Sleep disorder diagnosed in patients who suffer from excessive daytime sleepiness that cannot be traced to a specific, obvious cause. Literally means "excessive sleepiness without any known cause" or, in the vernacular, "tired as hell all the time and the doctors don't know why." Conceptually and symptomatically similar to Chronic Fatigue Syndrome, the two disorders are believed by many to be linked, yet no direct correlation has been demonstrated.
Patients with idiopathic hypersomnia are often diagnosed after the treatment of a primary sleep disorder has failed to relieve the patient of his or her symptoms. For example, suppose a polysomnogram (or "sleep study") reveals that a patient has sleep apnea--yet after the patient is treated for this disorder (via the use of a CPAP or BiPAP machine), s/he continues to suffer from excessive daytime sleepiness. The polysomnogram is repeated; if the patient's sleep apnea has indeed been treated/cured and no other sleep disorders (e.g. narcolepsy, Restless Leg Syndrome, etc.) are found, a diagnosis of idiopathic hypersomnia will often follow.
Idopathic hypersomnia is treated in much the same way as narcolepsy. Patients are given stimulant medications, such as amphetamines and methamphetamines (e.g. Ritalin, Dexedrine, Adderall), to help them stay awake and functional throughout the day. Another option is Provigil (modafinil), a newer narcolepsy medication that often works without the side effects common to CNS stimulants.
Patients suffering from idiopathic hypersomnia may wish to visit some of the many online support groups available to assist sufferers of sleep disorders. One should especially investigate http://www.sleepnet.com, a site that gives a great deal of information about sleep disorders and also hosts dozens of discussion forums for individuals suffering from those problems.