Previously used terms:
Hypnic headache syndrome; “alarm clock” headache.
Frequently-recurring headache attacks developing only during sleep, causing wakening and lasting for up to four 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 days per month for >3 months
D. Lasting ≥15 min and for up to 4 hr 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 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.