Amyotrophic lateral sclerosis: a clinical review

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder affecting primarily the motor system, but in which extra‐motor manifestations are increasingly recognized. The loss of upper and lower motor neurons in the motor cortex, the brain stem nuclei and the anterior horn of the spinal cord gives rise to progressive muscle weakness and wasting. ALS often has a focal onset but subsequently spreads to different body regions, where failure of respiratory muscles typically limits survival to 2–5 years after disease onset. In up to 50% of cases, there are extra‐motor manifestations such as changes in behaviour, executive dysfunction and language problems. In 10%–15% of patients, these problems are severe enough to meet the clinical criteria of frontotemporal dementia (FTD). In 10% of ALS patients, the family history suggests an autosomal dominant inheritance pattern. The remaining 90% have no affected family members and are classified as sporadic ALS. The causes of ALS appear to be heterogeneous and are only partially understood. To date, more than 20 genes have been associated with ALS. The most common genetic cause is a hexanucleotide repeat expansion in the C9orf72 gene, responsible for 30%–50% of familial ALS and 7% of sporadic ALS. These expansions are also a frequent cause of frontotemporal dementia, emphasizing the molecular overlap between ALS and FTD. To this day there is no cure or effective treatment for ALS and the cornerstone of treatment remains multidisciplinary care, including nutritional and respiratory support and symptom management. In this review, different aspects of ALS are discussed, including epidemiology, aetiology, pathogenesis, clinical features, differential diagnosis, investigations, treatment and future prospects.     

Increased expression of TDP‐43 in the skin of amyotrophic lateral sclerosis

Suzuki M, Mikami H, Watanabe T, Yamano T, Yamazaki T, Nomura M, Yasui K, Ishikawa H, Ono S. Increased expression of TDP‐43 in the skin of amyotrophic lateral sclerosis. Acta Neurol Scand: 2010: 122: 367–372. © 2010 The Authors Journal compilation © 2010 Blackwell Munksgaard. Objectives – Transactivation‐responsive DNA‐binding protein‐43 (TDP‐43) was indentified as a major component of the ubiquitin‐positive inclusions in sporadic amyotrophic lateral sclerosis (ALS). However, there has been no study of TDP‐43 in ALS skin. The present study investigates TDP‐43 in ALS skin. Materials and methods – We made a quantitative immunohistochemical study of the expression of TDP‐43 in the skin from 15 patients with ALS and 15 control subjects. Results – The proportion of TDP‐43‐positive (TDP‐43+) cells in the epidermis in ALS patients was significantly higher (P < 0.001) than in controls. There was a significant positive relationship (r = 0.62, P < 0.02) between the proportion and duration of illness in ALS patients. The optical density of TDP‐43+ cells in the epidermis in ALS patients is markedly stronger (P < 0.001) than in controls. There was a significant positive relation (r = 0.72, P < 0.01) between the immunoreactivity and duration of illness in ALS patients. Conclusions – These data suggest that changes of TDP‐43 in ALS skin are likely to be related to the disease process and that metabolic alterations of TDP‐43 may take place in the skin of patients with ALS.     

Diagnostic problems and delay of diagnosis in amyotrophic lateral sclerosis

Objective

Initial symptoms of amyotrophic lateral sclerosis (ALS) mimic several neurological syndromes that may decelerate a correct diagnosis. The aim of our study was to investigate if diagnostic and therapeutic parameters have influence on the time of diagnosis.

Methods

We retrospectively reviewed the medical records of 100 consecutive ALS patients focusing on clinical and diagnostic data, the timing of diagnosis and treatments attributed to the onset of symptoms of ALS.

Results

Among 100 consecutive patients with ALS, 12% underwent surgery due to symptoms retrospectively attributable to ALS. The comparison of duration from first symptoms to correct diagnosis showed a significant difference between operated and non-operated patients. 35% of all ALS patients had bulbar onset symptoms. The mean time from first symptoms to diagnosis was 9 months in this group. In patients without bulbar onset it was 16.4 months which also represents a significant difference. In 44% of patients other diagnoses were considered and medically treated previous to correct diagnosis, but there was no significant delay of diagnosis.

Conclusion

Our study confirms that diagnosis of ALS is still a common clinical problem and shows the need of sensitive and specific diagnostic tests.     

Deleted 4977-bp mitochondrial DNA mutation is associated with sporadic amyotrophic lateral sclerosis: a hospital-based case-control study

We investigated the relationship between the most common 4977-bp deleted mitochondrial DNA (mtDNA) mutations and the occurrence of sporadic amyotrophic lateral sclerosis (ALS). Primer-shift and quantitative polymerase chain reaction (PCR) were used to determine the 4977-bp deleted mtDNA in the muscle specimens from 36 patients with sporadic ALS and 69 age-matched controls with other neuromuscular disorders. We found that the 4977-bp deleted mtDNA mutations were significantly higher in the ALS patients than controls in both frequency (50.0% vs. 8.7%, P < 0.01) and amount (0.35 +/- 0.53% vs. 0.085 +/- 0.35%, P < 0.05). Subjects with, rather than without, deleted mtDNA were at a significantly higher risk for having ALS after adjustment for age and sex. Moreover, male subjects had a higher risk than female subjects of having sporadic ALS. This study suggested that 4977-bp deleted mtDNA is significantly associated with the occurrence of sporadic ALS.     

Degeneration of the human Betz cell due to amyotrophic lateral sclerosis.

The giant pyramidal cell of Betz is known to be partially affected in cases of amyotrophic lateral sclerosis (ALS). Though biochemical, physiologic, and histologic properties of the diseased Betz soma have been investigated, the morphologic status of the largest portion of cell membrane, that of its vast dendritic array, has not. Precentral cortex from six patients, ages 51 to 64 years, who had succumbed to the sequelae of ALS was examined using variants of the Golgi techniques. ALS is shown to be a degenerative disorder which causes a decline in the integrity of the Betz dendritic arbor as well as of the soma of origin. Dendritic fragmentation occurs and numerous irregularities appear, while the number of dendritic spines declines. Concomitantly, a reactive gliosis encroaches upon the soma and may extend onto initial dendritic segments. These observations are remarkably similar to those of the Betz cell in normal aging. The correlation of qualitative histologic data in these conditions is meaningful in light of suggestions that aging and ALS may be related processes. This could provide some clue as to the etiology of Betz cell degeneration and of motor neuron disease.     

Emotional responding in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease, leaving the patient in a partially or completely deafferented state. In an explorative study, we investigated responses to visual socio–emotional stimuli in ALS patients. Pictures from the International Affective Picture System (IAPS) were verbally judged by 12 moderately affected ALS patients with a spinal onset and a slow progression and 18 age–matched controls, and data were compared with psychophysiological responses. Verbal emotional judgments of patients were more positive than ratings of controls. Regarding arousal, patients neutralized extreme pictures, in that they rated calm pictures as more exciting than controls and exciting pictures as more calm. These changes of emotional processing were unrelated to depression or frontal lobe dysfunction. There were no major differences between patients and controls concerning physiological responses to emotional stimuli. We conclude that emotional responses of ALS patients tend to be altered towards positive valence and towards a more balanced arousal state in early stages of the disease. These findings contradict assumptions of a generally negative impact of the disease on the emotional disposition and may indicate compensatory cognitive or neuroplastic changes.     

p.N345K mutation in TARDBP in a patient with familial amyotrophic lateral sclerosis: An autopsy case

We report the neuropathology of a patient with a family history of amyotrophic lateral sclerosis (ALS) and a p.N345K mutation in the transactivation response DNA‐binding protein 43 kDa (TDP‐43) gene (TARDBP). A 62‐year‐old man had bulbar palsy with progressive weakness in the extremities. Neurological examination revealed evident upper motor neuron signs and lower motor neuron involvement corroborated by needle electromyography. The patient was diagnosed as having probable ALS according to the revised El Escorial diagnostic criteria and was eventually diagnosed with familial ALS. At 65 years of age, respiratory failure became critical, and artificial ventilation was initiated. At 70 years of age, the patient died from a urinary tract infection. Histopathological investigation showed Bunina bodies in the remaining motor neurons and anterolateral funicular myelin pallor in the spinal cord. TDP‐43‐positive cytoplasmic inclusions were quite rare in the spinal cord motor neurons, being predominantly present in the glial cells (especially astrocytes) of the spinal cord anterior horn. Although the reason for the preferential vulnerability of spinal glial cells to TARDBP mutations remains unclear, our findings indicate that TARDBP p.N345K mutation could have an influence on the topography of TDP‐43 aggregation.     

Primary lateral sclerosis: Upper‐motor‐predominant amyotrophic lateral sclerosis with frontotemporal lobar degeneration – immunohistochemical and biochemical analyses of TDP‐43

Primary lateral sclerosis (PLS) is clinically defined as a disorder selectively affecting the upper motor neuron (UMN) system. However, recently it has also been considered that PLS is heterogeneous in its clinical presentation. To elucidate the association of PLS, or disorders mimicking PLS, with 43‐kDa TAR DNA‐binding protein (TDP‐43) abnormality, we examined two adult patients with motor neuron disease, which clinically was limited almost entirely to the UMN system, and was followed by progressive frontotemporal atrophy. In the present study, the distribution and severity, and biochemical profile of phosphorylated TDP‐43 (pTDP‐43) in the brains and spinal cords were examined immunohistochemically and biochemically. Pathologically, in both cases, frontotemporal lobar degeneration with ubiquitin inclusions (FTLD‐U) was evident, with the most severe degeneration in the motor cortex. An important feature in both cases was the presence of Bunina bodies and/or ubiquitin inclusions, albeit very rarely, in the well preserved lower motor neurons. The amygdala and neostriatum were also affected. pTDP‐43 immunohistochemistry revealed the presence of many positively stained neuronal cytoplamic inclusions (NCIs) and dystrophic neurites/neuropil threads in the affected frontotemporal cortex and subcortical gray matter. By contrast, such pTDP‐43 lesions, including NCIs, were observed in only a few lower motor neurons. pTDP‐43 immunoblotting revealed that fragments of ～25‐kDa were present in the cortices, but not in the spinal cord in both cases. Genetically, neither of the patients had any mutation in the TDP‐43 gene. In conclusion, we consider that although PLS may be a clinically significant disease entity, at autopsy, the majority of such clinical cases would present as upper‐motor‐predominant amyotrophic lateral sclerosis with FTLD‐TDP.     

An autopsy case of familial amyotrophic lateral sclerosis with a TARDBP Q343R mutation

We describe a Japanese autopsy case of familial amyotrophic lateral sclerosis (FALS) with a TARDBP Q343R mutation. This male patient developed dysarthria at the age of 52 years, and bulbar symptoms progressed, with weakness and atrophy in the extremities. His mental status was normal, but he became bedridden, received artificial respiratory support at 54 years of age, and gradually acquired a locked‐in state and died at 58 years of age. Microscopically, marked diffuse myelin pallor was observed in the anterolateral columns of the spinal cord. The remaining anterior horn cells contained Bunina bodies and phosphorylation‐dependent transactivation response DNA‐binding protein of 43 kDa (pTDP‐43)‐positive neuronal cytoplasmic inclusions (NCIs). Glial cytoplasmic inclusions (GCIs) were also observed. The number of ubiquitin‐ and p62‐positive inclusions was markedly lower than that of pTDP‐43‐positive inclusions. NCIs and many fine dot‐like pTDP‐43‐positive granules in the neuropil were mainly seen in the temporal and motor cortices, and striatum. NCIs were rare in hippocampal granular cells. Immunoblotting of samples from the cerebral cortex using an anti‐pTDP‐43 antibody was slightly different from previous TDP‐43 pathological subtypes.     

Duration of amyotrophic lateral sclerosis is age dependent

Since 1985, we prospectively followed 246 patients with ALS. The relation ship between the age of developing neurological impairment and disease duration was analyzed in 138 patients (86 men and 52 women) who died. Mean disease duration was 4.0 ± 3.8 years for men and 3.2 ± 2.5 years for women. There was an inverse, exponential, relationship between onset age and duration (goodness-of-fit P > 0.05). Mean duration at onset age 40 years was 8.2 ± 5.0 years compared with 2.6 ± 1.4 years for patients aged 61 to 70 years (P > 0.001). The ratio of young (40 years) men to women was 3.6:1. When matched for age, disease duration was the same for patients with bulbar and nonbulbar onsets. We conclude that onset age, but no sex, is the most significant predictor determining disesae duration in ALS. Longer survival in younger patients probably reflects their greater neuronal reserve. © 1993 John Wiley & Sons, Inc.     

Determination of urine thiocyanate in patients with amyotrophic lateral sclerosis

It has been reported that amyotrophic lateral sclerosis-Parkinsonism-dementia in Guam might be related to the eating of Cycas seeds, which contain cyanide. Based on this assumption, we determined the urinary thiocyanate excretion level in patients with ALS and compared this with that of other neurological diseases. The assay method was designed to use column chromatography with Amberlite IRA 402. The thiocyanate level was determined using pyridine-barbiturate method. The 24-h thiocyanate level was higher in the ALS patients of the middle stages than in the normal control group (Wilcoxon's test, P less than 0.02). There were no significant differences between the ALS patient groups of the early and terminal stages, Kugelberg-Welander disease group, Duchenne type muscular dystrophy group and control group. From these results, we concluded that ALS patients were contaminated with cyanide or thiocyanate and that, along with rapid muscular atrophy, the thiocyanate excretion levels were high.     

Co-occurrence of argyrophilic grain disease in sporadic amyotrophic lateral sclerosis

K. Soma, Y.‐J. Fu, K. Wakabayashi, O. Onodera, A. Kakita and H. Takahashi (2012) Neuropathology and Applied Neurobiology 38, 54–60 Co‐occurrence of argyrophilic grain disease in sporadic amyotrophic lateral sclerosis Aims: Phosphorylated TDP‐43 (pTDP‐43) is the pathological protein responsible for amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. Recently, it has been reported that accumulation of pTDP‐43 can occur in the brains of patients with argyrophilic grain disease (AGD), in which phosphorylated 4‐repeat tau is the pathological protein. To elucidate the association of ALS with AGD, we examined the brains from 37 consecutively autopsied patients with sporadic ALS (age range 45–84 years, mean 71.5 ± 9.0 years). Methods: Sections from the frontotemporal lobe were stained with the Gallyas‐Braak method and also immunostained with antibodies against phosphorylated tau, 4‐repeat tau and pTDP‐43. Results: Fourteen (38%) of the 37 ALS patients were found to have AGD. With regard to staging, 5 of these 14 cases were rated as I, 4 as II and 5 as III. pTDP‐43 immunohistochemistry revealed the presence of positive neuronal and glial cytoplasmic inclusions in the affected medial temporal lobe in many cases (93% and 64%, respectively). On the other hand, pTDP‐43‐positive small structures corresponding to argyrophilic grains were observed only in one case. A significant correlation was found between AGD and the Braak stage for neurofibrillary pathology (stage range 0–V, mean 2.1). However, there were no significant correlations between AGD and any other clinicopathological features, including dementia. Conclusions: The present findings suggest that co‐occurrence of AGD in ALS is not uncommon, and in fact comparable with that in a number of diseases belonging to the tauopathies or α‐synucleinopathies.     

Relationship between Bunina bodies and TDP‐43 inclusions in spinal anterior horn in amyotrophic lateral sclerosis

F. Mori, K. Tanji, Y. Miki, A. Kakita, H. Takahashi and K. Wakabayashi (2010) Neuropathology and Applied Neurobiology 36, 345–352
Relationship between Bunina bodies and TDP‐43 inclusions in spinal anterior horn in amyotrophic lateral sclerosis Aims: Amyotrophic lateral sclerosis (ALS) is characterized by upper and lower motor neurone involvement with Bunina bodies (BBs) and TDP‐43 inclusions. To elucidate the relationship between BBs and TDP‐43 inclusions, we examined the spinal cord from 18 patients with ALS. Methods: Five serial sections from lumbar cord were first stained with haematoxylin and eosin to detect BBs and subsequently immunostained with anti‐TDP‐43 antibody. Immunoelectron microscopy was performed on vibratome sections from two cases of ALS. Results: BBs were found in 15 out of 18 cases. TDP‐43 inclusions were found in all the cases. The average incidence of anterior horn cells with BBs and TDP‐43 inclusions relative to the total number of neurones was 17.1% and 46.4%, respectively. The concurrence of both inclusions in the same neurones was found in 15 cases. The incidence of co‐localization of BBs and TDP‐43 inclusions was 15.7% of total neurones. The frequency of TDP‐43 inclusions was significantly higher in neurones with BBs than in those without. Ultrastructurally, TDP‐43‐immunoreactive filamentous structures were intermingled with early‐stage BBs, but not associated with advanced‐stage BBs. Conclusion: These findings suggest that there is a close relationship in the occurrence between BBs and TDP‐43 inclusions.     

Amyotrophic lateral sclerosis and neurosarcoidosis: A case report

Amyotrophic lateral sclerosis (ALS) remains a clinical diagnosis without definable biomarkers. The pathomechanism of motor neuron degeneration in ALS has yet to be elucidated. Here we present a case of limb‐onset ALS, with autopsy findings of Bunina bodies and skein‐like inclusions, as well as sarcoid granulomas predominating among motor neurons. The targeting of the motor neurons by the sarcoid inflammation raises questions regarding the role of cellular immunity in the pathomechanisms for ALS. Muscle Nerve, 2009     

An autopsy case of sporadic amyotrophic lateral sclerosis associated with the I113T SOD1 mutation

A 64‐year‐old man noticed weakness in his arms and dyspnea upon exertion. Four months later he was admitted to our hospital, where muscle atrophy and hyperactive deep tendon reflexes in the arms were observed upon examination. A needle electromyograph study revealed acute and chronic denervation in the extremities, and he was diagnosed as having amyotrophic lateral sclerosis (ALS). Seven months after onset of the disease, he died of respiratory failure. Neuropathologically, neuronal cell loss was observed in the motor cortex, hypoglossal nuclei, cervical and lumbar anterior horns and Clarke's nuclei. Some of the remaining neurons contained neurofilamentous conglomerate inclusions (CIs). A small number of Lewy body‐like hyaline inclusions (LBHIs) were also observed. No the Bunina bodies, skein‐like inclusions or basophilic inclusions were detectable. Tract degeneration was moderate in the dorsal and ventral spinocerebellar tracts, mild in the pyramidal tract, but not discerned in the posterior column. Immunohistochemical examinations revealed that the CIs were strongly positive for phosphorylated neurofilament and moderately positive for ubiquitin and Cu/Zn superoxide dismutase 1 (SOD1). Moreover, a number of phosphorylated tau protein‐positive globose neurofibrillary tangles (NFTs) and threads were observed in the periaqueductal gray matter, oculomotor nuclei and trochlear nuclei. Although the family history was negative for neuromuscular diseases, the neuropathological findings indicated features of familial ALS with a SOD1 mutation. In fact, DNA analysis of frozen‐brain tissue revealed the presence of the I113T SOD1 mutation. This case represents the first one of this mutation in a patient who showed CIs as well as LBHIs in the motor neurons at the same time, in addition to the NFTs in the mesencephalic tegmentum.     

Disease progression in amyotrophic lateral sclerosis: predictors of survival

Predicting the rate of disease progression has become important as trials of new medical treatments for amyotrophic lateral sclerosis (ALS) are planned. Bulbar onset, early impairment of forced vital capacity, and older age have all been associated with shorter survival. We performed a retrospective study to compare survival factors with disease progression in a German ALS population. We analyzed disease progression in 155 patients at intervals of 4 months over a period of 3 years. To evaluate disease progression, the ALS functional rating scale (ALS-FRS), forced vital capacity (FVC%), and a Medical Research Council (MRC) compound score based on a nine-step modified MRC scale were used. We compared age (< 55 years vs. > or =55 years), different sites of disease onset (bulbar vs. limb), and gender to the rate of disease progression and performed survival analyses. No overall significant difference could be detected when analyzing these subgroups with regard to disease progression. By contrast, significantly longer survival was observed in the younger age group (56 months vs. 38 months, P < 0.0001) and in patients with limb-onset disease (51 months vs. 37 months, P = 0.0002). Using Cox analyses values we found that the declines of ALS-FRS, FVC%, and MRC compound score were predictive of survival (P < 0.0001, P = 0.002, and P = 0.003, respectively). Future studies are needed to clarify whether nonspecific factors including muscle atrophy, dysphagia, and coexisting diseases influence prediction of survival in ALS patients. A more precise set of predictors may help to better stratify patient subgroups for future treatment trials.     

Telephone follow-up for patients with amyotrophic lateral sclerosis

The relentless evolution of amyotrophic lateral sclerosis (ALS), a severe neurodegenerative disorder of the upper and lower motoneurons, leads to an increasing level of disability. Most patients, during the course of the disease, become unable to attend the tertiary clinical care center and are thus prevented from enrolling in clinical trials or benefiting from specialized care and management. The main objective of this study was to verify whether the ALS functional rating scale (ALSFRS) could be reliably administered by telephone to patients, when unable to attend the ALS clinic, or to their caregivers. ALSFRS is a validated instrument that assesses the functional status and the disease progression in ALS. We first administered the functional rating scale directly in the clinic to 30 patients, with definite or probable ALS, and to their respective caregivers, and found a very high agreement between the two groups for the total score and the majority of the rating items. Next, we showed, in both patients and caregivers, a high degree of correlation between the total score of the ALSFRS measured by telephone and that reported in the clinic. This indicates that ALSFRS is a reliable instrument for monitoring the disease progression in homebound patients, even when the person contacted by telephone is the caregiver. We also performed a telephone clinic, based on an unstructured interview, with 16 ALS patients at an advanced stage of the disease and unable to attend the ALS clinic. On some occasions, the person interviewed was the caregiver. The symptoms most frequently reported were a worsening of muscle strength, swallowing and breathing problems, constipation, and inability to clear lung secretions. Several patients asked for assistive and adaptive equipment. All patients and caregivers found the telephone clinic very useful and considered it a good complement to the management and care programme.     

Co‐localization of Bunina bodies and TDP‐43 inclusions in lower motor neurons in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron involvement with Bunina bodies (BBs) and transactivation response DNA protein 43 (TDP‐43) inclusions. We examined the spinal cord (n = 20), hypoglossal nucleus (n = 6) and facial nucleus (n = 5) from ALS patients to elucidate the relationship between BBs and TDP‐43 inclusions. BBs were found in the anterior horn in 16 of 20 cases, in the hypoglossal nucleus in all six cases and in the facial nucleus in four out of five cases. TDP‐43 inclusions were found in each region of all the cases. Co‐localization of BBs and TDP‐43 inclusions was found in 15.2% of total neurons in the anterior horn, 29.2% in the hypoglossal nucleus and 17.3% in the facial nucleus. The frequency of TDP‐43 inclusions was significantly higher in neurons with BBs than in those without in each region. Ultrastructurally, TDP‐43‐positive filamentous structures were intermingled with BBs. These findings suggest that there is a close relationship in the occurrence between BBs and TDP‐43 inclusions.     

Sporadic amyotrophic lateral sclerosis of long duration is associated with relatively mild TDP-43 pathology

Recently, sporadic amyotrophic lateral sclerosis (SALS), a fatal neurological disease, has been shown to be a multisystem proteinopathy of TDP-43 in which both neurons and glial cells in the central nervous system are widely affected. In general, the natural history of SALS is short (<5 years). However, it is also known that a few patients may survive for 10 years or more, even without artificial respiratory support (ARS). In the present study using TDP-43 immunohistochemistry, we examined various regions of the nervous system in six patients with SALS of long duration (10–20 years) without ARS, in whom lower motor-predominant disease with Bunina bodies and ubiquitinated inclusions (UIs) in the affected lower motor neurons was confirmed. One case also showed UIs in the hippocampal dentate granule cells (UDG). In all cases, except one with UDG, the occurrence of TDP-43-immunoreactive (ir) neuronal cytoplasmic inclusions (NCIs) was confined to a few regions in the spinal cord and brainstem, including the anterior horns. In one case with UDG, TDP-43-ir NCIs were also detected in the substantia nigra, and some regions of the cerebrum, including the hippocampal dentate gyrus (granule cells). The number of neurons displaying NCIs in each region was very small (1–3 per region, except the dentate gyrus). On the other hand, the occurrence of TDP-43-ir glial cytoplasmic inclusions (GCIs) was more widespread in the central nervous system, including the cerebral white matter. Again, however, the number of glial cells displaying GCIs in each region was very small (1–3 per region). In conclusion, compared to the usual form of SALS, TDP-43 pathology shown in SALS of long duration was apparently mild in degree and limited in distribution, corresponding to the relatively benign clinical courses observed. It is now apparent that SALS of long duration is actually part of a TDP-43 proteinopathy spectrum.