Table 1.

Main features of the primary headaches treated with nVNS, modified from the ICHD-3, International Classification of Headache Disorders, 3rd edition.

	Hemicrania continua	Paroxysmal hemicrania	SUNA	Primary cough headache
Frequency	Persistent	>5 attacks/24 h	>1 attack/24 h	Unspecified
Chrono-biology of headache	Present for >3 months	At least 20 attacks Episodic: At least two bouts lasting from 7 days to 1 year (when untreated) and separated by pain-free remission periods of >3 months Chronic: Occurring without a remission period or with remissions lasting <3 months, for at least 1 year	Unspecified number Episodic: At least two bouts lasting from 7 days to 1 year (when untreated) and separated by pain-free remission periods of >3 months Chronic: Occurring without a remission period or with remissions lasting <3 months, for at least 1 year	2 attacks
Duration	Constant	2–30 min	1–600 s	1 s–2 h
Description	Strictly unilateral, with exacerbations of moderate or greater intensity	Severe unilateral orbital supraorbital and/or temporal pain	Moderate or severe unilateral head pain, with orbital, supraorbital, temporal, and/or other trigeminal distribution and occurring as single stabs, series of stabs, or in a saw-tooth pattern	Sudden onset. Induced by and occurring only in association with coughing, straining, and/or Valsalva manoeuvre
Indomethacin response	Responds fully to therapeutic doses of indomethacin		NA	NA
Cranial-autonomic symptoms	At least one of the following, ipsilateral to the pain (a)conjunctival injection/lacrimation (b)nasal congestion and/or rhinorrhoea (c)eyelid oedema (d)forehead and facial sweating (e)miosis and/or ptosis If cranial-autonomic symptoms are absent, a sense of restlessness or agitation, or aggravation of the pain by movement is experienced.			NA
	Not better accounted for by another ICHD-3

nVNS, non-invasive vagus nerve stimulation; NA, not applicable.