'Fou rire prodromique' as the heralding symptom of lenticular infarction, caused by dissection of the internal carotid artery in a 12-year-old boy.

A 12-year-old, right-handed boy experienced a pathological fit of laughter before a sudden right hemiplegia. Magnetic resonance imaging showed a left basal ganglia infarction, induced by a left internal carotid dissection. Arteriography revealed an underlying fibromuscular dysplasia. This case study demonstrates that cerebral artery dissection can occur in children and that a basal ganglia infarction may be preceded by pathological laughter called 'fou rire prodromique'. The clinical and anatomical relationship of this paroxysmal event are discussed.