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Findings: T-1 weighted and double echo T-2 weighted sagittal T-1 and gradient echo axial, and contrast-enhanced T- 1 weighted sagittal and axial images of the thoracic spine were obtained.

Extensive abnormal collection in the posterior epidural space extending from the cervical region through the lowermost visualized portions of the thoracic spine. The signal is of intermediate on the T-1 and proton density images and of increased signal on the T-2 weighted images. Subsequent to the injection of gadolinium, there is enhancement of the dura as well as peripheral enhancement surrounding this collection. However, there is no evidence of spinal cord enhancement. There are multiple strands of epidural fat extending through the aforementioned enhancing fluid collection with a loculated appearance. At multiple levels the fluid collection appears to extend into the left neural foramina. The signal intrinsically within the cord, vertebral bodies, and disc spaces are all normal.

Diagnosis: Extensive posterior epidural abscess. This was confirmed surgically with 35 cc of pus removed.

Discussion: Spinal epidural infection.

The incidence is 2 per 10,000 hospital admissions. The risk factors are diabetes mellitus, IV drug use, chronic renal failure, and alcohol abuse. The symptoms are back pain, sensory motor deficits, fever, and obtundation. The organism is usually staph aureus in approximately 62% of infected individuals. The location is 25% confined to the cervical spine; 25% to the lumbar spine; and 50% to the thoracic spine. Two-thirds of the cases are along the anterior epidural space or circumferentially oriented and associated with anterior osteomyelitis or discitis.

MRI is now the preferred imaging modality for evaluating the possibility of a spinal epidural abscess. The two most common appearances were homogeneous or heterogeneous enhancement of the solid portion of the spinal epidural abscess, and a thin or thick enhancement around the liquefied collections of pus. Dural enhancement is seen in patients with lengthy vertebral involvement. Changes in abscess size correlate well with clinical improvement or deterioration. Persistent contrast enhancement is noted frequently at concommitant sites of discitis, osteomyelitis, or surgical drainage sites despite clinical improvement.

References:
1. Smith AS, Blaser Sl. Infections and inflammatory processes of the spine.
Radiologic Clinics of America 1991; 29: 809-827.
2. Hlavin ML, Kaminski HJ, Ross JS et al Spinal epidural abscesses; a ten-year
perspective. Journal of Neurosurgery 1990; 27: 177-184.
3. Numaguchi Y. Rigamonti D. Spinalepidural abscess; evaluation with gadolinium-
enhanced MR imaging. Radiographics 1993; 13: 545-559.

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