Hemicrania continua (HC) is an indomethacin responsive primary headache disorder which is characterized by a continuous and strictly unilateral headache, with cranial autonomic symptoms and agitation during the episodes of pain exacerbation. (Prakash et al, 2018).
- Hemicrania continua (HC) is currently classified as a subtype of trigeminal autonomic cephalalgias (TACs).
- HC can be misdiagnosed easily by clinicians because it can mimic migraine, cluster, and many secondary headaches as well.
- The “hallmark” feature of HC is continuous background headaches.
- HC predominantly affects females.
- During the exacerbation phases of HC, patients usually will complain of feeling of foreign body sensation in the eye (or sand in eye sensation or itching eye).
Possible peripheral and central mechanisms involved in HC
The main structure that is involved in HC is the hypothalamus.
- Activation of certain structures (the contralateral posterior hypothalamus, ipsilateral ventrolateral midbrain, ipsilateral dorsal rostral pons, and bilateral pontomedullary junction).
- Dysregulation of the systems influencing the function of the hypothalamus (orexinergic, somatostatinergic, opioidergic, and serotoninergic systems).
- The cranial autonomic symptoms in HC is the result of hypothalamus malfunction which is responsible for the disinhibition of the trigeminal autonomic reflex.
ICHD-3 diagnostic criteria for the diagnosis of hemicrania continua (Hameed et al, 2022)
Unilateral headache fulfilling criteria 2-4
- Present for greater than 3 months, with exacerbations of moderate or greater intensity.
- Either or both of the following:
- At least one of the following symptoms or signs, ipsilateral to the headache:
- Conjunctival injection and/or lacrimation
- Nasal congestion and/or rhinorrhea
- Eyelid edema
- Forehead and facial sweating
- Miosis and/or ptosis
- A sense of restlessness or agitation, or aggravation of the pain by movement
- Responds absolutely to therapeutic doses of indomethacin.
- Not better accounted for by another ICHD-3 diagnosis.
Exclusion of intracranial and extracranial pathologies that may simulate HC is an essential diagnostic step. This should include a thorough physical and neurological examinations. For this reason, the diagnostic workup should include the following:
- Cranial nerves screening
- MRI study (which should include the screening of pituitary, orbit, and trigeminal pathway).
- MRA (especially in patients who present with a recent neck trauma and neck tenderness).
- Chest x-ray (for smokers and patients with a suspected lung cancer).
Indomethacin response for the diagnosis and management of primary HC (Indotest)
- Injectable indomethacin “INDOTEST” 50–100 mg IM is one way we can use indomethacin for the diagnosis of HC. In this approach, a complete response should be noted within 2 h of injection.
- Oral indomethacin is the typical way that is used for HC diagnosis and is usually started at the dose of 25 mg three times a day and slowly titrated (25 mg tid every 3–5 days) up to 100 mg tid or until the patient gets complete relief.
- immediate reappearance of headache (within 6–24 h) on skipping indomethacin is important in determining the response to indomethacin.
A gradual reduction of the dose is recommended every 3–6 months to find out the lowest effective dose. Dose reduction is usually done by 25 mg every 3 days, until either the pain reappears, or the patient gets completely off indomethacin.
Prakash S, Adroja B. Hemicrania Continua. Ann Indian Acad Neurol. 2018 Apr;21(Suppl 1):S23-S30. doi: 10.4103/aian.AIAN_352_17. PMID: 29720815; PMCID: PMC5909130.
Prakash S, Rawat KS. Hemicrania Continua: An Update. Neurol India. 2021 Mar-Apr;69(Supplement):S160-S167. doi: 10.4103/0028-3886.315976. PMID: 34003161.
Hameed S, Sharman T. Hemicrania Continua. 2022 Jun 27. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 32491500.
https://www.healthline.com/health/hemicrania-continua#:~:text=Hemicrania%20continua%20(HC)%20is%20a,half%20the%20head%E2%80%9D%20in%20Latin.