Does explosive head syndrome occur in Non-Rapid Eye Movement (NREM) or Rapid Eye Movement (REM) sleep?

Exploding Head Syndrome Occurs During the Transition Between Wake and Sleep (NREM Stage 1)

Exploding head syndrome (EHS) primarily occurs during the transition between wakefulness and sleep, specifically during NREM stage 1 sleep, rather than during REM sleep. 1, 2

Clinical Characteristics of Exploding Head Syndrome

• EHS is characterized by the perception of a sudden loud noise or explosive feeling in the head that occurs during sleep-wake transitions 2
• Common accompanying symptoms include:
  • Tachycardia (rapid heart rate)
  • Fear/anxiety
  • Muscle jerks or twitches
  • Visual phenomena (in approximately 27% of cases) 3
  • Respiratory difficulties in severe cases

Sleep Stage Association

EHS episodes typically occur during:

• Wake-to-sleep transitions (sleep onset) 2, 4
• Sleep-to-wake transitions 1
• NREM stage 1 sleep (the lightest stage of non-REM sleep) 1

According to polysomnographic studies, EHS is not associated with any specific sleep pattern beyond its occurrence during sleep transitions 2. This distinguishes it from other parasomnias that occur during specific sleep stages such as REM sleep behavior disorder or slow-wave sleep parasomnias.

Epidemiology and Clinical Significance

• EHS is more common than previously thought, affecting approximately 18% of college students in one study 5
• Female to male ratio is approximately 1.5:1 2
• Median age of onset is 54 years, though it can occur in younger individuals 2, 5
• Frequency varies from one attack per week to several attacks per night 2
• Only 11% of sufferers report their symptoms to healthcare professionals 3

Diagnostic Considerations

• Polysomnography is not routinely used to diagnose EHS but may be performed to exclude other sleep disorders 1
• Important differential diagnoses include:
  • Primary and secondary headache disorders
  • Nocturnal seizures
  • Sleep-related breathing disorders

Management Approach

• Most patients do not require treatment due to the benign nature of the condition 2
• Reassurance about the benign nature of the condition is often sufficient 6
• For patients with frequent or distressing episodes:
  • Tricyclic antidepressants may be helpful in some cases 2
  • Stress management techniques may be beneficial as emotional stress appears to be related to attack frequency 4

Clinical Pearls and Pitfalls

• EHS is often misdiagnosed or overlooked due to limited awareness among clinicians
• The condition can cause significant fear and sleep avoidance in some patients, potentially leading to insomnia and daytime fatigue 1
• EHS can be associated with isolated sleep paralysis in approximately 36.9% of cases 5
• The supine sleeping position may increase the likelihood of episodes 3
• Despite being frightening, EHS is not associated with any serious neurological pathology

Understanding that EHS occurs during sleep-wake transitions in NREM stage 1 rather than during REM sleep helps differentiate it from REM-related parasomnias and guides appropriate patient education and management.