MR-Pathologic Comparison of the Upper Spinal Cord in Different Motor Neuron Diseases

Quantitative and Computational Spinal Imaging in Neurodegenerative Conditions and Acquired Spinal Disorders: Academic Advances and Clinical Prospects

Introduction: Quantitative spinal cord imaging has facilitated the objective appraisal of spinal cord pathology in a range of neurological conditions both in the academic and clinical setting. Diverse methodological approaches have been implemented, encompassing a range of morphometric, diffusivity, susceptibility, magnetization transfer, and spectroscopy techniques. Advances have been fueled both by new MRI platforms and acquisition protocols as well as novel analysis pipelines. The quantitative evaluation of specific spinal tracts and grey matter indices has the potential to be used in diagnostic and monitoring applications. The comprehensive characterization of spinal disease burden in pre-symptomatic cohorts, in carriers of specific genetic mutations, and in conditions primarily associated with cerebral disease, has contributed important academic insights. Methods: A narrative review was conducted to examine the clinical and academic role of quantitative spinal cord imaging in a range of neurodegenerative and acquired spinal cord disorders, including hereditary spastic paraparesis, hereditary ataxias, motor neuron diseases, Huntington's disease, and post-infectious or vascular disorders. Results: The clinical utility of specific methods, sample size considerations, academic role of spinal imaging, key radiological findings, and relevant clinical correlates are presented in each disease group. Conclusions: Quantitative spinal cord imaging studies have demonstrated the feasibility to reliably appraise structural, microstructural, diffusivity, and metabolic spinal cord alterations. Despite the notable academic advances, novel acquisition protocols and analysis pipelines are yet to be implemented in the clinical setting.

Propagation patterns in motor neuron diseases: Individual and phenotype-associated disease-burden trajectories across the UMN-LMN spectrum of MNDs

Motor neuron diseases encompass a divergent group of conditions with considerable differences in clinical manifestations, survival, and genetic vulnerability. One of the key aspects of clinical heterogeneity is the preferential involvement of upper (UMN) and lower motor neurons (LMN). While longitudinal imaging patters are relatively well characterized in ALS, progressive cortical changes in UMN,- and LMN-predominant conditions are seldom evaluated. Accordingly, the objective of this study is the juxtaposition of longitudinal trajectories in 3 motor neuron phenotypes; a UMN-predominant syndrome (PLS), a mixed UMN-LMN condition (ALS), and a lower motor neuron condition (poliomyelitis survivors). A standardized imaging protocol was implemented in a prospective, multi-timepoint longitudinal study with a uniform follow-up interval of 4 months. Forty-five poliomyelitis survivors, 61 patients with amyotrophic lateral sclerosis (ALS), and 23 patients with primary lateral sclerosis (PLS) were included. Cortical thickness alterations were evaluated in a dual analysis pipeline, using standard cortical thickness analyses, and a z-score-based individualized approach. Our results indicate that PLS patients exhibit rapidly progressive cortical thinning primarily in motor regions; ALS patients show cortical atrophy in both motor and extra-motor regions, while poliomyelitis survivors exhibit cortical thickness gains in a number of cerebral regions. Our findings suggest that dynamic cortical changes in motor neuron diseases may depend on relative UMN and/or LMN involvement, and increased cortical thickness in LMN-predominant conditions may represent compensatory, adaptive processes.

The upper cervical spinal cord in ALS assessed by cross-sectional and longitudinal 3T MRI

The upper cervical spinal cord is measured in a large longitudinal amyotrophic lateral sclerosis (ALS) cohort to evaluate its role as a biomarker. Specifically, the cervical spinal cord´s cross-sectional area (CSA) in plane of the segments C1–C3 was measured semi-automatically with T1-weighted 3T MRI sequences in 158 ALS patients and 86 controls. Six-month longitudinal follow-up MRI scans were analyzed in 103 patients. Compared to controls, in ALS there was a significant mean spinal cord atrophy (63.8 mm² vs. 60.8 mm², p = 0.001) which showed a trend towards worsening over time (mean spinal cord CSA decrease from 61.4 mm² to 60.6 mm² after 6 months, p = 0.06). Findings were most pronounced in the caudal segments of the upper cervical spinal cord and in limb-onset ALS. Baseline CSA was related to the revised ALS functional rating scale, disease duration, precentral gyrus thickness and total brain gray matter volume. In conclusion, spinal cord atrophy as assessed in brain MRIs in ALS patients mirrors the extent of overall neurodegeneration and parallels disease severity.

Cross-sectional and longitudinal assessment of the upper cervical spinal cord in motor neuron disease

Background

Amyotrophic lateral sclerosis (ALS) is a progressive neuromuscular disease characterized by both upper and lower motor neuron degeneration. While neuroimaging studies of the brain can detect upper motor neuron degeneration, these brain MRI scans also include the upper part of the cervical spinal cord, which offers the possibility to expand the focus also towards lower motor neuron degeneration. Here, we set out to investigate cross-sectional and longitudinal disease effects in the upper cervical spinal cord in patients with ALS, progressive muscular atrophy (PMA: primarily lower motor neuron involvement) and primary lateral sclerosis (PLS: primarily upper motor neuron involvement), and their relation to disease severity and grey and white matter brain measurements.

Methods

We enrolled 108 ALS patients without C9orf72 repeat expansion (ALS C9–), 26 ALS patients with C9orf72 repeat expansion (ALS C9+), 28 PLS patients, 56 PMA patients and 114 controls. During up to five visits, longitudinal T1-weighted brain MRI data were acquired and used to segment the upper cervical spinal cord (UCSC, up to C3) and individual cervical segments (C1 to C4) to calculate cross-sectional areas (CSA). Using linear (mixed-effects) models, the CSA differences were assessed between groups and correlated with disease severity. Furthermore, a relationship between CSA and brain measurements was examined in terms of cortical thickness of the precentral gyrus and white matter integrity of the corticospinal tract.

Results

Compared to controls, CSAs at baseline showed significantly thinner UCSC in all groups in the MND spectrum. Over time, ALS C9– patients demonstrated significant thinning of the UCSC and, more specifically, of segment C3 compared to controls. Progressive thinning over time was also observed in C1 of PMA patients, while ALS C9+ and PLS patients did not show any longitudinal changes. Longitudinal spinal cord measurements showed a significant relationship with disease severity and we found a significant correlation between spinal cord and motor cortex thickness or corticospinal tract integrity for PLS and PMA, but not for ALS patients.

Discussion

Our findings demonstrate atrophy of the upper cervical spinal cord in the motor neuron disease spectrum, which was progressive over time for all but PLS patients. Cervical spinal cord imaging in ALS seems to capture different disease effects than brain neuroimaging. Atrophy of the cervical spinal cord is therefore a promising additional biomarker for both diagnosis and disease progression and could help in the monitoring of treatment effects in future clinical trials.

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Atrophy of upper cervical spinal cord is shown in the motor neuron disease spectrum.

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Progressive cervical spinal cord thinning occurs over time for all but PLS patients.

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Cervical spinal cord imaging is a potential biomarker for disease progression in ALS.

Central nervous system abnormalities in spinal and bulbar muscular atrophy (Kennedy's disease)

Spinal and bulbar (bulbospinal) muscular atrophy (BSMA, SBMA, Kennedy's disease) is a progressive motor neuron disease with rare involvement of structures other than the lower motor neuron, such as the endocrine system and the central nervous system (CNS). Aim of the review was to study type and frequency of clinical, imaging, and functional (CNS) abnormalities in SBMA patients. The most frequent clinical CNS manifestations in SBMA are postural or kinetic tremor predominantly of the hands and mild cognitive impairment. The most frequent instrumental CNS abnormality in SBMA patients are white matter lesions, visible on voxel-based morphometry, magnetic resonance spectroscopy, or diffusion tensor imaging. Single patients with enlarged pituitary volume, or diminished somato-sensory representation in the cortex have been also reported. Seizures, epilepsy, ataxia, spasticity, dystonia, or migraine have not been found in SBMA patients. Only supportive treatment is available for CNS manifestations in SBMA. It is concluded that the most frequent CNS abnormalities in SBMA are tremor, cognitive impairment, and white matter lesions on new imaging modalities. CNS involvement in SBMA should not be neglected as a phenotypic manifestation of SBMA and, apart from cognitive involvement, may help to differentiate clinically SBMA from other types of motor neuron disease.

Biomarkers of Spinal and Bulbar Muscle Atrophy (SBMA): A Comprehensive Review

Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy's disease, is a rare, X-linked, late onset neuromuscular disorder. The disease is caused by a CAG trinucleotide repeat expansion in the first exon of the androgen receptor gene. It is characterized by slowly progressive lower motor neurons degeneration, primary myopathy and widespread multisystem involvement. Respiratory involvement is rare, and the condition is associated with a normal life expectancy. Despite a plethora of therapeutic studies in mouse models, no effective disease-modifying therapy has been licensed for clinical use to date. The development of sensitive monitoring markers for the particularly slowly progressing pathology of SBMA is urgently required to aid future clinical trials. A small number of outcome measures have been proposed recently, including promising biochemical markers, which show correlation with clinical disability and disease-stage and progression. Nevertheless, a paucity of SBMA-specific biomarker studies persists, delaying the development of monitoring markers for pharmaceutical trials. Collaborative efforts through international consortia and multicenter registries are likely to contribute to the characterization of the natural history of the condition, the establishment of disease-specific biomarker panels and ultimately contribute to the development of disease-modifying drugs.

X-linked spinal and bulbar muscular atrophy (Kennedy's disease): the first case described in the Brazilian Amazon

The X-linked spinal and bulbar muscular atrophy (Kennedy’s disease) is a rare X-linked, recessive, lower motor neuron disease, characterized by weakness, atrophy, and fasciculations of the appendicular and bulbar muscle. The disease is caused by an expansion of the CAG repetition in the androgen receptor gene. Patients with Kennedy’s disease have more than 39 CAG repetitions. We report a case of 57-year-old man, resident of Monte Dourado (PA, Brazil) who complained of brachiocrural paresis evolving for 3 years along with fasciculations and tremors of extremities. In addition, he also developed dysarthria, dysphagia, and sexual dysfunction. The patient clinical picture included gait impairment, global hyporeflexia, proximal muscle atrophy of upper limbs, deviation of the uvula to right during phonation and tongue atrophy with fasciculations. The patient reported that about 30 years ago he had undergone gynecomastia surgery. His electroneuromyography suggested spinal muscular atrophy, and nuclear magnetic resonance imaging showed tapering of the cervical and thoracic spinal cord. Patient’s creatine kinase level was elevated. In view of the findings, an exam was requested to investigate Kennedy’s disease. The exam identified 46 CAG repetitions in the androgen receptor gene, which confirmed the diagnostic suspicion. This was the first case of Kennedy’s disease diagnosed and described in the Brazilian Amazon. To our knowledge only other four papers were published on this disease in Brazilian patients. A brief review is also provided on etiopathogenic, clinical and diagnostic aspects.

Neuroimaging in amyotrophic lateral sclerosis: insights into structural and functional changes

In the past two decades, structural and functional neuroimaging findings have greatly modified longstanding notions regarding the pathophysiology of amyotrophic lateral sclerosis (ALS). Neuroimaging studies have shown that anatomical and functional lesions spread beyond precentral cortices and corticospinal tracts, to include the corpus callosum; frontal, sensory, and premotor cortices; thalamus; and midbrain. Both MRI and PET studies have shown early and diffuse loss of inhibitory cortical interneurons in the motor cortex (increased levels of functional connectivity and loss of GABAergic neurons, respectively) and diffuse gliosis in white-matter tracts. In ALS endophenotypes, neuroimaging has also shown a diverse spreading of lesions and a dissimilar impairment of functional and structural connections. A possible role of PET in the diagnosis of ALS has recently been proposed. However, most neuroimaging studies have pitfalls, such as a small number and poor clinical characterisation of patients, absence of adequate controls, and scarcity of longitudinal assessments. Studies involving international collaborations, standardised assessments, and large patient cohorts will overcome these shortcomings and provide further insight into the pathogenesis of ALS.

Lessons of ALS imaging: Pitfalls and future directions - A critical review

Background

While neuroimaging in ALS has gained unprecedented momentum in recent years, little progress has been made in the development of viable diagnostic, prognostic and monitoring markers.

Objectives

To identify and discuss the common pitfalls in ALS imaging studies and to reflect on optimal study designs based on pioneering studies.

Methods

A “PubMed”-based literature search on ALS was performed based on neuroimaging-related keywords. Study limitations were systematically reviewed and classified so that stereotypical trends could be identified.

Results

Common shortcomings, such as relatively small sample sizes, statistically underpowered study designs, lack of disease controls, poorly characterised patient cohorts and a large number of conflicting studies, remain a significant challenge to the field. Imaging data of ALS continue to be interpreted at a group-level, as opposed to meaningful individual-patient inferences.

Conclusions

A systematic, critical review of ALS imaging has identified stereotypical shortcomings, the lessons of which should be considered in the design of future prospective MRI studies. At a time when large multicentre studies are underway a candid discussion of these factors is particularly timely.

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Stereotypical shortcomings can be identified in ALS neuroimaging studies.

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A systematic discussion of ALS study limitations is particularly timely.

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Individual patient data meta-analyses and multicentre studies are urgently required.

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The gaps identified in ALS imaging indicate exciting research opportunities.

Structural changes of central white matter tracts in Kennedy's disease - a diffusion tensor imaging and voxel-based morphometry study

OBJECTIVES

Spinobulbar muscular atrophy [Kennedy's disease (KD)] is a rare X-linked neurodegenerative disorder of mainly spinal and bulbar motoneurons. Recent studies suggest a multisystem character of this disease. The aim of this study was to identify and characterize structural changes of gray (GM) and white matter (WM) in the central nervous system.

MATERIAL AND METHODS

Whole-brain-based voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) analyses were applied to MRI data of eight genetically proven patients with KD and compared with 16 healthy age-matched controls.

RESULTS

Diffusion tensor imaging analysis showed not only decreased fractional anisotropy (FA) values in the brainstem, but also widespread changes in central WM tracts, whereas VBM analysis of the WM showed alterations primarily in the brainstem and cerebellum. There were no changes in GM volume. The FA value decrease in the brainstem correlated with the disease duration.

CONCLUSION

Diffusion tensor imaging analysis revealed subtle changes of central WM tract integrity, while GM and WM volume remained unaffected. In our patient sample, KD had more extended effects than previously reported. These changes could either be attributed primarily to neurodegeneration or reflect secondary plastic changes due to atrophy of lower motor neurons and reorganization of cortical structures.

Neuroimaging in amyotrophic lateral sclerosis

The catastrophic system failure in amyotrophic lateral sclerosis is characterized by progressive neurodegeneration within the corticospinal tracts, brainstem nuclei and spinal cord anterior horns, with an extra-motor pathology that has overlap with frontotemporal dementia. The development of computed tomography and, even more so, MRI has brought insights into neurological disease, previously only available through post-mortem study. Although largely research-based, radionuclide imaging has continued to provide mechanistic insights into neurodegenerative disorders. The evolution of MRI to use advanced sequences highly sensitive to cortical and white matter structure, parenchymal metabolites and blood flow, many of which are now applicable to the spinal cord as well as the brain, make it a uniquely valuable tool for the study of a multisystem disorder such as amyotrophic lateral sclerosis. This comprehensive review considers the full range of neuroimaging techniques applied to amyotrophic lateral sclerosis over the last 25 years, the biomarkers they have revealed and future developments.

Spinal cord markers in ALS: diagnostic and biomarker considerations

Despite considerable involvement of the spinal cord in amyotrophic lateral sclerosis (ALS), current biomarker research is primarily centred on brain imaging and CSF proteomics. In clinical practice, spinal cord imaging in ALS is performed primarily to rule out alternative conditions in the diagnostic phase of the disease. Quantitative spinal cord imaging has traditionally been regarded as challenging, as it requires high spatial resolution while minimizing partial volume effects, physiological motion and susceptibility distortions. In recent years however, as acquisition and post-processing methods have been perfected, a number of exciting and promising quantitative spinal imaging and electrophysiology techniques have been developed. We performed a systematic review of the trends, methodologies, limitations and conclusions of recent spinal cord studies in ALS to explore the diagnostic and prognostic potential of spinal markers. Novel corrective techniques for quantitative spinal cord imaging are systematically reviewed. Recent findings demonstrate that imaging techniques previously used in brain imaging, such as diffusion tensor, functional and metabolic imaging can now be successfully applied to the human spinal cord. Optimized electrophysiological approaches make the non-invasive assessment of corticospinal pathways possible, and multimodal spinal techniques are likely to increase the specificity and sensitivity of proposed spinal markers. In conclusion, spinal cord imaging is an emerging area of ALS biomarker research. Novel quantitative spinal modalities have already been successfully used in ALS animal models and have the potential for development into sensitive ALS biomarkers in humans.

Complementary image analysis of diffusion tensor imaging and 3-dimensional t1-weighted imaging: white matter analysis in amyotrophic lateral sclerosis

INTRODUCTION

in order to obtain detailed information on disease-associated changes in the integrity of cerebral white matter (WM), complementary image analysis (CIA) was applied to patients with amyotrophic lateral sclerosis (ALS) and controls.

METHODS

both diffusion tensor imaging and T1-weighted 3-dimensional data were analyzed with respect to WM microstructure and T1 signal intensity alterations, respectively, in a sample of 19 ALS patients. Covariate information was added in the form of clinical parameters. All results were obtained in one common analysis software environment (Tensor Imaging and Fiber Tracking).

RESULTS

complementary analysis and display were performed for WM directionality and structure. Significant WM differences between ALS patients and controls were observed both in the motor system, that is, the bilateral corticospinal tracts, and in extramotor brain areas, in part correlating with clinical parameters. The performance of all analyses in one software environment enabled the synopsis of results obtained from various analyses.

DISCUSSION/CONCLUSION

within the application of CIA to a neurodegenerative disease for the whole brain-based analysis of WM alterations together with clinical characteristics, it could be demonstrated that ALS was associated with WM changes within and outside the motor system.

EFNS guidelines on the use of neuroimaging in the management of motor neuron diseases

BACKGROUND AND PURPOSE

These European Federation of Neurological Societies guidelines on neuroimaging of motor neuron diseases (MNDs) are designed to provide practical help for the neurologists to make appropriate use of neuroimaging techniques in patients with MNDs, which ranges from diagnostic and monitoring aspects to the in vivo study of the pathobiology of such conditions.

METHODS

Literature searches were performed before expert members of the Task Force wrote proposal. Then, consensus was reached by circulating drafts of the manuscript to the Task Force members and by discussion of the classification of evidence and recommendations.

RESULTS AND CONCLUSIONS

The use of conventional MRI in patients suspected of having a MND is yet restricted to exclude other causes of signs and symptoms of MN pathology [class IV, level good clinical practice point (GCPP)]. Although the detection of corticospinal tract hyperintensities on conventional MRI and a T2-hypointense rim in the pre-central gyrus can support a pre-existing suspicion of MND, the specific search of these abnormalities for the purpose of making a firm diagnosis of MND is not recommended (class IV, level GCPP). At present, advanced neuroimaging techniques, including diffusion tensor imaging and proton magnetic resonance spectroscopic imaging, do not have a role in the diagnosis or routine monitoring of MNDs yet (class IV, level GCPP). However, it is strongly advisable to incorporate measures derived from these techniques into new clinical trials as exploratory outcomes to gain additional insights into disease pathophysiology and into the value of these techniques in the (longitudinal) assessment of MNDs (class IV, level GCPP).

MR imaging findings in autosomal recessive hereditary spastic paraplegia

BACKGROUND AND PURPOSE

Hereditary spastic paraplegia (HSP) is a disorder characterized by degeneration of the corticospinal tracts and posterior column of the spinal cord. Previously described radiologic findings included nonspecific brain abnormalities such as brain atrophy and white matter lesions, as well as atrophy of the spinal cord. In our study, we aimed to better characterize brain and spine MR imaging findings in a series of patients with HSP.

MATERIALS AND METHODS

Nine patients from 4 different Lebanese families with the autosomal recessive form of HSP were included in the study. All patients underwent brain and whole-spine MR imaging. We assessed the presence of white matter abnormalities mainly along the corticospinal tracts, brain atrophy, thinning of the corpus callosum, and the presence of spinal cord atrophy or abnormal signal intensity.

RESULTS

Imaging revealed mild brain atrophy (44%), atrophy of the corpus callosum (55%), white matter lesions (67%), abnormal T2 high signal intensity in the posterior limb of the internal capsule (55%), and mild spinal cord atrophy (33%).

CONCLUSIONS

The MR imaging findings of HSP are nonspecific and variable; however, the most prominent features include atrophy of the corpus callosum, T2 signal intensity in the posterior limb of the internal capsule, and spinal cord atrophy.

Widespread white matter changes in Kennedy disease: a voxel based morphometry study

OBJECTIVE

X linked spinobulbar muscular atrophy (Kennedy disease (KD)), which is clinically characterised mainly by neuromuscular and endocrine symptoms, has to be considered as a multisystem disorder. Based on clinical evidence of central nervous system involvement, potential KD associated cerebral volume alterations were analysed in vivo.

METHODS

Whole brain based analysis of optimised voxel based morphometry (VBM) was applied to three dimensional MRI data from 18 genetically confirmed KD patients and compared with age matched controls.

RESULTS

Subtle decreases in grey matter volume, mainly localised in frontal areas, were found, but extensive white matter atrophy was observed, particularly in frontal areas, but also involving multiple additional subcortical areas, the cerebellar white matter and the dorsal brainstem from the midbrain to the medulla oblongata.

CONCLUSION

The VBM results demonstrated a morphological correlate of central nervous system involvement in KD, in agreement with aspects of the clinical phenotype (behavioural abnormalities, central-peripheral axonopathy) and with pathohistological findings.

Classification of Phenotype Characteristics in Adult-Onset Spinal Muscular Atrophy

BACKGROUND/AIMS

Degenerative lower motor neuron diseases (LMND) encompass a group of rare clinically and genetically heterogeneous disorders with the hallmark of anterior horn cell degeneration in the spinal cord and brainstem. In a recently proposed classification, LMND were subdivided according to the clinical disease pattern and time course. This study was performed to investigate the clinical practicability of the classification.

METHODS

In 22 patients with adult LMND (mean disease duration, 24 years), the disease course and detailed clinical, electrophysiological, magnetic resonance imaging, laboratory, and genetic investigations were analyzed.

RESULTS

All patients could be assigned to the distinct disease subgroups, i.e. 11 patients to the slowly progressive generalized form (group 1), one to the distal form (group 2), 3 to the segmental distal form (group 3a), and seven to the segmental proximal form (group 3b).

CONCLUSIONS

The proposed classification was confirmed to be a practicable tool, and additional implications for the classification of LMND could be drawn from the data in our patient sample.

Magnetic resonance investigation of the upper spinal cord in pure and complicated hereditary spastic paraparesis

Neuropathological studies of hereditary spastic paraparesis (HSP) have described axonal loss involving corticospinal and somatosensory tracts in the spinal cord. This MRI-based study was intended to investigate in vivo diameter alterations of the spinal cord in HSP, including both pure HSP (p-HSP, n = 20) and complicated HSP (c-HSP, n = 10). Standard MRI examinations of the cervical and thoracic spinal cord in HSP patients and a control group (n = 54) were analyzed by standardized spinal cord planimetry. In HSP patients, significant atrophy of the upper spinal cord compared to controls was observed at p < 0.001 both at the cervical and at the thoracic level. Myelon diameters at both levels were also significantly reduced in the two HSP subgroups in an additional comparison with age-matched subgroups of controls each, but p-HSP and c-HSP groups themselves did not differ. Marked atrophy of the upper spinal cord seems to be associated with HSP, assumedly due to the central-distal axonopathy. However, the differences between p-HSP and c-HSP could not be visualized by structural MRI at spinal cord level.