There are several different categories of spinal infections, including vertebral osteomyelitis, discitis, spinal epidural abscess, spinal subdural empyema, meningitis, and spinal cord abscess. These infections typically present with back pain, fever, and overlying spine tenderness. Major risk factors include diabetes, IV drug abuse, chronic renal failure, alcoholism, and older age. Staphylococcus aureus is the most common infectious agent.
Osteomyelitis
Vertebral osteomyelitis comprises 2-4% of all cases of osteomyelitis and occurs most commonly at the lumbar spine. As the vertebrae receive a rich blood supply, infections may spread hematogenously from distant sites, or they may directly extend from a local infection caused by surgery, trauma, or lumbar puncture. MRI imaging, blood cultures and possible biopsy guide treatment. Over 90% of cases are treated with antibiotics and immobilization. In rare cases with spinal instability due to bony deformity, or those that are refractory to medical treatment, surgery may be needed.
Discitis and Spondylodiscitis
Discitis is inflammation or infection of the nucleus pulposis of the intervertebral disc. This may occur in the pediatric or adult populations. Spondylodiscitis is a combination of discitis and spondylitis, which is inflammation of one or more of the spinal vertebrae. Spondylodiscitis is the most common complication of sepsis or local infection, usually in the form of an abscess. The main causative organisms are Staphylococci and Mycobacterium tuberculosis.Immunocompromised individuals are at risk, especially those with cancer, infection, or who are taking immunosuppressive drugs used for organ transplantation. The most common organisms are Staphylococcus aureus and Escherichia coli. Diagnosis of spondylodiscitis is made via spinal MRI. Most cases are managed non-surgically with antibiotics and immobilization. There is no standard therapeutic guideline; however, IV antibiotics are recommended for 2-4 weeks. Spinal fixation, debridement, and neural decompression may be necessary depending on extent of infection.
Epidural Abscess
Spinal epidural abscess is often associated with vertebral osteomyelitis and discitis. The thoracic spine is most commonly affected. If the spinal cord or nerve roots are involved, the patient may experience symptoms of myelopathy or radiculopathy in addition to fever and local pain. Imaging of choice is MRI. Treatment is controversial. Early surgical drainage combined with antibiotics is recommended in most cases to ensure preservation of neurologic function. Those who present with neurologic deficit such as paralysis rarely recover function, despite undergoing surgery.
Subdural Abscess/Empyema
Subdural abscess or empyema is infection between the outermost layer of the meninges of the spinal cord, the dura and arachnoid mater. Symptoms include back pain, and, in severe cases, myelopathy and caudaequina syndrome from spinal cord cord and nerve root compression.Subdural empyema is a rare infection and is most often due to hematogenous spread of distant infection or adjacent spread from osteomyelitis. The most common organisms are Staphylococcus aureus and streptococci. MRI with contrast is the diagnostic modality of choice, although CT myelography may be considered. Treatment for all cases requires prompt surgical drainage and antibiotic therapy.
References
- Greenlee JE. Subdural empyema. Curr Treat Options Neurol. 2003; 5(1): 13-22.