Hypnic headache (HH) is a rare primary headache disorder (primary headache disorders are those that cannot be attributed to another condition.) It's most identifying feature is that it only develops during sleep and wakes the sufferer.
The International Headache Society's International Classification of Headache Disorders, 2nd Edition (ICHD-II), 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-II:
4.5 Hypnic headache
Previously used terms: Hypnic headache syndrome, ‘alarm clock’ headache
Description: Attacks of dull headache that always awaken the patient from asleep.
- Dull headache fulfilling criteria B–D
- Develops only during sleep, and awakens patient
- At least two of the following characteristics:
- occurs 15 or more times per month
- lasts 15 or more minutes after waking
- first occurs after age of 50 years
- No autonomic symptoms and no more than one of nausea, photophobia or phonophobia
E. Not attributed to another disorder1
1 Intracranial disorders must be excluded. Distinction from one of the trigeminal autonomic cephalalgias is necessary for effective management.
The pain of hypnic headache is usually mild to moderate, but severe pain is reported by approximately 20% of patients. Pain is bilateral in about two-thirds of cases. The attack usually lasts from 15 to 180 minutes, but longer durations have been described. Caffeine and lithium have been effective treatments in several reported cases.
What does it all mean?
Characteristics of HH:
- Pain is usually mild to moderate, but sometimes severe.
- Develops during sleep and awakens the sufferer.
- Usually lasts 15 to 180 minutes.
- Symptoms include only ONE of nausea, photophobia (sensitivity to light), and phonophobia (sensitivity to sound).
- Usually occurs first after the age of 50, although more data shows the age of onset to usually be between the ages of 40 and 82.
Headache occurs at a consistent time each night, usually between 1 and 3 a.m.