Magnetic resonance imaging of the corticospinal tracts in amyotrophic lateral sclerosis

The Lateral Corticospinal Tract Sign: An MRI Marker for Amyotrophic Lateral Sclerosis

Background Radially sampled averaged magnetization inversion-recovery acquisition (rAMIRA) imaging shows hyperintensity in the lateral corticospinal tract (CST) in patients with motor neuron diseases. Purpose To systematically determine the accuracy of the lateral corticospinal tract sign for detecting patients with amyotrophic lateral sclerosis (ALS) at rAMIRA MRI. Materials and Methods This study included prospectively acquired data from participants in ALS and other motor neuron disease imaging studies at the University Hospital Basel, Switzerland. All participants underwent 3-T axial two-dimensional rAMIRA imaging at four cervical intervertebral disk levels. The lateral CST sign was defined as spinal cord white matter hyperintensity dorsolateral to the anterior horns, with higher signal intensity than in the dorsal columns on axial rAMIRA images. Marker accuracy was assessed in a study data set and in an independent validation data set. Postmortem rAMIRA imaging and histopathologic analysis were performed in one participant who died during the study. Results Participants with ALS (study data set: 38 participants [mean age, 61 years; IQR, 15 years], 22 male participants; validation data set: 10 participants [mean age, 61 years; IQR, 21 years], seven male participants), post-polio syndrome (study data set: 25 participants [mean age, 68 years; IQR, 8 years], 12 male participants), spinal muscular atrophy (study data set: 10 participants [mean age, 43 years; IQR, 14 years], eight male participants; validation data set: five participants [mean age, 38 years; IQR, 19 years], two male participants), and healthy control participants (study data set: 60 participants [mean age, 57 years; IQR, 20 years], 36 male participants; validation data set: 10 participants [mean age, 44 years; IQR, 17 years], seven male participants) were included. The sensitivity and specificity of rAMIRA for ALS were 60% (23 of 38) and 97% (91 of 94) in the study data set and 100% (10 of 10) and 93% (14 of 15) in the validation data set, respectively. Histopathologic analysis showed distinct loss of myelinated axons in the localization of the hyperintensities observed at rAMIRA imaging performed in situ and after organ extraction. Conclusion The recently defined marker at rAMIRA MRI may be a promising tool for assessing upper motor neuron degeneration in the lateral CST in patients with ALS. Clinical trials registration no. NCT03561623, NCT05764434, NCT06137612 © RSNA, 2024 Supplemental material is available for this article.

Novel approaches to assessing upper motor neuron dysfunction in motor neuron disease/amyotrophic lateral sclerosis: IFCN handbook chapter

Identifying upper motor neuron (UMN) dysfunction is fundamental to the diagnosis and understanding of disease pathogenesis in motor neuron disease (MND). The clinical assessment of UMN dysfunction may be difficult, particularly in the setting of severe muscle weakness. From a physiological perspective, transcranial magnetic stimulation (TMS) techniques provide objective biomarkers of UMN dysfunction in MND and may also be useful to interrogate cortical and network function. Single, paired- and triple pulse TMS techniques have yielded novel diagnostic and prognostic biomarkers in MND, and have provided important pathogenic insights, particularly pertaining to site of disease onset. Cortical hyperexcitability, as heralded by reduced short interval intracortical inhibition (SICI) and increased short interval intracortical facilitation, has been associated with the onset of lower motor neuron degeneration, along with patterns of disease spread, development of specific clinical features such as the split hand phenomenon, and may provide an indication about the rate of disease progression. Additionally, reduction of SICI has emerged as a potential diagnostic aid in MND. The triple stimulation technique (TST) was shown to enhance the diagnostic utility of conventional TMS measures in detecting UMN dysfunction in MND. Separately, sophisticated brain imaging techniques have uncovered novel biomarkers of neurodegeneration that have bene associated with progression. The present review will discuss the utility of TMS and brain neuroimaging derived biomarkers of UMN dysfunction in MND, focusing on recently developed TMS techniques and advanced neuroimaging modalities that interrogate structural and functional integrity of the corticomotoneuronal system, with an emphasis on pathogenic, diagnostic, and prognostic utility.

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

Dystonias represent a heterogeneous group of movement disorders responsible for sustained muscle contraction, abnormal postures, and muscle twists. It can affect focal or segmental body parts or be generalized. Primary dystonia is the most common form of dystonia but it can also be secondary to metabolic or structural dysfunction, the consequence of a drug's side-effect or of genetic origin. The pathophysiology is still not elucidated. Based on lesion studies, dystonia has been regarded as a pure motor dysfunction of the basal ganglia loop. However, basal ganglia lesions do not consistently produce dystonia and lesions outside basal ganglia can lead to dystonia; mild sensory abnormalities have been reported in the dystonic limb and imaging studies have shown involvement of multiple other brain regions including the cerebellum and the cerebral motor, premotor and sensorimotor cortices. Transcranial magnetic stimulation (TMS) is a non-invasive technique of brain stimulation with a magnetic field applied over the cortex allowing investigation of cortical excitability. Hyperexcitability of contralateral motor cortex has been suggested to be the trigger of focal dystonia. High or low frequency repetitive TMS (rTMS) can induce excitatory or inhibitory lasting effects beyond the time of stimulation and protocols have been developed having either a positive or a negative effect on cortical excitability and associated with prevention of cell death, γ-aminobutyric acid (GABA) interneurons mediated inhibition and brain-derived neurotrophic factor modulation. rTMS studies as a therapeutic strategy of dystonia have been conducted to modulate the cerebral areas involved in the disease. Especially, when applied on the contralateral (pre)-motor cortex or supplementary motor area of brains of small cohorts of dystonic patients, rTMS has shown a beneficial transient clinical effect in association with restrained motor cortex excitability. TMS is currently a valuable tool to improve our understanding of the pathophysiology of dystonia but large controlled studies using sham stimulation are still necessary to delineate the place of rTMS in the therapeutic strategy of dystonia. In this review, we will focus successively on the use of TMS as a tool to better understand pathophysiology, and the use of rTMS as a therapeutic strategy.

Effects of hematopoietic stem cell transplantation on acyl-CoA oxidase deficiency: a sibling comparison study

OBJECTIVE

Acyl-CoA oxidase (ACOX1) deficiency is a rare disorder of peroxisomal very-long chain fatty acid oxidation. No reports detailing attempted treatment, longitudinal imaging, or neuropathology exist. We describe the natural history of clinical symptoms and brain imaging in two siblings with ACOX1 deficiency, including the younger sibling's response to allogeneic unrelated donor hematopoietic stem cell transplantation (HSCT).

METHODS

We conducted retrospective chart review to obtain clinical history, neuro-imaging, and neuropathology data. ACOX1 genotyping were performed to confirm the disease. In vitro fibroblast and neural stem cell fatty acid oxidation assays were also performed.

RESULTS

Both patients experienced a fatal neurodegenerative course, with late-stage cerebellar and cerebral gray matter atrophy. Serial brain magnetic resonance imaging in the younger sibling indicated demyelination began in the medulla and progressed rostrally to include the white matter of the cerebellum, pons, midbrain, and eventually subcortical white matter. The successfully engrafted younger sibling had less brain inflammation, cortical atrophy, and neuronal loss on neuro-imaging and neuropathology compared to the untreated older sister. Fibroblasts and stem cells demonstrated deficient very long chain fatty acid oxidation.

INTERPRETATION

Although HSCT did not halt the course of ACOX1 deficiency, it reduced the extent of white matter inflammation in the brain. Demyelination continued because of ongoing neuronal loss, which may be due to inability of transplant to prevent progression of gray matter disease, adverse effects of chronic corticosteroid use to control graft-versus-host disease, or intervention occurring beyond a critical point for therapeutic efficacy.

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.

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.

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).

Brain metabolites in definite amyotrophic lateral sclerosis

Biomarkers beyond clinical assessment are needed in patients who suffer from amyotrophic lateral sclerosis (ALS). Here, single-voxel proton magnetic resonance spectroscopy ((1)H MRS) of the gray matter of the motor cortex and the white matter including the pyramidal tracts was used to investigate concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myoinositol, glutamate, and glutamine in patients with definite ALS in a longitudinal design (three measurements at study inclusion, after 3 and 6 months). A volume-corrected analysis of gray and white matter fractions within the volumes of interest (VOI) was performed for the identification of the absolute metabolite concentrations. The patient group showed a significant decline of the compound NAA over time in the motor cortex areas both of the clinically more and less affected hemisphere between first measurement and month 6 and for the less affected side additionally between first measurement and month 3. For the NAA/(Cr + Cho) ratio, significant decline in the less affected hemisphere was observed from the first measurement to month 3 and to month 6 as well as from month 3 to month 6. In contrast, neither NAA nor the NAA/(Cr + Cho) ratios in the white matter areas showed any significant alterations. All other compounds showed no significant changes over time. In summary, the longitudinal changes of cortical metabolite concentrations in the course of ALS could be assessed by optimized (1)H MRS techniques at group level, so that (1)H MRS parameters, in particular volume-corrected values of NAA in the clinically less affected hemisphere, seem to have the potential to serve as a surrogate marker for monitoring ALS disease progression.

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

This MRI study was performed to evaluate in vivo alterations of the spinal cord in defined subgroups of motor neuron diseases. Standard MRI examinations of the cervical and thoracic spinal cord in sporadic amyotrophic lateral sclerosis (ALS; n = 39), sporadic lower motor neuron disease (LMND; n = 19), Kennedy's disease (KD; n = 19) and a control group (n = 96) were analyzed with respect to spinal cord signal changes and the thickness of the spinal cord. No significant changes in thickness or signal alterations were observed when comparing ALS, LMND and control groups with one another. However, in KD patients significant upper spinal cord atrophy was detected at the cervical level as compared with all other groups. At the thoracic level, KD patients had significant upper cord atrophy as compared with controls and LMND. Marked atrophy of the upper spinal cord seems to be a feature of the KD-associated central-peripheral distal axonopathy.

Reduction in metabolite transverse relaxation times in amyotrophic lateral sclerosis

BACKGROUND

Proton magnetic resonance spectroscopy (1H MRS) is used frequently to evaluate normal and pathological states in brain. MRS results are often reported as ratios of peak areas from spectra acquired at a single echo time, primarily for the peaks arising from N-acetyl groups (NA), creatine/phosphocreatine (t-Cr), and choline (Cho). Peak areas, however, are affected not only by metabolite concentration, but also by transverse relaxation times (T(2)). While the ratio approach appears to be valid in normal brain, pathology may affect T(2), thereby leading to misinterpretation of the apparent changes in metabolite ratios. The objective of the present study was to determine if any T(2) changes might affect the apparent metabolite ratio measures, which we have previously reported as being abnormal in amyotrophic lateral sclerosis (ALS).

METHODS

1H MRS data were acquired from the brainstems of ALS and control subjects, for a range of TE times, to calculate T(2) times for each of NA, t-Cr, and Cho. Metabolite ratios were measured experimentally at TE=120 ms and calculated for TE=0 ms, based on measured T(2) values.

RESULTS

The T(2)'s for the ALS vs. control group were NA=272+/-10 ms vs. 351+/-58 ms (p<0.01), t-Cr=132+/-17 vs. 184+/-42 ms (p<0.02), and Cho=223+/-55 vs. 245+/-50 ms (p>0.05). The effect of these T(2) changes on metabolite ratios showed both the NA/t-Cr (ALS=0.98+/-0.13, Control=1.44+/-0.10, p<0001) and Cho/t-Cr (ALS=1.01+/-0.12, Control=1.34+/-0.24, p<0.001) ratios to differ significantly between groups.

CONCLUSION

This study confirms the presence of significant abnormalities in metabolite concentration in ALS brainstem and the importance of evaluating the effects of metabolite T(2) values when making ratio measurements in disease states.

Amyotrophic lateral sclerosis: objective upper motor neuron markers

The diagnosis of amyotrophic lateral sclerosis (ALS) remains a clinical diagnosis. It is based on the combination of both upper and lower motor neuron signs in the neurologic examination. With several new therapeutic agents on the horizon, effective and objective disease markers for diagnosis and surrogate outcome measures in clinical trials are crucial. Whereas the presence of lower motor neuron signs on neurologic examination can be ascertained by electromyography, there is no widely accepted marker for upper motor neuron involvement. Neuroimaging changes of the corticospinal tract in ALS patients have been studied using magnetic resonance (MR) imaging, but appear to lack sensitivity and specificity. MR spectroscopy, a technique that allows one to evaluate biochemical tissue composition in vivo, has been widely used to establish the progressive decrease in N-acetylaspartate, a marker of neuronal integrity, in the course of ALS. More recently, diffusion tensor imaging, a newer MR technique, has demonstrated changes in diffusivity along the corticospinal tract in ALS patients. Metabolic aspects in the brains of ALS patients have been evaluated using positron emission tomography. Transcranial magnetic stimulation is a more established technique that evaluates the neurophysiologic integrity of upper motor neurons in ALS. This article reviews the progress that has been made over the past two decades towards establishing valid diagnostic and natural history markers of upper motor neuron involvement in ALS.

MRI-FLAIR images of the head show corticospinal tract alterations in ALS patients more frequently than T2-, T1- and proton-density-weighted images

In some patients with amyotrophic lateral sclerosis (ALS), T2-weighted and proton-density-weighted magnetic resonance imaging (MRI) shows hyperintense or hypointense signals at the corticospinal tract. Fluid-attenuated inversion recovery (FLAIR) sequences increase the sensitivity of MRI to detect cortical and subcortical tissue changes. In 31 ALS patients and 33 controls, we studied the frequency and the extent of signal abnormalities in FLAIR images compared to T2-, T1- and proton-density-weighted images. Hyperintense signals at the corticospinal tract were significantly more frequent in FLAIR images than in all other tested sequences. In FLAIR images of ALS patients only, distinct hyperintense signals at the subcortical precentral gyrus (five patients), the centrum semiovale (eight patients), the crus cerebri (nine patients) and the pons (four patients) as well as mild hyperintense signals in the medulla oblongata (three patients) were seen. More frequently, but not exclusively in ALS patients, FLAIR images showed mild hyperintense signals at the subcortical precentral gyrus (15 patients vs. 1 control). Quantitative analysis confirmed the significant difference between ALS patients and controls at the subcortical precentral gyrus in FLAIR images. In T1-weighted images, the corticospinal tract at the capsula interna was hypointense in significantly more controls than ALS patients. Also this difference was confirmed in the quantitative analysis. Similar to previous results, MR image alterations did correlate poorly to clinical data of upper motor neuron affliction.MR images of the head, including FLAIR images, provide additional information regarding corticospinal tract involvement in ALS patients. Because of an overlap with physiological findings, they have to be interpreted cautiously, with the exception of hyperintense signals at the subcortical precentral gyrus.

Review neuroimaging in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a chronic degenerative disorder of unknown etiology affecting the motor system. Conventional and non-conventional neuroimaging techniques can provide essential help both to increase the confidence in ALS diagnosis and to assess the disease evolution. Signal abnormalities at the level of the motor cortex and the corticospinal tract on conventional T2-weighted magnetic resonance (MR) images are a potentially useful marker of ALS pathology. However, the prognostic value of these conventional MR abnormalities is still hampered by their low pathological specificity. Non-conventional MR techniques with a higher pathological specificity, such as MR spectroscopy, magnetization transfer imaging and diffusion-weighted imaging, seem to have some potential not only for ALS diagnosis, but also for monitoring disease evolution either naturally or when modified by experimental treatments.

Reduced MTR in the corticospinal tract and normal T2 in amyotrophic lateral sclerosis

The objective of this study was to test the hypothesis that magnetization transfer ratios (MTR) are decreased in the corticospinal tract of patients with amyotrophic lateral sclerosis (ALS); to determine if T2 is increased in corticospinal tract or reduced in motor cortex in ALS; to determine if corticospinal tract MTR correlates with a clinical measure of motor neuron function in ALS. Ten ALS patients and 17 age-matched controls were studied. Double spin echo MRI and 3D gradient echo MRI with and without off-resonance saturation were acquired on each subject. 3D data sets were coregistered and resliced to match the spin echo data set. MTR was calculated for corticospinal and non-corticospinal tract white matter. T2 was calculated for corticospinal and non-corticospinal tract white matter, motor cortex and non-motor cortex. MTR was reduced by 2.6% (p < .02) in corticospinal, but not in non-corticospinal, tract white matter in ALS. There was no difference in T2 in any brain region. The correlation between a clinical measure of motor neuron function and corticospinal tract MTR was statistically significant. These findings are consistent with the known pathology in ALS and suggest that MTR is more sensitive than T2 for detecting involvement of the corticospinal tract. Quantitative MTR of the corticospinal tract may be a useful, objective marker of upper motor neuron pathology in ALS.

[Amyotrophic lateral sclerosis and herpes virus. Report of an unusual case: a cause or casual association?]

OBJECTIVE

To present a curious case of amyotrophic lateral sclerosis (ALS).

CASE

A forty-seven year old man claimed of paresis in the arms since four years. The electrical study of the muscles and nerves diagnosis was ALS, type Vulpian-Bernardt. The cerebrospinal fluid study revealed an inflammatory process and the positivity of immulogical reactions for Herpes simplex I. The blood-brain barrier study showed the possibility that immunological response for Herpes simplex I was produced in the spinal fluid space. A magnetic resonance suggested cystic myelopathy of cervical spinal cord expanding from C2 to C4. The patient received endovenous acyclovir for 21 days. Until two months after the medication we did not submit the patient to other subsidiary examinations.

DISCUSSION

Until now there is no specific drug treatment for ALS. The notion that there is a "syndrome of ALS" related with various causes may help to treat some patients.