[A case of multiple sclerosis with pathological laughing caused by pontine base lesions].

We report a case of multiple sclerosis (MS) with pathological laughing for which lesions in pontine bases are considered to be responsible. A 30-year-old man was diagnosed as having MS based on left hemiparesis, and pathological laughing, and MRI findings showing a plaque in the right pontine base as well as several plaques in the bilateral periventricular deep white matter. After remission for 6 years, his pathological laughing exacerbated in association with development of right hemiparesis. A new lesion in the left pontine base was demonstrated by MRI studies in addition to a few supratentorial lesions. Steroid pulse therapy was effective for both pathological laughing and right hemiparesis. We speculate that the anatomical lesion responsible for the pathological laughing is located in the pontine base.