Abstract
Well delineated precipitating factors of migraine or incapacitating headaches are well known in the literature. Few peculiar and under-recognized precipitants are crying, shouting, straining in stools, urination, orgasm, childbirth, powerlifting. We present a case of a young student whose laughing aloud is a potent headache precipitant and is consistently reproducible despite normal brain imaging. It is worth mentioning here that laugh-induced headache has recently been assigned a place in the International Classification of Headache Disorders (ICHD-III) in 2018. The proposed pathophysiology in our case could be loud laugh induced Valsalva maneuver raising intra-abdominal and intra-thoracic pressure momentarily causing venous congestion of head presenting as episodic headache. Another plausible explanation related to craniospinal pressure dissociation and the concept of dural elasticity and compliance needs to be explored if the symptoms persist and repeat scans show no pathology. Momentarily rise of intracranial pressure due to vigorous laugh could press the tonsils or distal cerebellar portion to herniate down transiently, causing symptoms and may be back to normal position once the laugh ceases. Social laughter releases enormous endogenous opioids, which is supported using positron emission tomography (PET) and u-opioid-receptor (MOR)-specific ligand carfentanil. A mirthful laugh could trigger a primary laugh headache. The role of modulated opioidergic activity and social mirthful laugh, if connected with such rare headaches requires further study.