**Question:** A patient with complaints of somnambulism has fallen asleep. She passes from light sleep into a deeper sleep. Just before she experiences an episode of somnambulism, her electroencephalogram is likely to show:

A. Increased delta waves
B. Decreased delta waves
C. Increased theta waves
D. Decreased alpha waves

**Correct Answer:**

**Core Concept:** In the process of sleep progression, there is a transition from lighter stages (e.g., non-rapid eye movement sleep) to deeper sleep stages (e.g., rapid eye movement sleep), accompanied by changes in electroencephalogram (EEG) patterns. Somnambulism is a parasomnia characterized by sleepwalking, sleep-talking, or other inappropriate or harmful behaviors that occur during sleep.

**Why the Correct Answer is Right:** In the transition from light sleep to deeper sleep, EEG patterns change, reflecting the progression of sleep stages. Somnambulism occurs in the transition between stages. Just before an episode of somnambulism, the EEG would show increased delta waves. Delta waves are the slowest and deepest waves in the EEG spectrum, representing slow, deep sleep. This is because the brain is transitioning from lighter sleep stages to the more profound sleep stages where somnambulism is likely to occur.

**Why Each Wrong Option is Incorrect:**

A. Increased delta waves: This option contradicts the correct answer, indicating that the EEG would show decreased delta waves instead of increased delta waves just before somnambulism.

B. Decreased delta waves: Similar to option A, decreased delta waves would indicate deeper sleep, not the transition to somnambulism.

C. Increased theta waves: Theta waves are intermediate frequency waves (4-8 Hz) and do not specifically indicate the transition from light sleep to deeper sleep stages, unlike delta waves.

D. Decreased alpha waves: Alpha waves (8-12 Hz) are associated with wakefulness or transition to sleep, not the transition from light sleep to deeper sleep stages where somnambulism is likely to occur.

**Clinical Pearl:** Understanding sleep stages and EEG patterns can help differentiate between various sleep disorders and provide valuable information for diagnosis and management. It is essential to recognize these patterns to effectively assess and treat patients presenting with sleep-related problems like somnambulism.