Spontaneous epidural abscess: analysis of 15 cases with emphasis on diagnostic and prognostic factors.

Purpose: To describe the incidence and characterize the clinical manifestations, diagnosis and outcome of spontaneous epidural abscess (SEA) not associated with neurosurgical procedures or instrumentation of the spine.

Methods: Review of cases of SEA over 10 years. Diagnosis was made by imaging-techniques and surgical examination.

Results: Fifteen patients were studied. The incidence of SEA was 0.4 cases per 100,000 person-years. Infection gained access to the epidural space haematogenously in 9 patients (60%). SEA was located at the lumbar (7 cases), cervical (4), cranial (2) and thoracic (1) areas. Local pain was the most common manifestation (93.3%); fever was absent in 40%. One third did not show neurologic abnormalities. Staphylococcus aureus was the most commonly isolated agent (87% of cases). All the patients received antimicrobial therapy for a mean period of 6.1+/-3.9 weeks. In addition, open surgical drainage or CT-guided needle aspiration was successfully performed in 10 and 3 patients respectively. Two patients were managed with antibiotics alone. Poor outcome occurred more frequently in patients with abscess at higher levels (67% in cranial or cervical abscesses versus 0% in thoracic or lumbosacral abscesses). An association was found between delayed diagnosis and poor outcome (p<0.05). Overall, 54% of our patients recovered without sequelae.

Conclusions: SEA resulted from the extension of nearby or distant infections into the epidural space. Diagnosis was frequently delayed and the patient's neurologic status at presentation was the most important predictor of the outcome. The onset of spinal pain in patients with focal infections should prompt MRI of the spine, even in the absence of neurologic abnormalities or fever.