Acute pathological laughter.

Pseudobulbar affect is a condition characterized by uncontrollable episodes of inappropriate laughing or crying that are disproportionate and discordant to the situation at hand. We report on a 16-year-old woman presenting with acute pathological laughter in the context of CNS demyelinating disease. Brain MRI scans fortuitously obtained before and after the onset of this symptom demonstrated acute gadolinium-enhancing lesions in the cerebral peduncles. The etiology of this condition remains theoretical; however, the results here provide further insights into the pathways of emotional control.