Examkin

Question

Difficulty: MediumSleep-Wake Disorders

A 31-year-old woman, gravida 2, para 1, at 28 weeks gestation is evaluated in the outpatient clinic for severe insomnia. Over the past month, she has been unable to fall asleep because of an uncomfortable, aching sensation deep within her calves. She states, "I feel an overwhelming urge to move my legs to make the feeling stop." These symptoms occur exclusively when she lies down to rest at night and improve significantly when she gets out of bed and paces around the house. Her medical history includes generalized anxiety disorder, which has been stable on sertraline for the past two years. Her prenatal course has been uncomplicated, and vital signs are normal. Neurological examination reveals normal muscle strength, tone, and deep tendon reflexes in the lower extremities. Which of the following is the most appropriate initial step in the evaluation or management of this patient's sleep complaint?

  1. Measure serum ferritin concentrationAnswer
  2. B
    Reassure the patient that these sensations are normal physiologic changes of late pregnancy
  3. C
    Discontinue sertraline and immediately initiate phenelzine
  4. D
    Increase the dosage of sertraline to manage somatic anxiety symptoms
  5. E
    Schedule an in-laboratory polysomnography evaluation

Answer

The most appropriate initial step is to measure the serum ferritin concentration.
The correct answer is to measure the serum ferritin concentration. This patient's clinical presentation—an irresistible urge to move her legs that worsens at night and during rest, and improves with movement—is diagnostic of Restless Legs Syndrome (RLS). RLS is a sensorimotor sleep-wake disorder that can be primary or secondary. Secondary causes are common and include pregnancy, uremia, diabetes mellitus, and medications (especially SSRIs, SNRIs, and antiemetics). Crucially, depleted iron stores in the central nervous system play a major role in the pathophysiology of RLS. Therefore, measuring a serum ferritin level is the standard initial step in evaluation for all patients with new-onset RLS, even if a complete blood count shows no overt anemia. A ferritin level below 75 ng/mL warrants iron supplementation.

Step-by-Step Solution

1
Analyze the patient's symptoms based on timing and alleviating factors.
The irresistible urge to move the legs, worsening at rest and at night, and relief with movement indicate a clinical diagnosis of Restless Legs Syndrome (RLS).
Accurate diagnosis of the sleep-wake disorder guides appropriate workup and prevents unnecessary testing.
2
Identify potential secondary causes or exacerbating factors present in the patient's history.
The patient is pregnant and taking an SSRI (sertraline), both of which are strong risk factors for developing or worsening RLS.
Understanding the multifactorial etiology of RLS helps in managing reversible causes.
3
Determine the standard initial diagnostic workup for new-onset RLS.
Evaluate iron stores by measuring a serum ferritin concentration.
Iron deficiency, even without overt anemia, is a primary reversible cause of RLS, and central nervous system iron depletion contributes to the disorder's pathophysiology.

Key Concept

The diagnosis of Restless Legs Syndrome is primarily clinical. All patients with new-onset symptoms should have their serum ferritin concentration checked, as iron deficiency is a common, reversible cause of the disorder.
Estimated Time:1m 15s
Rate this question

Topics

Sleep-Wake Disorders

More questions from this topic