Hypnic headache (HH) is a rare, sleep-related primary headache disorder. (Primary headache disorders are those that cannot be attributed to another condition.) Its hallmark feature is that it only develops during sleep and wakes the sufferer. Research with sleep studies suggest that hypnic headache develops during rapid eye movement (REM) sleep and that serotonin and melotonin dysregulation may play an important part in the pathophysiology of HH.
The International Headache Society’s International Classification of Headache Disorders, 3rd Edition (ICHD-3), is the “gold standard” for diagnosing and classifying headache disorders. Here are the description, diagnostic criteria, and symptoms of HH as set forth in the ICHD-3
4.9 Hypnic headache
Previously used terms:
Hypnic headache syndrome; ‘alarm clock’ headache.
Frequently recurring headache attacks developing only during sleep, causing wakening and lasting for up to 4 hours, without characteristic associated symptoms and not attributed to other pathology.
A. Recurrent headache attacks fulfilling criteria B-E
B. Developing only during sleep, and causing wakening
C. Occurring on 10 or more days per month for more than three months
D. Lasting 15 minutes or more and for up to four hours after waking
E. No cranial autonomic symptoms or restlessness
F. Not better accounted for by another ICHD-3 diagnosis.
4.9 Hypnic headache usually begins after age 50 years, but may occur in younger people. The pain is usually mild to moderate, but severe pain is reported by one-fifth of patients. Pain is bilateral in about two-thirds of cases. Attacks usually last from 15 to 180 minutes, but longer durations have been described. Most cases are persistent, with daily or near daily headaches, but an episodic subform (on less than 15 days per month) may occur. Although it was thought that the features of 4.9 Hypnic headache were generally tension-type-like, recent studies found that patients could present with migraine-like features and some patients had nausea during attacks.
Onset of 4.9 Hypnic headache is probably not related to sleep stage. A recent MRI study showed grey matter volume reduction in the hypothalamus in patients with 4.9 Hypnic headache.
Lithium, caffeine, melatonin, and indomethacin have been effective treatments in several reported cases. Distinction from one of the subtypes of 3. Trigeminal autonomic cephalalgias, especially 3.1 Cluster headache, is necessary for effective management.
Other possible causes of headache developing during and causing wakening from sleep should be ruled out, with particular attention given to sleep apnoea, nocturnal hypertension, hypoglycaemia and medication overuse; intracranial disorders must also be excluded. However, the presence of sleep apnoea syndrome does not necessarily exclude the diagnosis of 4.9 Hypnic headache.
What does it all mean?
Characteristics of hypnic headache:
- Pain is usually mild to moderate, but sometimes severe
- Headache occurs at a consistent time each night, usually between 1 and 3 a.m.
- Usually lasts 15 to 180 minutes
- Symptoms include only ONE of the following:
- Usually occurs first after the age of 50, although newer data seems to indicate the age of onset to usually be between the ages of 40 and 82
Diagnosis of hypnic headache:
Before assigning a diagnosis of hypnic headache, imaging studies should be performed to rule out any organic issues.
Treatment of hypnic headache:
- Lithium carbonate, 300 mg at bedtime, is frequently used to stop HH, but must be used with caution, especially in the presence of renal disease, dehydration, or use of diuretics.
- Bedtime doses of caffeine, flunarizine (a calcium channel blocker), and indomethacin have been shown effective in some cases.
- Some case studies have shown daily preventive use of topiramate (Topamax) also to be effective in some cases.
Hypnic headache is rare, and should be diagnosed only after any organic physical causes have been ruled out. Hypnic headache begins during sleep and wakes the sufferer, then generally lasts 15 to 180 minutes. Lithium carbonate, caffeine, flunarizine, indomethacin, and topiramate have been successful in treating HH.
Headache Classification Committee of the International Headache Society. “The International Classification of Headache Disorders, 3rd edition (beta version).” Cephalalgia. July 2013 vol. 33 no. 9 629-808 10.1177/0333102413485658
Young W, Silberstein S, Nahas J, Marmura M. Jefferson Headache Manual. Demos Medical Publishing, LLC. 2011.
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