Abstract
Background
Exploding head syndrome (EHS) is characterized by attacks of a sudden noise or explosive feeling experienced in the head occurring during the transition from wake to sleep or from sleep to wake.
Methods
We present six new cases extending the clinical experience with the syndrome. We also reviewed all available cases from the scientific literature and evaluated the typical features of EHS.
Results
The female to male ratio is 1.5 to 1. The median age at onset is 54. In average, one attack per day to one attack per week occurs. Some patients suffer from several attacks per night. In about half of all patients, a chronic time course can be observed but episodic or sporadic occurrence is also common. The most frequent accompanying symptoms beside the noise are fear and flashes of light. Polysomnographic studies do not reveal any specific sleep pattern associated with EHS. Tricyclic antidepressants are helpful in some patients. However, most patients do not need treatment because of the benign nature of the syndrome.
Conclusion
EHS is a well‐defined disease entity with a benign nature.
Introduction
Criteria of exploding head syndrome according to the International Classification of Sleep Disorders (5).
Note: In a minority of cases, a flash of light or myoclonic jerk may accompany the event.
Here, we report six further cases of EHS and try to give a complete review of all published cases to date. Furthermore, we discuss possible pathophysiological mechanisms of the syndrome.
Case reports
Demographic data, associated symptoms, and concomitant diseases of the six new exploding head syndrome patients.
All patients suffered from an explosion-like feeling in the head at the transition from wakefulness to sleep lasting for one second maximum. The sensation was gone by the time the patients were wide awake. The sensation was unpleasant and associated with an anxious feeling.
Patient 1 experienced EHS nearly every evening. An external polysomnography (PSG) was unremarkable without any evidence of parasomnia or a sleep-related breathing disorder. During PSG, no attack occurred. Despite his problems falling asleep, this patient reached a score of 6 on the Epworth Sleepiness Scale (out of a possible score of 24), suggesting no increased daytime sleepiness. His chronic tension-type headache partially responded to amitriptyline (25 mg in the evening, higher doses were not tolerated because of dizziness). Amitriptyline had no significant effect on his EHS. The patient was informed about the harmlessness of EHS and did not wish any other treatment attempts.
Patient 2 suffered from EHS with increasing frequency. On first examination, EHS attacks occurred one to several times each night. With amitriptyline (up to 50 mg in the evening) attack frequency significantly decreased to one to three attacks per week. Treatment caused side effects (dry mouth, dizziness) and was stopped after six weeks without exacerbation. At follow-up examination four years later, the patient reported further remission of EHS with sporadic attacks every few months. Further treatment was not necessary.
Patient 3 suffered from mild EHS with infrequent attacks every few months.
Patient 4 also suffered from mild EHS with infrequent attacks only once or twice a year. Obstructive sleep apnea had been diagnosed with PSG prior to EHS onset and was treated with continuous positive-airway pressure therapy for several years. Follow-up examination five years later revealed no increase of attack frequency. In patients 3 and 4, no treatment was required.
Patient 5 experienced one single attack every evening. Amitriptyline (25 mg in the evening) caused almost complete remission. He was lost to follow-up after three months.
Patient 6 regularly suffered from up to eight attacks per night, causing insomnia. Treatment attempts with zopiclone and bromazepam had been without success. Treatment with amitriptyline and PSG were recommended. She was lost to follow-up.
Review of the literature
We performed a literature search in MedLine, Science Citation Index, and Embase with the phrase “exploding head syndrome.” All cases published in the literature and fulfilling the criteria of Table 1 were collected (3,4,7–17). Our own six cases were included. In total, data from 76 cases could be analyzed.
Demographic data of all published and cases with exploding head syndrome (missing data from some patients for some variables possible).
For the largest case series (n = 40), there are incomplete data for concomitant diseases (4). The other patients (n = 36) most frequently also suffered from arterial hypertension (n = 8) and from primary headaches (10 patients, one with three different primary headaches). Most common primary headache was migraine without aura (n = 6). Migraine with aura, chronic migraine, primary stabbing headache, chronic tension-type headache, primary exercise headache, and primary headache associated with sexual activity were present in one patient each. Other concomitant diseases were restless legs syndrome (n = 2), and suspected epilepsy (n = 1). As a symptom, tinnitus was associated in three patients.
PSG was performed in 16 patients, detecting obstructive sleep apnea (OSA) in one patient (16). Eight patients experienced at least one EHS attack during PSG. The largest study conducting PSG in EHS examined nine patients, six of them for one to two hours in the daytime following one night’s sleep deprivation and three of them for 24–48 hours in their homes using a portable tape recorder (8). In this study, all EHS attacks (24 attacks in five different patients, two of them examined in the daytime) took place when the patients were awake and relaxed. Apart from alerting effects (alpha blocking, increase in beta and electromyography (EMG) activity), there were no specific pathological changes in EEG (8). Three other patients experienced EHS attacks during PSG (14–16). In these, attacks evolved at the transition from wakefulness to sleep (non-rapid eye movement (NREM) stage 1 sleep) and from NREM stage 2 sleep (14), at the transition from NREM stage 1 sleep to wake (15), and from NREM stage 1 sleep and NREM stage 2 sleep (16). In one patient, treatment of OSA was associated with a remission of EHS attacks (16).
To date, there have been no clinical trials of therapies for EHS. In three patients, clomipramine (50 mg at night) has been used with success (8). Other drugs reported as effective were flunarizine (10 mg per day, n = 2), nifedipine (90 mg per day, n = 1) and topiramate (200 mg per day, n = 1) (11,13,15). We treated three patients with amitriptyline (25–50 mg at night), which was effective in two patients (see Case Reports).
Discussion
EHS was described as an entity for the first time in 1988 (3). After this, several other cases have been published. Analyzing the data, it is striking how uniform the complaints of EHS are presented even in older sources of the scientific literature on sleep medicine (1,2,18). EHS is characterized by a loud noise or bang in the head occurring most often during transition from wakefulness to sleep or during sleep. In addition to the eponymous sensation of an explosion in the head, feelings of fear or anxiousness with tachycardia and sweating, flashes of light, and rarely myoclonic jerks or mild jab-like pain can appear. In the largest case series, some patients also reported a curious sensation as if they stopped breathing and had to make a deliberate effort to breathe again (4).
Although this syndrome has been described in all ages, it occurs predominantly in older people with a median age at onset of 54 years. Females are more often affected. About half of the sufferers have a chronic occurrence of the attacks with a very variable frequency from one attack every few days to several attacks per night. Sporadic infrequent (<1 attack per month) occurrence and episodic appearance with prolonged or total remissions are less frequent time courses.
The syndrome is very frightening for the sufferer. The patient usually fears cerebral hemorrhage, stroke, or brain tumor (4), but no organic explanations could be found in all sufferers. The prognosis is good and no sequelae have been reported in follow-up examinations up to several decades later.
The most important differential diagnoses are primary headache disorders. Hypnic headache exclusively begins during sleep and can be experienced as an explosion but its main symptom is pain lasting at least 15 minutes. Other primary headache disorders such as migraine, cluster headache, and paroxysmal hemicrania can cause awakening from sleep but they also last longer than EHS and present with intensive pain, the latter being the main symptom also for trigeminal neuralgia. Other short-lasting headaches such as short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), primary stabbing headache or primary thunderclap headache occur only very rarely isolated in combination with sleep. Nocturnal seizures are prone to occur in the NREM stages of sleep but patients are mostly amnestic about the seizures (17). Simple focal, rarely also complex focal epileptic seizures can also be experienced as an explosion-like feeling by patients but they typically do not occur during the transition to sleep. In particular, cephalic aura (i.e. epileptic aura with headache as the main symptom) must be considered in this context (19). In the field of sleep disorders, nightly panic attacks present a differential diagnosis but are not associated with the feeling of a noise or a bang. Nightmares are typically associated with complex and longer lasting visual memories. Finally, pure myoclonic jerks during sleep can be experienced as frightening but occur necessarily together with motor symptoms.
Nothing is known about the pathophysiology of EHS. Some early reports postulated sudden involuntary movement of middle ear components or the Eustachian tube (3,4). Since the attacks most often occur during the transition from wakefulness to sleep and sometimes are accompanied by myoclonic jerks, similarities with hypnagogic symptoms have been proposed. The most feasible explanation might be a delay in the reduction of activity in selected areas of the brain stem reticular formation as the patient passes to sleep (10,12). However, the rare PSG examinations could not establish a distinct association with specific sleep stages (8,14–16). A specific form of migraine aura combined with sleep paralysis has also been suggested (12,14) but our review of the literature does not confirm an exceptional comorbidity with migraine or other primary headaches. There is one case of a patient with EHS and primary stabbing headache relieved by nifedipine (11). The report gives reason to the speculation that EHS might arise from a transient calcium channel dysfunction, similar to episodic ataxia and familial hemiplegic migraine, that results from a mutation in the CACNA1A gene (11,20). A positive family history was reported in four EHS patients (4,15) but all other reports do not support significant genetic predisposition.
To date, there have been no clinical trials for EHS treatment. In the majority of cases, firm reassurance about the benign nature of EHS seems appropriate and drug therapy is not necessary. In some cases, insomnia due to several EHS attacks can impair quality of life. Tricyclic antidepressants (clomipramine, amitriptyline) and flunarizine decreased the attack frequency and intensity in some patients (8,13). However, hitherto existing treatment experiences are essentially anecdotal in absence of a controlled study and because of the variable natural history of EHS.
In conclusion, the uniform description of well-defined symptoms and the exclusion of differential diagnoses confirm EHS as a disease entity with a benign nature. More PSG studies might help to define the relationship of EHS attacks to sleep stages and clarify pathophysiological mechanisms.
Clinical relevance
Exploding head syndrome literature review
Footnotes
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Conflict of interest
None declared.