Cognitive function in patients with late stage amyotrophic lateral sclerosis

Background: Subtle cognitive deficits have been found in a substantial percentage of patients with early stage amyotrophic lateral sclerosis (ALS). Cognitive function in later stages of the disease remain to be investigated because the neuropsychological tests that are usually employed, such as written or verbal fluency tests, cannot be performed by those patients because of motor or speech impairment, or both. Methods: In the present study, 11 patients with late stage ALS who were severely physically impaired and matched controls underwent a neuropsychological test battery to explore their cognitive function with respect to disease related functional status. Testing was restricted to tasks that used a binary (yes/no) signal and did not require verbalisation or measures of reaction time to index performance. Results: Although some patients displayed deficits in aspects of executive function, learning and memory, overall test results indicated normal cognitive function. A statistically highly significant negative correlation was found between the performance on two learning and memory tasks and the functional status of the patients. Conclusion: The results of this study indicate a superior performance on learning and memory tasks of patients whose disease had further progressed. This may have important implications for our view on cognitive function in relation to the course of the disease.