Reduced Occipital Cortex Excitability in Amyotrophic Lateral Sclerosis

Purpose: In addition to motor cortex involvement, sensory abnormalities have been demonstrated in amyotrophic lateral sclerosis (ALS), including structural and metabolic alterations in the occipital cortex. The aim of this study was to examine occipital excitability changes in ALS. Methods: Twenty-one patients with ALS and 16 healthy subjects were enrolled into the study. Phosphene experience and phosphene threshold were studied to assess occipital excitability. Cognitive function was evaluated in both groups by means of Montreal Cognitive Assessment and Addenbrooke's Cognitive Examination-Revised visuospatial score tests. Results: Phosphene was experienced in 13 (81.3%) healthy subjects and 9 (42.9%) patients with ALS ( P = 0.04). The mean phosphene threshold was not significantly different between the two groups. No correlation existed between phosphene threshold and motor cortical excitability parameters, ALS Functional Rating Scale Revised, Montreal Cognitive Assessment, and Addenbrooke's Cognitive Examination-Revised scores. Conclusions: Visual cortex is affected, and the occipital excitability is reduced in ALS, without any relation to motor cortical excitability changes, providing another clue suggestive of sensory involvement in ALS.