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Difficulty: HardDiagnostic Workup and Test Sequencing

A 58-year-old man presents to the emergency department with a 3-day history of progressively worsening mid-back pain and subjective fevers. Over the past 12 hours, he has noted profound weakness in both legs and an inability to urinate. His medical history is significant for type 2 diabetes mellitus and opioid use disorder, with his last intravenous injection occurring one week ago. His temperature is 38.6°C (101.5°F), blood pressure is 110/70 mmHg, pulse is 108/min, and respiratory rate is 18/min. Physical examination reveals focal tenderness to percussion over the midthoracic spine. Neurologic examination demonstrates 3/5 motor strength in the bilateral lower extremities, decreased pinprick sensation below the umbilicus, and absent patellar and Achilles reflexes. Digital rectal examination reveals markedly diminished anal sphincter tone. Which of the following diagnostic tests are indicated as the most appropriate next steps in this patient's evaluation? (Select all that apply)

  1. Magnetic resonance imaging of the entire spine with and without contrastAnswer
  2. Peripheral blood culturesAnswer
  3. C
    Computed tomography of the thoracic and lumbar spine without contrast
  4. D
    Lumbar puncture for cerebrospinal fluid analysis
  5. E
    Image-guided percutaneous needle aspiration of the epidural space

Answer

The most appropriate immediate diagnostic steps are magnetic resonance imaging of the entire spine with and without contrast, and peripheral blood cultures.
This patient's presentation of fever, focal back pain, and acute myelopathy in the setting of intravenous drug use is highly suspicious for a spinal epidural abscess (SEA) causing acute spinal cord compression. The diagnostic workup must rapidly confirm the presence and extent of the abscess and identify the causative pathogen simultaneously. Magnetic resonance imaging of the entire spine with and without gadolinium contrast is the gold-standard imaging modality. The entire spine is evaluated because synchronous, non-contiguous skip lesions are common. Concurrently, peripheral blood cultures should be obtained before initiating empiric antimicrobial therapy, as they are frequently positive and can often obviate the need for invasive epidural tissue sampling.

Step-by-Step Solution

1
Analyze the clinical presentation and physical examination findings.
The patient exhibits the classic triad of spinal epidural abscess (SEA): severe back pain, fever, and acute neurologic deficits (paraparesis, sensory level, urinary retention, and diminished rectal tone). The risk is elevated by his history of intravenous drug use and diabetes.
Recognizing the syndrome of acute spinal cord compression secondary to infection dictates the urgency and type of the diagnostic workup.
2
Determine the optimal imaging strategy.
Urgent magnetic resonance imaging (MRI) of the entire spine with and without gadolinium contrast is indicated.
MRI provides the necessary soft-tissue resolution to identify an epidural abscess and assess cord compression. The entire spine must be imaged because non-contiguous 'skip' lesions occur in nearly 10% of cases.
3
Determine the appropriate microbiologic diagnostic sequencing.
Peripheral blood cultures must be drawn concurrently with the arrangement for imaging.
Blood cultures will identify the causative organism (most commonly Staphylococcus aureus) in over 60% of cases. They must be obtained prior to the administration of empiric broad-spectrum antibiotics to guide definitive therapy.

Key Concept

Diagnostic Workup and Test Sequencing for suspected spinal epidural abscess requires immediate, concurrent execution of non-invasive definitive imaging (whole-spine MRI) and microbiologic sampling (blood cultures), while strictly avoiding contraindicated procedures like lumbar puncture.
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Diagnostic Workup and Test Sequencing

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