Abstract
Hypnic headache is a rare, primary headache disorder of the elderly, initially described by Raskin in 1988 (1). Based on a series of reports over the past 16 years (1–19), the disorder was included in the 2004 Classification of Headache Disorders of the International Headache Society (IHS) (20). IHS criteria for hypnic headache require headaches of short duration which occur exclusively during sleep without autonomic accompaniments. The pain is generally dull in nature and regularly awakens sufferers during sleep. Though the overwhelming majority of cases occur in the elderly, to date the youngest reported age at onset of hypnic headache was 36 years (21). Herein, we report a 9-year-old fulfilling the diagnostic criteria for hypnic headache.
Case report
A 9-year-old right-handed girl was seen in our paediatric neurology outpatient clinic with a 2-month history of strictly nocturnal headaches. Two to three nights per week, she was awakened between 0100h to 0200h, 5–6 h after falling asleep, with a pounding/throbbing headache of moderate to severe intensity localized to the right frontal and temporal regions of the head. The pain was neither exacerbated by movement nor relieved by rest. Bathing and applying Vicks formula lotion to the affected regions on her head provided minimal relief during the attacks. Out of a concern about medication side-effects, she had not taken any medication. Each attack resolved completely after 30 min, and occurred only once per night. The patient was able to return to sleep and awaken without headache.
The headaches had no known triggering factors. The attacks were not associated with any visual, motor, or sensory disturbances. She denied accompanying symptoms of nausea, vomiting, photophobia, phonophobia, and osmophobia. There were no autonomic features such as lacrimation, nasal congestion, rhinorrhea, forehead/facial sweating, miosis, ptosis, eyelid oedema or conjunctival injection.
She was in 4th grade and performed very well in school. There were no particular stressors at home or at school. She had good sleep hygiene, going to bed at 2000h each night. She denied any medical problems and had no prior history of headaches, sleepwalking or car sickness. There was no family history of headaches. There were no pets at home, and she had not travelled recently. Her general medical and neurological examinations were normal. MRI of the brain and sleep-deprived EEG were un-remarkable, as were routine haematologic tests. Following the initial evaluation, these headaches resolved spontaneously and did not recur by 2 months of follow-up. As a result, neither preventative nor abortive medications were required.
Discussion
The headache history and normal diagnostic tests make a secondary headache disorder most unlikely. The differential diagnosis of short-lived (<4 h), relatively infrequent (<15 days per month) primary headaches in this child includes nocturnal seizures, the trigeminal autonomic cephalalgias (TACs), cough headache, exertional headache, migraine, tension-type headache and hypnic headache. The history and normal sleep-deprived EEG make nocturnal seizures unlikely. Though the TACs enter into the differential of short-lived, nocturnal primary headache, the absence of autonomic features excludes these disorders. Similarly cough and exertional headache are excluded by the absence of these exacerbating factors. While migraine should be considered because of the unilateral and throbbing qualities of her headache, it is unlikely given the absence of aura, nausea, photophobia and phonophobia. Though a history of these features may be difficult to elicit in a younger child, the patient and her mother explicitly denied both these features and the corresponding behaviours (i.e. squinting, turning off lights, avoiding sounds) which suggest them. While tension-type headache can not be excluded, the nocturnal pattern and unilateral distribution are atypical.
The nocturnal pattern, the short duration, and the absence of autonomic symptoms are highly suggestive of hypnic headache. The consistent time of awakening which this patient displays, lead to an alternative term for hypnic headache, ‘alarm clock headache’ (5). The unilateral location and throbbing quality are slightly atypical though nearly 40% of hypnic headache patients have these features (21). Half of Raskin's initial series also had throbbing pain (1). The young age at onset is very unusual.
Though described as a headache disorder of the elderly, the age range of hypnic headache is much broader than generally appreciated. In a review of 71 cases fulfilling diagnostic criteria for hypnic headache, the age at onset range from 36 to 83 years with a mean of 63 years (21). With the exception of two features (occurrence after the age of 50 years at a frequency greater than 15 times per month) the headaches reported by our patient meet the diagnostic criteria for hypnic headache. They are nocturnal headaches of short duration that reliably awaken her from sleep at the same time each night without autonomic or migrainous features. To our knowledge, this is the youngest person reported who fulfills the diagnostic criteria for hypnic headache. As hypnic headache is rare and is often described as a headache disorder of the elderly, it is difficult to assess the frequency of the disorder in children or the extent of underdiagnosis. Nonetheless, clinicians who care for children and adolescents with headache should be aware that the age spectrum of hypnic headache may be more extensive than previously believed.
The vast majority of patients with hypnic headache experience a chronic headache course, ranging from > 3 months to a maximum of 35 years, before a diagnosis is established (1–10, 12–18). Twelve cases in the literature experienced spontaneous relief of their hypnic headaches; none of them have documented time courses (21). In our patient, the length of the hypnic headache period lasted for 2 months and then resolved spontaneously without the use of medication. Whether this shorter period is part of the natural history of hypnic headache or is exclusive of children with this headache disorder remains to be seen.
Prompt recognition of this rare, recurrent primary headache disorder is important because there are effective treatments for hypnic headache. Acetylsalicylic acid shows moderate efficacy in treating acute attacks of hypnic headache (21). Lithium has the greatest efficacy as a prophylactic agent, but is limited by its side-effect profile in the elderly (5, 21). A cup of coffee (caffeine) at bedtime has been effective in many cases and is the most benign prophylactic agent (5). Other prophylactic agents reported to show some efficacy include indomethacin, flunarizine, gabapentin, and acetazolamide (21).