Idiopathic hypersomnia

Sleep disorder characterised by excessive sleep and daytime sleepiness without a known cause

Idiopathic Hypersomnia is a neurological disorder characterized primarily by excessive sleep and excessive daytime sleepiness (EDS). It is often difficult to diagnose at an early stage and is usually a lifelong chronic disease. Idiopathic Hypersomnia has historically been rarely diagnosed, leading to low public awareness and stigma for those who suffer from it. There is currently no cure, but several off-label treatments, which are primarily FDA-approved narcolepsy medications, can help alleviate symptoms.

In the medical literature, Idiopathic Hypersomnia may also be referred to as IH, IHS, primary hypersomnia, central hypersomnia, or hypersomnia of brain origin. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) defines Idiopathic Hypersomnia as EDS without narcolepsy or the associated features of other sleep disorders. It occurs in the absence of medical problems or sleep disruptions, such as sleep apnea, that can cause secondary hypersomnia.

Signs and Symptoms

Those who suffer from Idiopathic Hypersomnia have recurring episodes of excessive sleep and daytime sleepiness (EDS). Sleep is usually deep, with significant difficulty arousing from sleep, even with use of several alarm clocks. In fact, patients with IH often must develop elaborate rituals to wake, as alarm clocks and even physical attempts by friends/family to wake them may fail. Despite getting more hours of sleep than typically required by the human body, patients awake unrefreshed and may also suffer sleep inertia, known more descriptively in its severe form as sleep drunkenness (significant disorientation upon awakening). While people without sleep disorders may wake up and briefly want to return to sleep, in people with Idiopathic Hypersomnia, this sleep-to-wake transition is much more difficult and prolonged. Sleep seems to leave a mental fogginess, which can remain throughout the few hours that people with IH can remain awake. Thinking clearly and carrying out even basic physical tasks can be difficult. Daytime naps are generally very long (up to several hours) and are also unrefreshing, as opposed to the short refreshing naps associated with narcolepsy.

Some studies have shown increased frequencies of other symptoms in patients with Idiopathic Hypersomnia, although it is not clear whether these symptoms are caused by the disorder. These symptoms include palpitations, digestive problems, difficulty with body temperature regulation, and cognitive problems, especially deficits in memory, attention, and concentration. Anxiety and depression are often increased in Idiopathic Hypersomnia, most likely as a response to chronic illness. In addition, peripheral vascular symptoms, such as cold hands and feet (Raynaud's-type phenomena), fainting episodes (syncope), dizziness upon arising (orthostatic hypotension), and headaches (possibly migrainous in quality) may also occur.

Causes

Unlike narcolepsy with cataplexy, which has a known cause (autoimmune destruction of hypocretin-producing neurons), the cause of Idiopathic Hypersomnia has, until recently, been largely unknown. However, researchers have identified a few abnormalities associated with IH, which with further study may help to clarify the etiology. Destruction of noradrenergic neurons has produced hypersomnia in experimental animal studies, and injury to adrenergic neurons has also been shown to lead to hypersomnia. Idiopathic Hypersomnia has also been associated with a malfunction of the norepinephrine system and decreased cerebrospinal fluid (CSF) histamine levels. Researchers have recently found an abnormal hypersensitivity to GABA in a subset of patients with central hypersomnia, including Idiopathic Hypersomnia, narcolepsy without cataplexy, and long sleepers. They have identified

Classification

Idiopathic hypersomnia is classified as a central hypersomnia, along with narcolepsy and Kleine-Levin syndrome. "Central hypersomnia is a disorder of the central nervous system in which the urge to sleep cannot be suppressed." The severity of central hypersomnia is dependent on the number and duration of sleep episodes, which can range from relatively mild to severely debilitating.

Prognosis

Idiopathic hypersomnia is a chronic condition that can be very debilitating, negatively affecting the patient's ability to work, study, and maintain relationships. Although there is currently no cure, there are several off-label treatments that can help manage the symptoms. However, these treatments may not be effective for all patients, and even with medication, patients may continue to struggle with daily activities. It is important for patients to work closely with their healthcare providers to find the best treatment plan for their individual needs.

Public awareness

There is a low level of public awareness about idiopathic hypersomnia, which can lead to stigma and misunderstanding for those who suffer from it. Many patients report feeling isolated and unsupported due to the lack of understanding about their condition. Increased education and awareness about the disorder may help reduce the stigma and improve the quality of life for those affected by it.

Research

There is ongoing research into the causes and treatment of idiopathic hypersomnia. Researchers are investigating abnormalities in the norepinephrine system, GABA hypersensitivity, and decreased histamine levels in the cerebrospinal fluid, among other areas. These studies may lead to a better understanding of the underlying causes of the disorder and more effective treatments in the future.

Melatonin

There have been a few studies suggesting melatonin could be helpful in the treatment of idiopathic hypersomnia. One small study used a dose of 2 mg slow release melatonin at bedtime and showed 50% of patients with "shortened nocturnal sleep duration, decreased sleep drunkenness and relieved daytime sleepiness."

Hypocretin agonists

Hypocretin-1 has been shown to be strongly wake-promoting in animal models, but it does not cross the blood-brain barrier. Suvorexant, a hypocretin receptor antagonist, has been developed to limit the natural effects of hypocretin in patients with insomnia. It is therefore possible that a hypocretin agonist may be similarly developed for the treatment of hypersomnia.

Sodium oxybate

Sodium oxybate is a medication that can be used for the treatment of idiopathic hypersomnia, a sleep disorder characterized by excessive sleepiness during the day, despite getting adequate sleep at night. Sodium oxybate is a central nervous system depressant and is believed to work by increasing the amount of slow-wave sleep, which is the deep, restorative sleep that the body needs to function properly.

Sodium oxybate is a prescription medication that is only available through a specialty pharmacy program called the Xyrem REMS Program. The medication is taken orally in two doses, one at bedtime and one in the middle of the night. It is important to follow the dosing instructions carefully, as taking too much can be dangerous.

Like all medications, sodium oxybate can have side effects, including nausea, dizziness, and difficulty sleeping. It can also be habit-forming, so it is important to take the medication only as prescribed by a doctor.

External links

Classification	ICD-10: G47.1 , ICD-10-CM G47.11, ICD-10-CM G47.12 MeSH: D020177
External resources	MedlinePlus: 000803 eMedicine: med/3129 Orphanet: 33208

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