Continuing Education Activity

Exploding head syndrome (EHS) is a benign sensory parasomnia characterized by the sensation of hearing a loud sound, such as an explosion or gunshot, during transitions between sleep and wakefulness. This sensation often leads to abrupt awakening, accompanied by distress but without significant pain. The diagnostic criteria for the condition have only recently been established, and research is still in its early stages, primarily consisting of case studies and series. The underlying etiology remains unclear but may involve brainstem dysfunction, aberrant attentional processing, or neurotransmitter imbalances. Additionally, the literature on its demographics continues to evolve.

EHS is often underrecognized and misdiagnosed, resulting in unnecessary testing and treatment. Patients often find it distressing, as they may perceive it as a serious medical issue. Accurate diagnosis and reassurance are crucial for alleviating anxiety and providing relief. EHS is typically diagnosed based on clinical criteria, as no objective tests exist. Management centers on patient education, reassurance, and addressing stress or sleep-related issues. This activity reviews the current diagnostic criteria for EHS, updates clinicians on the established neurobiology of the condition, and offers guidance on differential diagnosis. This activity also discusses treatments that have shown efficacy and emphasizes the importance of interprofessional collaboration among healthcare providers in treating patients with the condition.

Objectives:

• Identify the key clinical features of exploding head syndrome, including the perception of loud noises during sleep transitions and the absence of significant pain.

• Implement appropriate diagnostic criteria for exploding head syndrome using a clinical-based approach, as no objective tests are currently available.

• Apply reassurance and education strategies to alleviate patient concerns and provide relief from the distress caused by exploding head syndrome episodes.

• Collaborate with other healthcare providers to ensure comprehensive care for patients with exploding head syndrome, including possible referrals to sleep specialists or mental health professionals if needed.

Introduction

Exploding Head Syndrome (EHS) is a benign parasomnia characterized by the perception of a sudden loud noise during sleep, leading to abrupt awakening.[1] These episodes occur during the transition between wake-sleep and sleep-wake periods and typically last less than a second.[2] Patients often report flashes of light and distress during episodes, although significant pain is not present, which is an essential criterion for diagnosis.[3][4] Although the perceived sounds are commonly described as explosions, gunshots, or thunder, they can be almost any loud noise.[4] The frequency of episodes varies, with some individuals experiencing prolonged remission between episodes.[1][5] EHS may be more common when sleeping in the supine position.[3] 

EHS was first described in medical literature in 1876 by American neurologist Silas Weir Mitchell, who documented 2 patients experiencing nocturnal sensations of loud sounds, which he termed "sensory shocks."[6] Although EHS had been described in earlier case reports, it was not officially recognized as a sleep disorder until 2005, when it was included in the International Classification of Sleep Disorders, Second Revision (ICSD-2).[7] The term "episodic cranial sensory shock" has also been proposed to describe this phenomenon.[6] Many patients may find the experience frightening, especially if they are unaware of its benign nature. Patients often fear a more serious underlying cause, such as a stroke, brain tumor, or brain hemorrhage, leading them to seek medical evaluation. However, EHS is frequently underdiagnosed and underreported, as patients may feel embarrassed discussing their symptoms, and healthcare providers may be unfamiliar with the condition.[2]

According to the American Academy of Sleep Medicine's International Classification of Sleep Disorders, Third Revision (ICSD-3), the diagnostic criteria for EHS include:

• A sudden perception of a loud noise or explosive sensation in the head, which occurs during the transition from wakefulness to sleep or upon awakening during the night.
• An abrupt arousal following the event, which is often accompanied by a sense of fear or distress.
• The experience is not associated with significant pain.

Etiology

Proposed Etiological Hypotheses for Exploding Head Syndrome

The etiology of EHS remains unclear, although several hypotheses have been proposed, which are mentioned below.

• Aberrant attentional processing during the sleep-wake transition has been proposed as a potential mechanism. In addition to typical alpha-activity observed during pre-sleep wakefulness and wakefulness after sleep-onset periods, researchers have identified a distinct low alpha–high theta frequency pattern. This "alpha-coactivation" (ACA) activity is primarily distributed in the centroparietal region, rather than the occipital region, where typical alpha-activity is usually observed. The ACA band was weaker in the occipital distribution, while the alpha-band was weaker in the centroparietal distribution, a pattern not observed in control subjects. The ACA band originated from mesial structures, including the thalamic pulvinar and posterior cingulate cortex.[5]
• Brainstem neuronal dysfunction during wake-sleep transitions.[4]
• Dysfunction in serotonergic circuits, given the condition's response to serotonergic agents.[8]
• Transient calcium channel dysfunction, based on the condition's response to nifedipine.[9]
• Dysfunction of the middle ear or Eustachian tube, labyrinthine membrane rupture, or perilymph fistula.[4]
• Aberrant activity in the occipital network, as suggested by a case study in which a patient's attacks were triggered by intermittent photic stimulation.[10] 
• Compromised gamma-aminobutyric acid (GABA)-ergic transmission to the dorsal raphe nucleus has also been proposed as a hypothesis.[11] This theory stems from a case report of a woman with extrapulmonary sarcoidosis and a pontomesencephalic lesion. The lesion was T2-hyperintense, extending from near the periaqueductal gray to the tegmentum. While amitriptyline, citalopram, doxepin, and trimipramine did not alleviate her symptoms, benzodiazepines (bromazepam and clonazepam) were effective in reducing them. 

Secondary Causes of Exploding Head Syndrome

Several secondary conditions have been linked to the onset of EHS, which are mentioned below.

• Opioid-induced central hypoventilary hypopnea: A patient on methadone for chronic pain, in the context of Ehlers-Danlos syndrome, may have experienced sleep-onset hypoventilation, potentially contributing to EHS. The use of continuous positive airway pressure (CPAP) resulted in mild improvement in symptoms.[12]
• Sick sinus syndrome with transient cardiac asystole: Implantation of a cardiac pacemaker resulted in the cessation of symptoms.[13]
• Migraine with brainstem aura: A patient experienced episodes of a sensation of explosion in the head, visual flashes, and other neurological symptoms, followed by a migraine headache. Treatment with 50 mg of nortriptyline nightly reduced the frequency of symptoms to 4 times per year.[14] Another patient had a migraine aura that included brief EHS symptoms, followed by 6 seconds of sleep paralysis, and then bitemporal migraines lasting for hours.[15]
• Sudden withdrawal from selective serotonin reuptake inhibitors or benzodiazepines.[4]
• Hypochromic-microcytic anemia due to menorrhagia, which resolved after normalizing ferritin levels.[16]

Epidemiology

Most journal articles on EHS consist of case reports, and accurate prevalence rates are unavailable.[4] A definitive gender predominance has not been established. A study found that women were slightly more likely to report EHS than men,[17] whereas other studies did not show a higher prevalence in women.[18] In a study, up to 16% of college students reported experiencing EHS episodes.[3][18] 

A scoping review of data since 2005 revealed significant variability in the prevalence of EHS, depending on the assessment method and sample populations.[1] Several cases of EHS have been reported alongside sleep paralysis.[19] In a study, nearly 37% of subjects with a history of sleep paralysis also reported experiencing EHS symptoms at least once.[18] Although no consistent precipitant has been identified, some patients have noted an association between increased event frequency and insomnia or periods of heightened stress.[3]

Pathophysiology

The exact pathophysiology of EHS remains unknown, and the condition may result from abnormal activity of neurons in the brainstem involved in sleep initiation.[20]

History and Physical

The diagnostic criteria for EHS, as outlined in the American Academy of Sleep Medicine's ICSD-3, include:[4]

• A sudden loud noise or sensation of an explosion in the head occurring at the wake-sleep transition or upon waking during the night.
• Abrupt arousal following the event, often accompanied by a sense of fright.
• The experience is not associated with significant pain.

Reports of pain should prompt further evaluation to rule out alternative diagnoses, particularly sudden headache syndromes. When assessing EHS, physicians should inquire about other sleep disorders, as well as medical and psychiatric conditions.[19] EHS may also serve as a precursor to insomnia.[5] A psychological evaluation can help identify underlying stress or anxiety.[10] 

The physical examination should include a general assessment and a thorough neurological evaluation, covering mental status, cranial nerves, muscle strength, muscle tone, reflexes, cerebellar function, gait, and sensory testing.[9] Findings from the physical examination in EHS are typically unremarkable and do not differ from those of a normal neurological examination.[1]

Evaluation

Objective tests for diagnosing EHS are currently unavailable.[1] Diagnosis is based on clinical assessment using the ICSD-3 criteria.[3] A secondary headache disorder should be considered if the patient's history or examination findings suggest an alternative cause.

Depending on the clinical presentation, neuroimaging, electroencephalogram (EEG), or a sleep study may be ordered; however, results are typically normal in individuals with EHS.[21][22] Polysomnography findings include:

• Normal sleep duration and architecture.[10][23]
• A study found that, despite the perception of sleep, patients exhibited predominantly alpha-waves during events, with interspersed theta-activity.[21]
• Another study identified additional oscillatory activity co-occurring with alpha-waves during events, differing in both source and frequency.[5]

Treatment / Management

The primary approach to managing EHS involves patient education and reassurance about its benign nature.[24][16][25] Symptom frequency often decreases with reassurance alone.[21][26] Addressing anxiety may further reduce the frequency of episodes.[10][23] Identifying and managing stressors, maintaining consistent and healthy sleep habits, and treating coexisting sleep disorders are essential components of care.[3][27] 

Pharmacological Treatment Options for Exploding Head Syndrome

Research on medications for treating EHS is limited.[24] However, in cases where symptoms are severely distressing and non-pharmacological interventions prove ineffective, the below-mentioned treatments have been reported to reduce symptoms: 

• Clomipramine: Resolution of symptoms was achieved in all 3 patients treated.[21]
• Amitriptyline: In a case series, 3 patients were successfully treated with amitriptyline.[16] In another case series, 4 patients were treated with amitriptyline. One patient showed no response at 25 mg nightly (due to intolerance of higher doses), one achieved remission at 25 mg nightly, one achieved remission at 50 mg nightly, and one patient was lost to follow-up. [24]
• Topiramate: In a patient with migraine, topiramate reduced the intensity of symptoms, but not the frequency, in a dose-dependent manner. Symptoms improved with 150 mg daily, and the intensity of the noise decreased to a mildly noticeable level at 200 mg daily.[28]
• Duloxetine: In a case report, duloxetine was ineffective at a dosage of 20 mg 3 times a day.[27] However, in another case report, duloxetine reduced the intensity and frequency of events in a patient at an unspecified dose.[10]
• Nifedipine: In a case report, slow-release nifedipine at 90 mg daily completely resolved symptoms that had not responded to valproic acid, amitriptyline, propranolol, oxycodone, or gabapentin.[9]
• Flunarizine: In a report of 2 cases, flunarizine 10 mg daily significantly decreased the frequency of symptoms in one patient, while the same dose completely eliminated symptoms in a second patient.[29]
• Clobazam: This drug induced remission in a patient with comorbid epilepsy.[30]
• Clonazepam: In a case study, reassurance combined with clonazepam at a dosage of 0.25 mg daily reduced the frequency of EHS symptoms to once a week. Previous treatment with ethyl loflazepate was ineffective.[8]
• Single-pulse transcranial magnetic stimulation (sTMS): In a patient with chronic migraine, sTMS reduced the frequency of EHS attacks from an average of 9 to 4 episodes per night. Additionally, the attacks became less bothersome and frightening. However, upon discontinuation of sTMS, the EHS symptoms returned.[31]
• Sleep hygiene and cognitive behavioral therapy: In a case study, improvements in insomnia through sleep hygiene and CBT led to the remission of EHS symptoms.[16]

Differential Diagnosis

Differential diagnoses for EHS include:

• Primary headache disorders: Conditions such as migraine, cluster headache, and paroxysmal hemicrania can awaken individuals from sleep and present with intense pain.[24]
• Nocturnal seizures: These seizures occur during non-rapid eye movement (non-REM) sleep. However, unlike EHS, patients with nocturnal epilepsy typically have no memory of the seizures.[24]
• Hypnic headache: This condition is characterized by recurrent painful headaches that begin during sleep, lasting from 15 minutes to 4 hours. These headaches cause awakening and occur 10 or more days per month for over 3 months.[22] 
• Idiopathic stabbing headache: This condition is characterized by brief 1- to 2-second stabs of pain that occur at irregular frequency. 
• Thunderclap headache: A rapidly developing, extremely intense headache that may indicate a serious condition, such as an intracranial aneurysm, dural sinus venous thrombosis, or pituitary apoplexy, and requires further investigation.[9]
• Myoclonic jerks or sleep starts: Sudden motor movements occurring at the sleep-wake transition, without any association with the perception of loud noises.[24]
• Posttraumatic stress disorder and nightmare disorder: Individuals with posttraumatic stress disorder or nightmare disorder may experience flashbacks or nightmares accompanied by loud noises. In contrast, individuals with EHS do not report symptoms occurring within the context of nightmares, dreams, or flashbacks.[4][24]
• Nocturnal panic attacks: These events wake patients from sleep and cause arousal, but they are not associated with the perception of loud noises.[24]

Compared to other headache syndromes, EHS events are more frightening and distressing than painful.[4]

Pertinent Studies and Ongoing Trials

Currently, no ongoing trials are studying EHS.

Prognosis

EHS is a benign condition with a favorable prognosis. No sequelae have been reported.[24] The frequency and intensity of episodes often decrease after initial reassurance and may remit over time.[22] 

Complications

Hypnagogic (at sleep onset) and hypnopompic (at sleep offset) hallucinations, nightmares, and lucid dreaming (where the dreamer is aware they are dreaming) may co-occur with EHS.[32]

Consultations

The EHS studies in a scoping review identified the below-mentioned comorbidities by discipline.[1]

• Sleep medicine: Insomnia, sleep apnea, restless legs syndrome, central hypoventilary hypopnea, somniloquy, narcolepsy, poor sleep hygiene, and REM sleep disorder.
• Neurology: Seizure disorder, chronic headache, migraine, stroke, hemianopia, Lewy body disease, and brain stem lesion.
• Psychiatry: History of psychiatric illness.
• Cardiology: Arrhythmia and hypertension.
• Endocrinology: Diabetes mellitus.
• Audiology: Hyperacusis and tinnitus.

Deterrence and Patient Education

Patients should be encouraged to openly discuss any unusual sleep experiences, as they may withhold symptoms due to embarrassment.[4] If EHS is diagnosed, patients should be reassured that it is a benign condition that does not cause physical harm. The main complication is often the distress or fright caused by the perception of a serious disease or disruption to sleep.[24]

Stress and uncontrolled anxiety are potential triggers for EHS; therefore, patients should be encouraged to share any concerns or anxieties they may have.[3] 

Pearls and Other Issues

Key facts to keep in mind regarding EHS include:

• EHS is a benign condition distinguished by the perception of a loud, explosive noise that usually occurs while falling asleep.
• EHS can be frightening or distressing, but it is not painful.
• EHS symptoms are often mistaken for headache disorders. A thorough workup should be conducted if the patient reports pain or neurological symptoms.
• The exact mechanism of EHS is unknown.
• The treatment for EHS primarily involves reassurance, although some case reports suggest that medications or sTMS may be effective in some cases.

Enhancing Healthcare Team Outcomes

Patients with EHS are at high risk for fear and distress despite the benign prognosis. Early identification and management are crucial in reducing anxiety. The care of patients with EHS requires a collaborative approach among healthcare professionals to ensure patient-centered care and improve overall outcomes while minimizing unnecessary testing. Neurologists, emergency medicine physicians, advanced practitioners, nurses, pharmacists, and other healthcare team members should have the clinical expertise to accurately diagnose and manage EHS. This includes proficiency in recognizing diverse clinical presentations and understanding diagnostic techniques such as EEG, polysomnography, and neuroimaging. Patient and caregiver education is vital to reduce distress and enhance outcomes.

A strategic approach is essential, incorporating evidence-based strategies to optimize treatment plans and minimize adverse effects. Ethical considerations should guide decision-making, ensuring informed consent and respecting patient autonomy in treatment choices. Each healthcare professional must be aware of their responsibilities and contribute their expertise to the patient's care plan, fostering a multidisciplinary approach. Effective interprofessional communication is crucial, enabling seamless information exchange and collaborative decision-making among healthcare team members. Care coordination has a vital role in managing the patient's journey from diagnosis to treatment and follow-up, minimizing errors and enhancing patient safety. By embracing principles of skill, strategy, ethics, responsibilities, interprofessional communication, and care coordination, healthcare professionals can deliver patient-centered care, improving patient outcomes and enhancing team performance in managing EHS.