RPSGT RPSGT Sleep Disorders & Pathophysiology 5 — Questions and Answers
Question 1: Which criterion best distinguishes idiopathic hypersomnia from narcolepsy type 1 on MSLT?
- Mean sleep latency under 8 minutes with no SOREMPs
- Mean sleep latency under 8 minutes with fewer than 2 SOREMPs (Correct answer)
- Mean sleep latency over 10 minutes with 1 SOREMP
- Mean sleep latency under 5 minutes with 3 or more SOREMPs
Correct answer: Mean sleep latency under 8 minutes with fewer than 2 SOREMPs
Idiopathic hypersomnia shows a mean sleep latency ≤8 minutes on MSLT with fewer than 2 sleep-onset REM periods, distinguishing it from narcolepsy which requires ≥2 SOREMPs.
Question 2: Restless legs syndrome (RLS) is most closely associated with dysfunction in which physiological system?
- Serotonergic signaling in the cortex
- Iron-dopamine metabolism in the basal ganglia and spinal cord (Correct answer)
- Cholinergic signaling in the brainstem
- Glutamatergic activity in the thalamus
Correct answer: Iron-dopamine metabolism in the basal ganglia and spinal cord
RLS pathophysiology involves impaired iron metabolism reducing dopaminergic function in the basal ganglia and spinal cord, explaining the response to dopaminergic medications.
Question 3: A 35-year-old shift worker complains of inability to sleep at the right times and excessive sleepiness at work. Actigraphy over 14 days shows normal total sleep time but misaligned timing. What is the most likely diagnosis?
- Psychophysiological insomnia
- Shift work sleep disorder (Correct answer)
- Advanced sleep-wake phase disorder
- Non-24-hour sleep-wake rhythm disorder
Correct answer: Shift work sleep disorder
Shift work sleep disorder is characterized by insomnia and/or excessive sleepiness caused by a work schedule that overlaps with the usual sleep period.
Question 4: Which of the following is the minimum SpO2 threshold and duration used by AASM to score sleep-related hypoxemia in adults?
- SpO2 below 85% for at least 5 minutes
- SpO2 below 88% for at least 5 minutes cumulative during sleep (Correct answer)
- SpO2 below 90% for at least 10 minutes cumulative
- SpO2 below 88% for any single continuous episode
Correct answer: SpO2 below 88% for at least 5 minutes cumulative during sleep
Per AASM criteria, sleep-related hypoxemia in adults is scored when SpO2 is below 88% for ≥5 cumulative minutes during sleep.
Question 5: In the pathophysiology of obstructive sleep apnea, which anatomical factor is the PRIMARY determinant of pharyngeal collapsibility?
- Tracheal tug caused by lung volume reduction
- Negative intraluminal pressure during inspiration relative to upper airway muscle tone (Correct answer)
- Increased thyromental distance
- Hypercapnic drive to the genioglossus
Correct answer: Negative intraluminal pressure during inspiration relative to upper airway muscle tone
OSA occurs when inspiratory negative intraluminal pressure exceeds the capacity of pharyngeal dilator muscles (especially genioglossus) to maintain airway patency.
Question 6: A patient's PSG shows frequent brief arousals after each PLMS. Which AASM rule governs whether a PLMS-associated arousal is scored?
- The arousal must precede the PLMS onset by at least 2 seconds
- The arousal must start no more than 0.5 seconds before or after the PLMS termination and the PLMS must be at least 8 seconds long
- The arousal must begin within 2 seconds of PLMS onset and last at least 3 seconds (Correct answer)
- The PLM must cause a 4% desaturation for the arousal to be counted
Correct answer: The arousal must begin within 2 seconds of PLMS onset and last at least 3 seconds
AASM rules score a PLMS-associated arousal when the arousal begins no more than 2 seconds before or after PLMS onset (not termination) for limb movements ≥0.5 seconds.
Question 7: Which feature on PSG distinguishes central sleep apnea from obstructive sleep apnea during an apnea event?
- Duration of the apnea exceeding 20 seconds
- Absence of respiratory effort on thoracic and abdominal channels during airflow cessation (Correct answer)
- Oxygen desaturation nadir below 85%
- Occurrence exclusively during REM sleep
Correct answer: Absence of respiratory effort on thoracic and abdominal channels during airflow cessation
Central apneas are scored when both respiratory effort channels (thoracic and abdominal) show absent effort throughout the entire airflow cessation, unlike obstructive events which maintain effort.
RPSGT RPSGT Sleep Disorders & Pathophysiology 5
Which criterion best distinguishes idiopathic hypersomnia from narcolepsy type 1 on MSLT?