Cluster headache (CH) is a type of primary headache that mostly affects adult men. Patients present with recurrent attacks of agonizing, strictly unilateral headaches in the periorbital and forehead region (areas innervated by the trigeminal nerve) that last from fifteen minutes up to three hours. These attacks are associated with ipsilateral symptoms of increased cranial autonomic activity, e.g., lacrimation, conjunctival injection, rhinorrhea, or partial Horner syndrome. Cluster headaches tend to occur in episodic patterns (called cluster periods or cluster bouts) followed by months of remission; they are considered chronic if remission between bouts lasts less than three months. Diagnosis is based on the patient's history, in particular on the exact description and timing of the headaches. In patients with red flag symptoms for headache, secondary headache should be ruled out using an MRI. Acute episodes are treated with 100% oxygen and/or triptans, and verapamil is most commonly used as prophylaxis.
- Agonizing pain
- Strictly unilateral, periorbital, and/or temporal
Quickly developing (within minutes), short, recurring attacks; that usually occur in a cyclical pattern (“cluster periods”)
- May become chronic (less common), with interruptions of less than three months between cluster bouts 
- Attacks often wake patients up during sleep.
- Ipsilateral autonomic symptoms
- Restlessness and agitation
- Perform a .
- Rule out .
- Apply diagnostic criteria for cluster headaches.
- Subclassify into cluster periods. or , based on the characteristics of
- Consider obtaining an initial MRI head to rule out . 
- Consider screening for at diagnosis.
Diagnostic criteria 
Diagnostic criteria for cluster headache
A diagnosis of cluster headache can be established in the presence of ≥ 5 attacks that fulfill criteria 1–4.
- Severe unilateral, orbital, supraorbital, and/or temporal pain for a duration of 15–180 minutes (if untreated)
- At least one of the following:
- Frequency: from 1 every other day to 8 per day
- Not better explained by another diagnosis
See the article on “” for more information regarding differential diagnoses.
- Clinical features
- Treatment: no established treatment for acute attacks
- Prevention: indomethacin
Short-lasting unilateral neuralgiform headache attacks
- Definition: a form of trigeminal autonomic cephalgia characterized by unilateral throbbing pain and autonomic symptoms (i.e., conjunctival injection and/or tearing)
- Unilateral throbbing, piercing, and/or burning head pain with temporal, orbital, or supraorbital distribution
- Attacks are frequent
- At least 1 per day
- Last between 1 second and 10 minutes as single stabs, a series of stabs, or in a saw-tooth pattern
- At least one cranial autonomic symptom is usually present
- Attacks can be triggered without a refractory period
- Diagnosis: mainly clinical following a history of at least 20 attacks; CT or MRI may be used to rule out other causes (e.g., tumor)
- Treatment: no abortive treatment
The differential diagnoses listed here are not exhaustive.
- Treat acute attacks using and/or .
- Initiate prophylactic treatment (e.g., verapamil) to reduce the frequency of attacks.
- Avoid .
- Neuromodulation therapy may be considered for patients with refractory symptoms.
Acute treatment 
- Second-line: if first-line treatment is insufficient or not tolerated
To improve absorption, apply nasal sprays in the nostril unaffected by congestion.
Prophylactic treatment 
- Verapamil (off-label) : usually the first choice despite mixed evidence 
- If verapamil is ineffective or not tolerated, consider either of the following :
- May be stopped after the episodic CH period has ceased, or continued long-term for chronic CH.
- Transitional treatment options: Consider as a until prophylactic agents become effective. 
Transitional therapy with shorter onset latencies may be necessary until prophylactic treatment takes effect.
Neuromodulation is usually reserved for cluster headache refractory to multiple medical treatments.
- Noninvasive neurostimulation: noninvasive vagus nerve stimulation 
Invasive neurostimulation: e.g., sphenopalatine ganglion stimulation and occipital nerve stimulation 
- Disadvantages: uncertain benefits, potential for serious adverse effects
- Advantages: possible acute and prophylactic effects
- Evaluate for red flags for headache, including sudden onset and neurological deficits.
- Consider MRI brain to rule out secondary headache in patients with a new diagnosis of cluster headache or any red flags.
- Initiate oxygen therapy with 100% FiO2 through a nonrebreather mask at 6–12 L/min.
- If oxygen is not available or ineffective, treat with subcutaneous sumatriptan or intranasal zolmitriptan.
- Start concurrent prophylactic therapy (e.g., verapamil) with or without transitional therapy (e.g., glucocorticoids).
- Consider admission to neurology in patients with a first episode of cluster headache, suicidal ideation, or refractory pain.