Pathological laughter in Gilles de la Tourette syndrome: an unusual phonic tic.

Patients with Gilles de la Tourette syndrome (GTS) can display socially inappropriate behaviors as part of their multiform tic phenomenology. Pathological laughter (PL), defined as the presence of episodic and contextually inappropriate outbursts of laughter, has been detailed as a symptom of various psychiatric and neurological conditions. We present a case series of eight subjects diagnosed with GTS who reported PL as part of their tic repertoire. All subjects experienced PL as a simple phonic tic, accompanied by characteristic premonitory urges and significant impairment in social interactions. In addition, all patients presented with multiple tic-related symptoms (mainly self-injurious behaviors and echolalia, n = 7; palilalia, n = 6; coprolalia/mental coprolalia, n = 5), and six patients had comorbid conditions (in particular obsessive-compulsive disorder/behaviors, n = 7; attention-deficit hyperactivity disorder, n = 4). We suggest that the pathophysiological mechanisms underlying the expression of PL as a tic could involve a dissociation between frontostriatal and limbic networks.