Facial palsy in multiple sclerosis.

Facial palsy occurred in 21 (19.6%) of 107 Japanese patients with multiple sclerosis (MS) during a mean follow-up period of 4.3 years. We observed residual signs of facial palsy in five other patients in whom acute onset was confirmed from medical records. Facial palsy began on average 7.6 years after the onset of MS but in five patients (4.7%) was the first symptom of MS, preceding the next MS symptom by 0.5-3 years. Facial palsy was usually associated with other brainstem signs, while two patients showed only facial palsy 1 and 3 years after the onset of MS. Twenty-one (84.0%) of the 25 patients who underwent brain magnetic resonance imaging (MRI) showed brainstem lesions in the pontine tegmentum ipsilateral to the facial palsy. However, the two patients without other symptoms or signs had no apparent causal lesion on MRI, which suggests difficulty in differentiating idiopathic Bell's palsy from MS- associated facial palsy by MRI, although it has an excellent capacity to detect causal lesions of facial palsy associated with MS.