Abstract

The site of lesions in Miller Fisher syndrome, especially those causing ataxia, has been controversial. A 50 year old man with features of Miller Fisher syndrome in whom MRI showed enhancing lesions in the spinocerebellar tracts at the level of the lower medulla is reported. Peripheral involvement of cranial nerves was also indicated by an abnormal blink reflex and by clinical manifestations: complete external ophthalmoplegia, bilateral peripheral facial weakness, convergence disturbance, absence of Bell's phenomenon, oculocephalic, and oculovestibular reflex. Abnormal lesions on MRI disappeared and the blink reflex became normal with clinical improvement. The case is regarded as Miller Fisher-Guillain-Barré overlap syndrome, a postinfectious allergic reaction involving both peripheral nerves in the cranium and neuraxis in the spinocerebellar tract. The lesions in the spinocerebellar tracts are responsible for cerebellar ataxia in this syndrome.