Back pain is usually localized to the midline, with marked tenderness to percussion of the spinous process.²⁷ Radicular pain or neurological deficits are found in 62% and 41% of patients, respectively.²⁵

When assessing for cord compression, it is important to note that the physical examination is less sensitive than a history of urinary retention. Several features of the examination can be helpful. For example, sensory and motor deficits, as well as a positive straight leg raising test, occur in about 80% of cases.²⁷ More specific findings include saddle anesthesia, which has a sensitivity of about 75%, and diminished anal sphincter tone with a slightly higher sensitivity.²⁷ In addition, it is important that during the physical exam, particular attention is given to the entire integumentary and musculoskeletal system to assess all potential sources of infection.

Diagnostic Studies

Recommended laboratory studies include blood cultures (which have excellent correlation with pathogenic abscess organisms and are helpful in guiding antibiotic therapy),^14,15 complete blood count, and erythrocyte sedimentation rate (ESR).

A normal white blood cell count (WBC) is insufficient to rule out the diagnosis. In fact, in Davis et al., the WBC count was elevated in only 60% of patients. However, the ESR was elevated above 20 mm/h in 98% of patients, although it was frequently obtained after admission and in patients in whom the diagnosis was already suspected.²⁵ The ESR may also be used to guide therapy, because it has been shown to correlate with disease resolution.^14,15

Conventional radiographic investigations are not helpful,^10,14,16,21 as sclerotic changes are present only after the SEA has developed into a chronic condition.²⁸ Gadolinium-enhanced MRI is the imaging modality of choice, as it is accurate in defining the extent of the abscess along with the degree of thecal sac compression.²⁹ MRI also aids in the differentiation of SEA from spinal tumors, hematomas, transverse myelitis, spinal cord infarction, or intervertebral disk prolapse.²⁹

If MRI is unavailable, CT myelography is an equally sensitive diagnostic option^{10,14,15,21,24,30} and is the most commonly used diagnostic method worldwide,⁷ despite possessing an inherent increased risk of infection.^31,32 CT without myelography is noninvasive but can make delineation of the spinal cord from the epidural space difficult.³²

Lumbar puncture is contraindicated, as it carries the risk of spreading bacteria into the subarachnoid space with resultant meningitis, and should not be performed.^7,26

Management

Surgical drainage and associated laminectomy within 24 hours of presentation are the mainstay of therapy.^4,14 Laminotomy also has been performed in an attempt to preserve the integrity of the spine following operative drainage^33-35 and is especially advantageous for children by allowing for attempted closure of the posterior covering of the spinal canal.⁷ Interventional radiology is an alternative for cases in which the SEA is small and therefore suitable for attempted CT-guided aspiration and drainage.⁴