You cannot see enough on the CT scan, which shows only the vertebral body and the spinal canal, with no detail. This test is inadequate. You need the MRI scan (below), which shows a spinal epidural abscess (SEA) (white arrow). DM was this patient’s only risk factor. Her presentation, including the initial miss by her primary care physician, is fairly classic. She was taken emergently to surgery for evacuation of the abscess.
The diagnosis of SEA, a somewhat rare condition, often is late because its presentation is indolent and the vast majority of patients who present with similar complaints have other, less serious conditions, such as musculoskeletal back pain and renal disorders.
If the diagnosis is early, surgical evacuation and antibiotics can provide a chance for a good outcome. However, delays in diagnosis and care often result in permanent neurological deficits. The patient’s future hangs in the balance, and the astute clinician who remains vigilant will be best positioned to make a “great save.”
Clues that help differentiate SEA from more routine causes of back pain are as follows:
• Pain with SEA usually develops insidiously and is most common in the thoracic area; other spinal conditions primarily affect the cervical and lumbar areas.
• Fever is a major red flag for this condition, but it may not be present, especially early in the course of disease.
• Cord tethering may be noted as a positive straight-leg raise test result or, more frequently, as meningismus, especially when the thoracic spine is involved.
• Any potential neurological complaint that involves more than one extremity is a big clue, as in this case, that the spinal cord and not just a nerve root is being affected.
• Constipation and urinary difficulty certainly may be caused by narcotic medications, such as hydrocodone(Drug information on hydrocodone), but they should be assumed to be the result of cord compression until proved otherwise.
• A post-void residual urine volume measurement and a rectal examination can help distinguish a neurological condition from a medication adverse effect, but if doubt still exists, neuroimaging is required.
• Risk factors for SEA include injection drug abuse; any invasive procedure; immunosuppression, such as with DM; and a concomitant bacterial infection (Table).
The diagnostic study of choice for SEA is spine MRI; the thoracic spine should be included even when neurological findings appear to come from the cervical or lumbar area. If MRI is unavailable, CT myelography is an acceptable alternative.
A CT scan with contrast may be considered as a screening test because results often are available more rapidly. However, it should not be used to exclude the diagnosis of SEA because false negatives may occur for a variety of reasons, including obesity, as in this case.
SEA is very unlikely to occur in the setting of a normal erythrocyte sedimentation rate.