Pathological laughter and crying in neurological disorders: recognition and treatment.

Pathological laughter and crying is a disabling symptom complex associated with damage to various central nervous system pathways that control the reflex motor component of emotional expression. Many underlying conditions-including neurodegenerative diseases, CNS inflammation, vascular lesions and traumatic brain injury-can be associated with disinhibition of emotional reflex control. This suggests a disruption of anatomical and functional networks, rather than any specific unifying pathological process. There is a wide differential diagnosis, including depression, dementia and other forms of behavioural disturbance. Diagnostic criteria and rating scales can help with clinical assessments and facilitate clinical trials. There is now good-quality evidence for a combination of dextromethorphan and quinidine, with weaker evidence for tricyclic and selective serotonin reuptake inhibitor antidepressants. Pathological laughter and crying is disabling and underdiagnosed but potentially treatable, and its wider recognition is important.