A 58-year-old man is brought to the emergency department by his husband due to severe, wor… — USMLE Step 3

A $58$ -year-old man is brought to the emergency department by his husband due to severe, worsening mid-back pain over the past week. The patient has a history of type 2 diabetes mellitus and intravenous substance use. Over the last $12$ hours, he has developed profound weakness in both legs and has been unable to urinate. His temperature is $38.9^\circ\text{C}$ ( $102.0^\circ\text{F}$ ), blood pressure is $118/76\text{ mm Hg}$ , pulse is $108/\text{min}$ , and respirations are $18/\text{min}$ . Physical examination reveals marked tenderness to percussion over the midthoracic spine. Neurological examination shows $3/5$ muscle strength in the bilateral lower extremities, decreased sensation to pinprick below the umbilicus, and hyperreflexia at the patellae with bilateral upgoing plantar reflexes. Digital rectal examination demonstrates decreased anal sphincter tone. Which of the following are the most appropriate immediate steps in this patient's diagnostic workup? (Select all that apply)

Urgent magnetic resonance imaging of the entire spine with gadoliniumAnswer
Blood cultures from two separate peripheral sitesAnswer
C
Lumbar puncture for cerebrospinal fluid cell count and culture
D
Non-contrast computed tomography of the thoracic and lumbar spine
E
Plain radiography of the thoracic and lumbar spine

Answer

The correct diagnostic steps are urgent magnetic resonance imaging of the entire spine with gadolinium and blood cultures from two separate peripheral sites.

This patient's acute presentation of severe back pain, fever, and signs of spinal cord compression (lower extremity weakness, sensory level, bowel/bladder dysfunction, and hyperreflexia) in the setting of intravenous substance use is highly suspicious for a spinal epidural abscess (SEA). SEA is a neurosurgical emergency. The initial diagnostic workup must rapidly establish the anatomic extent of the disease and the causative organism without causing harm. Urgent magnetic resonance imaging (MRI) of the entire spine with gadolinium is the gold standard diagnostic test to visualize the epidural collection and the severity of cord compression. Concurrently, blood cultures must be drawn from two separate sites to identify the pathogen and allow for appropriately targeted long-term intravenous antibiotic therapy.

Step-by-Step Solution

Identify the primary clinical syndrome based on the patient's presentation.

The patient demonstrates the classic triad for a spinal epidural abscess (SEA): severe focal back pain, fever, and progressive neurological deficits (leg weakness, sensory level, urinary retention, and upper motor neuron signs).

Recognizing this neurological emergency is critical to prevent permanent paralysis and dictates immediate diagnostic sequencing.

Determine the optimal neuroimaging modality.

Urgent magnetic resonance imaging (MRI) of the spine with contrast is selected.

MRI is the most sensitive and specific test for diagnosing SEA, evaluating the exact location and size of the abscess, and assessing the degree of spinal cord compression to guide surgical decompression.

Select the appropriate initial laboratory workup for identifying the etiology.

Blood cultures from two separate venipuncture sites are selected.

Identifying the microbiologic cause (most commonly Staphylococcus aureus) is essential for tailoring long-term antibiotic therapy. Blood cultures are positive in approximately 60% of cases and must be drawn before initiating empiric antibiotics.

Key Concept

Patients presenting with signs of a spinal epidural abscess with cord compression require an immediate diagnostic workup consisting of an urgent spinal MRI with contrast and concurrent peripheral blood cultures to facilitate rapid neurosurgical intervention and targeted antimicrobial therapy.

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