Spinal abscess

Etiology

• Bacterial infection of the vertebrae or intervertebral disc with subsequent abscess formation.
• Usually form secondary to a primary focus of infection, eg navel ill , lung abscessation, infected injection site, foot lesion) via hematogenous spread.
• Can be the result of direct extension from a primary insult, eg injection into the neck muscle extending into the vertebral column, epidural injection Epidural or tail docking.
• May result from external trauma to the vertebral column.
• Association with parasitic migration, and invasion from abscesses in surrounding structures have also been reported.
• Trueperella pyogenes Trueperella pyogenes is most commonly isolated but this may not necessarily be the primary bacterial cause. Pasteurella spp Pasteurella multocida, Fusobacterium necrophorum Fusobacterium necrophorum, Streptococcus spp Streptococcus spp and Salmonella dublin Salmonella spp have all been cultured from these lesions.

Predisposing factors

General

• Bacterial infection, eg navel ill Umbilicus disorders: overview, pneumonia Aspiration pneumonia, injection site abscess Skin abscess, foot lesions Necrotic hoof lesions.

Specific

• Injecting into the muscle close to the vertebral column Injecting cattle (Farmer Factsheet).
• Epidural injection Epidural. 
• Tail docking Tail amputation.

Pathophysiology

• A primary focus of infection, eg navel ill, may produce septic emboli.
• The vertebral vascular anatomy, and pressure and flow rate of blood in the vertebral venous system creates a tendency for vascular stasis which provides ideal conditions for the lodging of an embolus.
• The septic emboli lodge in the intervertebral discs or in the body of the vertebrae causing osteomyelitis +/- diskospondylitis and abscess formation.
• Large abscesses can compress the spinal cord and cause degeneration of nerves. There may also be an associated meningitis.
• Remodeling and proliferation of the vertebral bone secondary to the infection can also lead to further narrowing of the spinal canal and compression of the spinal cord.

Timecourse

• Abscesses can take weeks - months to form and develop before clinical signs are seen.

Epidemiology

• Sporadic.