Hypnagogic Hallucinations

Hypnagogic or hypnopompic hallucinations are visual, tactile, auditory, or other sensory events, usually brief but occasionally prolonged, that occur at the transition from wakefulness to sleep (hypnagogic) or from sleep to wakefulness (hypnopompic). The person may hear sounds that are not there and see visual hallucinations. These visual and auditory images are very vivid and may be bizarre or disturbing.

Usually it is part of the tetrad of narcolepsy that includes:

• Excessive daytime sleepiness
• Cataplexy
• Hypnagogic hallucinations
• Sleep paralysis.

This tetrad is rarely seen in children.

• Narcolepsy has 2 peaks of onset. One is in the mid-teens and the other in the mid 30s.
• The prevalance in the UK is 4 in 10,000¹. It may be higher as diagnosis is often delayed by about 10 years from onset.
• Hypnagogic hallucinations can occur without narcolepsy. People may be reluctant to admit to them for fear of being thought mentally ill.
• Sex ratio is equal.
• A telephone interview of nearly 5,000 people aged 15 to 100 in the UK¹ showed that 37% of the sample reported experiencing hypnagogic hallucinations and 12.5% reported hypnopompic hallucinations. Both types of hallucinations were significantly more common among subjects with symptoms of insomnia, excessive daytime sleepiness or mental disorders. Hypnagogic and hypnopompic hallucinations were much more common than expected, with a prevalence that far exceeds that which can be explained by the association with narcolepsy. Hypnopompic hallucinations may be a better indicator of narcolepsy than hypnagogic hallucinations in subjects reporting excessive daytime sleepiness.

• There is a tendency for it to be associated with certain HLA phenotypes.
• Prazosin, an alpha1-antagonist, worsens symptoms.

• Hypnagogic hallucinations can occur at the onset of sleep, either by day or at night. They are usually quite vivid and visual.
• Visual hallucinations usually consist of simple forms such as coloured circles or parts of objects that may be constant or changing in size. A formed image of an animal or a person may appear and it is often in colour.
• Auditory hallucinations are common, but other senses are seldom involved. Auditory hallucinations can range from a few sounds to an elaborate melody. Threats or criticism are also reported.
• Another type of hallucination that is sometimes reported at the onset of sleep involves elementary cenesthopathic feelings (such as experiencing picking, rubbing, or light touching), changes in location of body parts (such as an arm or a leg), or feelings of levitation or extracorporeal experiences (like moving the body in space or floating above the bed) that may be quite elaborate.
• There may be a history of narcolepsy with the ability to fall asleep if at all tired or bored, often with social embarrassment. It may lead to the inability to hold down a job.

Catalepsy

Around 70% of people with narcolepsy also have catalepsy. Catalepsy is episodes of muscular weakness which may range from a barely perceptible slackening of the facial muscles to the dropping of the jaw or head, weakness at the knees, or total collapse on the floor. Speech is slurred, diplopia and inability to focus occur but hearing and awareness remain undisturbed. Attacks are triggered by strong emotions such as exhilaration and laughter, anger and surprise. Cataplexy may be most severe when tired and can lead to considerable anxiety. The attacks last some minutes and may end in resumption of normal behaviour or slipping into sleep sometimes prolonged.

Cataplexy is virtually pathognomonic of narcolepsy.

Children

Children often deny excessive daytime sleepiness. Academic deterioration is common. Presentation often varies with age.²

• Children less than 5 years old have unexplained falls and "drop attacks," aggressive behaviour, abrupt irritability, sleep terrors, and abrupt dropping of objects.
• In children aged 5 to 10, the most common presenting complaint is repetitive sleepiness, followed by difficulty with waking in the morning associated with aggressive behaviour and abrupt falls in school. These children often were misdiagnosed as having attention deficit hyperactivity disorder (ADHD), learning disability, or another neurological disorder.
• In children aged 10-12 years, poor academic performance was a common complaint. Other presenting symptoms included inappropriate low level of alertness, falling asleep in class, and inability to wake up in the morning.

Signs

There are usually no abnormal physical signs.

• It is important to decide if this is narcolepsy as it is a treatable condition
• Schizophrenia can cause hallucinations including derogatory auditory remarks. In people who experience hypnogogic or hypnopompic images but do not have narcolepsy, the tendency towards psychosis is greater than in others.³
• Musical release hallucinations are complex auditory phenomena, affecting mostly the deaf elderly population, in which individuals hear vocal or instrumental music. Progressive hearing loss from otosclerosis disrupts the usual external sensory stimuli necessary to inhibit the emergence of memory traces within the brain, thereby "releasing" previously recorded perceptions. The atypical antipsychotic, quetiapine can produce benefit.⁴
• There may be drug abuse
• Sleep terrors in children
• Partial seizures
• Absence seizures.

• Blood tests and imaging are likely to be normal.
• Referral to a special sleep laboratory may be required to diagnose narcolepsy.
• An overnight polysomnogram followed by a multiple sleep latency test (MSLT) is used. They provide information about daytime sleepiness by measuring sleep latency and sleep-onset REM periods (SOREMPs).
• The MSLT involves 4 or 5 opportunities to nap at 2-hour intervals over the day. The overnight polysomnogram findings typically are normal in narcolepsy, although they may show unusual sleep fragmentation.
• MSLT cannot be used alone to confirm or rule out narcolepsy.
• Diagnosing narcolepsy in children presents numerous difficulties.
• Serial MSLTs may be required, and usually multiple confounding factors are involved, such as increased alertness in the novel environment of the sleep laboratory.
• Establish the diagnosis with careful history and physical examination supported by an overnight polysomnogram and MSLTs.
• In some cases with early onset and cataplexy, sleep studies may not be necessary.

Several questionnaires have been validated to assess sleepiness. The 8-question Epworth Sleepiness Scale is most often used although it was devised to assess the impact of obstructive sleep apnoea.⁵

• Patients answer each question on a scale from 0 (not at all likely to fall asleep) to 3 (very likely to fall asleep).
• This gives a possible score of 0 to 24.
• There is no firm criterion for abnormal sleepiness but generally, scores of 10 or more are regarded as indicative.

Non-Drug

• It is important to get enough sleep at night.
• Scheduled naps during the day may help.
• Counsel about suitable careers and hobbies.
• If a driver, DVLA and insurance should know if the patient has narcolepsy. The driver should cease on diagnosis but driving will be permitted when satisfactory control of symptoms is achieved. If there is not narcolepsy, it is not a risk.
• Avoid alcohol and illicit drugs as they may exacerbate symptoms.
• Encourage children to participate in activities and sports. Exercise can be beneficial and stimulating. A child with narcolepsy should refrain from activities if he or she appears drowsy.

Drugs

• CNS stimulants such as methylphenidate and dexamphetamine are used to treat the narcolepsy.
• Modafinil was discovered recently as a novel wake-promoting agent. It is an alpha1 agonist. It seems safe and effective.⁶

These are treatments for narcolepsy rather than specifically for hypnogogic hallucinations

• Tricyclic antidepressants hold back the dreaming state and may be beneficial. However, A Cochrane review was unimpressed by the evidence.⁷

Patients should inform employers of their condition and drug treatment. They may be accused of drug abuse and some employers do random drug testing. They will test positive for amphetamines.

If the patient has narcolepsy the prognosis is as for that disease. If not, reassurance is all that is required. If it is disturbing, tricylic antidepressants may be used intermittently.