The incidence of spontaneous epidural abscess in Olmsted County from 1990 through 2000: a rare cause of spinal pain.

OBJECTIVE: The primary objective of this study is to determine the population-based incidence of spontaneous epidural abscess. The secondary objective is to characterize the clinical course of patients with this rare infectious disease.

DESIGN: The records-linkage system of the Rochester Epidemiology Project was used to identify incident cases of spontaneous epidural abscess in residents of Olmsted County, Minnesota, USA, from 1990 through 2000.

SETTING: Tertiary referral medical center.

PATIENTS: All patients were residents of Olmsted County and had spontaneous epidural abscesses that were radiographically or surgically confirmed.

RESULTS: Eight patients, including six women, were identified and the mean age was 56 years (range, 40-80). The incidence of epidural abscess was 0.88 cases per 100,000 person-years (95% confidence interval, 0.27-1.48). The median time from symptom onset to diagnosis was 18 days (interquartile range, 4-30 days). Six patients presented with spinal pain and one presented with focal neurological deficits. Risk factors were identified in all patients, including concomitant infections, diabetes mellitus, immunosuppression, and intravenous substance abuse. Staphylococcus aureus was cultured in six patients and streptococcal species were cultured in two patients. Three patients were treated surgically and five received medical treatment. One patient treated surgically and one patient treated medically had residual neurological deficits. One patient, who was immunosuppressed and received medical treatment died of pneumonia.

CONCLUSIONS: This is the first published report of the population-based incidence of spontaneous epidural abscess. These findings could serve as a reference point for further epidemiological research related to this uncommon infection.