A Norse contribution to the history of neurological diseases.

Multiple sclerosis (MS) is prevalent in areas with many inhabitants of Scandinavian descent, and a 'Viking gene' hypothesis has been suggested for the dissemination of the disease. It is therefore relevant to search Norse sagas for descriptions of clinical pictures which could have been MS. The saga of Bishop Thorlak describes a woman named Halldora, who suffered from transient paresis between 1193 and 1198. The diagnosis is uncertain, but the story shows that symptoms associated with MS were known in Iceland at the end of the 11th century.