[Imotivated laughter: report of 3 cases].

The authors present three cases where the involuntary, imotivated laughter was a distinct finding. The first patient was a 29-year-old engineer, who had had several bursts of neurologic deficits, either sensitive or motor, which recovered almost completely and was diagnosed as suffering from multiple sclerosis. During and after one of the episodes he presented involuntary laughter and has been like this since then, albeit in much less extension. The second patient was a 35-year-old housewife, who presented several episodes of brain infarction in both hemispheres which were considered as being the result of arteritis. No specific collagen disease was found. The CAT scan showed several hypodense areas in both hemispheres. The third patient was a 52-year-old man of Japanese ancestry who presented three years ago a sudden ischemic stroke with difficulty in the speech and left sided weakness, followed by bursts of imotivated laughter, which persisted since then. Subsequently he had another stroke. He is hypertensive and diabetic. The authors searched the literature for the different causes of involuntary laughter. The occurrence in multiple sclerosis, although reported by several authors is by no means a common finding. In the literature available no case of cerebral arteritis with involuntary laughter could be found. The pathophysiology of this rare symptom was discussed.