Epidemiology

Spinal epidural abscess (SEA) is uncommon. Reported incidence has risen over the past three decades: earlier studies reported an incidence of approximately 0.2 to 2.0 cases per 10,000 hospital admissions, but more recent estimates are around 2 to 12.5 cases per 10,000 admissions.[2][6][7][8][9] This increase may in part be due to a genuine rise in specific risk factors (e.g., spinal surgery and intravenous drug use); SEA after spinal anaesthesia is increasing in industrialised nations.[4][5] However, increased detection by improved imaging (chiefly magnetic resonance imaging) is also likely to contribute to the greater reported incidence.[2][9][10]

The prevalence rate of SEA shows a male-to-female ratio of 1.66:1; however, this likely relates to the predominance of the risk factors rather than any predilection as such.[9]

In one meta-analysis, thoracic SEA accounted for 55% of cases, lumbar for 30%, and cervical for 15%; 80% of SEAs were situated in the posterior epidural space and 20% anteriorly.[11] SEA commonly occurs within the thoracic and lumbar regions due to the larger epidural space, an abundance of infection-liable fat, and the presence of a low-pressure vertebral venous system (Batson venous plexus) that communicates freely with the abdominal and pelvic venous systems.[9]​ Infection can span different anatomical levels.

Mortality due to SEA has decreased; reported mortality rates range from 16% in a meta-analysis published in 2000 to more recent estimates of 3.7% to 11.8%.[9][12][13][14][15]​ Among older adults aged ≥80 years with SEA, in-hospital mortality rates of 5.6% and 11.8% have been reported.[14][15]​ At 5 years post diagnosis, a single centre study found an overall all-cause mortality of 14% among patients with SEA.​​​[16]​ Mortality is mostly following sepsis or meningitis.

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