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Objective: Cognitive decline is common in patients with amyotrophic lateral sclerosis (ALS), especially in carriers of the mutation C9ORF72HRE. However, cognitive impairment is poorly understood in carriers of mutations in other genes causing ALS. We performed a comprehensive neuropsychological testing in patients with mutations in the SOD1 (mSOD1) gene.

Methods: We examined 5 cognitive domains in 48 symptomatic patients with either hereditary or sporadic ALS. These were compared with 37 matched controls.

Results: Carriers of SOD1-mutations and sporadic ALS had circumscribed deficits, but in a pattern different from C9ORF72HRE. All groups had deficits in working memory, although mSOD1-carriers significantly outperform sporadic ALS and C9ORF72HRE in an attention-driven visuospatial task involving copying a complex figure. Carriers of the D90A-SOD1 mutation overall performed as well as or better than carriers of other SOD1-mutations, except complex working memory. Bayesian analyses suggest (with evidence of moderate strength) that tasks involving the language domain did not differ between controls, mSOD1 and sporadic ALS.

Conclusion: Distinct cognitive impairments are prevalent in different ALS-syndromes and vary in patients with different pathogenic SOD1 mutations. The type and degree of impairment differed depending on genotype and was significantly least pronounced in patients homozygous for the D90A SOD1 mutation. The presence of cognitive deficits may influence optimal clinical management and intervention. We propose that cognitive assessment should be included in the routine examination of new patients suspected of ALS. Neuropsychological assessment is an under-recognized outcome parameter in clinical drug trials.