Examkin

Question

Difficulty: Very hardDiagnostic Workup and Test Sequencing

A 64-year-old man is evaluated in the emergency department for a 5-day history of progressively worsening, severe mid-back pain. He describes the pain as a dull, constant ache that is not relieved by position changes or over-the-counter analgesics. Over the past 12 hours, he has developed bilateral leg heaviness and difficulty initiating micturition. His medical history is significant for type 2 diabetes mellitus, hypertension, and a recent episode of methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia secondary to a peripheral intravenous catheter infection 3 weeks ago. He completed a 14-day course of oral cephalexin for the bacteremia. His temperature is 38.2°C (100.8°F), blood pressure is 145/88 mmHg, and pulse is 98/min. Physical examination reveals focal tenderness to percussion over the T8-T10 spinous processes. Neurological examination demonstrates 4/5 strength in the bilateral lower extremities, diminished deep tendon reflexes at the knees and ankles, and decreased sensation to pinprick below the umbilicus. A bladder scan shows a post-void residual volume of 450 mL.

Which of the following diagnostic steps should be prioritized and performed concurrently in this patient's initial evaluation? (Select 2)

  1. Magnetic resonance imaging of the entire spine with and without intravenous contrastAnswer
  2. Two sets of peripheral blood culturesAnswer
  3. C
    Lumbar puncture for cerebrospinal fluid analysis
  4. D
    Non-contrast computed tomography of the thoracic spine
  5. E
    Measurement of serum human leukocyte antigen B27

Answer

The correct diagnostic steps to perform concurrently are magnetic resonance imaging of the entire spine with and without intravenous contrast, and obtaining two sets of peripheral blood cultures.
The correct diagnostic steps are magnetic resonance imaging (MRI) of the entire spine with contrast and two sets of peripheral blood cultures. This patient's presentation of fever, severe focal back pain, and acute neurological deficits (paraparesis, sensory level, urinary retention) in the setting of recent staphylococcal bacteremia is highly suspicious for a spinal epidural abscess (SEA). SEA is a life-threatening neurological emergency. MRI of the entire spine with and without contrast is the definitive imaging modality of choice due to its superior soft-tissue resolution, which allows for precise localization of the abscess and evaluation of spinal cord compression. The entire spine should be imaged because up to 15% of patients with SEA have noncontiguous 'skip' lesions. Concurrently, two sets of peripheral blood cultures must be drawn prior to the administration of empiric broad-spectrum antibiotics. Blood cultures are positive in over 60% of SEA cases and are crucial for identifying the causative pathogen (most commonly Staphylococcus aureus) and tailoring long-term antimicrobial therapy.

Step-by-Step Solution

1
Identify the clinical syndrome based on the classic triad of symptoms and signs.
The patient presents with focal back pain, fever, and new-onset neurological deficits (lower extremity weakness, sensory loss, urinary retention with high post-void residual), which is the classic presentation for a spinal epidural abscess (SEA).
Recognizing this triad is essential because SEA is a neurological emergency requiring rapid diagnosis and intervention to prevent irreversible paralysis.
2
Recognize the predisposing risk factors.
The patient has a history of type 2 diabetes mellitus and recent MSSA bacteremia, both of which significantly increase the risk for hematogenous seeding to the epidural space.
Identifying these risk factors strongly increases the pre-test probability of SEA, dictating the urgency of the diagnostic workup.
3
Select the definitive concurrent diagnostic studies.
The patient requires urgent Magnetic Resonance Imaging (MRI) of the entire spine with contrast to confirm the anatomical location and extent of the abscess, concurrently with two sets of peripheral blood cultures to identify the causative organism.
MRI is the gold standard for visualizing soft tissue infections in the epidural space. Blood cultures must be obtained before initiating empiric antibiotics to guide targeted antimicrobial therapy, as hematogenous spread is the most common etiology.

Key Concept

The initial evaluation of a suspected spinal epidural abscess requires urgent magnetic resonance imaging (MRI) of the spine with contrast to assess structural compromise, concurrently with peripheral blood cultures to establish a microbiologic diagnosis before starting empiric antibiotics.
Estimated Time:2m 0s
Rate this question

Topics

Diagnostic Workup and Test Sequencing

More questions from this topic