A 63-year-old man presents to his primary care physician complaining of excessive daytime sleepiness. He explains that this problem has worsened slowly over the past few years but is now interfering with his ability to play with his grandchildren. He worked previously as an overnight train conductor, but he has been retired for the past 3 years. He sleeps approximately 8-9 hours per night and believes his sleep quality is good; however, his wife notes that he often snores loudly during sleep. He has never experienced muscle weakness or hallucinations. He has also been experiencing headaches in the morning and endorses a depressed mood. His physical exam is most notable for his large body habitus, with a BMI of 34. What is the best description of the underlying mechanism for this patient's excessive daytime sleepiness?

Circadian rhythm sleep-wake disorder

Deficiency of the neuropeptides, orexin-A and orexin-B

An 11-year-old boy with a history of attention deficit disorder presents to a general medicine clinic with leg pain. He is accompanied by his mother. He reports dull, throbbing, diffuse pain in his bilateral lower extremities. He reports that the pain feels deep in his muscles. He has awakened several times at night with the pain, and his symptoms tend to be better during the daylight hours. He denies fatigue, fever, or pain in his joints. On physical examination, his vital signs are stable, and he is afebrile. Physical examination reveals full range of motion in the hip and knee joints without pain. He has no joint effusions, erythema, or warmth. What is the next best step in management?

Lower extremity venous ultrasound

Sleep-related movement disorders for USMLE Step 1: High-Yield Psychiatry Lessons

Restless Legs Syndrome (RLS) - Jumping Beans at Bedtime

Core Feature: An irresistible urge to move the legs, often with uncomfortable crawling, pulling, or creeping sensations.
Diagnostic Criteria (📌 Mnemonic: URGE):
- Urge to move legs.
- Rest-induced (symptoms worsen with inactivity).
- Gets better with movement.
- Evening or nighttime worsening (circadian pattern).
Key Associations & Secondary Causes:
- Iron deficiency (check ferritin!).
- Uremia (ESRD), pregnancy, diabetes.
- Medications: Antidepressants, antipsychotics, antihistamines.
Management:
- Treat underlying cause; supplement iron if ferritin < 75 ng/mL.
- First-line: Dopamine agonists (Pramipexole, Ropinirole).
- Alternatives: Alpha-2-delta ligands (Gabapentin, Pregabalin).

⭐ High-Yield: The link between RLS and iron deficiency is frequently tested. Low CNS iron is a primary hypothesis for RLS pathophysiology, making ferritin level a crucial initial lab test.

Pathophysiology of Restless Legs Syndrome

Periodic Limb Movement Disorder (PLMD) - Night Kicks Unchained

What: Repetitive, stereotyped limb movements (typically leg dorsiflexion, "night kicks") occurring primarily during NREM sleep. Patients are usually unaware of the movements themselves.
Clinical Picture: Presents as excessive daytime sleepiness, frequent nocturnal awakenings, or insomnia due to sleep fragmentation. Often first reported by a bed partner.
Diagnosis: Polysomnography (PSG) is the definitive diagnostic tool.
- Diagnostic threshold: PLM index (PLMI) ≥ 15 movements/hour in adults.
Associations: Strong overlap with Restless Legs Syndrome (RLS), but can occur independently. Also check for iron deficiency, uremia, and medication side effects (e.g., SSRIs, TCAs).
Management:
- Treat underlying conditions (e.g., iron supplementation).
- First-line agents: Dopamine agonists (Pramipexole, Ropinirole).

Polysomnography of periodic limb movements in sleep

⭐ High-Yield: PLMD is a polysomnographic diagnosis, not a clinical one. Unlike RLS, the urge to move is absent, and the movements occur during sleep, not while awake. The primary complaint is non-restorative sleep, not the movements themselves.

Other Movement Disorders - The Night Shift Grind

Bruxism (Teeth Grinding):
- Involuntary, forceful clenching or grinding of teeth, primarily during sleep.
- Associated with stress, anxiety, obstructive sleep apnea (OSA), and medications.
- Leads to jaw pain (TMD), morning headaches, and significant tooth wear.
- Management: Custom dental guards, stress reduction, treating associated OSA.

⭐ SSRI-Associated Bruxism: A notable side effect, particularly with fluoxetine. May require dose adjustment, switching the agent, or adding buspirone.

Rhythmic Movement Disorder (RMD):
- Repetitive, stereotyped movements involving large muscle groups, often at sleep onset (e.g., head banging, body rocking).
- Primarily a disorder of infancy/childhood; typically benign and self-limited.

Effects of Bruxism vs. Healthy Teeth

High‑Yield Points - ⚡ Biggest Takeaways

Restless Legs Syndrome (RLS) is a clinical diagnosis characterized by an irresistible urge to move the legs, which is worse at night and relieved by movement.

Always evaluate for iron deficiency anemia (check ferritin), a key secondary cause of RLS.

First-line pharmacotherapy includes dopamine agonists (pramipexole, ropinirole) or gabapentin.

Periodic Limb Movement Disorder (PLMD) involves stereotyped limb jerks during sleep, diagnosed via polysomnography.

Unlike the clinical diagnosis of RLS, PLMD is a polysomnographic finding.

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Sleep-related movement disorders