Sleep Fragments

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A surprising cause of cyclical recurrence of nocturnal activity

Contributed by Lukas L. Imbach and Christian R. Baumann, Department of Neurology, University Hospital Zurich, Frauenklinikstrasse 26, 8091 Zürich, Switzerland.

A 48 year-old female Turkish immigrant was referred to our clinic for evaluation of longstanding excessive daytime sleepiness. At clinical presentation the patient reports rare snoring without apnea, short muscle twitches in both arms during sleep onset and an occasional nocturnal short-lasting  holocranial “burning sensation” of mild. Co-morbidities included essential hypertension, chronic fibromyalgia and depression, treated with sertraline 50mg/d. Except for successful surgical decompression for chronic trigeminal neuralgia a few years ago, her personal medical history was uneventful.  At initial assessment, she presented with excessive daytime sleepiness (Epworth Sleepiness Scale: 17/24) and fatigue (Fatigue Severity Scale: 6/7). Clinical examination was unremarkable. 8h polysomnography was performed and showed normal sleep architecture without relevant sleep related pathologies. The MSLT showed an average sleep latency of 3.6 min (first 4 naps) without sleep onset REM. Actigraphy was performed for 2 weeks and is shown below.


What’s your differential diagnosis?

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This actigraphy shows a stereotype pattern of late nocturnal activity with a metronomic regularity onset at 5 a.m. lasting for about 30 minutes.

Recurrent nocturnal activity has a broad differential diagnosis and can be seen in numerous sleep-wake disorders such as restless legs syndrome, parasomnias, or nocturnal epilepsy. However, the observed clock-like regularity narrowed our differential diagnosis to nocturnal primary headaches or circadian rhythm abnormalities.

Based on the strict circadian pattern, this recurrent activity is suggestive for episodic cluster headache: Attacks striking at a precise time of day each morning or night is typical for cluster headache. Attacks last between 15 min and 3 hours and are observed predominantly during sleep with approximately 75% of the attacks occurring between 9 p.m and 10 a.m. [1]. They are associated with either the first or the subsequent REM sleep bout [2], which may be the explanation for the metronomic regularity of pain onset. Pain attacks appear in clusters lasting from one week up to one year. Rarer forms of primary headaches include paroxysmal hemicrania (shorter attacks with higher frequency) or hypnic headache. The latter also present with clocklike regularity (for a review of rare primary nocturnal headaches see [3]).  This patient however reports rather unspecific, mild and episodic holocranial headaches which are not typical for cluster headache.

Advanced sleep phase syndrome is characterized by early sleep onset and awakening earlier than desired [4]. However, as opposed to the presented case, there is typically a phase shift of several hours, with resulting wake times in the early morning hours and most importantly an inability to fall asleep after awakening.

Other differential diagnoses (NREM parasomnia, REM sleep behavior disorder, or nocturnal epilepsy) were video-polysomnographically excluded, and the sleep electroencephalogram did not reveal any signs of epileptiform activity. Furthermore, parasomnias and epileptic seizures usually do not display such a metronomic regularity of onset.
After all above-mentioned examinations, we had further discussions with the patient on the nocturnal activity we have observed during her actigraphy studies. Finally, the patient gave us further insights into her nocturnal life, which led to a more trivial yet surprising explanation of the problem: the ritual morning prayer of the practicing Muslim, which begins at dawn and ends with sunrise, explained the early morning activity, resulting in an uncommon case of behaviorally induced insufficient sleep syndrome.

In summary, it remains unclear whether or not the brief interruptions of sleep account for excessive daytime sleepiness in this patient. Vigilance is probably further diminished by the severe depressive episode.


1. Russell D. Cluster headache: severity and temporal profiles of attacks and patient activity prior to and during attacks. Cephalgia 1981 Dec;1(4):209-16

2. Dexter JD, Weitzman ED The relationship of nocturnal headaches to sleep stage patterns. Neurology 1970  20:513-518.

3. Cohen AS, Kaube H. Rare nocturnal headaches.
Curr Opin Neurol. 2004 Jun;17(3):295-9. Review.

4. Sack, RL; Auckley, D; Auger, RR; Carskadon, MA; Wright, KP; Vitiello, MV; Zhdanova, IV. Circadian Rhythm Sleep Disorders: Part II, Advanced Sleep Phase Disorder, Delayed Sleep Phase Disorder, Free-Running Disorder, and Irregular Sleep. Sleep, 2007 Nov 1;30(11):1484-501.

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