From the Research
Idiopathic hypersomnia is diagnosed when a patient experiences excessive daytime sleepiness despite adequate or prolonged nighttime sleep, without another medical or psychiatric cause, and is characterized by chronic excessive daytime sleepiness occurring for at least three months, an absence of cataplexy, and a mean sleep latency of less than 8 minutes on the Multiple Sleep Latency Test (MSLT) 1. The diagnostic criteria for idiopathic hypersomnia include:
- Chronic excessive daytime sleepiness occurring for at least three months
- An absence of cataplexy (sudden muscle weakness triggered by emotions)
- A mean sleep latency of less than 8 minutes on the Multiple Sleep Latency Test (MSLT)
- Either fewer than two sleep-onset REM periods on the MSLT or no sleep-onset REM periods if an REM period was observed on the preceding polysomnogram
- A polysomnogram showing a total sleep time of at least 6 hours
- Patients typically report unrefreshing naps, difficulty waking up (sleep inertia), and prolonged nighttime sleep (often more than 10-11 hours) 2. These symptoms cannot be better explained by another sleep disorder, medical or neurological condition, medication effect, or substance use 3. The diagnosis is essentially one of exclusion, requiring thorough evaluation to rule out other causes of hypersomnia such as narcolepsy, sleep apnea, insufficient sleep syndrome, or medication effects 4. It is worth noting that idiopathic hypersomnia can be divided into two subtypes: with long sleep duration and without long sleep duration, with the former being characterized by a younger age at disease onset, longer MSLT latency, and more severe sleep inertia and fatigue 4.