What is hypnic headache?If you have a Hypnic Headache you will go to bed pain free, but will usually dread wakening in the middle of the night as you have a severe pain in your head.The key feature is that the pain will waken you from sleep and only from sleep. It does not start while you are awake. I have known cases where the pain is very localised e.g. over one eye, or is a very diffuse pain. The pain can last from minutes to one or two hours. Your sleep is usually disrupted, as the pain is too intense to allow you to settle to sleep once more. The pain can be so intense that you may even try and avoid going to bed for as long as possible. What is strange about this headache is that the pain can waken at about the same time each night - some people use the term "alarm-clock headache" instead of hypnic headache.
How is this "Alarm-Clock" Headache Diagnosed?The diagnosis is based upon review of the headache history. The disorder typically occurs in older people. 1The key feature is that the pain will waken you from sleep and only from sleep. It does not start while you are awake. Other headache conditions can waken from sleep - e.g. migraine headache or cluster headache, but these headaches will occur during the daytime as well. The pain can affect any part of the head, but it is usually very intense. However, in most people, hypnic headache is diffuse and bilateral, and there is no specific part of the head that is most likely to be affected. In each case the headache usually feels the same e.g. if you usually experience a dull, diffuse headache that wakens you from sleep you are not likely to experience a one-sided pain. The pain usually has a dull quality. Throbbing can occur in hypnic head pains, and about one quarter of people will report nausea or intolerance of light or noise. Vomiting is rare. If the pattern of headache wakening from sleep and only ever occurring from sleep is not appreciated then the diagnosis can be missed. Autonomic symptoms like tear flow, nasal congestion or reddening of the eye have not been reported to date.
The pain of Hypnic Headache can be throbbing, severe and feelings of nausea can occur. However, this headache usually occurs for the first time in older age, whereas most people will have had their first migraine long before they reach middle or old age. Before a diagnosis is made, migraine treatments will often have been tried and proven ineffective. People with hypnic head pains may also have had migraine headaches in the past, but the pain which wakens from sleep will be different in timing and quality.
What clinical features have been reported in the medical literature?One series of 17 patients, studied in depth with polysomnography (detailed sleep monitoring of blood oxygen levels, heart rate, blood pressure, breathing rate, video recording and EEG), showed that 70% awoke at a fixed point each night (the alarm clock phenomenon).23 out of 17 experienced the headache during daytime naps (they were asleep at onset!). Eleven out of seventeen had a headache duration of 15 to 30 minutes. The headache can last several hours, but is usually thought to be short-lived in most. A bad headache that wakens from you from sleep is unpleasant and intrusive, as restful sleep is prevented by repeated bouts of headache. As well as poor sleep, you may start to get anxious that something serious is causing the headache. What is the cause of this bad headache wakening me from sleep?In most people, brain scans are normal. However, in my own review of eleven people with Hypnic Headaches, 4 out of 11 cases had signs of small vessel cerebrovascular disease.Small vessel cerebrovascular disease is the type of narrowing of small brain blood vessels that is more common as people age, or happens in hypertension (high blood pressure), diabetes or in prolonged cigarette smoking. From large studies of adults, we know that about 7% of all adults will have this sort of change on a MRI Brain Scan. Small vessel changes occurred in almost 40% of my hypnic headache cases - suggesting an association. I know of one case published in 2003 of a 5x5 cm benign brain tumour (called a meningioma of the posterior fossa) which presented with hypnic headache. The tumour in that case caused a lot of brainstem compression, so presumably the Reticular-Activating System was prevented from working properly.5 The Reticular Activating System controls the sleep-wake cycle, and runs the length of the upper brainstem.3 There is a case of a patient who took a small stroke in the brainstem, and then developed typical hypnic headaches.6 Another case, published in 2008 shows a pituitary tumour causing acromegaly in association with this nocturnal headache disorder.7 There is a case of a lady whose started treatment for high blood pressure which then led to relief of her severe headaches.8 Can anything help this severe headache wakening me every night?The classic treatment is a powerful medicine called Lithium Carbonate.The published cases suggest that about 75% of people will get significant relief with Lithium, and I know that 50% of my own cases became headache-free when using Lithium. Lithium probably works by influencing the levels of melatonin in your brain. Melatonin is involved in the control between sleeping and wakening, so there is some logic using it for a headache syndrome associated with the wakening from sleep. Other medicines that can be used include - Amitryptiline (a type of anti-depressant, even though hypnic headche sufferers are not depressed) and Gabapentin. Topiramate and Indomethacin have also been reported as successful. Caution is always required when using lithium, but the doses required are well below those used in other conditions. Long term complications are therefore less likely. Lithium toxicity can cause tremor, drowsiness, an overactive thyroid gland and polyuria. In the UK, the British National Formulary (BNF) recommends that the Lithium level in the blood needs to be monitored weekly until a stable blood level is reached. Monthly blood levels for 3 months, then 3 monthly lithium levels are needed until treatment is discontinued.
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