A patient exhibiting excessive daytime sleepiness (EDS) but without REM onset would be classified as having what condition?

The classification of a patient exhibiting excessive daytime sleepiness (EDS) but without REM onset is indeed consistent with idiopathic hypersomnia. This condition is characterized by excessive daytime sleepiness even after a prolonged sleep period, often accompanied by difficulties in waking up, but notably, patients typically do not experience the REM sleep characteristics associated with narcolepsy.

In idiopathic hypersomnia, patients may have longer nighttime sleep durations but still feel excessively sleepy during the day. Unlike narcolepsy, where REM sleep onset is present and often associated with distinct sleep episodes, particularly cataplexy, idiopathic hypersomnia lacks these REM-related features. Therefore, the absence of REM onset distinguishes idiopathic hypersomnia as the appropriate diagnosis for this patient.

Other conditions, such as sleep apnea, primarily involve disrupted sleep due to breathing difficulties and may not directly cause excessive daytime sleepiness without being linked to REM sleep characteristics. Similarly, idiopathic insomnia is marked by difficulty falling or staying asleep without the significant daytime sleepiness or REM sleep disturbance aspect. Hence, idiopathic hypersomnia is the correct identification for this condition.