Working Memory Functions at Prestroke Stage of CADASIL

Abstract

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leucoencephalopathy (CADASIL) is a severe disease of midadulthood leading to variable neurological symptoms and dementia. The onset of the cognitive decline in CADASIL remains unresolved, and there is considerable debate concerning the presence of cognitive defects at prestroke stage of CADASIL.

To address this issue, we examined the performance of clinically asymptomatic CADASIL patients on tests of working memory. Seven asymptomatic genetically confirmed CADASIL-gene carriers and seven matched controls were administered a battery of neuropsychological tests and computerized working memory (n-back) tests. On the standardized neuropsychological tests, CADASIL patients' performance was significantly impaired on measures reflecting the speed of processing (timed verbal fluency). On the computerized working memory tasks requiring memory for visual shapes, letters, or locations, the CADASIL group showed increased response times and decreased performance accuracy. Specifically, both the accuracy of performance and the response times of the CADASIL group were significantly impaired in the letter task compared to the controls; in all other n-back tasks the CADASIL group’s test results showed a nonsignificant impairment trend. The CADASIL patients’ performances, however, were not disproportionally deteriorated compared to the control group as the mnemonic load increased. The results of the present study suggest that cognitive slowing might be an early manifestation of incipient CADASIL and detectable cognitive decline can be assessed already at the prestroke stage of the disease.

Key words: CADASIL, vascular dementia, neuropsychology, n-back task, working memory