California Verbal Learning Test performance is associated with fibre impairment in multiple sclerosis: evidence from DTI

Background: Verbal memory deficits are reported frequently in patients with multiple sclerosis (MS). The California Verbal Learning Test (CVLT) is recognized as a standard clinical tool for assessing episodic memory difficulties in MS, but its neural correlates are yet to be examined in detail in this patient population.

Methods: We combined neuropsychological testing, with the CVLT to examine the various stages of the memory process, and DTI analysis, to assess 53 MS-patients with a relapsing-remitting disease course. The frequency of impairment on various CVLT-scores was determined by comparison with 23 age-, gender- and education – matched healthy controls. We investigated the impairment of ventromedial and dorsolateral prefrontal streams, as reflected in the uncinate fascicle (uf) and the superior longitudinal fascicle (slf), as well as the limbic white matter, including the fornix (fx) and the cingulum (cg).

Results: The patients were impaired in all stages of memory. Regression analyses showed that encoding scores were related to impairment of the right uf, while consolidation scores were associated with the degree of impairment of the right fx and the left cg.

Conclusions: Our results provide evidence for segregated fibre pathways subserving encoding and consolidation in MS. Further, the findings support the notion that studies presumably finding retrieval deficits in MS need to account for encoding and consolidation deficits.