[Three Japanese cases of hypnic headache]

We described three cases of hypnic headache with successful treatment by lithium carbonate or caffeine. This is the first detail report of Japanese cases. An endocrinological test and rhythm analyses of ambulatory blood pressure (ABP) and heart rate variability in a case suggested possible association between hypnic headache and hypothalamic-pituitary dysfunction. Case 1: A 48-year-old female migraineur complained of new-onset nocturnal headaches. Her headache awakened her from sleep between 1 AM and 2 AM. The headache occurred 3-4 times per week and lasted from 1 hour to 2 hours. The headache were moderate intensity and bilateral dull throbbing pain that located in the forehead to temples. There was no accompanying symptoms such as nausea, phonophobia, photophobia, nor the other autonomic features including conjunctival injection or tearing during the headache attacks. Physical and neurological examinations showed normal results except slight weakness and mild dysesthesia of the left arm due to a vertebral disk herniation at C5/6 level. In the pituitary endocrinological test, the prolactin level remarkably increased in response to the TRH loading. The single cosinor analysis demonstrated significant circadian rhythm of ABP parameters. However, the analysis did not demonstrate any significant circadian rhythm of Holter ECG parameters of time domain analysis and frequency analysis. Receiving 200 mg lithium bicarbonate before sleep, her nocturnal headache completely disappeared. Case 2: A 68-year-old woman had been followed up by her chronic tension-type headache since her forties. At her 66-years, she suffered from a new nocturnal headache. She awoke from sleep by the headache about 3 AM and the headache lasted 30 min. Moderate, dull headache located on her left temple to parietal head, 3-4 times/week. She was able to go back asleep without any medication after spontaneous headache cessation. She first complained the nocturnal headache at the 10 months later of the new headache appearance. She received 200 mg caffeine just before sleep and her headache has been disappeared. Case 3: 70-year-old women had been regularly visited our clinics for her migraine and chronic tension-type headache. She received amitriptyline and her headaches was well controlled. At her 69 years, she complained nocturnal headache. It occured every other day. The headache was moderate pulsative dull pain on the occipital region and lasted 90 minutes without any autonomic symptoms. Headache began between midnight and 1 AM. She told us her new nocturnal headache one year later of the onset. Oral caffeine (200 mg) just before sleep did not improve her headache and caused insomnia. Receiving 100 mg lithium before sleep, her hypnic headache disappeared completely. These three cases are compatible with the diagnostic criteria proposed in ICHD-II. There were some patients with hypnic headache in Japan and neurologists should pay attentions to this form of benign headache, because some beneficial treatments are currently available.