All of the following are NREM sleep disorders except
**Core Concept**
NREM sleep, which accounts for approximately 75% of total sleep time, is characterized by slow-wave brain activity and reduced body temperature. NREM sleep disorders are conditions that disrupt this stage of sleep, leading to impaired sleep quality and daytime functioning.
**Why the Correct Answer is Right**
NREM sleep disorders, such as sleep apnea, insomnia, and restless legs syndrome, typically involve disruptions to the normal sleep-wake cycle and are often associated with underlying physiological or anatomical abnormalities. These conditions can be caused by factors such as sleep stage transitions, respiratory issues, or neurological problems.
**Why Each Wrong Option is Incorrect**
**Option A:** Restless legs syndrome is a classic NREM sleep disorder characterized by an irresistible urge to move the legs, often accompanied by uncomfortable sensations. It is typically associated with iron deficiency, dopamine dysregulation, and genetic predisposition.
**Option B:** Periodic limb movement disorder (PLMD) is another NREM sleep disorder that involves repetitive movements of the legs during sleep, often disrupting sleep quality.
**Option C:** Sleepwalking (somnambulism) is a parasomnia disorder that typically occurs during NREM sleep, particularly during the deep sleep stage.
**Clinical Pearl / High-Yield Fact**
It is essential to distinguish between NREM sleep disorders and REM sleep disorders, such as narcolepsy and REM sleep behavior disorder, which have distinct pathophysiological mechanisms and clinical presentations.
**Correct Answer:** D.