Cognition and multiple sclerosis: a historical analysis of medical perceptions.

The earliest descriptions of multiple sclerosis (MS) rarely distinguished cognitive impairment from the general category of "mental symptoms", which also encompassed a broad range of affective disorders. Case-study methods led to disputes about the extent and nature of these symptoms, exacerbated by different national medical traditions. Appropriate scientific methods were only used to investigate cognitive performance in a modest number of studies up to the 1960s, and it was being argued as late as the mid 1970s that affective processes rather than cognitive processes were the key to understanding the psychological aspects of MS. However, the early 1980s, saw major developments in test procedures for the detection of subtle and selective cognitive changes, in the use of brain imaging techniques, and in collaboration between neurologists and neuropsychologists. Pressure to use research findings to improve patients' daily lives suggests a need to reconsider the connection between affective and cognitive processes in MS.