Paroxysmal hemicrania (PH) is a primary headache disorder belonging to the group of trigeminal autonomic cephalalgias(TACs). Patients typically experience intense lateralzsed headaches with pain primarily in the ophthalmic trigeminal distribution (V1) associated with superimposed ipsilateral cranial autonomic features. PH is distinguished from other TACs by an exquisite responsiveness to therapeutic doses of indomethacin. (Osman & Bahra, 2018).
Paroxysmal hemicrania is a rare but treatable primary headache disorder, meaning that it’s not caused by another condition. The name paroxysmal hemicrania describes the hallmark features of this headache:
Thus, as the name implies, paroxysmal hemicrania is a recurrent one-sided headache usually located around or behind the eye. Episodes of paroxysmal hemicrania typically occur from 5 to 40 times per day and last 2 to 30 minutes. Along with the attacks of one-sided headache, it also causes episodes of redness or tearing of the eye, runny or stuffy nose, sweating or flushing of the face on the same side of the headache (called unilateral cranial autonomic symptoms). In addition, paroxysmal hemicrania resolves completely with taking indomethacin (a medicine in the NSAID family) and this exquisite responsiveness to indomethacin is required to make the diagnosis.
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. (Kumar & Uniyal, 2021).
Osman C, Bahra A. Paroxysmal Hemicrania. Ann Indian Acad Neurol. 2018 Apr;21(Suppl 1):S16-S22. doi: 10.4103/aian.AIAN_317_17. PMID: 29720814; PMCID: PMC5909129.
Paliwal VK, Uniyal R. Paroxysmal Hemicrania: An Update. Neurol India. 2021 Mar-Apr;69(Supplement):S135-S143. doi: 10.4103/0028-3886.315982. PMID: 34003159.
https://americanmigrainefoundation.org/resource-library/parosyxmal-hemicrania/