Paroxysmal Hemicrania: An Update.

Paroxysmal Hemicrania (PH) is classified under trigeminal autonomic cephalalgia (TAC) as per the International Classification of Headache Disorders (ICHD). Since the first description by 0ttar Sjaastad and Inge Dale in 1974, PH has been reported by many authors. A greater understanding of PH phenotype and pathophysiology has resulted in the evolution of its diagnostic criteria, and management. We tabulated major case series of PH to describe the epidemiology, clinical features and recent updates of PH. PH is a rare headache characterized by daily, multiple paroxysms of unilateral, short-lasting (mean duration <20 minutes), side-locked headache in the distribution of ophthalmic division of trigeminal nerve with associated profound cranial autonomic symptoms. Recent ICHD classification added "restlessness" to the criteria for PH. Pain should completely respond to indomethacin to fulfil the diagnostic criteria of PH. PH should be differentiated from cluster headache, SUNCT/SUNA, and other short-lasting side-locked headaches. Trigeminal afferents possibly produce pain in PH and trigeminal-autonomic reflex explains the occurrence of autonomic features. Recently, a "permissive" central role of the hypothalamus is unveiled based on functional imaging studies. Other Cox-2 inhibitors, topiramate, calcium-channel blockers, epicranial nerve blocks have been shown to improve headache in some patients of PH who cannot tolerate indomethacin. Hypothalamic deep brain stimulation has been used in treatment-refractory cases.