Are Painless Cluster Attacks Possible?

Although rare, there are reports of painless cluster attacks or painful attacks without the autonomic symptoms characteristic of cluster headache. The hypothalamus is connected to both the trigeminal nerve and the autonomic nervous system. It’s possible that one of these pathways can be triggered without setting off the other. Because they are separate systems, it’s unlikely that eye watering, eyelid dropping, facial sweating, and nasal congestion or runny nose are caused by the pain itself. Instead, they occur in parallel to the pain. It is possible that one may be triggered without the other.

The authors suggest this is a possible subtype of cluster headache. The ICHD-3 allows for a probable diagnosis when patients report these unusual symptom patterns.

3.5 Probable trigeminal autonomic cephalalgia

Description: Headache attacks which are believed to be a type or subtype of trigeminal autonomic cephalalgias, but which are missing one of the features required to fulfil all criteria for any of the types and subtypes coded above, and do not fulfil all criteria for another headache disorder.

Diagnostic criteria:

    1. Headache attacks fulfilling all but one of criteria A-D for 3.1 Cluster headache, criteria A-E for 3.2 Paroxysmal hemicrania, criteria A-D for 3.3 Short-lasting unilateral neuralgiform headache attacks or criteria A-D for 3.4 Hemicrania continua
    2. Not fulfilling ICHD-3 criteria for any other headache disorder
    3. Not better accounted for by another ICHD-3 diagnosis.

Comment: Patients may be coded 3.5.1 Probable cluster headache, 3.5.2 Probable paroxysmal hemicrania, 3.5.3 Probable short-lasting unilateral neuralgiform headache attacks or 3.5.4 Probable hemicrania continua. Such patients either have not had a sufficient number of typical attacks (for example, only a first bout of cluster headache), or have had a sufficient number but fail to fulfil one of the other criteria.

Description of case reports

56-year old male without autonomic symptoms*

  • symptoms resembled chronic paroxysmal hemicrania
  • lower frequency of attacks
  • 20-30 minute duration
  • temporal features not usually associated with TACs
  • severe, unilateral headache without autonomic symptoms
  • indomethacin-responsive

54-year-old female with painless cluster attacks*

  • symptoms for 15 years
  • autonomic symptoms
  • seven to eight times per day
  • periods of 20-30 days
  • no headache

30-year old male with painful and painless cluster attacks*

  • cluster headache attacks with cycle duration of 30-35 days
  • between cycles, daily attacks without pain for 10-15 minutes

Deceased male without autonomic symptoms*

  • attacks from age 18 to 35
  • two to three attacks daily lasting 15-30 minutes
  • no autonomic symptoms
  • no remission period

*Biological relatives

Future implications

The current diagnostic criteria does not cover every possible variation of symptoms. That’s why probable diagnoses are included. If enough patients begin to experience (and report!) symptoms that do not fit the current criteria, it will capture the attention of researchers. Over time, with enough study, the criteria for existing diagnoses may change or new diagnoses added. Case reports are helpful, in that they can alert doctors to possible symptom pattern they might not have considered. However, a handful of reports is hardly sufficient evidence to dramatically change the ICHD-3.


  1. International Headache Society. Probable cluster headache. International Classification of Headache Disorders 3rd edition. Accessed online 2 Jun 2019 at
  2. Leone, M., Rigamonti, A., & Bussone, G. (2002). Cluster Headache Sine Headache: Two New Cases in One FamilyCephalalgia22(1), 12–14.
  3. Pugach, N (2008). An unusal form of TAC-TAC sine autonnomic phenomena. J Headache Pain (2008) 9:331-332.

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