Pathological laughter, multiple sclerosis, behavioural abnormality

Abstract

Pathological laughter (Fou rire prodromique) is an uncommon clinical manifestation of lesion involving cerebro-brainstem-cerebellar pathways which control the laughter [1]. Existence of laughing centre has been hypothecated in the basal pons. Pre motor cortex, and anterior cingulate gyrus initiates motor component of the laughter and basal temporal and limbic system along with inhibitory impulse from cerebellum influences the emotional content of the laughter via an integrator in the hypothalamus [2, 3, 4]. Various aetiologies in the region of prefrontal, temporal cortex, internal capsule, hypothalamus, thalamus, lesions in and around brainstem and the cerebellar pathways have been known to be associated with pathological laughter [2, 3, 5, 6]. Gelastic seizures seen in hypothalamic hamartomas sometimes mimics pathological laughter [7]. The prevalence of pathological laughter in Multiple Sclerosis (MS) is about 10%. It is found in a chronic progressive phase of the disease and associated with mild cognitive impairment, which carries a bad prognosis [8, 9]. Pathological laughter as a presenting symptom in the relapsing phase of MS due to pontine lesion is rare and on literature search, only one such case could be found [10].