Early detection and longitudinal changes in amyotrophic lateral sclerosis by (1)H MRSI

Advances in molecular pathology, diagnosis, and treatment of amyotrophic lateral sclerosis

Although the past two decades have produced exciting discoveries in the genetics and pathology of amyotrophic lateral sclerosis (ALS), progress in developing an effective therapy remains slow. This review summarizes the critical discoveries and outlines the advances in disease characterization, diagnosis, imaging, and biomarkers, along with the current status of approaches to ALS care and treatment. Additional knowledge of the factors driving disease progression and heterogeneity will hopefully soon transform the care for patients with ALS into an individualized, multi-prong approach able to prevent disease progression sufficiently to allow for a dignified life with limited disability.

Measuring disease progression in primary lateral sclerosis

Quantitative measures of disease severity are essential outcome measures for clinical trials. The slow progression of disease in primary lateral sclerosis (PLS) requires clinical measures that are sensitive to changes occurring within the time frame of a clinical trial. Proposed clinical outcome measures include the PLS functional rating scale (PLSFRS), burden scores derived from clinical examination findings, and quantitative measures of motor performance. The PLSFRS has good inter-rater reliability and showed greater longitudinal change over 6- and 12-months compared to the revised ALS functional rating scale. Examination-based upper motor neuron burden (UMNB) scales also have good reliability, and longitudinal studies are in process. Quantitative measures of strength, dexterity, gait, and speech have the potential to provide objective and precise measures of clinical change, but have been the least studied in persons with PLS.

Progressive Neurochemical Abnormalities in Cognitive and Motor Subgroups of Amyotrophic Lateral Sclerosis: A Prospective Multicenter Study

OBJECTIVE

To evaluate progressive cerebral degeneration in amyotrophic lateral sclerosis (ALS) by assessing alterations in N-acetylaspartate (NAA) ratios in the motor and prefrontal cortex within clinical subgroups of ALS.

METHODS

Seventy-six patients with ALS and 59 healthy controls were enrolled in a prospective, longitudinal, multicenter study in the Canadian ALS Neuroimaging Consortium. Participants underwent serial clinical evaluations and magnetic resonance spectroscopy at baseline and 4 and 8 months using a harmonized protocol across 5 centers. NAA ratios were quantified in the motor cortex and prefrontal cortex. Patients were stratified into subgroups based on disease progression rate, upper motor neuron (UMN) signs, and cognitive status. Linear mixed models were used for baseline and longitudinal comparisons of NAA metabolite ratios.

RESULTS

Patients with ALS had reduced NAA ratios in the motor cortex at baseline (p < 0.001). Ratios were lower in those with more rapid disease progression and greater UMN signs (p < 0.05). A longitudinal decline in NAA ratios was observed in the motor cortex in the rapidly progressing (p < 0.01) and high UMN burden (p < 0.01) cohorts. The severity of UMN signs did not change significantly over time. NAA ratios were reduced in the prefrontal cortex only in cognitively impaired patients (p < 0.05); prefrontal cortex metabolites did not change over time.

CONCLUSIONS

Progressive degeneration of the motor cortex in ALS is associated with more aggressive clinical presentations. These findings provide biological evidence of variable spatial and temporal cerebral degeneration linked to the disease heterogeneity of ALS. The use of standardized imaging protocols may have a role in clinical trials for patient selection or subgrouping.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that MRS NAA metabolite ratios of the motor cortex are associated with more rapid disease progression and greater UMN signs in patients with ALS.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT02405182.

Spectroscopic markers of neurodegeneration in the mesial prefrontal cortex predict survival in ALS

Background and objective: N-acetylaspartate (NAA) and myo-inositol (mIns) are spectroscopic markers of neuronal integrity and astrogliosis, respectively. We performed a survival analysis to determine the prognostic value of the NAA/mIns metabolite ratio in ALS after a period of two and five years. Methods: Twenty-four patients with ALS (two with ALS-FTD) were recruited to participate in a high-field MR spectroscopy study of the mesial prefrontal cortex. Univariate and multivariate Cox proportional hazards analyses were used to assess NAA/mIns as a predictor of survival alongside other demographic and clinical measures. Census dates were set at two and five years after the time of MR scan for each patient. Survival curves were calculated using the Kaplan-Meier method. Results: After a five-year observation period, 19 patients had died and five were still alive. Median survival time from date of scan was 1.95 years. Univariate and multivariate Cox analysis showed NAA/mIns to be a significant independent predictor of survival at two years after scanning, but not at five years. Conclusion: Cerebral degeneration in the mesial prefrontal cortex as detected by the NAA/mIns metabolite ratio is predictive of survival in ALS in a time-dependent manner.

Evolution of the neurochemical profiles in the G93A-SOD1 mouse model of amyotrophic lateral sclerosis

In vivo ¹H magnetic resonance spectroscopy (¹H-MRS) investigations of amyotrophic lateral sclerosis (ALS) mouse brain may provide neurochemical profiles and alterations in association with ALS disease progression. We aimed to longitudinally follow neurochemical evolutions of striatum, brainstem and motor cortex of mice transgenic for G93A mutant human superoxide dismutase type-1 (G93A-SOD1), an ALS model. Region-specific neurochemical alterations were detected in asymptomatic G93A-SOD1 mice, particularly in lactate (-19%) and glutamate (+8%) of brainstem, along with γ-amino-butyric acid (-30%), N-acetyl-aspartate (-5%) and ascorbate (+51%) of motor cortex. With disease progression towards the end-stage, increased numbers of metabolic changes of G93A-SOD1 mice were observed (e.g. glutamine levels increased in the brainstem (>+66%) and motor cortex (>+54%)). Through ALS disease progression, an overall increase of glutamine/glutamate in G93A-SOD1 mice was observed in the striatum (p < 0.01) and even more so in two motor neuron enriched regions, the brainstem and motor cortex (p < 0.0001). These ¹H-MRS data underscore a pattern of neurochemical alterations that are specific to brain regions and to disease stages of the G93A-SOD1 mouse model. These neurochemical changes may contribute to early diagnosis and disease monitoring in ALS patients.

Magnetic Resonance Spectroscopy in ALS

Proton magnetic resonance spectroscopy (MRS) provides a means of measuring cerebral metabolites relevant to neurodegeneration in vivo. In amyotrophic lateral sclerosis (ALS), neurochemical changes reflecting neuronal loss or dysfunction (decreased N-actylaspartate [NAA]) is most significant in the motor cortex and corticospinal tracts. Other neurochemical changes observed include increased myo-inositol (mIns), a putative marker of gliosis. MRS confirmation of involvement of non-motor regions such as the frontal lobes, thalamus, basal ganglia, and cingulum are consistent with the multi-system facet of motor neuron disease with ALS being part of a MND-FTD spectrum. MRS-derived markers exhibit an encouraging discriminatory ability to identify patients from healthy controls, however more data is needed to determine its ability to assist with the diagnosis in early stages when upper motor neuron signs are limited, and in distinguishing from disease mimics. Longitudinal change of NAA and mIns do not appear to be reliable in monitoring disease progression. Technological advances in hardware and high field scanning are increasing the number of accessible metabolites available for interrogation.

Tracking a Fast-Moving Disease: Longitudinal Markers, Monitoring, and Clinical Trial Endpoints in ALS

Amyotrophic lateral sclerosis (ALS) encompasses a heterogeneous group of phenotypes with different progression rates, varying degree of extra-motor involvement and divergent progression patterns. The natural history of ALS is increasingly evaluated by large, multi-time point longitudinal studies, many of which now incorporate presymptomatic and post-mortem assessments. These studies not only have the potential to characterize patterns of anatomical propagation, molecular mechanisms of disease spread, but also to identify pragmatic monitoring markers. Sensitive markers of progressive neurodegenerative change are indispensable for clinical trials and individualized patient care. Biofluid markers, neuroimaging indices, electrophysiological markers, rating scales, questionnaires, and other disease-specific instruments have divergent sensitivity profiles. The discussion of candidate monitoring markers in ALS has a dual academic and clinical relevance, and is particularly timely given the increasing number of pharmacological trials. The objective of this paper is to provide a comprehensive and critical review of longitudinal studies in ALS, focusing on the sensitivity profile of established and emerging monitoring markers.

Imaging Biomarkers for the Diagnosis and Prognosis of Neurodegenerative Diseases. The Example of Amyotrophic Lateral Sclerosis

The term amyotrophic lateral sclerosis (ALS) comprises a heterogeneous group of fatal neurodegenerative disorders of largely unknown etiology characterized by the upper motor neurons (UMN) and/or lower motor neurons (LMN) degeneration. The development of brain imaging biomarkers is essential to advance in the diagnosis, stratification and monitoring of ALS, both in the clinical practice and clinical trials. In this review, the characteristics of an optimal imaging biomarker and common pitfalls in biomarkers evaluation will be discussed. Moreover, the development and application of the most promising brain magnetic resonance (MR) imaging biomarkers will be reviewed. Finally, the integration of both qualitative and quantitative multimodal brain MR biomarkers in a structured report will be proposed as a support tool for ALS diagnosis and stratification.

In-vivo evaluation of neuronal and glial changes in amyotrophic lateral sclerosis with diffusion tensor spectroscopy

Diffusion tensor spectroscopy (DTS) combines features of magnetic resonance spectroscopy and diffusion tensor imaging and permits evaluating cell-type specific properties of microstructure by probing the diffusion of intracellular metabolites. This exploratory study investigates for the first time microstructural changes in the neuronal and glial compartments of the brain of patients with amyotrophic lateral sclerosis (ALS) using DTS. To this end, the diffusion properties of the neuronal metabolite tNAA (N-acetylaspartate + N-acetylaspartylglutamate) and the predominantly glial metabolites tCr (creatine + phosphocreatine) and tCho (choline-containing compounds) were evaluated in the primary motor cortex of 24 ALS patients and 27 healthy controls. Significantly increased values in the diffusivities of all three metabolites were found in ALS patients relative to controls. Further analysis revealed more pronounced microstructural alterations in ALS patients with limb onset than with bulbar onset relative to controls. This observation may be related to the fact that the spectroscopic voxel was positioned in the part of the motor cortex where the motor functions of the limbs are represented. The higher diffusivities of tNAA may reflect neuronal damage and/or may be a consequence of mitochondrial dysfunction in ALS. Increased diffusivities of tCr and tCho are in line with reactive microglia and astrocytes surrounding degenerating motor neurons in the primary motor cortex of ALS patients. This pilot study demonstrates for the first time that cell-type specific microstructural alterations in the brain of ALS patients may be explored in vivo and non-invasively with DTS. In conjunction with other microstructural magnetic resonance imaging techniques, DTS may provide further insights into the pathogenic mechanisms that underlie neurodegeneration in ALS.

Automated Voxel Placement: A Linux-based Suite of Tools for Accurate and Reliable Single Voxel Coregistration

Background

Single-voxel proton magnetic resonance spectroscopy (¹H MRS) is a powerful technique for studying in vivo neurochemistry, but has an often-overlooked source of error variance: inconsistent voxel placement between scans. We developed and evaluated an Automated Voxel Placement (AVP) procedure for accurate and reliable ¹H MRS voxel prescription. AVP is a suite of Linux-based programs that facilitate automated template-driven single-voxel coregistration.

Methods

Three studies were conducted to evaluate AVP for prescription of one voxel: left dorsolateral prefrontal cortex. First, we evaluated how robust AVP was to ‘extreme’ subject head positions/angulations within the scanner head coil. Second, subjects (N = 13) were recruited and underwent MR scans. Manual voxel prescription (n = 5) was contrasted with AVP (n = 8). A subset of AVP subjects (n = 4) completed a second scan. Third, ongoing data collection (n = 16; recruited for a separate study) helped evaluate AVP. Voxel placement accuracy was quantified as 3D geometric voxel overlap percentage between each subject’s voxel and the template voxel. Reliability was quantified as 3D geometric voxel overlap percentage across subjects at each time point and within subjects who completed two scans.

Results

Results demonstrated that AVP was robust to ‘extreme’ head positions (97.5% - 97.9% overlap with the template voxel). AVP was significantly more accurate (baseline and follow-up: 96.2% ± 3.0% and 97.6% ± 1.4% overlap) than manual voxel placement (67.7% ± 22.8% overlap; ps<.05). AVP was reliable within- (97.9%) and between-subjects (94.2% and 97.2% overlap; baseline and follow-up; respectively). Finally, ongoing data collection indicates AVP is accurate (96.0%).

Conclusion

These pilot studies demonstrated that AVP was feasible, accurate, and reliable method for automated single voxel coregistration.

Detecting neuronal dysfunction of hand motor cortex in ALS: A MRSI study

BACKGROUND

Although hand motor cortex (HMC) has been constantly used for identification of primary motor cortex in magnetic resonance spectroscopy (MRS) studies of amyotrophic lateral sclerosis (ALS), neurochemical profiles of HMC have never been assessed independently. As HMC has a constant location and the clinic-anatomic correlation between hand motor function and HMC has been established, we hypothesize that HMC may serve as a promising region of interest in diagnosing ALS.

PATIENTS AND METHODS

Fourteen ALS patients and 14 age- and gender-matched healthy controls (HC) were recruited in this study. An optimized magnetic resonance spectroscopic imaging (MRSI) method was developed and for each subject bilateral HMC areas were scanned separately (two-dimensional multi-voxel MRSI, voxel size 0.56 cm³). N-acetyl aspartate (NAA)-creatine (Cr) ratio was measured from HMC and the adjacent postcentral gyrus.

RESULTS

Compared with HC, NAA/Cr ratios from HMC and the postcentral gyrus were significantly reduced in ALS. However, in each group the difference of NAA/Cr ratios between HMC and the postcentral gyrus was not significant. Limb predominance of HMC was not found in either ALS or HC. In ALS, there was a significant difference in NAA/Cr ratio between the most affected HMC and the less affected HMC. A positive relationship between NAA/Cr ratio of HMC and the severity of hand strength (assessed by finger tapping speed) was demonstrated.

CONCLUSION

Neuronal dysfunction of HMC can differentiate ALS patients from HC when represented as reduced NAA/Cr ratio. Postcentral gyrus could not serve as normal internal reference tissue in diagnosing ALS. Asymmetrical NAA/Cr ratios from bilateral HMC may serve as a promising diagnostic biomarker of ALS at the individual level.

Neuroimaging Endpoints in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative, clinically heterogeneous syndrome pathologically overlapping with frontotemporal dementia. To date, therapeutic trials in animal models have not been able to predict treatment response in humans, and the revised ALS Functional Rating Scale, which is based on coarse disability measures, remains the gold-standard measure of disease progression. Advances in neuroimaging have enabled mapping of functional, structural, and molecular aspects of ALS pathology, and these objective measures may be uniquely sensitive to the detection of propagation of pathology in vivo. Abnormalities are detectable before clinical symptoms develop, offering the potential for neuroprotective intervention in familial cases. Although promising neuroimaging biomarker candidates for diagnosis, prognosis, and disease progression have emerged, these have been from the study of necessarily select patient cohorts identified in specialized referral centers. Further multicenter research is now needed to establish their validity as therapeutic outcome measures.

Further development of biomarkers in amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is an idiopathic neurodegenerative disease usually fatal in less than three years. Even if standard guidelines are available to diagnose ALS, the mean diagnosis delay is more than one year. In this context, biomarker discovery is a priority. Research has to focus on new diagnostic tools, based on combined explorations.

AREAS COVERED

In this review, we specifically focus on biology and imaging markers. We detail the innovative field of 'omics' approach and imaging and explain their limits to be useful in routine practice. We describe the most relevant biomarkers and suggest some perspectives for biomarker research. Expert commentary: The successive failures of clinical trials in ALS underline the need for new strategy based on innovative tools to stratify patients and to evaluate their responses to treatment. Biomarker data may be useful to improve the designs of clinical trials. Biomarkers are also needed to better investigate disease pathophysiology, to identify new therapeutic targets, and to improve the performance of clinical assessments for diagnosis and prognosis in the clinical setting. A consensus on the best management of neuroimaging and 'omics' methods is necessary and a systematic independent validation of findings may add robustness to future studies.

Advanced magnetic resonance neuroimaging in bulbar and limb onset early amyotrophic lateral sclerosis

Introduction:

Amyotrophic lateral sclerosis (ALS) is a fatal and most common motor neuron disease, caused by progressive loss of motor neurons. Diffusion tensor imaging (DTI) and magnetic resonance spectroscopic (MRS) studies detect pathological changes in neuronal fibers in vivo. We evaluated the role of DTI and MRS in early course of the disease, which may prove beneficial in the early diagnosis and better management.

Materials and Methods:

Twenty-one patients with ALS and 13 age-matched controls received 1.5T DTI and three-dimensional multi-voxel MRS. Fractional anisotropy (FA), apparent diffusion coefficient, N-acetyl aspartate (NAA)/Creatine (Cr), and NAA/Choline (Ch) ratios were analyzed in various regions of the brain and compared with healthy controls. ALS patients were classified as definite, possible, and probable category, and patients were also studied in limb versus bulbar onset.

Results:

Decreased FA and increase mean diffusivity values in regions of corticospinal tract (CST) and corpus callosum (CC) was consistent finding in definite and probable disease category (P < 0.05). In possible disease, CC involvement was not significant. NAA/Cr and NAA/Ch ratios were lower in CC and regions of CST. However, in possible disease, CC involvement was not significant, while regions of CST were showing significant reduction in NAA/Cr and NAA/Ch ratios (P < 0.05).

Conclusion:

DTI and MRS detect changes associated with ALS even in the early phase of the disease. Bulbar onset and limb onset ALS patients show different pattern of involvement. Extramotor involvement suggested by CC involvement is a feature seen in bulbar onset patient and can suggest poor outcome in such patients. The present findings may be helpful for designing further studies in the direction of more early diagnosis of disease and its management.

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.

[What are the applications of biomarkers in ALS today?]

Numerous biomarkers studies in ALS used targeted and non-targeted approaches, to help for the diagnosis, the prognosis or to identify new pathophysiological ways. The emerging approaches such as "omics" studies are very promising, but the practical and technical limits do not enable their optimization. Even if some biomarkers such as cystatin C or glutamate are highlighted in ALS, to date, no biomarker is currently used in routine practice. Diffusion-based neuroimaging has emerged as a tool to identify the involvement of the central neuron, but a recent meta-analysis shows a poor sensitivity and specificity. Spinal cord imaging has the advantage of simultaneoulsy investigating both the corticospinal tract and the peripheral motor neurons in the anterior horns of the spinal cord. Its interest to provide biomarkers in ALS is illustrated by recent studies that used a multiparametric approach. The limits of biomarkers studies are principally based on small cohorts, involving a control population who does not allow to assess specificity. The discrepancies between the biomarkers identified in the different studies are based on a strong heterogeneity of the disease and a lack of standardization of the research methodology, including the step of the validation of these molecules in independent cohorts. The perspectives in biomarker research in ALS imply the combination of analytical methods, human abilities and harmonization of the strategies.

Neurodegenerative changes are prevented by Erythropoietin in the pmn model of motoneuron degeneration

Motoneuron diseases are fatal neurodegenerative disorders characterized by a progressive loss of motoneurons, muscle weakness and premature death. The progressive motor neuronopathy (pmn) mutant mouse has been considered a good model for the autosomal recessive childhood form of spinal muscular atrophy (SMA). Here, we investigated the therapeutic potential of Erythropoietin (Epo) on this mutant mouse. Symptomatic or pre-symptomatic treatment with Epo significantly prolongs lifespan by 84.6% or 87.2% respectively. Epo preserves muscle strength and significantly attenuates behavioural motor deficits of mutant pmn mice. Histological and metabolic changes in the spinal cord evaluated by immunohistochemistry, western blot, and high-resolution (1)H-NMR spectroscopy were also greatly prevented by Epo-treatment. Our results illustrate the efficacy of Epo in improving quality of life of mutant pmn mice and open novel therapeutic pathways for motoneuron diseases.

Multi-parametric spinal cord MRI as potential progression marker in amyotrophic lateral sclerosis

Objective

To evaluate multimodal MRI of the spinal cord in predicting disease progression and one-year clinical status in amyotrophic lateral sclerosis (ALS) patients.

Materials and Methods

After a first MRI (MRI₁), 29 ALS patients were clinically followed during 12 months; 14/29 patients underwent a second MRI (MRI₂) at 11±3 months. Cross-sectional area (CSA) that has been shown to be a marker of lower motor neuron degeneration was measured in cervical and upper thoracic spinal cord from T2-weighted images. Fractional anisotropy (FA), axial/radial/mean diffusivities (λ_⊥, λ_//, MD) and magnetization transfer ratio (MTR) were measured within the lateral corticospinal tract in the cervical region. Imaging metrics were compared with clinical scales: Revised ALS Functional Rating Scale (ALSFRS-R) and manual muscle testing (MMT) score.

Results

At MRI₁, CSA correlated significantly (P<0.05) with MMT and arm ALSFRS-R scores. FA correlated significantly with leg ALFSRS-R scores. One year after MRI₁, CSA predicted (P<0.01) arm ALSFSR-R subscore and FA predicted (P<0.01) leg ALSFRS-R subscore. From MRI₁ to MRI₂, significant changes (P<0.01) were detected for CSA and MTR. CSA rate of change (i.e. atrophy) highly correlated (P<0.01) with arm ALSFRS-R and arm MMT subscores rate of change.

Conclusion

Atrophy and DTI metrics predicted ALS disease progression. Cord atrophy was a better biomarker of disease progression than diffusion and MTR. Our study suggests that multimodal MRI could provide surrogate markers of ALS that may help monitoring the effect of disease-modifying drugs.

Neuroimaging to investigate multisystem involvement and provide biomarkers in amyotrophic lateral sclerosis

Neuroimaging allows investigating the extent of neurological systems degeneration in amyotrophic lateral sclerosis (ALS). Advanced MRI methods can detect changes related to the degeneration of upper motor neurons but have also demonstrated the participation of other systems such as the sensory system or basal ganglia, demonstrating in vivo that ALS is a multisystem disorder. Structural and functional imaging also allows studying dysfunction of brain areas associated with cognitive signs. From a biomarker perspective, numerous studies using diffusion tensor imaging showed a decrease of fractional anisotropy in the intracranial portion of the corticospinal tract but its diagnostic value at the individual level remains limited. A multiparametric approach will be required to use MRI in the diagnostic workup of ALS. A promising avenue is the new methodological developments of spinal cord imaging that has the advantage to investigate the two motor system components that are involved in ALS, that is, the lower and upper motor neuron. For all neuroimaging modalities, due to the intrinsic heterogeneity of ALS, larger pooled banks of images with standardized image acquisition and analysis procedures are needed. In this paper, we will review the main findings obtained with MRI, PET, SPECT, and nuclear magnetic resonance spectroscopy in ALS.

Biological and neuroimaging biomarkers for amyotrophic lateral sclerosis: 2013 and beyond

SUMMARY Amyotrophic lateral sclerosis is an idiopathic, incurable neurodegenerative disease that is fatal for most patients in less than 3 years from the time weakness first appears. Alongside identification of etiologies and stronger neuroprotective agents, the development of biomarkers is a main research priority. Since the original description, diagnosis and progression measurement in amyotrophic lateral sclerosis has been clinical. The time from symptom onset to diagnosis is usually more than a year, and clinical research studies utilize clinical end points that have low sensitivity. Few eligible patients and inefficient trials mean that just one or a few new therapies can be tested each year. Biological markers are needed not only to improve the sensitivity of clinical assessments, but also to better examine disease pathophysiology in vivo.

A prospective pilot study measuring muscle volumetric change in amyotrophic lateral sclerosis

Our objective was to investigate the potential of muscle volume, measured with magnetic resonance (MR), as a biomarker to quantify disease progression in patients with amyotrophic lateral sclerosis (ALS). In this longitudinal pilot study, we first sought to determine the stability of volumetric muscle MR measurements in 11 control subjects at two time-points. We assessed feasibility of detecting atrophy in four patients with ALS, followed at three-month intervals for 12 months. Muscle power and MR volume were measured in thenar eminence (TEm), first dorsal interosseous (1DIO), tibialis anterior (TA) and tongue. Changes over time were assessed using linear regression models and t-tests. Results demonstrated that, in controls, no volumetric MR changes were seen (mean volume variation in all muscles < 5%, p > 0.1). In patients, between-subject heterogeneity was identified. Trends for volume loss were found in TEm (mean, - 26.84%, p = 0.056) and TA (- 8.29%, p = 0.077), but not in 1DIO (- 18.47%, p = 0.121) or tongue (< 5%, p = 0.367). In conclusion, volumetric muscle MR appears a stable measure in controls, and progressive volume loss was demonstrable in individuals with ALS in whom clinical weakness progressed. In this small study, subclinical atrophy was not demonstrable using muscle MR. Clinico-radiological discordance between muscle weakness and MR atrophy could reflect a contribution of upper motor neuron pathology.

Brain iron MRI: a biomarker for amyotrophic lateral sclerosis

PURPOSE

To evaluate the usefulness of MRI detection of hypointensity areas (iron deposits) in the brain using a dedicated MRI technique in patients with ALS in establishing this sign as a potential surrogate biomarker that correlates with the severity of disease.

MATERIALS AND METHODS

Forty-six ALS patients and 26 age-matched controls were examined by MRI. The ALS Functional Rating Scale (ALSFRS) score was determined before the first MRI examination. The sub-set of 25 ALS patients was re-examined around 6 months after the first MRI examination. The MRI examination consisted of routine T1W, T2W, and FLAIR sequences with the addition of a thin slice heavily T2* weighted sequence to accentuate magnetic susceptibility artifacts.

RESULTS

T2*W sequence is superior to any other MRI sequence in detecting hypointensities in the brain of ALS patients. Hypointensities were found only in the precentral gyruses gray matter (PGGM) and were detected in 42 patients. The extent of hypointensities was measured and scored (0-3) and correlated with ALSFRS (r = -0.545). Twenty-five patients were re-examined 6 months later, and the majority of them showed the shift toward higher MRI scores. No control subjects had hypointensities in PGGM.

CONCLUSION

The detection of hypointensities in PGGM appears to be a very promising surrogate MRI biomarker for ALS due to its simplicity, high sensitivity and specificity, suitability for longitudinal studies, and relationship with the pathogenesis of the disease.

Amyotrophic Lateral Sclerosis and Metabolomics: Clinical Implication and Therapeutic Approach

Amyotrophic lateral sclerosis (ALS) is one of the most common motor neurodegenerative disorders, primarily affecting upper and lower motor neurons in the brain, brainstem, and spinal cord, resulting in paralysis due to muscle weakness and atrophy. The majority of patients die within 3–5 years of symptom onset as a consequence of respiratory failure. Due to relatively fast progression of the disease, early diagnosis is essential. Metabolomics offer a unique opportunity to understand the spatiotemporal metabolic crosstalks through the assessment of body fluids and tissue. So far, one of the most challenging issues related to ALS is to understand the variation of metabolites in body fluids and CNS with the progression of disease. In this paper we will review the changes in metabolic profile in response to disease progression condition and also see the therapeutic implication of various drugs in ALS patients.

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.

Magnetic resonance imaging in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disorder which is incurable to date. As there are many ongoing studies with therapeutic candidates, it is of major interest to develop biomarkers not only to facilitate early diagnosis but also as a monitoring tool to predict disease progression and to enable correct randomization of patients in clinical trials. Magnetic resonance imaging (MRI) has made substantial progress over the last three decades and is a practical, noninvasive method to gain insights into the pathology of the disease. Disease-specific MRI changes therefore represent potential biomarkers for ALS. In this paper we give an overview of structural and functional MRI alterations in ALS with the focus on task-free resting-state investigations to detect cortical network failures.

Presymptomatic spinal cord neurometabolic findings in SOD1-positive people at risk for familial ALS

OBJECTIVE

It has been speculated that amyotrophic lateral sclerosis (ALS) is characterized by a premanifest period during which neurodegeneration precedes the appearance of clinical manifestations. Magnetic resonance spectroscopy (MRS) was used to measure ratios of neurometabolites in the cervical spine of asymptomatic individuals with a mutation in the SOD1 gene (SOD1+) and compare their neurometabolic ratios to patients with ALS and healthy controls.

METHODS

A cross-sectional study of (1)H-MRS of the cervical spine was performed on 24 presymptomatic SOD1+ volunteers, 29 healthy controls, and 23 patients with ALS. All presymptomatic subjects had no symptoms of disease, normal forced vital capacity, and normal electromyographic examination. Relative concentrations of choline (Cho), creatine (Cr), myo-inositol (Myo), and N-acetylaspartate (NAA) were determined.

RESULTS

NAA/Cr and NAA/Myo ratios are reduced in both SOD1+ subjects (39.7%, p = 0.001 and 18.0%, p = 0.02) and patients with ALS (41.2%, p < 0.001 and 24.0%, p = 0.01) compared to controls. Myo/Cr is reduced (10.3%, p = 0.02) in SOD1+ subjects compared to controls, but no difference was found between patients with ALS and controls. By contrast, NAA/Cho is reduced in patients with ALS (24.0%, p = 0.002), but not in presymptomatic SOD1+ subjects compared to controls.

CONCLUSIONS

Changes in neurometabolite ratios in the cervical spinal cord are evident in presymptomatic SOD1+ individuals in advance of symptoms and clinical or electromyographic signs of disease. These changes reflect a reduction in NAA/Cr and NAA/Myo. Neurometabolic changes in this population resemble changes observed in patients with clinically apparent ALS. This suggests that neurometabolic changes occur early in the course of the disease process.

Writing error may be a predictive sign for impending brain atrophy progression in amyotrophic lateral sclerosis: a preliminary study using X-ray computed tomography

AIM

To investigate whether writing errors are predictive of longitudinal brain atrophy progression in patients with amyotrophic lateral sclerosis (ALS).

METHODS

The frequency of writing errors in 6 ALS patients without dementia was compared with longitudinal changes in lateral ventricular areas of the bilateral anterior and inferior horns on X-ray computed tomography scans. The increase in area per month for the anterior and inferior horns was used as a measure of longitudinal brain atrophy progression, and was calculated as: (area on the initial scan - area on the follow-up scan)/scan interval (month).

RESULTS

The longitudinal rate of increase in the area of the anterior horns showed significant associations with the rates of total writing errors (r = 0.886, p = 0.0152), kana errors (r = 0.887, p = 0.0148) and kana omission (r = 0.856, p = 0.0268), whereas that for the inferior horns size showed no significant association with any writing errors.

CONCLUSION

The increased area of the anterior horns indicates frontal-lobar atrophy, and writing errors may be a predictive sign for impending brain atrophy progression in the frontal lobes, which reflects the development of anterior-type dementia.

Magnetic resonance spectroscopy of the cervical cord in amyotrophic lateral sclerosis

The objective of this study was to use magnetic resonance spectroscopy (MRS) to compare metabolite ratios in the cervical spinal cord of ALS patients to healthy controls. Fourteen ALS patients and 16 controls were scanned using a 3T scanner. A rectangular voxel (8 × 5 × 35 mm) was placed along the main axis of the cord with the lower limit at the inferior aspect of the C2 vertebral body. MRS was performed with a point-resolved spectroscopy (PRESS) sequence. Water signals were suppressed using a three-pulse chemical shift selective (CHESS) saturation sequence. Relative concentrations of choline (Cho), creatine (Cr), myo-inositol (Myo), and NAA were computed from metabolite peaks. Differences in metabolite ratios between ALS patients and controls were assessed with a Wilcoxon rank-sum test. The relationship of metabolite ratios to clinical measures (ALSFRS-R and FVC) was determined by Pearson correlation. The NAA/Cr and NAA/Myo ratios were reduced by 40% and 38%, respectively, in ALS patients. The reduction in NAA/Myo and NAA/Cho correlated significantly with FVC, with correlation coefficients of 0.66 and 0.60, respectively. In conclusion, MR spectra can reliably be obtained from the cervical spinal cord in ALS. MRS of the cervical cord may be a useful biomarker of disease progression.

Degeneration of the mid-cingulate cortex in amyotrophic lateral sclerosis detected in vivo with MR spectroscopy

BACKGROUND AND PURPOSE

Various lines of evidence implicate cerebral involvement beyond the motor cortex in ALS, including the cingulate gyrus and the thalamus. The purpose of this study was to assess neurodegeneration in these regions in vivo by using MRSI.

MATERIALS AND METHODS

Fourteen patients with ALS and 14 healthy controls underwent MRSI by using a coronal acquisition scheme. The NAA/Cho ratio was quantified in the MCC, thalamus, and motor cortex (PCG).

RESULTS

NAA/Cho was reduced in the MCC in patients with ALS compared with the controls (P = .0004). There was no difference in NAA/Cho in the thalamus (P = .59). We also found a strong correlation of NAA/Cho among the PCG, MCC, and the thalamus in controls, which was absent in patients with ALS.

CONCLUSIONS

Neurodegeneration beyond the motor cortex is present in the MCC in ALS. The significant correlation of NAA/Cho among the PCG, MCC, and the thalamus in healthy subjects likely reflects the neuronal connectivity among these regions. The loss of these relationships in patients with ALS suggests that such connectivity is not responsible for the pattern of degeneration in these regions.

Advances in the application of MRI to amyotrophic lateral sclerosis

IMPORTANCE OF THE FIELD: With the emergence of therapeutic candidates for the incurable and rapidly progressive neurodegenerative condition of amyotrophic lateral sclerosis (ALS), it will be essential to develop easily obtainable biomarkers for diagnosis, as well as monitoring, in a disease where clinical examination remains the predominant diagnostic tool. Magnetic resonance imaging (MRI) has greatly developed over the past thirty years since its initial introduction to neuroscience. With multi-modal applications, MRI is now offering exciting opportunities to develop practical biomarkers in ALS. AREAS COVERED IN THIS REVIEW: The historical application of MRI to the field of ALS, its state-of-the-art and future aspirations will be reviewed. Specifically, the significance and limitations of structural MRI to detect gross morphological tissue changes in relation to clinical presentation will be discussed. The more recent application of diffusion tensor imaging (DTI), magnetic resonance spectroscopy (MRS), functional and resting-state MRI (fMRI & R-fMRI) will be contrasted in relation to these more conventional MRI assessments. Finally, future aspirations will be sketched out in providing a more disease mechanism-based molecular MRI. WHAT THE READER WILL GAIN: This review will equip the reader with an overview of the application of MRI to ALS and illustrate its potential to develop biomarkers. This discussion is exemplified by key studies, demonstrating the strengths and limitations of each modality. The reader will gain an expert opinion on both the current and future developments of MR imaging in ALS. TAKE HOME MESSAGE: MR imaging generates potential diagnostic, prognostic and therapeutic monitoring biomarkers of ALS. The emerging fusion of structural, functional and potentially molecular imaging will improve our understanding of wider cerebral connectivity and holds the promise of biomarkers sensitive to the earliest changes.

Evaluation of corticospinal tract impairment in the brain of patients with amyotrophic lateral sclerosis by using diffusion tensor imaging acquisition schemes with different numbers of diffusion-weighting directions

Amyotrophic lateral sclerosis is characterized by degeneration of upper and lower motor neurons. Diffusion tensor imaging (DTI) indexes obtained along the corticospinal tracts distinguish ALS patients and control subjects. Diffusion tensor imaging can be estimated from at least 6 diffusion-weighted images; however an acquisition scheme with a higher number of diffusion directions allows a more robust estimation of DTI indexes. The aim of the study was to establish if a higher number of diffusion encoding gradients increases the diagnostic accuracy of DTI in ALS. We studied 18 patients and 16 control subjects acquiring 2 DTI data sets with 6 and 31 gradient orientations. The mean diffusivity and fractional anisotropy values were measured along the corticospinal tract. Mean diffusivity in ALS was significantly increased (P = 0.026) with respect to control subjects in acquisition scheme with 31 but not (P = 0.214) with 6 diffusion-weighting directions. Fractional anisotropy was significantly lower in patients both with 6 (P = 0.0036) and with 31 (P = 0.0004) diffusion-weighting directions (0.538 vs 0.588 and 0.530 vs 0.594). Fractional anisotropy receiver operating characteristic curve analysis showed a higher diagnostic accuracy by using 31 diffusion-weighting direction (85.76%) with respect to 6 directions (79.86%). Diffusion tensor imaging confirms its potentials in diagnosing ALS with a good accuracy; the acquisition scheme with a higher diffusion-weighting directions seems to better discriminate between ALS patients and control subjects.

The application of biomarkers in clinical trials for motor neuron disease

The interest and research into disease-related biomarkers has greatly accelerated over the last 10 years. The potential clinical benefits for disease-specific biomarkers include a more rapid and accurate disease diagnosis, and potential reduction in size and duration of clinical drug trials, which would speed up drug development. The application of biomarkers into the clinical arena of motor neuron disease should both determine if a drug hits its proposed target and whether the drug alters the course of disease. This article will highlight the progress made in discovering suitable biomarker candidates from a variety of sources, including imaging, neurophysiology and proteomics. For biomarkers to have clinical utility, specific criteria must be satisfied. While there has been tremendous effort to discover biomarkers, very few have been translated to the clinic. The bottlenecks in the biomarker pipeline will be highlighted as well as lessons that can be learned from other disciplines, such as oncology.

Reproducibility of serial whole-brain MR spectroscopic imaging

The reproducibility of serial measurements using a volumetric proton MR Spectroscopic Imaging (MRSI) acquisition implemented at 3 Tesla and with lipid suppression by inversion-recovery has been evaluated. Data were acquired from two subjects at five time points, and processed using fully-automated procedures that included rigid registration between studies. These data were analyzed to determine coefficients of variance (COV) for each metabolite and for metabolite ratio images based on an individual voxel analysis, as well as for average and grey-matter and white-matter values from atlas-defined brain regions. The volumetric MRSI acquisition was found to obtain data of sufficient quality for analysis over 70 +/- 6% of the total brain volume, and spatial distributions of the resultant COV values were found to reflect the known distributions of susceptibility-induced magnetic field inhomogeneity. Median values of the resultant voxel-based COVs were 6.2%, 7.2%, and 9.7% for N-acetylaspartate, creatine, and choline respectively. The corresponding mean values obtained following averaging over lobar-scale brain regions within the cerebrum were 3.5%, 3.7%, and 5.2%. These results indicate that longitudinal volumetric MRSI studies with post-acquisition registration can provide an intra-subject reproducibility for voxel-based analyses that is comparable to previously-reported single-voxel MRS measurements, while additionally enabling increased sensitivity by averaging over larger tissue volumes.

The present and the future of neuroimaging in amyotrophic lateral sclerosis

In patients with ALS, conventional MR imaging is frequently noninformative, and its use has been restricted to excluding other conditions that can mimic ALS. Conversely, the extensive application of modern MR imaging-based techniques to the study of ALS has undoubtedly improved our understanding of disease pathophysiology and is likely to have a role in the identification of potential biomarkers of disease progression. This review summarizes how new MR imaging technology is changing dramatically our understanding of the factors associated with ALS evolution and highlights the reasons why it should be used more extensively in studies of disease progression, including clinical trials.

In vivo morphological changes in animal models of amyotrophic lateral sclerosis and Alzheimer's-like disease: MRI approach

Magnetic resonance imaging (MRI) is the only noninvasive technique that provides structural information on both cell loss and metabolic changes. After reviewing all the results obtained in clinical studies, reliable biomarkers in neurological diseases are still lacking. Diffusional MRI, MR spectroscopy, and the assessment of regional atrophy are promising approaches, but they cannot be simultaneously used on a single patient. Thus, for further research progress, reliable animal models are needed. To this aim, we have used the clinical MRI to assess neurodegenerative processes in the hSOD-1(G93A) ALS rat model and in the trimethyltin (TMT)-treated model of Alzheimer's-like disease. T2-weighted (T2W) hyperintensive neurodegenerative foci were found in the brainstem of the ALS rat with apparent lateral ventricle dilation (T1W-hypointensity vs. T2W-hyperintensity). Degenerative processes in these areas were also confirmed by confocal images of GFAP-positive astrogliosis. MRI after i.v.i. of magnetic anti-CD4 antibodies indicated an accumulation of inflammatory cells near dilated ventricles. TMT-treated rats also revealed the dilation of lateral ventricles. Expected deterioration in the hippocampus was not observed by clinical MRI, but immunocytochemistry could reveal significant redistribution of macro- and microglia in this structure. In both models, Gd-DTPA contrast revealed a compromised blood brain barrier that may serve as the passage for inflammatory immune cells in the vicinity of dilated lateral ventricles. Moreover, in both models the midbrain region of the dorsal hippocampus was the target of BBB compromise, thus revealing a potentially vulnerable point that can be the primary target of neurodegeneration in the central nervous 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).

[New biological and radiological markers in amyotrophic lateral sclerosis]

The only specific marker of sporadic amyotrophic lateral sclerosis (ALS), that represent about 90% of all cases, is neuropathological and based on the demonstration of motoneuronal degeneration associated with typical inclusions positive for ubiquitine and TDP-43. The gene encoding the superoxide dismutase 1 (SOD1) is implicated in about 10-20% of familial ALS. A mutation in the SOD1 gene can be considered as a genetic marker of ALS, and not a polymorphism, if the mutation has been shown to be pathogenic or to segregate to the disease in familial cases. Studies in blood or cerebral spinal fluid have shown biological changes involving different physiopathological pathways (oxidative stress, inflammation, excitotoxicity...). These abnormalities are neither sensitive nor specific enough to provide a diagnostic tool. The ectopic expression of Nogo-A in muscle biopsy is a promising marker but further studies are needed to demonstrate its value as a diagnostic tool in ALS. Studies in series of ALS patients have shown that MR-spectroscopy and diffusion tensor imaging can detect cortico-spinal degeneration. However, because of an overlap between patients and normal subjects, spectroscopic and DTI-parameters cannot be used as diagnostic tool in individual patients. In the future, a combination of biological, radiological and electrophysiological markers, rather than a single marker, may provide diagnostic tool for the diagnosis and follow-up of ALS patients.

Magnetic resonance spectroscopic imaging detects abnormalities in normal-appearing frontal lobe of patients with Sturge-Weber syndrome

BACKGROUND

In Sturge-Weber syndrome (SWS), structural MRI abnormalities are most common in the posterior brain regions. Frontal lobe involvement increases the risk of motor impairment. The goal of this study was to determine whether Magnetic Resonance Spectroscopic Imaging (MRSI) can improve detection of frontal lobe involvement in children with SWS.

METHODS

Sixteen children (age: .9-10.4 years) with unilateral SWS underwent MRI with MRSI prospectively. N-acetyl-aspartate (NAA) and choline asymmetries in the posterior and frontal regions were measured.

RESULTS

Eight children presented normal-appearing frontal lobes on conventional MRI, but 7 of them showed abnormal NAA and/or choline content in the frontal lobe of the affected hemisphere. Lower frontal lobe gray matter NAA was associated with earlier onset of seizures (r= .76; P= .04) and impaired motor function (r=-.89, P < .001). Frontal NAA asymmetry was an independent predictor of motor function in a regression analysis (P= .01)

CONCLUSION

MRSI is more sensitive than conventional structural MRI for detection of frontal lobe involvement in SWS. Decreased frontal lobe NAA is an excellent predictor of motor functions. Thus, MRSI can provide complementary information for the assessment of normal-appearing brain regions, and may assist prognosis evaluation in children with SWS.