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Trigeminal autonomic cephalalgias (TACs) are a group of primary headache disorders characterised by strictly or predominantly unilateral pain together with ipsilateral cranial autonomic symptoms. The group includes cluster headache, paroxysmal hemicrania, hemicrania continua, and short-lasting unilateral neuralgiform headache attacks classified as SUNCT and SUNA.
These syndromes differ primarily in attack duration and frequency, clinical course and characteristic treatment response. Accurate recognition of the phenotype is therefore essential.
TACs are a small but clinically important group of primary headache disorders. They are unified by activation of trigeminal-autonomic mechanisms, manifesting as unilateral pain together with cranial autonomic features on the same side.
Cluster headache is among the most intense primary pain disorders. A typical attack consists of severe or very severe strictly unilateral pain in the orbital, supraorbital and/or temporal region.
One or more cranial autonomic symptoms usually occur on the painful side: lacrimation, conjunctival injection, nasal congestion, rhinorrhoea, eyelid oedema, facial sweating, miosis or ptosis.
Unlike a typical migraine attack, during which movement commonly worsens pain and the patient often prefers to lie still, cluster headache usually produces marked motor restlessness: patients may pace, rock, or find it difficult to remain seated or recumbent.
Cluster headache shows a striking temporal organisation. Attacks may occur at approximately the same time each day, frequently at night, and active periods may recur seasonally.
During an active cluster period, alcohol can rapidly trigger an attack in many patients, whereas this association typically disappears during remission.
Within a single cluster period, attacks almost always occur on the same side. In most patients the side remains stable, although in some individuals it may alternate between different cluster periods.
Cluster headache is rare compared with migraine. Onset most commonly occurs between 20 and 40 years of age. Historically, a marked male predominance was reported, although sex differences appear less pronounced in more recent clinical series.
The intensity of pain, recurrent nocturnal attacks and anticipation of the next attack may lead to marked anxiety, depressive symptoms and substantial impairment in quality of life.
The diagnosis is clinical. ICHD-3 requires at least five attacks meeting the characteristic temporal and clinical features.
During a smaller part of the active disease period, attacks may be shorter or longer, less severe, or occur somewhat more or less frequently than the formal limits.
An isolated deviation from the “ideal” temporal profile does not necessarily exclude the diagnosis.
In episodic cluster headache, active periods last from 7 days to 1 year and are separated by remissions lasting at least 3 months. In routine practice, cluster periods more commonly last several weeks to several months.
In chronic cluster headache, attacks continue for at least 1 year without remission or with remission periods lasting less than 3 months.
Attack duration, attack frequency, presence of continuous background pain, mechanical triggers, and a characteristic response to indomethacin are particularly useful in practical differential diagnosis.
| Syndrome | Typical duration | Frequency / course | Autonomic features | Triggers / behaviour | Key feature |
|---|---|---|---|---|---|
| Cluster headache | 15–180 min | 1 every other day to 8/day; often in cluster periods | Prominent, ipsilateral | Marked restlessness; alcohol may trigger attacks during an active bout | Response to oxygen and subcutaneous sumatriptan; verapamil for prevention |
| Paroxysmal hemicrania | 2–30 min | Usually more than 5/day | Often prominent | May be associated with restlessness | Absolute response to indomethacin |
| Hemicrania continua | Continuous pain with exacerbations | Continuous unilateral pain for more than 3 months | May occur during exacerbations | Restlessness or worsening with movement may occur during exacerbations | Absolute response to indomethacin |
| SUNCT / SUNA | 1–600 sec | At least 1/day by criteria, often dozens per day | At least one cranial autonomic symptom is required | Often triggered by touch, chewing, washing the face | Very short neuralgiform attacks; lamotrigine is the principal long-term preventive option |
| Trigeminal neuralgia | Fraction of a second – 2 min | Repeated short paroxysms | Usually not dominant | Typical trigger zones: touch, shaving, tooth brushing, chewing | Electric shock-like or shooting pain in one or more trigeminal divisions |
Even a very typical clinical phenotype does not remove the need to consider secondary causes, particularly at first presentation or when the clinical course is atypical.
The choice of urgent investigation depends on the clinical situation and may include CT, MRI and vascular imaging.
See also: new headache and red flags .
TACs are primary headache disorders, but a similar phenotype may rarely occur as a manifestation of structural disease. Neuroimaging therefore remains important at first diagnosis, in atypical cases, or when the neurological examination is abnormal.
In most situations, high-quality brain MRI, with contrast when appropriate, forms the basis of structural assessment.
Particular attention is paid to regions capable of mimicking a TAC phenotype, including the sellar and parasellar regions, cavernous sinus, posterior fossa and trigeminal nerve pathways.
Routine dedicated pituitary imaging was previously proposed for all patients with cluster headache. Later data do not support a separate pituitary MRI protocol for every patient.
A dedicated pituitary protocol is more appropriate when standard imaging shows an abnormality in this region or when symptoms, history or laboratory findings suggest pituitary disease.
MRA or CTA may be appropriate when a vascular cause is suspected, for example with an atypical Horner syndrome, prominent neck pain, suspected arterial dissection or other red flags.
Hormonal testing, sleep studies or other investigations are not required routinely. They are selected when the history, examination or imaging raises a specific clinical question.
Management has three major goals: to stop an individual attack rapidly, to suppress attacks during the beginning of an active cluster period, and to reduce subsequent attack frequency.
The best-supported options are:
An intranasal triptan may be an alternative in selected situations, although onset is generally slower.
Transitional therapy is used to suppress attacks quickly while preventive therapy is beginning to take effect.
Transitional treatment does not replace longer-term prevention.
Verapamil remains the principal preventive medication. Doses may exceed those commonly used in routine cardiovascular practice, so ECG monitoring is required before and during dose escalation.
Alternatives include lithium and topiramate, depending on the clinical context.
Galcanezumab, a monoclonal antibody targeting CGRP, demonstrated efficacy in a clinical trial of episodic cluster headache and is included in EAN guidance as an alternative option for the episodic form.
Its regulatory status for cluster headache differs between jurisdictions. For example, the EMA did not extend the European indication for Emgality to episodic cluster headache. Local registration therefore needs to be considered.
According to EAN guidance, non-invasive vagus nerve stimulation has evidence of efficacy in episodic cluster headache, but comparable efficacy has not been demonstrated for chronic cluster headache.
Invasive approaches are not routine therapy and are considered only for carefully selected patients with very severe, refractory disease in specialised headache centres.
Electrical stimulation of the greater occipital nerve is not recommended by EAN for routine use because of the balance between benefit and complications.
Cluster headache can begin in childhood or adolescence, although it is much less common than in adults. Because of its rarity, diagnostic delay may be particularly pronounced in younger patients.
During pregnancy, treatment choices must be individualised according to gestational age, attack frequency and severity, and potential treatment risks. Oxygen has an obvious advantage as a non-pharmacological acute treatment.
Use of triptans and preventive medication requires an individual decision taking obstetric context and current safety data into account.
When severe disease does not respond to several adequately performed treatment strategies, the diagnosis should be reviewed, a secondary TAC phenotype reconsidered, and management discussed in a specialised headache centre.
SUNCT and SUNA belong to the group of short-lasting unilateral neuralgiform headache attacks. They are characterised by very short attacks of moderate or severe unilateral pain in the distribution of the trigeminal nerve together with cranial autonomic symptoms.
SUNCT is defined by the presence of both conjunctival injection and lacrimation on the side of the pain.
In SUNA, one or both of these two specific signs may be absent — that is, conjunctival injection and lacrimation are not both required.
This does not mean that cranial autonomic symptoms can be absent altogether: at least one ipsilateral cranial autonomic feature is still required for the diagnosis.
The clinical overlap with trigeminal neuralgia can be considerable. Both may produce brief electric shock-like pains triggered by touch or chewing.
Prominent cranial autonomic features and the characteristic attack pattern support SUNCT/SUNA, whereas classical trigeminal neuralgia more typically presents with triggerable electric shock-like pain without such a prominent autonomic component.
In SUNCT/SUNA, structural causes should be excluded, particularly lesions involving the posterior fossa, sellar and parasellar regions, and possible neurovascular compression of the trigeminal root.
The MRI protocol depends on the clinical context, and dedicated sequences for the trigeminal nerve and neurovascular relationships may be used when appropriate.
Because individual attacks are extremely short, conventional treatment of a single attack is generally impractical. The principal strategy is prevention.
The strongest contemporary observational evidence supports lamotrigine as the principal preventive treatment.
Oxcarbazepine is an important alternative. Topiramate, carbamazepine and several other antiepileptic medications may also be considered, although evidence and tolerability vary.
During very frequent, severe and refractory attacks, intravenous lidocaine may be used as transitional treatment in an inpatient setting with appropriate monitoring.
The largest prospective series showed a substantial response in many patients, but this approach requires specialist use.
This page is intended as medical reference material and does not replace individual diagnosis. Regulatory status of medications, availability of specific treatments and local clinical protocols may differ between countries.