Idiopathic hypersomnia with long sleep time

This code signifies a primary central nervous system hypersomnia characterized by excessive daytime sleepiness despite adequate or prolonged nocturnal sleep, often exceeding 10 hours. Patients experience significant difficulty waking, sleep inertia, and unrefreshing naps.

Assign this code when documentation confirms a diagnosis of idiopathic hypersomnia where polysomnography (PSG) demonstrates a total sleep time (TST) of 10 hours or more per 24-hour period, or a mean sleep latency of less than 8 minutes on a multiple sleep latency test (MSLT) with no evidence of other sleep disorders or medical conditions explaining the hypersomnia. Supporting documentation includes sleep study reports and physician's diagnostic statements.

• Differentiate from narcolepsy; narcolepsy involves cataplexy or specific PSG findings like sleep-onset REM periods.
• Ensure the "long sleep time" component is explicitly documented to justify this specific subcategory.
• Exclude secondary hypersomnias caused by medical conditions, medications, or other sleep disorders.