The Clinical Syndrome

Discitis is an often misdiagnosed cause of spine pain that, if undiagnosed, can result in paralysis or life-threatening complications. Although discitis can occur anywhere in the spine, the lumbar spine is affected most often, followed by the thoracic, then the cervical spine. Discitis occurs more commonly in males and can occur spontaneously by hematogenous seeding, most frequently as a result of urinary tract infections that spread to the spinal epidural space through Batson’s plexus. More commonly, discitis occurs after instrumentation of the spine, including surgery, diskography, and epidural nerve blocks. There is a bimodal age distribution in patients suffering from discitis with a peak before the age of 20 and a second peak between the ages of 50 and 70.

Not surprisingly, the infectious agents most frequently responsible for discitis are the same agents that cause urinary tract infections. The literature has suggested that the administration of steroids into the epidural space causes immunosuppression, with a resultant increase in the incidence of discitis. Although this suggestion is theoretically plausible, the statistical evidence, given the thousands of epidural steroid injections performed around the United States on a daily basis, calls this concept into question. Discitis has a 2 : 1 male predominance in adult patients. The average age of occurrence in children is approximately 7 years, and in adults it is the fifth decade of life. Untreated, the mortality associated with discitis approaches 10%.

The patient with discitis initially presents with ill-defined pain and spasm of the paraspinous musculature in the segment of the spine affected (e.g., cervical, thoracic, or lumbar) ( Fig. 86.1 ). This pain becomes more intense and localized as the infection involves more of the disks and adjacent vertebral bodies and compresses neural structures. Low-grade fever and vague constitutional symptoms, including malaise and anorexia, progress to frank sepsis with high-grade fever, rigors, and chills. At this point, the patient begins to experience sensory and motor deficits, as well as bowel and bladder symptoms as a result of neural compromise. As the infection continues to expand into the epidural space, compromise of the vascular supply to the affected spinal cord and nerve occurs, with resultant ischemia and, if untreated, spinal cord infarction and permanent neurologic deficits. Even with antibiotic therapy, there is an approximate 3% mortality associated with discitis.

If discitis is not promptly diagnosed, compression of the involved neural structures may continue, and the patient’s neurologic status may deteriorate rapidly. If diagnosis is not made and treatment initiated, irreversible motor and sensory deficit will result.

Signs and Symptoms

The patient with discitis initially presents with ill-defined pain in the general area of the infection. At this point, the patient may have mild pain on range of motion of the affected segments. The neurologic examination is within normal limits. A low-grade fever or night sweats may be noted. Theoretically, if the patient has received steroids, these constitutional symptoms may be attenuated or their onset may be delayed. As the abscess increases in size, the patient appears acutely ill, with fever, rigors, and chills. The clinician may be able to identify neurologic findings suggestive of spinal nerve root or spinal cord compression. Subtle findings that point to the development of myelopathy (e.g., Babinski’s sign, clonus, and decreased perineal sensation) may be overlooked if not carefully sought. As compression of the involved neural structures continues, the patient’s neurologic status may deteriorate rapidly. If the correct diagnosis is not made, irreversible motor and sensory deficit will result.

Testing

Plain radiographs often reveal the evidence of disk space narrowing and end-plate changes that are suggestive of discitis; however, these changes may not be present early in the course of the disease ( Fig. 86.2 ). Early diagnosis is best made with the use of radionucleotide scanning with gallium-67 and technetium-99m ( Fig. 86.3 ). Both magnetic resonance imaging (MRI) and computed tomography (CT) are highly accurate in the diagnosis of discitis and are probably more accurate than myelography in the diagnosis of intrinsic disease of the spinal cord and spinal tumor, among other disorders ( Fig. 86.4 ). Needle or open surgical biopsy for culture should strongly be considered in all patients thought to be suffering from discitis, but antibiotic treatment should not be delayed if these procedures are not readily available ( Fig. 86.5 ).

A, Plain film shows loss of disk space and end-plate destruction at T12–L1. This appearance is highly suggestive of infection. B, Axial magnetic resonance imaging at the same level indicates a paravertebral collection.

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