Relation between cognitive dysfunction and reduced vital capacity in amyotrophic lateral sclerosis

Background: Many patients with amyotrophic lateral sclerosis (ALS) with cognitive impairment have fronto-temporal dysfunction. Whereas in some patients with ALS the fronto-temporal dysfunction is undoubtedly due to the degenerative process associated with the disease, in others dysfunction cannot be accounted for by an irreversible degenerative process alone, as it also appears to involve a reversible process. We hypothesised that reduced vital capacity can be a key contributor to the fronto-temporal dysfunction observed in patients with ALS. Objective: To investigate the association between frontotemporal dysfunction and reduced vital capacity in ALS. Methods: 16 consecutive patients who conformed to a diagnosis of definite or probable ALS (El escorial criteria) were grouped by vital capacity, and their clinical characteristics and cognitive functions, including disease duration, attention, executive function and memory, were measured. Results: Patients with a reduced vital capacity performed significantly poorer in memory retention (p = 0.028), retrieval efficacy (p = 0.003), spoken verbal fluency (p = 0.03) and spoken verbal fluency indexes (p = 0.016) than those with a normal vital capacity. Conclusion: The fronto-temporal dysfunction in ALS might be attributable to potentially reversible secondary effects associated with reduced vital capacity, as well as to the primary degenerative process.