Chapter 52: Diskitis

DEFINITIONS AND EPIDEMIOLOGY

The term diskitis (or discitis) refers to an infection of the intervertebral disk. Diskitis typically occurs in children aged 1–5 years, but older children and adolescents are occasionally affected.^1,2 The infection spreads to adjacent vertebral endplates, resulting in vertebral osteomyelitis in association with the diskitis (spondylodiskitis).^1,2 As a result of a frequent delay in presentation or diagnosis, most children present with spondylodiskitis rather than isolated diskitis. In comparison to other forms of acute hematogenous osteomyelitis in children, spondylodiskitis is uncommon, with one series reporting only six cases in a 3-year period among 212 children with osteomyelitis involving the musculoskeletal system. Given an estimated incidence of childhood osteomyelitis ranging from 1 to 5 per 10,000 children, it would be reasonable to attribute an incidence of spondylodiskitis to be less than 1 in 100,000 children.²³ Boys are more frequently affected than girls (male : female ratio 1.7 : 1).^1–5

PATHOGENESIS

Diskitis is thought to be caused by bacterial seeding of the disk space following a transient bacteremia. Historically, it has been widely suggested that diskitis is nonbacterial, or inflammatory in nature; however, this perspective is no longer considered accurate, given the findings of bacteria grown in tissue culture when needle aspiration or open surgical biopsy is performed.³ There is also substantial clinical experience in managing this condition effectively with sequential parenteral to oral antibiotic treatment.^1,4,6 Treatment should therefore be based on the presumption of a bacterial etiology.

Bacteria reach the disk space via the spinal arteries, which form one median and two lateral anastomotic chains along the posterior surface of the vertebral bodies. In young children, the bacteria pass through vascular channels into the cartilaginous region of the disk space, which serves as a conduit for the spread to the bone of each adjacent vertebral body.^1,7–10 Diskitis is more common in the anterior part of the vertebrae (body). The lumbar vertebrae are involved in at least 50% of cases of vertebral osteomyelitis with the lower lumbar levels affected more frequently than the upper lumbar vertebrae. The thoracic spine is the next most common area of involvement, followed by the cervical region.¹¹ During the evolution of the disease, the intervertebral disk and the contiguous vertebral body surfaces are often damaged, which leads to disc space narrowing and bony erosion.⁹

CLINICAL PRESENTATION

The presentation in infants or toddlers is usually nonspecific, which contributes to diagnostic delay. In one case series, diagnosis was established an average of 42 days after symptom onset.¹² Affected children seldom appear ill. They may be irritable or fussy. They may have poorly localized back, hip, or abdominal pain or may refuse to walk or stand. Physical findings may include tenderness on palpation in the area of the involved disk, ...