[1] They are moderate, throbbing, bilateral or unilateral headaches that wake the sufferer from sleep once or multiple times a night.
[3] There is normally no nausea, photophobia, phonophobia or autonomic symptoms associated with the headache.
They commonly occur at the same time every night possibly linking the headaches with circadian rhythm, but polysomnography has recently revealed that the onset of hypnic headaches may be associated with REM sleep.
Included in the differential diagnosis of a new onset nighttime headaches in the elderly is drug withdrawal, temporal arteritis, Sleep apnea, oxygen desaturation, pheochromocytoma, intracranial causes, primary and secondary neoplasms, communicating hydrocephalus, subdural hematoma, vascular lesions, migraines, cluster headaches, chronic paroxysmal hemicrania, headaches due to bruxism,[4] and hypnic headache.
It has also been shown that 1–2 cups of coffee or 100–200 mg of caffeine before bed can prevent hypnic headaches.