Neuronal loss associated with cognitive performance in amyotrophic lateral sclerosis: an (11C)-flumazenil PET study

Amyotrophic lateral sclerosis (ALS) is a multi-system disorder. Mild cognitive deficits are present in a subgroup of non-demented patients with ALS. Detailed neuropsychological assessments reveal deficits of word retrieval including impairments on tests of verbal fluency and confrontation naming. The PET GABA(A) receptor ligand [11C]-flumazenil is a marker of neuronal dysfunction in ALS. This study used [11C]-flumazenil PET to identify correlations between cortical regions and impairments in word retrieval. Twelve patients with ALS underwent [11C]-flumazenil PET and neuropsychological assessment, including tests of written letter fluency and confrontation naming. Poorer performance on verbal fluency correlated with decreased [11C]-flumazenil binding in a region including the right inferior frontal gyrus, superior temporal gyrus, and anterior insula. Poorer performance on a test of confrontation naming correlated with decreased binding in the left middle frontal gyrus (extending to Broca's area) and left cuneus. This study indicates that [11C]-flumazenil PET can be used to help localize cortical regions associated with cognitive deficits in ALS.