Sometimes the cause is bacteremia due to medical instrumentation, a dental procedure, or IV drug use. Rarely, a similar abscess occurs in the subdural space.
[msdmanuals.com]
[…] back pain, particularly when there is focal percussion tenderness over the spine, or if they have a fever or have had a recent infection or dental procedure.
[merckmanuals.com]
An underlying infection is often present; it may be remote (eg, endocarditis, furuncle, dental abscess) or contiguous (eg, vertebral osteomyelitis, pressure ulcer, retroperitoneal
[msdmanuals.com]