In retrospect, the intraoperative films obtained a month earlier showed subtle irregularities of the end plates. Gram's staining showed numerous white cells but no organisms. Cytologic evaluation showed no evidence of cancer. Culture of the fluid grew Staphylococcus epidermidis. Two sets of blood cultures and a urine culture were negative.
Older patients can have a chronic infection without having a fever or an elevated white-cell count.
The patient did not have an epidural abscess at surgery, but the findings of nonmechanical back pain, an elevated erythrocyte sedimentation rate, and worsening anemia are all consistent with the presence of an unrecognized, smoldering infection. I am uncertain whether S. epidermidis is the actual pathogen or a contaminant. The patient received six weeks of intravenous vancomycin. Over the next several months, his back pain resolved, his erythrocyte sedimentation rate normalized to 20 mm per hour, and radiographs of his spine showed gradual improvement. The improvement in the patient's symptoms and the normalization of his erythrocyte sedimentation rate with antibiotic therapy confirm my suspicion that infection was the cause of his problems.