Language functions in incipient cognitive decline in multiple sclerosis.

Although the mechanisms of cognitive impairment in multiple sclerosis (MS) have been extensively studied, evaluation of language functions has been given little attention. In the present study, we evaluated whether impairment of language functions is associated with cognitive decline in MS. We studied naming, reading, and writing performance of two carefully matched patient groups differing only with respect to cognitive status. In language tasks, the patients with incipient cognitive decline not only demonstrated performance slowness but also made more errors than the patients with preserved cognitive capacity and the healthy controls. The comprehensive naming error analysis revealed that the cognitively deteriorated patients produced error types not present in the other two study groups. Contrary to previous suggestions, the present study indicates that impaired language performances in MS are attributable to mild cognitive deterioration rather than to sensory or motor factors. Thus, assessment of language functions should be included in neuropsychological evaluations of MS patients.