Preliminary Diagnosis: Epidural Abscess
I. What imaging technique is first-line for this diagnosis
MRI of the spine with and without contrast. STIR and post-contrast fat-saturated images should be included.
II. Describe the advantages and disadvantages of this technique for diagnosing epidural abscess.
Advantages
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Highest sensitivity for detecting epidural abscess.
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Can detect early signs of infection, such as epidural thickening, before a discrete abscess forms.
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Can detect signal alteration in the spinal cord and narrowing of the neural foramina.
Disadvantages
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Requires significant patient cooperation to minimize motion artifact, as the exam time is lengthy.
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Expensive.
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Adequate renal function with GFR >60 is needed for IV contrast administration. Patients with GFR 30-60 can be evaluated for contrast administration on a case-by-case basis.
III. What are the contraindications for the first-line imaging technique?
Contraindicated in patients with non-MRI compatible metallic hardware or foreign bodies.
IV. What alternative imaging techniques are available?
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CT of the spine with intravenous contrast
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CT Myelography
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of epidural abscess.
CT of the spine with intravenous contrast
Advantages
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Can be obtained quickly, reducing chances of significant motion artifact in an uncooperative patient.
Disadvantages
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Less sensitive and specific for detection of abscess compared to MRI.
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Requires adequate renal function for administration of IV contrast, generally creatinine <1.7.
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Utilizes ionizing radiation.
CT myelography
Advantages
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Better at detecting deformity of the thecal sac and block of CSF flow than CT with IV contrast.
Disadvantages
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Requires lumbar puncture for administration of intrathecal contrast.
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Not specific for abscess. Herniated disc or epidural hematoma can produce similar imaging findings.
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Utilizes ionizing radiation.
VI. What are the contraindications for the alternative imaging techniques?
CT of the spine with intravenous contrast
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Contraindicated in pregnant patients.
CT Myelography
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Contraindicated in pregnant patients.
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Contraindicated in patients with platelets <50,000 or INR >1.7 due to risk of epidural hematoma secondary to lumbar puncture.
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