Semantic deficits in amyotrophic lateral sclerosis

Objective: To investigate, and establish neuroanatomical correlates of, semantic deficits in amyotrophic lateral sclerosis (ALS) and amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD), compared to semantic dementia (SD) and controls. Methods: Semantic deficits were evaluated using a naming and semantic knowledge composite score, comprising of verbal and non-verbal neuropsychological measures of single-word processing (confrontational naming, comprehension, and semantic association) from the Sydney Language Battery (SYDBAT) and Addenbrooke’s Cognitive Examination - Revised (ACE-R). Voxel-based morphometry (VBM) analysis was conducted using the region of interest approach. Results: In total, 84 participants were recruited from a multidisciplinary research clinic in Sydney. Participants included 17 patients with ALS, 19 patients with ALS-FTD, 22 patients with SD and 26 age- and education- matched healthy controls. Significant semantic deficits were observed in ALS and ALS-FTD compared to controls. The severity of semantic deficits varied across the clinical phenotypes; ALS patients were less impaired than ALS-FTD patients, who in turn were not as impaired as SD patients. Anterior temporal lobe atrophy significantly correlated with semantic deficits. Conclusion: Semantic impairment is a feature of ALS and ALS-FTD, and reflects the severity of temporal lobe pathology.