Pathological laughter and crying: A case series and proposal for a new classification

BACKGROUND: Disorders of laughter and crying (DLC) are seen in several neuropsychiatric conditions. Their nomenclature remains under debate. METHODS: We present the clinical and imaging findings of 17 patients with DLC and introduce a new classification based on phenomenology and pathogenesis. According to intensity and frequency of laughter and crying (observed behavioral output), patients were divided into hypoactive or hyperactive DLC and subdivided into 5 subtypes: sensory (positive and negative), motor (positive and negative), and mixed. The sensory subtype is represented by disorders of "feeling processing; whereas the motor subtype is represented by disorders of "emotion processing." "Positive" and "negative" describe elicitation by irritative vs destructive lesions, respectively. RESULTS: Among the patients studied, DLC resulted from ischemic stroke (n = 12), intracerebral hemorrhage (n = 2), gunshot wound (n = 1), amyotrophic lateral sclerosis (n = 1), or vestibular migraine (n = 1). Ten patients had lesions in the brainstem, 4 in the cerebral hemispheres, and 2 in subcortical-diencephalic structures. Six patients had negative motor DLC, 5 had positive sensory DLC, 4 had negative sensory DLC, and 2 had positive motor DLC. Phenomenology changed or progressed to mixed DLC in 7 patients. CONCLUSIONS: This novel phenomenological and pathomechanistic nomenclature explains all subtypes of DLC in neurologic, medical, and psychiatric conditions. Future studies are needed to validate it prospectively.