Frontotemporal Hypometabolism in Amyotrophic Lateral Sclerosis‐Dementia Complex

Abstract

Positron emission tomography (PET) with fluorine‐18‐2‐fluorodeoxyglucose (FDG) showed bifrontal and bitemporal hypometabolism in amyotrophic lateral sclerosis (ALS)‐dementia complex (n = 6; 5 by PET, 4 by postmortem examination) as compared to nondemented ALS (n = 10) and normal subjects (n = 10). Subjects were of comparable age, ALS patients were of comparable motor severity, and those with dementia were either mildly or moderately impaired at the time of PET study. ALS in all patients was of sporadic nature. Results, using Kruskai‐Wallis comparisons, revealed that normalized mean FDG values for the superior frontal and superior and mesial temporal cortical regions in ALS‐dementia patients were diffusely, symmetrically, and significantly lower (p < 0.005) than values from either the normal or the nondemented ALS group. FOG values for the caudate, putamen, lateral temporal cortex, occipital cortex, and cerebellum did not distinguish the groups. Pathological data in 4 ALS‐dementia complex patients revealed significant gross atrophy of gyri in both frontal lobes. The atrophy was less pronounced in the temporal lobes. The striking microscopic finding was an extensive proliferation of reactive astrocytes in the subcortical white matter. ALS‐dementia brains were free of Lewy bodies, Pick bodies, ischemic infarctions, and Alzheimer pathological changes. Neurobehavioral and neuropsychological data in ALS‐dementia patients revealed decrements in psychometricintelligence, memory, orientation aha attention, verbal fluency, concept formation and abstraction, mental speed and flexibility, and expressive language and writing skills, and relatively preserved stereognosis and visuospatial orientation.