Editor,
New headaches in the elderly raise the suspicion of serious pathology such as space occupying lesions, temporal arteritis, or cerebrovascular disease. Alternatively such headaches may simply represent the re-emergence of a previous headache such as migraine. However, benign headache syndromes are increasingly being recognised in this population.
The Hypnic Headache Syndrome (HHS) is a rarely reported disorder of the elderly characterised by recurrent nocturnal headaches of moderate severity that waken patients in a predictable pattern.
Case Report
A 79 year old man had a four week history of headaches occurring predictably 2-3 hours after falling asleep and lasting for about one hour, during which time he sat up believing that this relieved the headache. This recurred every night, once or twice per night, with no daytime headache. He described it as a ‘choking, full’ headache, distributed ‘like a cap’. It was associated with mild nausea but no vomiting or other autonomic features. There was no previous history of headaches.
Past history included ischaemic heart disease, a previous basal ganglia lacunar infarct, controlled epilepsy, hypertension, osteoarthritis, diverticulosis, prostatic hypertrophy, peripheral vascular disease and chronic renal impairment. Examination was normal.
Initial investigations revealed creatinine 134, sodium 129. Hyponatraemia was felt secondary to carbamazepine; a synacthen test and thyroid function were normal. Sodium subsequently normalised. Chest X-ray was normal and a CT scan of Brain showed mild cerebral atrophy and the previous infarct. Other investigations included a normal US abdomen/pelvis, normal CT chest/neck, normal FBP, Liver function tests, C reactive protein, CEA, CA19.9, PSA and urinary catecholamines.
Based on the above we diagnosed Hypnic Headache Syndrome and commenced the patient on 200mg lithium carbonate. Within 48 hours there was sustained complete resolution of the headache. After discharge the general practitioner discontinued the lithium because of concerns about drug interactions, and the headaches returned. Simple analgesia was substituted but headaches continued.
DISCUSSION
Hypnic Headache is a benign nocturnal headache which predominantly affects elderly people. This case illustrates some classic features of the syndrome. Evers and Goadsby 1 reviewed the 71 reported cases giving us the clearest picture of the syndrome to date. 37% were male and 63% female. Mean age of onset was 63 +/− 11 years (range 36-83). Headache was described as: Moderate – 67%, Severe – 31%; Dull – 57%, Throbbing/Pulsating – 38% and Sharp/Stabbing – 5%; Diffuse – 57%, Frontotemporal – 42%, Posterior – 1.6%. Average duration was 67 +/− 44 minutes (range 15-180). Onset was 60 – 120 minutes after falling asleep in 77%. Nausea was reported in 19%. The pathophysiology of HHS is currently theoretical, but associations with the sleep/wake cycle and circadian rhythms form the basis for theories of its nature. Polysomnography has revealed the onset of hypnic headaches may be associated with REM sleep.2 It may be that inactivation of antinociceptive structures, e.g. dorsal raphe, during REM mediates the headache.3
Commonly patients experience the headache at a predictable time each night, suggesting a link with the circadian rhythm, which is orchestrated by the suprachiasmatic nuclei in the hypothalamus (also involved in antinociception). These nuclei produce, among others, melatonin, an important mediator of circadian rhythm. With advancing age the function of the hypothalamus, and thus melatonin secretion, is impaired.4 This could also be involved in the pathogenesis of hypnic headache. Lithium is believed to increase melatonin levels 5 and may explain its mode of action. However, undoubtedly it is more complex than any one of these associations as many different drugs have been tried with variable success. Lithium remains the most effective but is often limited by side effects and interactions, and requires monitoring of plasma concentrations to avoid toxicity. Other reported treatments include indomethacin, caffeine, verapamil, prednisolone, gabapentin, melatonin, and acetazolamide.
Awareness of benign headaches is important to avoid unnecessary investigation but it must be stated that brain imaging and routine biochemical/haematological investigations are usually indicated when presented with new onset headaches in the elderly.
Acknowledgments
The Authors would like to thank Dr J Craig (Consultant neurologist, Royal Victoria Hospital).
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