Establishing subtypes of the continuum of frontal lobe impairment in amyotrophic lateral sclerosis

Abstract

This review summarizes recent advances in our understanding of the cognitive changes seen in patients with amyotrophic lateral sclerosis (ALS). Emphasis is placed on identifying and diagnosing subtypes of ALS patients with a continuum of frontotemporal impairment. The reviewed literature focuses on progress made in the past 20 years, with an emphasis on studies measuring abnormalities in ALS patients without dementia. We describe peer-reviewed journal articles using neuropsychological batteries and imaging techniques. We also discuss debates raised in recent meetings. In the past 2 decades, the field of ALS has been transformed in terms of its understanding of extramotor cerebral changes. Particularly in the past 10 years, investigators have invalidated the theory that cognitive abnormality in ALS patients is simply a rarely occurring, frank frontotemporal lobar degeneration syndrome. Instead, a growing body of evidence suggests that ALS patients with comorbid frontotemporal lobar degeneration lie on a spectrum of frontotemporal abnormality, with a large proportion of ALS patients possessing a range of behavioral and cognitive changes. As more investigations use standardized tools measuring behavior and cognition, distinct subtypes may be diagnosed.