Idiopathic hypersomnia without long sleep time

This code signifies a chronic neurological sleep disorder characterized by excessive daytime sleepiness despite adequate nighttime sleep, without an identifiable underlying cause. Patients experience persistent, unrefreshing sleepiness throughout the day, often struggling to stay awake in various situations.

Assign this code when documentation clearly indicates a diagnosis of idiopathic hypersomnia where the patient does not exhibit a significantly prolonged sleep duration (typically less than 10 hours per 24-hour period). Supporting documentation should include polysomnography results ruling out other sleep disorders and a Multiple Sleep Latency Test (MSLT) demonstrating objective sleepiness without meeting narcolepsy criteria.

• Differentiate from idiopathic hypersomnia with long sleep time, which is characterized by typical sleep durations exceeding 10 hours.
• Ensure narcolepsy (G47.4-) has been ruled out, as both conditions present with excessive daytime sleepiness.
• Documentation must explicitly state "idiopathic hypersomnia" and specify "without long sleep time" or provide objective sleep study data to support this distinction.