord atrophy measures in a cohort of healthy subjects and patients with aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorders and evaluated the discriminatory performance of mean upper cervical cord cross-sectional area compared with cervical cord volume and total cord volume.

MATERIALS AND METHODS

Mean upper cervical cord area, cervical cord volume, and total cord volume were measured using 3T MRIs from healthy subjects (n = 19) and patients with neuromyelitis optica spectrum disorders (n = 30). Group comparison and receiver operating characteristic analyses between healthy controls and patients with neuromyelitis optica spectrum disorders were performed.

RESULTS

Mean upper cervical cord area, cervical cord volume, and total cord volume measures showed similar and highly significant group differences between healthy control subjects and patients with neuromyelitis optica spectrum disorders (P < .01 for all). All 3 measures showed similar receiver operating characteristic-area under the curve values (mean upper cervical cord area = 0.70, cervical cord volume = 0.75, total cord volume = 0.77) with no significant difference between them. No associations among mean upper cervical cord cross-sectional area, cervical cord volume, or total cord volume with disability measures were found.

CONCLUSIONS

All 3 measures showed similar discriminatory power between healthy control and neuromyelitis optica spectrum disorders groups. Mean upper cervical cord area is easier to obtain compared with cervical cord volume and total cord volume and can be regarded as an efficient representative measure of spinal cord atrophy in the neuromyelitis optica spectrum disorders context.

Reliable and fast volumetry of the lumbar spinal cord using cord image analyser (Cordial)

OBJECTIVE

To validate the precision and accuracy of the semi-automated cord image analyser (Cordial) for lumbar spinal cord (SC) volumetry in 3D T1w MRI data of healthy controls (HC).

MATERIALS AND METHODS

40 3D T1w images of 10 HC (w/m: 6/4; age range: 18-41 years) were acquired at one 3T-scanner in two MRI sessions (time interval 14.9±6.1 days). Each subject was scanned twice per session, allowing determination of test-retest reliability both in back-to-back (intra-session) and scan-rescan images (inter-session). Cordial was applied for lumbar cord segmentation twice per image by two raters, allowing for assessment of intra- and inter-rater reliability, and compared to a manual gold standard.

RESULTS

While manually segmented volumes were larger (mean: 2028±245 mm³ vs. Cordial: 1636±300 mm³, p<0.001), accuracy assessments between manually and semi-automatically segmented images showed a mean Dice-coefficient of 0.88±0.05. Calculation of within-subject coefficients of variation (COV) demonstrated high intra-session (1.22-1.86%), inter-session (1.26-1.84%), as well as intra-rater (1.73-1.83%) reproducibility. No significant difference was shown between intra- and inter-session reproducibility or between intra-rater reliabilities. Although inter-rater reproducibility (COV: 2.87%) was slightly lower compared to all other reproducibility measures, between rater consistency was very strong (intraclass correlation coefficient: 0.974).

CONCLUSION

While under-estimating the lumbar SCV, Cordial still provides excellent inter- and intra-session reproducibility showing high potential for application in longitudinal trials.

KEY POINTS

• Lumbar spinal cord segmentation using the semi-automated cord image analyser (Cordial) is feasible. • Lumbar spinal cord is 40-mm cord segment 60 mm above conus medullaris. • Cordial provides excellent inter- and intra-session reproducibility in lumbar spinal cord region. • Cordial shows high potential for application in longitudinal trials.

A role for nutritional intervention in addressing the aging neuromuscular junction

The purpose of this review is to discuss the structural and physiological changes that underlie age-related neuromuscular dysfunction and to summarize current evidence on the potential role of nutritional interventions on neuromuscular dysfunction-associated pathways. Age-related neuromuscular deficits are known to coincide with distinct changes in the central and peripheral nervous system, in the neuromuscular system, and systemically. Although many features contribute to the age-related decline in neuromuscular function, a comprehensive understanding of their integration and temporal relationship is needed. Nonetheless, many nutrients and ingredients show promise in modulating neuromuscular output by counteracting the age-related changes that coincide with neuromuscular dysfunction. In particular, dietary supplements, such as vitamin D, omega-3 fatty acids, β-hydroxy-β-methylbutyrate, creatine, and dietary phospholipids, demonstrate potential in ameliorating age-related neuromuscular dysfunction. However, current evidence seldom directly assesses neuromuscular outcomes and is not always in the context of aging. Additional clinical research studies are needed to confirm the benefits of dietary supplements on neuromuscular function, as well as to define the appropriate population, dosage, and duration for intervention.

Automatic spinal cord localization, robust to MRI contrasts using global curve optimization

During the last two decades, MRI has been increasingly used for providing valuable quantitative information about spinal cord morphometry, such as quantification of the spinal cord atrophy in various diseases. However, despite the significant improvement of MR sequences adapted to the spinal cord, automatic image processing tools for spinal cord MRI data are not yet as developed as for the brain. There is nonetheless great interest in fully automatic and fast processing methods to be able to propose quantitative analysis pipelines on large datasets without user bias. The first step of most of these analysis pipelines is to detect the spinal cord, which is challenging to achieve automatically across the broad range of MRI contrasts, field of view, resolutions and pathologies. In this paper, a fully automated, robust and fast method for detecting the spinal cord centerline on MRI volumes is introduced. The algorithm uses a global optimization scheme that attempts to strike a balance between a probabilistic localization map of the spinal cord center point and the overall spatial consistency of the spinal cord centerline (i.e. the rostro-caudal continuity of the spinal cord). Additionally, a new post-processing feature, which aims to automatically split brain and spine regions is introduced, to be able to detect a consistent spinal cord centerline, independently from the field of view. We present data on the validation of the proposed algorithm, known as "OptiC", from a large dataset involving 20 centers, 4 contrasts (T₂-weighted n = 287, T₁-weighted n = 120, T₂^∗-weighted n = 307, diffusion-weighted n = 90), 501 subjects including 173 patients with a variety of neurologic diseases. Validation involved the gold-standard centerline coverage, the mean square error between the true and predicted centerlines and the ability to accurately separate brain and spine regions. Overall, OptiC was able to cover 98.77% of the gold-standard centerline, with a mean square error of 1.02 mm. OptiC achieved superior results compared to a state-of-the-art spinal cord localization technique based on the Hough transform, especially on pathological cases with an averaged mean square error of 1.08 mm vs. 13.16 mm (Wilcoxon signed-rank test p-value < .01). Images containing brain regions were identified with a 99% precision, on which brain and spine regions were separated with a distance error of 9.37 mm compared to ground-truth. Validation results on a challenging dataset suggest that OptiC could reliably be used for subsequent quantitative analyses tasks, opening the door to more robust analysis on pathological cases.

Spinal Cord Gray Matter Atrophy in Amyotrophic Lateral Sclerosis

BACKGROUND AND PURPOSE

There is an emerging need for biomarkers to better categorize clinical phenotypes and predict progression in amyotrophic lateral sclerosis. This study aimed to quantify cervical spinal gray matter atrophy in amyotrophic lateral sclerosis and investigate its association with clinical disability at baseline and after 1 year.

MATERIALS AND METHODS

Twenty-nine patients with amyotrophic lateral sclerosis and 22 healthy controls were scanned with 3T MR imaging. Standard functional scale was recorded at the time of MR imaging and after 1 year. MR imaging data were processed automatically to measure the spinal cord, gray matter, and white matter cross-sectional areas. A statistical analysis assessed the difference in cross-sectional areas between patients with amyotrophic lateral sclerosis and controls, correlations between spinal cord and gray matter atrophy to clinical disability at baseline and at 1 year, and prediction of clinical disability at 1 year.

RESULTS

Gray matter atrophy was more sensitive to discriminate patients with amyotrophic lateral sclerosis from controls (P = .004) compared with spinal cord atrophy (P = .02). Gray matter and spinal cord cross-sectional areas showed good correlations with clinical scores at baseline (R = 0.56 for gray matter and R = 0.55 for spinal cord; P < .01). Prediction at 1 year with clinical scores (R² = 0.54) was improved when including a combination of gray matter and white matter cross-sectional areas (R² = 0.74).

CONCLUSIONS

Although improvements over spinal cord cross-sectional areas were modest, this study suggests the potential use of gray matter cross-sectional areas as an MR imaging structural biomarker to monitor the evolution of amyotrophic lateral sclerosis.

Spinal cord imaging using averaged magnetization inversion recovery acquisitions

PURPOSE

To establish a novel approach for fast high-resolution spinal cord (SC) imaging using averaged magnetization inversion recovery acquisitions (AMIRA).

METHODS

The AMIRA concept is based on an inversion recovery (IR) prepared, segmented, and time-limited cine balanced steady state free precession sequence. Typically, for the fastest SC imaging without any signal averaging, eight consecutive images in time with an in-plane resolution of 0.67 × 0.67 mm² and 6 mm to 8 mm slice thickness are acquired in 51 s. AMIRA does not require parallel acquisition techniques.

RESULTS

AMIRA measures eight images of remarkable tissue contrast variation between spinal cord gray (GM) and white matter (WM) and cerebrospinal fluid (CSF). Following the AMIRA concept, averaging the first IR contrast images not only improves the signal-to-noise ratio but also offers a surprising enhancement of the contrast-to-noise ratio between GM and WM, whereas averaging the last images considerably improves the contrast-to-noise ratio between WM and CSF. These observations are supported by quantitative data.

CONCLUSION

The AMIRA concept provides 2D spinal cord imaging with multiple tissue contrasts and enhanced contrast-to-noise ratios with a typical 0.67 × 0.67 mm² in-plane resolution and a slice thickness between 4 mm and 8 mm acquired in only 1 to 2 min per slice. Magn Reson Med 79:1870-1881, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Spinal Cord as an Adjunct to Brain Magnetic Resonance Imaging in Defining "No Evidence of Disease Activity" in Multiple Sclerosis

Background

Monitoring patients with multiple sclerosis (MS) for “no evidence of disease activity” (NEDA) may help guide disease-modifying therapy (DMT) management decisions. Whereas surveillance brain magnetic resonance imaging (MRI) is common, the role of spinal cord monitoring for NEDA is unknown.

Objective

To evaluate the role of brain and spinal cord 3T MRI in the 1-year evaluation of NEDA.

Methods

Of 61 study patients (3 clinically isolated syndrome, 56 relapsing-remitting, 2 secondary progressive), 56 (91.8%) were receiving DMT. The MRI included brain fluid-attenuated inversion recovery and cervical/thoracic T2-weighted fast spin echo images. On MRI, NEDA was defined as the absence of new or enlarging T2 lesions at 1 year.

Results

Thirty-nine patients (63.9%) achieved NEDA by brain MRI, only one of whom had spinal cord activity. This translates to a false-positive rate for NEDA based on the brain of 2.6% (95% CI, 0.1%–13.5%). Thirty-eight patients (62.3%) had NEDA by brain and spinal cord MRI. Fifty-five patients (90.2%) had NEDA by spinal cord MRI, 17 of whom had brain activity. Of the 22 patients (36.1%) with brain changes, 5 had spinal cord changes. No evidence of disease activity was sustained in 48.3% of patients at 1 year and was the same with the addition of spinal cord MRI. Patients with MRI activity in either the brain or the spinal cord only were more likely to have activity in the brain (P = .0001).

Conclusions

Spinal cord MRI had a low diagnostic yield as an adjunct to brain MRI at 3T in monitoring patients with MS for NEDA over 1 year. Studies with larger data sets are needed to confirm these findings.

Topologically preserving straightening of spinal cord MRI

PURPOSE

To propose a robust and accurate method for straightening magnetic resonance (MR) images of the spinal cord, based on spinal cord segmentation, that preserves spinal cord topology and that works for any MRI contrast, in a context of spinal cord template-based analysis.

MATERIALS AND METHODS

The spinal cord curvature was computed using an iterative Non-Uniform Rational B-Spline (NURBS) approximation. Forward and inverse deformation fields for straightening were computed by solving analytically the straightening equations for each image voxel. Computational speed-up was accomplished by solving all voxel equation systems as one single system. Straightening accuracy (mean and maximum distance from straight line), computational time, and robustness to spinal cord length was evaluated using the proposed and the standard straightening method (label-based spline deformation) on 3T T₂ - and T₁ -weighted images from 57 healthy subjects and 33 patients with spinal cord compression due to degenerative cervical myelopathy (DCM).

RESULTS

The proposed algorithm was more accurate, more robust, and faster than the standard method (mean distance = 0.80 vs. 0.83 mm, maximum distance = 1.49 vs. 1.78 mm, time = 71 vs. 174 sec for the healthy population and mean distance = 0.65 vs. 0.68 mm, maximum distance = 1.28 vs. 1.55 mm, time = 32 vs. 60 sec for the DCM population).

CONCLUSION

A novel image straightening method that enables template-based analysis of quantitative spinal cord MRI data is introduced. This algorithm works for any MRI contrast and was validated on healthy and patient populations. The presented method is implemented in the Spinal Cord Toolbox, an open-source software for processing spinal cord MRI data.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;46:1209-1219.