Internal Medicine

Trigeminal autonomic cephalgias (TACs)

Short-lasting primary headaches (except HC) with a common clinical phenotype consisting of trigeminal pain with autonomic signs, which may include lacrimation, rhinorrhoea and miosis.


  • Cluster headache (M/C)
  • Paroxysmal hemicrania (PH)
  • Hemicrania continua (HC)
    • Continuous unilateral headache that waxes and wanes in its intensity without complete resolution
  • Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT)/short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA)
Clinical features of Trigeminal Autonomic Cephalalgias, based on studies cohort | Wei, D. Y., Yuan Ong, J. J., & Goadsby, P. J. (2018). Overview of Trigeminal Autonomic Cephalalgias: Nosologic Evolution, Diagnosis, and Management. Annals of Indian Academy of Neurology, 21(Suppl 1), S39–S44. doi:10.4103/aian.AIAN_348_17


Trigeminal-autonomic reflex with parasympathetic activation (hallmark feature):

  • Trigeminal-autonomic reflex: Consists of a brainstem connection between the trigeminal nerve and facial cranial nerve parasympathetic outflow
Schematic pathway representation summarizing the trigeminal-parasympathetic reflex | Cluster headache. (2018). Nature Reviews Disease Primers, 4(1), 18007.

Clinical features

All present with unilateral pain in the distribution of the trigeminal nerve with associated cranial autonomic features ipsilateral to the pain.


Short lasting (except HC) attacks of unilateral severe headache with severe ipsilateral cranial autonomic symptoms.

  • Patient is restless during attack
  • Ipsilateral cranial autonomic symptoms present
Pain location in TACs and migraine. TACs are characterized by orbital and periorbital pain. In paroxysmal hemicrania and hemicrania continua there are large adjacent areas affected. Migraine is largely unilateral but may be bilateral in up to 30% of cases (this has been marked by a lighter-shaded area contralaterally). The two-headed arrow above the diagram indicates side shift, which occurs in specific headache. | Benoliel R. (2012). Trigeminal autonomic cephalgias. British journal of pain, 6(3), 106–123. doi:10.1177/2049463712456355

Ipsilateral cranial autonomic symptoms:

  • Conjunctival injection and/or lacrimation
  • Nasal congestion and/or rhinorrhea
  • Eyelid oedema
  • Forehead & facial sweating
  • Aural fullness
  • Ptosis/miosis
Photograph of a patient with cluster headache during a right-sided painful attack. Note the ipsilateral ptosis and miosis. Additionally there is obvious ipsilateral lacrimation and rhinorrhoea (see upper lip) | Reprinted from Benoliel R and Sharav Y. Trigeminal autonomic cephalgias (TACs). In: Y Sharav and R Benoliel (eds) Orofacial pain and headache. Edinburgh: Mosby Elsevier, 2008; pp.223–254 with permission.


International Classification of Headache Disorders-3 beta (2013) diagnostic criteria:


Overview of the therapeutic targets for trigeminal autonomic cephalalgia conditions, identifying both molecular targets as well as the structural targets for neurostimulation and neuromodulation as outlined in this review. | TG = trigeminal ganglion; CGRP = calcitonin gene-related peptide; SPG = sphenopalatine ganglion; PACAP = pituitary adenylate cyclase polypeptide; TRPV1 = transient receptor vanilloid | Wei, D. Y., & Jensen, R. H. (2018). Therapeutic Approaches for the Management of Trigeminal Autonomic Cephalalgias. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 15(2), 346–360. doi:10.1007/s13311-018-0618-3

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