Breaking Down Trigeminal Autonomic Cephalalgias

Breaking Down Trigeminal Autonomic Cephalalgias

While saying Trigeminal Autonomic Cephalalgias (TACs) three times fast is not easy, what’s truly difficult is diagnosing and treating these rare headache conditions. Receiving a correct diagnosis is the first step in achieving pain relief and improving quality of life for people with these conditions. To do this, it’s necessary to understand the similarities and differences of the five subtypes of TACs.

TACs are characterized by attacks of pain on one side of the head along with autonomic symptoms on the same side, such as a tearing, red eye, stuffy or runny nose, and facial sweating. Most of the TACs can be broken into two forms: episodic and chronic. What differentiates the conditions from one another are the length, frequency, severity, and treatment of attacks. The conditions that are classified as Trigeminal Autonomic Cephalalgias are

  1. Cluster Headache
  2. Paroxysmal Hemicrania
  3. Short-lasting Unilateral Neuralgiform Headache Attacks
  • SUNCT (Short-lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing)
  • SUNA (Short-lasting Unilateral Neuralgiform Headache Attacks with Cranial Autonomic Symptoms) 

  4. Hemicrania Continua (Remitting and Unremitting) 

  5. Probable Trigeminal Autonomic Cephalalgia (This is the diagnosis when attacks don’t fulfill all criteria for other TAC types)

Length & Daily Frequency of TACs

Cluster Headache attacks have the longest duration compared to the other forms, lasting 15 minutes to three hours, and they can recur up to eight times in a day

SUNCT and SUNA attacks last mere seconds to ten minutes but can recur a whopping 200 times in 24 hours.7

Paroxysmal Hemicrania attacks may last for 2-30 minutes up to 40 times a day.

Hemicrania Continua is the standout for both length and frequency. Someone with this condition may have constant, dull pain with spikes of sharp, throbbing pain that last anywhere from 30 minutes to three days

The Severity of Pain & Treatment of TACs 

The severity of pain is often comparative between Cluster Headache, Paroxysmal Hemicrania, and SUNCT/SUNA. These conditions cause sudden attacks of severe pain that is stabbing or throbbing. The piercing or stabbing sensations of cluster headaches may be more severe. Cluster Headache and Paroxysmal Hemicrania also come with restlessness and agitation. People with these conditions may pace, rock back and forth, or hit themselves on the head’s affected side. The severity of Hemicrania Continua seems to wax and wane from mild to severe

Indomethacin is an anti-inflammatory medication used not only to treat some forms of TACs but to aid in diagnosis. Sometimes the only way to differentiate between Cluster Headache and Paroxysmal Hemicrania is to administer indomethacin. Both episodic and chronic Paroxysmal Hemicrania have a “complete and dramatic response” to indomethacin, which has helped patients who suffered for years go completely pain-free with a daily dose of the medication. Hemicrania Continua also responds to indomethacin, but not as well. A Cluster Headache diagnosis can be confirmed if there’s no improvement after taking indomethacin or if an attack can be induced with histamine or nitroglycerin

SUNCT/SUNA is often easier to pinpoint because the intense pain lasts seconds or minutes, but that also makes the attacks harder to treat with abortive therapies. Daily treatment with lamotrigine is effective for up to 68% of people with SUNCT. Topiramate can also work well for those with SUNCT or SUNA

Treatments for cluster headaches are quite unique compared to other TACs. High-flow oxygen at a flow rate up to 15 L/min with a nonrebreather mask aborts attacks within 15-20 minute for most patients.9 Both abortive and preventive cluster headache treatment using the psychedelic compounds of psilocybin mushrooms and LSD are being studied for their remarkable effects. Cluster Headache is the only form of TACs that has a circadian periodicity. That means that people with this condition experience head pain linked to their biological clock, including during seasonal changes. The attacks follow a 24-hour pattern and tend to wake patients from their sleep.1 Unlike other TACs, cluster headache patients often know the exact hour or minute attacks will occur. 

How Rare are TACs? 

All types of Trigeminal Autonomic Cephalalgias are considered rare in the medical world. Cluster Headache is the most common with a prevalence of one per 1,000 people or .1%, and SUNCT affects around 6.6 out of 100,000 people.6 The number of those with Hemicrania Continua and Paroxysmal Hemicrania is so low that there is not currently estimated prevalence of the disorders in the U.S. population or worldwide. The low incidences of TACs makes it difficult for people with these conditions to get a timely and correct diagnosis. However, gender may help break down the odds of each. 

The estimated male to female ratio of these headache disorders include1

  • Cluster Headache: 3:1
  • Paroxysmal Hemicrania: 1:1
  • Hemicrania Continua: 1:2
  • SUNCT/SUNA: 1.5:1 

However, gender should not be the identifying factor in diagnosis. Women with Cluster Headache have historically faced higher rates of misdiagnosis with migraine.

 What to Do If You Think You Have a TAC Type 

Many people with headache disorders experience delayed diagnosis or misdiagnosis. The higher prevalence of migraine disease makes medical professionals more prone to choosing a migraine diagnosis. However, if your attacks align with a type of Trigeminal Autonomic Cephalalgia discussed above, contact your doctor and ask for a referral to a headache specialist or neurologist if you don’t already have one. The way you respond to treatments for headache disorders can further narrow down the correct diagnosis so that you can enjoy a more pain-free life. 

Headache medicine is continually evolving, and new treatments become available each year. Advocate for yourself at every appointment, and don’t give up on your journey to a better quality of life. 


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  1. Wei, D. Y., & Jensen, R. H. (2018). Therapeutic Approaches for the Management of Trigeminal Autonomic Cephalalgias. Neurotherapeutics, 15(2), 346-360. doi:10.1007/s13311-018-0618-3
  2. Bahra, A., & Osman, C. (2018). Paroxysmal hemicrania. Annals of Indian Academy of Neurology, 21(5), 16. doi:10.4103/aian.aian_317_17
  3. Bogucki, A. (1990). Studies on Nitroglycerin and Histamine Provoked Cluster Headache Attacks. Cephalalgia, 10(2), 71-75. doi:10.1046/j.1468-2982.1990.1002071.x
  4. Gay-Escoda, C., Mayor-Subirana, G., Camps-Font, O., & Berini-Aytes, L. (2015). Sunct syndrome. Report of a case and treatment update. Journal of Clinical and Experimental Dentistry. doi:10.4317/jced.51854
  5. Matharu, M., & Levy, A. (2018). Short-lasting unilateral neuralgiform headache attacks. Annals of Indian Academy of Neurology, 21(5), 31. doi:10.4103/aian.aian_356_17
  6. Nagel, M. A., Burns, T. M., & Gilden, D. (2016). SUNCT headaches after ipsilateral ophthalmic-distribution zoster. Journal of the Neurological Sciences, 366, 207-208. doi:10.1016/j.jns.2016.05.027
  7. May, A., MD, Cohen, A. S., MD, & Goadsby, P. J., MD. (2019, July 26). Pathophysiology of the trigeminal autonomic cephalalgias (J. W. Swanson MD, MHPE & R. P. Goddeau DO, FAHA, Eds.). Retrieved July 31, 2020, from 
  8. International Headache Society. (2019). Trigeminal autonomic cephalalgias (TACs). Retrieved July 31, 2020, from
  9. Tepper, S. J., Duplin, J., Nye, B., & Tepper, D. E. (2017). Prescribing Oxygen for Cluster Headache: A Guide for the Provider. Headache: The Journal of Head and Face Pain, 57(9), 1428-1430. doi:10.1111/head.13180



Ashley S. Hattle has experienced episodic cluster headaches since 2007 and is a medical writer based in Southwest Michigan. She’s the award-winning author of Cluster Headaches: A Guide to Surviving One of the Most Painful Conditions Known to Man. Hattle is a passionate advocate for those living with cluster headache and other neurological disorders. Her episodic cluster headaches took over her life every six months for up to three months at a time, taking her away from school, work, friends, and family. After years of struggling to live with the condition, Hattle found Clusterbusters, a nonprofit dedicated to helping cluster headache patients, where she met her husband, who has chronic cluster headaches.
Hattle has given presentations at many conferences, including the American Headache Society Symposium, Mississippi Headache Symposium, Association of Migraine Disorders Symposium, and the Headache Cooperative of New England Annual Meeting. She has written for many publications online and in print on various topics, specializing in medical content.

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