Approach
The diagnosis of cluster headache, as with all primary headache disorders, is a clinical diagnosis. Cluster headache is frequently misdiagnosed, most commonly as migraine or trigeminal neuralgia, despite having distinct signs and symptoms. This leads to delays in diagnosis and treatment, sometimes of several years, which can severely affect the patient's quality of life.[1][5]
History
There is no standard test, and diagnosis is based on a detailed clinical history eliciting the features of severe unilateral pain, typically periorbital, with agitation and unilateral cranial autonomic features. Patient symptoms should fulfill International Headache Society (IHS) International Classification of Headache Disorders, 3rd edition (ICHD-3) diagnostic criteria, with any atypical features raising suspicion of a secondary cause.[2] See Criteria.
Symptoms and signs
Pain is unilateral, typically of rapid onset and in the orbital, periorbital, and/or temporal regions. It is excruciating, peaks within minutes, and lasts for approximately 15 to 180 minutes before rapidly subsiding. Patients are often restless or agitated and cannot lie still. By contrast, patients with migraine often report that routine physical activity exacerbates their pain, and remain as still as possible during an attack. Associated cranial autonomic symptoms ipsilateral to the pain include: lacrimation, conjunctival injection or reddening, nasal congestion, rhinorrhea, eyelid and/or facial swelling, ptosis, miosis, and facial and forehead sweating.
The frequency of attacks is from 1 every other day to a maximum of 8 per day, according to ICHD-3 criteria.[2] Higher numbers of attacks should raise suspicion of paroxysmal hemicrania and should prompt an indomethacin trial. Approximately 37% of patients report a predictable time of onset during the day, and 72% report predictable nocturnal attacks, which often wake them from sleep.
Patients might report associated symptoms, such as nausea and vomiting (approximately 28% in one study), and ipsilateral photophobia or phonophobia (approximately 60%).[3] Aura may be present before the attack, most often with visual or sensory symptoms (reported in between 7% and 23% of patients).[3][19][20] This may lead to misdiagnosis as migraine.[1]
Triggers
Triggers for cluster attacks include alcohol (reported in 40% to 80% of patients); sleep (including daytime naps, although attacks are more common during nighttime sleep); circadian disruption; strong smells (such as perfume or paint); sublingual nitroglycerin; and weather changes. In the case of alcohol and sublingual nitroglycerin, cluster attacks will usually be triggered within 1 hour of ingestion, in contrast to migraine, where attacks are triggered several hours later. For patients with episodic cluster headache, triggers do not elicit attacks outside a cluster period.[1]
Exam
Neurologic exam may reveal a persistent partial Horner syndrome or isolated ptosis, even between bouts. However, in most cases the exam will be normal, and any abnormal findings should prompt investigation of a secondary cause.
Laboratory tests
There is no laboratory test to detect cluster headache.
Erythrocyte sedimentation rate (ESR) is checked to exclude giant cell arteritis in all patients with a new onset headache over 50 years of age. Some centers will also check pituitary function with blood tests, including thyroid function tests (TFTs), luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin-like growth factor 1 (IGF-1), cortisol, prolactin, testosterone, estradiol, progesterone, glucose, and growth hormone.
Imaging and other investigations
There is no imaging test to detect primary cluster headache.
Magnetic resonance imaging (MRI) of the head, without and with intravenous contrast with particular pituitary and cavernous sinus views, is recommended at time of diagnosis to eliminate secondary structural causes, such as pituitary lesions or posterior fossa lesions.[21][22] In the presence of a partial Horner syndrome or medically refractory cases, magnetic resonance angiography (MRA) head and neck is recommended.[22][23] In patients with a history of smoking, additional imaging of the apex of the lung is recommended.[22] In practice, computed tomography may be used if MRI is contraindicated, but it is less sensitive and may not detect some lesions.
Other tests include:
Polysomnography for patients with a history that suggests sleep apnea (which has been suggested as being over-represented in patients with cluster headache) and for patients with medically intractable chronic cluster headache[22]
ECG to exclude conduction abnormalities before starting treatment with calcium-channel blocker (i.e., verapamil) or increasing verapamil dose.[24]
Do not routinely request electroencephalography (EEG) in patients with cluster headache. EEG has no advantage over clinical evaluation in diagnosing headache and does not improve outcomes.[25]
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