DIAGNOSTIC TESTING
Since, by definition, primary headaches are those without underlying organic causes, diagnostic tests and neuroimaging studies are generally not recommended,10,29 especially when the patient history and presentation confirm the required ICHD-II diagnostic criteria. However, neuroimaging is often recommended for a patient with CH or CH-like presentations.8,23,30-32
In a literature review published in 2006, Detsky et al30 examined the correlation between clinical features of headache (as described in the ICHD-II criteria) and intracranial abnormality (as found on CT or MRI). They found an increased risk for serious intracranial abnormalities among study subjects with cluster-type headache. In any patient with chronic headache, they found, abnormal neurologic findings on physical exam represent the greatest predictor for intracranial pathology.30
In a similar study of 1,872 consecutive patients with nonacute headaches who underwent CT or MRI, one of 20 patients with CH was found to have a pituitary adenoma.33 When Favier et al34 reviewed 31 cases of trigeminal autonomic cephalalgia (TAC), including 10 with atypical symptoms, they found that even typical TAC can result from underlying pathologies with rare warning signs and symptoms. In some patients, neuroimaging study results were normal on initial diagnosis, but pathologies were discovered later after symptoms worsened or treatments ceased to be effective, prompting further imaging studies.
In a review of case studies of patients with CLH, Mainardi et al23 found that of 38 patients who fulfilled the ICHD-II criteria for CH, 12 patients (31.6%) had vascular pathologies, 12 (31.6%) had tumors, and five (13.2%) had inflammatory or infectious pathologies. The researchers recommended that all patients with symptoms of CH or CLH undergo cerebral MRI with contrast medium, even though the yield for abnormal findings would likely be low.23 Wilbrink et al32 also found a wide range of pathologies without typical warning signs or symptoms among 56 case studies of TAC and TAC-like syndromes—and recommended that all such patients be considered candidates for neuroimaging.
Recommendations from both the Scottish Intercollegiate Guidelines Network (SIGN)8 and the Taiwan Headache Society treatment guidelines31 include neuroimaging of patients with CH or CLH.
MANAGEMENT
Clinicians may wish to consider referring patients to a neurologist at the initial diagnosis of CH. Patients with atypical symptomatology or neurologic abnormalities, and those who respond insufficiently to treatment warrant a neurology referral for further investigation.
The two treatment strategies for CH are first, symptomatic treatment for acute attacks; and second, intervention to prevent or reduce further attacks and to shorten the cluster period.8,11,14,35,36
Acute Treatment
Acute symptomatic treatment is aimed at aborting the pain within 15 to 30 minutes from headache onset.14,35,36 Currently, it is generally accepted that 100% oxygen and parenteral triptans (5-HT1B/1D, not through the alimentary tract) are considered first-line treatment options.8,11,13,14,35,36
For the majority of patients (particularly those with episodic CH), inhaled normobaric oxygen effectively relieves CH pain within 15 minutes.14,37-39 Oxygen is administered at 6 to 12 L/min with a nonrebreather mask for at least 15 to 20 minutes.8,14,13 Although associated adverse events are rare, oxygen is inconvenient to transport, and it poses a fire hazard. Additionally, high-flow oxygen is contraindicated in patients with chronic obstructive pulmonary disease, as these patients depend on the hypoxic drive and run the risk of respiratory depression.14,40,41
Triptans, too, have been found effective in the acute treatment of CH; administration by subcutaneous injection or intranasal delivery is considered more effective than the oral route due to faster onset of action,11,14,35 and oxygen use may enhance triptans’ efficacy.38 In two 2010 reviews of the relevant literature, subcutaneous sumatriptan, dosed at either 6 mg or 12 mg, provided effective pain relief within 15 minutes for most patients, with no statistical between-dosage differences.11,35 The most common adverse effects were injection-site reactions, nausea, vomiting, dizziness, fatigue, and paresthesias.35
Intranasal zolmitriptan (5 mg and 10 mg) and intranasal sumatriptan 20 mg were also found effective, with significant pain relief within 30 minutes. Bad taste is a common complaint.35 Of note, both sumatriptan and zolmitriptan are contraindicated in patients with cardiovascular or cerebrovascular disease.14
In an older study of efficacy, safety, and tolerability of subcutaneous sumatriptan, almost 70% of patients averaging between one and six CH attacks per day were found to be using more than the 12-mg maximum recommended daily dosage—as much as 36 mg in a 24-hour period.42 Nevertheless, the researchers concluded that subcutaneous sumatriptan was effective and well tolerated without decreased efficacy over one year in patients with CH.
Ergotamine, once commonly used for the acute treatment of CH, has fallen out of favor in recent years due to its vasoconstrictive effects and serious adverse effects profile.14,35 Dihydroergotamine (DHE) is most effective when administered by IV (though not easily accessible for an acute attack); however, evidence regarding its efficacy and tolerability in other forms is insufficient to recommend DHE for acute CH therapy.14,35