[Crazy laughter: first manifestation of a pontine tumour].

Crazy laughter (<<fou rire>>) was first described in 1903 as a prodromic symptom of an ischemic stroke and was later associated with brain lesions having a different location and etiology. We describe the case of a patient with a poorly differenciated pulmonary carcinoma who presented a centropontine image consistent with metastasis, whose initial manifestation was involuntary, persistent and unmotivated laughter that preceded other clinical manifestations. We revised, on the one hand, previous cases described in the literature of pathological laughter in relationship to structural lesions, of vascular or neoplastic etiology, and, on the other, the nervous centers and pathways that control the laughter mechanism.