Kim SM et al. (2007) Relation between cognitive dysfunction and reduced vital capacity in ALS. J Neurol Neurosurg Psychiatry [doi:10.1136/jnnp.2006.111195]

Up to 50% of patients with amyotrophic lateral sclerosis (ALS) have cognitive impairment, most commonly fronto-temporal dysfunction. Some patients seem to have reversible dysfunction in addition to the irreversible degenerative process associated with the ALS. Studies have indicated that ventilatory status could impact on cognitive dysfunction in individuals with ALS.

Kim et al. measured cognitive functions related to the frontal and temporal lobes in 16 patients with early-stage ALS stratified by their vital capacity. Patients with reduced vital capacity (forced vital capacity <80% predicted) performed significantly less well than those with a normal vital capacity (≥80% predicted) in tests of memory retention, retrieval efficacy, spoken verbal fluency and spoken verbal fluency index (which assessed time allocated for the task, time taken, and number of items generated). No such differences were evident when patients were grouped by disease severity rather than vital capacity.

The authors conclude that, in ALS, fronto-temporal dysfunction might be partly the result of potentially reversible secondary effects associated with reduced vital capacity, such as hypoxia or sleep fragmentation. The study was not able to determine the mechanism by which reduced vital capacity affects cognitive function, but a large long-term prospective study is underway to further investigate the relationship between ventilatory status and cognitive function in ALS.