Headache and Sleep

The relationship between sleep and headache has been known for more than a century. Headache and sleep disturbances are two of the most common disorders frequently encountered in the same patient.

There is a clear association between headache and sleep disturbances, especially headaches occurring during the night or early morning. The mechanism and causes are complex, multifactorial and poorly understood. An understanding of the anatomy and physiology of both conditions allows for a clearer understanding of this complex relationship and a more rational clinical and therapeutic approach. Recent biochemical and functional imaging studies in patients with primary headache disorders (migraine, cluster headache, chronic paroxysmal hemicrania and hypnic headache) has led to the identification of potential central generators which are also important for the regulation of normal sleep architecture. Hypothalamus, especially the suprachiasmatic nucleus, the noradrenergic locus ceruleus and the serotonergic dorsal raphe nucleus are all involved on the regulation of sleep and the pathogenesis of primary headaches. Sleep and primary headache, especially cluster headache, follow a circadian rhythm. Endogenous melatonin plays a role in the regulation of circadian rhythms, sleep and headache. Additional, both urinary melatonin and plasma melatonin have been shown to be decreased and phase shifted in patients with migraine, menstrual migraine, and status migrainosus. Indirect evidence for the potential role of melatonin in the pathogenesis of headaches comes from the ability of lithium, which is effective in treating both cluster headache and hypnic headache, to enhance absorption of tryptophan and promote its transformation to serotonin, which both serve as precursors for melatonin synthesis. A double-blind study of melatonin treatment significantly reduced headache frequency in episodic, but interestingly not chronic, cluster headache sufferers, although an open-label trial of melatonin as add-on therapy in two chronic cluster headache patients was successful.

Hypnic headache is a rare idiopathic headache syndrome first described by Raskin in 1988. The mean age of patients at onset of hypnic headache is over 60 years. It is a benign syndrome, characterized by a dull headache, occurring only during sleep, and wakes the patient at a consistent time. Evers & Goadsby, in a review on hypnic headache, used the following diagnostic criteria: a. Headaches occur at least 15 times per month for at least 1 month. b. Headaches awaken patients from sleep. c. Usual attack duration of 10-180 minutes. d. Pain not associated with cranial autonomic features. e. Patients should usually not have any of the following features associated with the headache: nausea, photophobia, phonophobia, aggravation of headache with routine physical activity. Besides the nocturnal occurrence of migraine, cluster headache, and paroxysmal hemicrania, other headache conditions reported in the literature with similarity to hypnic headache in that they appear only in close temporal relationship to sleep are the turtle headache, the exploding head syndrome, the nocturnal headache-hypertension syndrome, and the SUNCT syndrome. Several studies have shown that hypnic headache appears to be responsive to treatment with lithium, although side-effects may prohibit its use, especially in the elderly. Other treatments with reported benefit in hypnic headache include caffeine administered before bedtime, flunarizine, atenolol, indomethacin, and nimesulide.

Primary sleep disorders like insomnia P.L.M., hypersomnia, including sleep disordered breathing are also associated with and may cause headache. There are studies that confirm high percentage of cluster headache associated with sleep apnea syndrome. Headache is also a frequent symptom in patients with chronic pain syndromes, fibromyalgia, and depression or anxiety disorders that often cause a disturbance in quality of sleep. Studies documenting sleep disturbances in patients with headache often demonstrate that most of these patients have (1) tension type, "muscle contraction" headache, (2) "mixed-element, tension-vascular headache" or (3) headache associated with chronic substance abuse. The mechanism of the sleep disturbance in these chronic headache populations has therefore been attributed to the presence of an underlying depression or anxiety disorder.

Identifying and classifying the specific headache and sleep disorder in patients with both headache and sleep disturbances can facilitate an appropriate diagnostic evaluation.

Key words: Sleep, headache, hypnic headache.