Somnambulism

Etiology

Evidence for a genetic predisposition for sleepwalking has been observed in some patients. Monozygotic twins have a higher chance of somnambulism than dizygotic twins.[5][6] More Whites with somnambulism are found to be positive for the DQB1*0501 gene compared to Whites without somnambulism, which suggests that DQB1 genes are involved in motor disorders in sleep.[7] Some studies have also indicated that sleepwalking may have an autosomal dominant mode of inheritance, exhibiting reduced penetrance.[8] Some classes of medications such as antibiotics, anticonvulsants, antidepressants, benzodiazepines, lithium, antipsychotics, selective serotonin reuptake inhibitors (SSRIs), quinine, beta-blockers, and tricyclic antidepressants (TCAs) have been shown to trigger episodes of sleepwalking in patients with no previous history of somnambulism.[9] Specifically, the benzodiazepine receptor agonist zolpidem has been strongly associated with sleepwalking even without a prior history. Prolonged sleep deprivation, specifically more than 24 hours, promotes sleepwalking in predisposed individuals. Sleepwalking events are more explicit and complex behaviors when they follow sleep deprivation.[9] Hyperthyroidism has also been shown to cause sleepwalking in a few cases.[9][10]

Epidemiology

Somnambulism is a common arousal disorder. However, the epidemiology of this disorder is still ambiguous. The prevalence rate of sleepwalking is significantly higher in children than in adults. A systematic review and meta-analysis by Stallman and colleagues showed the estimated lifetime prevalence of sleepwalking is 6.9% without a significant difference in lifetime reports of sleepwalking between children and adults. The prevalence of sleepwalking within the past 12 months was reported to be significantly higher in children, 5.0% compared to 1.5% in adults. This is likely related to less slow-wave sleep during adulthood, leading to fewer prospects for sleepwalking.[11] Sleepwalking usually occurs in children but can continue into adulthood or appear de novo among the adult population.[11][12] Studies suggest that relatively few people start sleepwalking as adults, and adult-onset somnambulism is usually associated with medications and neurodegenerative diseases.[13][14]

Pathophysiology

Studies indicate decreased localized cerebral blood flow in the frontal and parietal areas of patients who sleepwalk compared to controls. Moreover, restricted perfusion in the dorsolateral prefrontal cortex and insula is congruous with the clinical signs of somnambulistic episodes. Changes in regional cerebral blood flow patterns occurring during the resting-state wakefulness of patients who sleepwalk may be related to functional problems observed in these patients during the daytime.[14]

History and Physical

The majority of patients have a history of witnessed episodes of sleepwalking with no memory of the event. Sometimes, the spouse reports episodes of sleepwalking and performing actions such as relocating belongings in the room. There have also been reports of concomitant sleep talking and inappropriate sexual behavior during sleep. Other patients have presented with "abnormal activity at night," for example, waking up to find uneaten food left out in the kitchen in the morning. These behaviors are usually intermittent, and patients do not promptly seek medical attention. Physical examination fails to reveal any specific findings in most patients.[15][16]

Evaluation

Our knowledge of somnambulism is still in its early stages. Polysomnography is the most reliable method to diagnose somnambulism. However, it is not recommended for an initial assessment of the condition because of its high cost and inconvenience. There are difficulties in capturing infrequent and irregular behavior, such as sleepwalking. A detailed history and reports from close contacts are usually enough to diagnose somnambulism. Polysomnography can be applied in forensic cases or when the differential diagnosis is uncertain.[2] Moreover, a complete review of the patient's medications, thyroid function tests, and screening for neurodegenerative diseases such as parkinsonism should be performed.[9][10][13]

Treatment / Management

Somnambulism is a common arousal disorder that is primarily benign and does not require treatment. No clinical studies have been conducted to assess the efficacy of somnambulism treatments. However, scheduled waking or hypnosis exhibits the greatest benefit with the least adverse effects in cases where sleepwalking is causing distress to the patient or family. Scheduled waking refers to waking the patient 15-30 minutes before their usual sleepwalking time. Hypnosis suggests that patients wake up if they touch the ground with their feet based on a similar concept of interrupting the sleepwalking phenomenon. Both interventions have to be practiced every day for 2 to 3 weeks.[2] Safety precautions like locking windows and external doors and removing breakable objects are recommended to decrease the risk of injuries. No medication has been approved to treat sleepwalking. Still, clinical experience indicates some benefit of gamma-aminobutyric acid (GABA) enhancing agents like clonazepam or gabapentin if taken 1 hour before sleep.

Differential Diagnosis

The following conditions should be ruled out while making a diagnosis of somnambulism.

• Neurodegenerative changes seen in Parkinson disease at the brainstem level can cause arousal from NREM/REM sleep and affect locomotion and muscle tone, leading to several sleep-associated behavioral disorders, including somnambulism.[13]
• Somnambulism due to medications such as antibiotics, anticonvulsants, antidepressants, benzodiazepines, lithium, antipsychotics, SSRIs, quinine, beta-blockers, and TCAs has been observed.[9]
• REM sleep behavior disorder[17]
• Smith-Magenis syndrome: In addition to other findings, this syndrome presents with sleep disturbance characterized by changes in circadian rhythm with frequent awakenings at night and daytime sleepiness, which causes patients and families significant distress.[18]

Prognosis

Somnambulism usually has a good prognosis for most patients. However, sometimes it can lead to bodily harm (eg, falling from a height or walking through a glass window) and embarrassing situations (eg, to be found naked wandering around in public).[2] Children generally improve sleepwalking behavior by adolescence and usually do not require any interventions or medications.

Complications

Somnambulism is usually a benign condition in most cases. However, there have been some reports of injuries associated with sleepwalking (eg, falling from a height or walking through a glass window). The majority of these patients did not need hospitalization, but major trauma is possible.[19]