Cognitive Change in ALS: a Prospective Study

Objectives: To investigate longitudinally the profile of cognitive impairment in nondemented patients with ALS.

Methods: Twenty nondemented patients with ALS and 18 controls were interviewed at two time points separated by a 6-month interval. The extensive battery was designed to accommodate the range of physical disability present in ALS, and included measures of executive, memory, language, and visuospatial functions, everyday behavior, and emotion.

Results: On a test of simple word retrieval (Computerised Sentence Completion Test) patients with ALS became slower over time, while controls became faster at completing sentences with appropriate words. This effect remained when the analysis accommodated for progressive speech disability. Patients with ALS also displayed an impairment in both written and spoken verbal fluency indices (time to think of each word) at both time points, but there was no evidence of deterioration over time. On the Short Inventory of Minor Lapses, carers of patients with ALS displayed increased awareness of cognitive dysfunction in everyday behavior while controls' ratings of their partners decreased. In addition, patients displayed more depressive symptomology (although well below clinical levels) on the second interview vs controls. Patients with ALS also displayed emotional lability at both time points, although this did not increase over time.

Conclusions: Cognitive deterioration in nondemented patients with ALS is a relatively slow process. Selective cognitive impairment in the form of verbal fluency deficits, most likely indicating executive dysfunction, appears relatively early on in the course of the disease, although language functions may become vulnerable as the disease progresses.