The trigeminal autonomic cephalalgias (TACs) are a group of uncommon primary headache disorders that share similar clinical features but differ in frequency, duration, triggers, and treatment. All TACs share an intense unilateral pain in a trigeminal nerve distribution associated with ipsilateral cranial autonomic features such as lacrimation, conjunctival injection, nasal congestion, and rhinorrhea.
¶ Pathophysiology (by Burish, 2019 and Newman 2015 )
The hypothalamus, trigeminocervical complex, autonomic system, and the vagus nerve all have roles in the pathophysiology of the TACs.
HYPOTHALAMUS
The hypothalamus is a collection of multiple nuclei that assist in many regulatory behaviors, including endocrine, metabolic, and limbic functions. In cluster headache, researchers have hypothesized that the abnormalities start in the hypothalamus and are then followed by trigeminal and autonomic involvement.
Both cluster headache and SUNCT are associated with ipsilateral activation of the hypothalamus (SUNCT has also been reported to have bilateral hypothalamic activation), whereas contralateral hypothalamic activation is seen with paroxysmal hemicrania and hemicrania continua
TRIGEMINOCERVICAL COMPLEX
Perhaps the most direct evidence for involvement of the trigeminovascular system is that complete sectioning of the trigeminal nerve in patients with chronic cluster headache resulted in pain freedom for 10 of 13 patients in a case series. Similarly, occipital nerve stimulation, which activates the cervical dorsal horn component of the trigeminocervical complex, has also shown promise in chronic cluster headache. The pain neuromatrix has also shown changes in cluster headache.
Both cluster headache and SUNCT are associated with ipsilateral activation of the hypothalamus (SUNCT has also been reported to have bilateral hypothalamic activation), whereas contralateral hypothalamic activation is seen with paroxysmal hemicrania and hemicrania continua
AUTONOMIC SYSTEM
The cranial autonomic features of the TACs primarily include parasympathetic overactivation with some evidence of sympathetic inactivation.
VAGUS
Although the exact involvement of the vagus nerve in the TACs is not clear, vagus nerve stimulation can modulate pain in the trigeminal nucleus.
The TACs are cluster headache (CH), paroxysmal hemicrania (PH), short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT)/short-lasting neuralgiform headache attacks with cranial autonomic features (SUNA) and hemicrania continua (HC).
CLUSTER HEADACHE
- Cluster headache is uncommon, affecting approximately 0.1% of the population, yet it is the most common of the TACs.
- Cluster headache affects men 3 to 4 times more often than women, and recent evidence suggests that, at least in some families, a genetic predisposition exists.
- These headaches are excruciatingly severe and a cause of significant disability.
- The vast majority of patients with cluster headache experience the episodic form, in which cluster cycles (the period of time during which attacks occur) last from weeks to months, separated by pain-free remission periods lasting from several months to years.
- When attacks recur for a year or more without remission periods or when the remission periods last less than a month, the term chronic cluster is used.
- During cluster cycles, attacks may recur from once every other day to 8 times a day. Attacks typically recur at the same time each day and may often awaken the patient from sleep, usually within 2 hours after falling asleep.
- The pain is maximal in, around, or behind the eye and may radiate into the ipsilateral temple, jaw, upper teeth, and neck.
- The pain is often described as boring or stabbing, often likened to a hot poker being thrust into the affected eye.
- The pain is excruciatingly severe, peaks rapidly, and lasts from 15 to 180 minutes.
- Attacks might be precipitated by alcohol, smoking, weather changes, altitude, stress, and effort.
PAROXYSMAL HEMICRANIA
- Paroxysmal hemicrania is characterized by recurrent short-lived headaches that are associated with ipsilateral cranial autonomic symptoms and two temporal profiles, chronic and episodic.
- Paroxysmal hemicrania has a higher daily attack frequency, shorter duration of individual attacks, and fewer nocturnal attacks
- Is more often chronic versus episodic.
- It has less propensity to trigger with alcohol but greater propensity to mechanical (eg, neck movement) trigger factors.
- Responsive to treatment with indomethacin.
- The headaches of paroxysmal hemicrania are typically one-sided, with pain in and above the eye, radiating into the ipsilateral temple.
- Headaches recur more than 5 times a day for more than half the time (mean 11) and last 2 to 30 minutes each (median 19 minutes).
- Acute attacks of paroxysmal hemicrania may be triggered by head bending or rotation or by pressing on the C2 root, greater occipital nerve, or transverse process of C4-C5.
SHORT LASTING HEADACHES
- SUNCT and SUNA, the two syndromes within this subcategory, are the rarest of TACs.
- Both SUNCT and SUNA are characterized by ultrabrief paroxysmal headache attacks typically lasting only seconds.
- The head pain in these syndromes is usually of a stabbing nature but may have a lancinating or burning quality, of moderate to severe intensity, and hemicranially located.
- Pain may occur anywhere in the head and is not limited to the orbitotemporal regions.
- As the name implies, SUNCT is associated with conjunctival injection and tearing (lacrimation), whereas SUNA has either one, or will be associated with at least one of the other features that are characteristic of the TACs.
HEMICRANIA CONTINUA
- Hemicrania continua is characterized by unilateral headache of mild to moderate intensity.
- Exacerbations of more severe pain occur at varying intervals (daily to near daily) and last from 30 minutes to 3 days.
- Patients are often restless or agitated during the exacerbations.
- When present, photophobia and phonophobia tend to be ipsilateral to the pain.
- Many patients with hemicrania continua also report superimposed episodes of brief stabbing pains (ice pick–like) and the sensation of a foreign body (eg, sand, grittiness) in the eye on the side of the headache.
https://n.neurology.org/content/74/11/e40#:~:text=The%20trigeminal%20autonomic%20cephalalgias%20(TACs,%2C%20lacrimation%2C%20and%20nasal%20congestion.
(2018). Cluster Headache and Other Trigeminal Autonomic Cephalalgias. CONTINUUM: Lifelong Learning in Neurology, 24 (4), 1137-1156. doi: 10.1212/CON.0000000000000625.
Burish MJ, Rozen TD. Trigeminal Autonomic Cephalalgias. Neurol Clin. 2019 Nov;37(4):847-869. doi: 10.1016/j.ncl.2019.07.001. Epub 2019 Aug 24. PMID: 31563236.
Eller M, Goadsby PJ. Trigeminal autonomic cephalalgias. Oral Dis. 2016 Jan;22(1):1-8. doi: 10.1111/odi.12263. Epub 2014 Aug 8. PMID: 24888770.
Newman, L. C. (2015). Trigeminal Autonomic Cephalalgias. CONTINUUM: Lifelong Learning in Neurology, 21 (4, Headache), 1041-1057. doi: 10.1212/CON.0000000000000190.