Spinal Infections

Ankur S. Narain, Fady Y. Hijji, Philip K. Louie, Daniel D. Bohl, and Kern Singh

15.1 Introduction

Spinal infections require early diagnosis in order to prevent both structural and neurologic compromises. The differential diagnoses related to symptoms associated with infection include degenerative disease, neoplasm, trauma, and vascular compromise. As such, knowledge of the specific clinical and imaging findings associated with infectious etiologies of the spine is crucial to ensure timely recognition of disease presentation and initiation of treatment (Table 15.1).

15.2 Vertebral Osteomyelitis and Diskitis

• Background and etiology:

– Infection of the vertebral body or intervertebral disk.

– Most commonly caused by hematogenous spread of Staphylococcus or Streptococcus spp.

∘ Spread from vascular end plates to:

▪ Avascular disk space (diskitis).

▪ Vertebral bodies (osteomyelitis).

– Most commonly affects lumbar (58%) > thoracic (30%) > cervical (11%) vertebrae.

– Risk factors include diabetes mellitus, intravenous drug use, corticosteroid therapy.

• Presentation:

– Common symptoms include axial pain (86%) and fever (35–60%).

– Neurologic symptoms (34%):

∘ Radiculopathy, limb weakness, dysesthesia, urinary retention.

• Clinical evaluation:

– Inquire about constitutional symptoms, travel history, recent spinal procedures with or without instrumentation.

– Labs:

∘ White blood cell (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP).

▪ ESR and CRP highly specific (98–100%).

▪ CRP correlates with response to treatment.

∘ Blood cultures:

▪ Positive in 58% of cases.

∘ Urinalysis and urine culture:

▪ To determine if urinary tract infection (UTI) is a source of the primary infection.

• Radiographic evaluation:

– Plain radiographs: findings occur several weeks after infection onset:

∘ Regional osteopenia, periosteal reaction/thickening, focal bone lysis or cortical loss, endosteal scalloping, loss of bony trabeculae.

– Magnetic resonance imaging (MRI; 94% sensitivity): preferred imaging modality if neurologic deficit is present:

∘ T2-weighted imaging shows edema and fluid within disks and adjacent soft tissue (Fig. 15.1).

– Computed tomography (CT) scan (94% sensitivity): performed if MRI contraindicated:

∘ Superior to plain radiographs and MRI at analyzing bony margins and identifying involucrum/sequestrum.

– Bone scan (67% sensitivity): positive within a few days of symptom onset, nonspecific.

• Treatment:

– Medical treatment:

∘ Preferred initial therapeutic option.

∘ Intravenous (IV) antibiotics for 6 to 8 weeks, initial broad coverage with narrowing to pathogen-specific regimen pending susceptibilities.

– Surgical therapy:

∘ Indications:

▪ Failure of medical management.

▪ Drainage of abscesses and debridement of infected tissue.

▪ Development of neurological deterioration.

▪ Decompression of neural structures.

▪ Spinal instability.

Fig. 15.1 (a) Sagittal T1-weighted MRI showing osteomyelitis involving the T12–L1 disk space, vertebral bodies, and surrounding soft tissue. (b) Sagittal T2-weighted MRI showing osteomyelitis involving the T12–L1 disk space, vertebral bodies, and surrounding soft tissue.