Sleep Disorders and Pathophysiology Flashcards

A 68-year-old male patient's bed partner reports that he frequently "acts out his dreams," sometimes punching or kicking, which has resulted in injury. A polysomnogram confirms the presence of REM sleep without atonia. These findings are most strongly associated with an increased future risk of developing which neurodegenerative disorder?

Answer: Parkinson's disease

REM Sleep Behavior Disorder (RBD), characterized by dream-enactment behavior and loss of normal muscle atonia during REM sleep, is a parasomnia strongly linked to neurodegenerative synucleinopathies. Studies have shown that a significant percentage of patients diagnosed with idiopathic RBD will later develop conditions like Parkinson's disease, Lewy body dementia, or multiple system atrophy.

Which of the following is the MOST common underlying medical condition associated with the pathophysiology of Cheyne-Stokes respiration?

Answer: Congestive Heart Failure (CHF)

Cheyne-Stokes respiration (CSR) is a specific pattern of periodic breathing characterized by a crescendo-decrescendo pattern of tidal volume, alternating with central apneas. The most common cause is severe congestive heart failure. The pathophysiology involves an increased circulatory time between the lungs and the brain's chemoreceptors, leading to an overcompensation in breathing effort that creates the classic waxing and waning pattern.

A patient describes an irresistible urge to move their legs, which is worse in the evening and temporarily relieved by movement. According to the essential diagnostic criteria for Restless Legs Syndrome (RLS), which feature is required for a clinical diagnosis?

Answer: Worsening of symptoms during periods of rest or inactivity.

The diagnosis of Restless Legs Syndrome (RLS), or Willis-Ekbom disease, is clinical and based on five essential criteria. A key criterion is that the urge to move or unpleasant sensations begin or worsen during periods of rest or inactivity, such as sitting or lying down. While PLMs are often present and dopaminergic agents are a common treatment, they are not part of the core diagnostic criteria.

A 19-year-old patient reports being unable to fall asleep before 2:00 AM, regardless of their efforts. When allowed to sleep on their own schedule, such as on weekends, they sleep soundly from 2:30 AM until 11:00 AM and feel rested. This pattern is most characteristic of which sleep disorder?

Answer: Delayed Sleep-Wake Phase Disorder

This scenario describes a classic presentation of Delayed Sleep-Wake Phase Disorder (DSWPD), a circadian rhythm disorder where the internal body clock is shifted several hours later than the conventional 24-hour cycle. The key diagnostic feature is a stable, but delayed, sleep pattern that leads to sleep-onset insomnia and difficulty waking at conventional times, but results in normal sleep quality and duration when the individual can follow their intrinsic schedule.

What is the primary pathophysiological mechanism underlying Narcolepsy Type 1?

Answer: A significant loss of hypocretin/orexin-producing neurons.

Narcolepsy Type 1 (which includes cataplexy) is caused by a profound and selective loss of neurons in the hypothalamus that produce the neuropeptides hypocretin (also known as orexin). These neuropeptides are crucial for promoting and stabilizing wakefulness; their absence leads to the inability to maintain stable states of sleep and wake, resulting in excessive daytime sleepiness and intrusions of REM sleep phenomena (like cataplexy) into wakefulness.

The pathophysiology of NREM parasomnias, such as sleepwalking (somnambulism) and sleep terrors, is best understood as a disorder of:

Answer: Incomplete arousal from slow-wave sleep.

NREM parasomnias like sleepwalking and sleep terrors are considered disorders of arousal. They occur when a person experiences an incomplete awakening from the deepest stage of sleep, N3 or slow-wave sleep. This results in a mixed state where parts of the brain responsible for complex motor behaviors are active, while higher cortical areas responsible for consciousness and memory remain asleep, leading to the characteristic amnesia for the event.