Objective: To present a rare case of Amyotrophic Lateral Sclerosis (ALS) with cerebellar ataxia onset.

Background: ALS is a fatal neurodegenerative disorder known to affect upper (UMN) and lower motor neurons (LMN). SOD1 mutations are the second most commonly found in familial and sporadic cases. Besides atypical parkinsonism described in ALS‐Parkinsonism Dementia Complex of Guam and ALS-Frontotemporal Dementia with C9orf72 mutations, other movement disorders in ALS are anecdotally reported.

Method: Case report.

Results: A 57-year-old male, with unremarkable family history, presented in 2011 with progressive gait impairment. In the first visit, neurologic examination revealed scandid dysarthria, brisk deep tendon reflexes, bilateral extensor plantar responses and marked limb and gait ataxia. Neuraxis MRI was unremarkable. Acquired ataxia aetiologies were excluded and genetic panels for dominant, recessive and x-linked ataxias were requested with negative results. Over the following years, the cerebellar ataxia became more severe and the patient start to complain of muscle cramps and weakness. Seven years after his first presentation, new UMN and LMN signs were notorious – spastic tetraparesis with brisk gag and jaw jerk reflexes, first interosseous, gastrocnemius and quadriceps atrophy alongside with tongue and quadriceps fasciculations. Electromyography revealed spontaneous activity with fibrillations and fasciculations, however the patient was uncooperative while testing voluntary activity, hence the exam did not meet neurophysiological ALS criteria. Finally, a neuroexome sequencing panel detected he was homozygous for a pathogenic mutation in SOD1 gene, confirming clinically definite ALS. The recent brain MRI showed diffuse cortical and cerebellar atrophy. A genetic consultation was requested for appropriate family members counselling.

Conclusion: ALS was traditionally deemed a pure motor disorder, however neuroimaging and pathologic studies have demonstrated a multisystem involvement, including the basal ganglia, substantia nigra and cerebellum. Specifically, in SOD1 mutations, dentate nucleus and spinocerebellar tracts degeneration has been documented; the reason why rare patients develop cerebellar ataxia and others do not still remains to be elucidated.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/amyotrophic-lateral-sclerosis-with-sod1-mutation-presenting-with-progressive-cerebellar-ataxia/