Diskitis, or spelled discitis, is an inflammation of the vertebral disk space often related to infection.
Considered with vertebral osteomyelitis, as these conditions are almost always present together.
Diskitis and vertebral osteomyelitis share much of the same pathophysiology, symptoms, and treatment.
More common in patients with immunodeficient disease such as HIV, cancer, diabetes, chronic kidney disease, and patients on glucocorticoids.
The lumbar region is most commonly affected, followed by the cervical spine and, lastly, the thoracic spine.
Incidence 1: 100,000- 1 in 250,000 cases per year.
Incidence is similar to that in the United States in other developed countries but in less developed nations, it is much more common.
In some areas of Africa, 11% of all patients seen for back pain were diagnosed with diskitis.
Infection does not ordinarily originate in the vertebra or disk space, but spreads there from other sites via the bloodstream.
Blood cultures may remain negative in infectious diskitis and leukocytosis may be absent.
Markers of inflammation such as C-reactive protein and ESR are usually markedly elevated.
Septic emboli travelling through the spinal arterial system enter the metaphyseal arteries, which have become end arteries in the adult, causing a large area of infarction.
Infarction of the vertebral endplates is followed by localized infection that subsequently spreads through the vertebral body and into the poorly vascularized disk space.
Infectious diskitis is usually associated with direct inoculation or hematogenous seeding from the primary source.
Rare cases of infectious diskitis include Pott’s disease from tuberculosis, invasive fungal disease, and brucellosis.
Infection can then spread to the epidural space or paraspinal soft tissues.
The venous system of the spine forms an anastomotic plexus, the Batson plexus, in the epidural space and this plexus drains each segmental level and is continuous with the pelvic veins.
Retrograde flow through this plexus during periods of high intra-abdominal pressure allows the spread of infection from the pelvic organs.
Pelvic disease is one of the most common primary sites of infection in patients with diskitis.
Male-to-female ratios ranging from 2:1 to as high as 5:1.
Childhood diskitis has a slight male prevalence, with a male-to-female ratio of 1.4:1.
Childhood diskitis affects patients with a mean age of 7 years.
The incidence decreases until middle age, when a second peak inincidence is observed at approximately 50 years of age.
Adult diskitis has a slow, insidious onset, which can cause diagnosis to be delayed for months.
Patients present with neck or back pain with localized tenderness.
Pain exacerbated by movement, and syptoms no alleviated with conservative treatment.
A high incidence of epidural extension of the infection exists, causing lower extremity weakness or plegia.
Fever, chills, weight loss, and symptoms of systemic disease may be present in adults but are not common.
In postoperative patients, symptoms usually begin days to weeks after surgery.
Symptoms are similar to those experienced by patients with spontaneous diskitis.
More acute course in children, with sudden onset of back pain, refusal to walk, and irritability are the most common symptoms.
In children fever is often present, accompanied by local tenderness and limited back motion.
Clinically tenderness over the involved area with concomitant paraspinal muscle spasm is the most common physical finding.
Patients have impaired mobility secondary to pain.
Accompanying neurologic deficits vary widely from 2% to 70%.
Cervical diskitis is associated with a much higher rate of neurologic deficit.
Thought to spread to the involved intervertebral disk via hematogenous spread of a systemic infection.
UTI, pneumonia, and soft-tissue infections seem to be the most common sites of origin.
Trauma has not been shown to be related.
The most common organsim involved is Staphylococcus aureus.
Escherichia coli and Proteus species are more common in patients with UTIs as the source.
Conditions that predispose patients to infections are associated with diskitis, and include HIV, diabetes, malignancies and chronic renal insufficiency.
Can also occur following surgical intervention at the site with direct inoculation of the operative site, with the rate of infection following anterior cervical diskectomy at 0.5% of cases, and the rate for lumbar diskectomy half that.
The most common organisms for direct inoculation is S aureus, but Staphylococcus epidermidis and Streptococcus species also should be considered.
Unlike adult disease childhood diskitis has not been consistently associated with a causative infection elsewhere in the body.
In children S aureus is the most common agent.
Laboratory testing is associated with an elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).
The mean ESR for patients with diskitis is 85-95 mm per hour, and it can be monitored serially to evaluate the adequacy of treatment.
The ESR may not return to normal levels despite adequate therapy.
Leukocytosis is frequently absent in diskitis, but may be present in systemic disease.
Blood cultures must be obtained in suspected disease, and empirical antibiotics initiated.
The presenc of positive blood cultures obviates the need for invasive tests.
Blood cultures are positive in only one third to one half of cases.
Sputum and urine cultures may be necessary to locate any other sources of infection,
X-rays may show disk-space narrowing, irregularities and erosion of the adjacent endplates and calcification of the anulus around the affected disk, loss of the normal trabeculation of the vertebra.
Gallium-67 and technetium-99m radionuclide scan have been utilized to detect diskitis.
Radionuclide scanning has demonstrated a high degree of sensitivity.
Indium scan shown to have a low sensitivity for diskitis.
CT scanning can detect diskitis earlier than plain radiographs, and findings include hypodensity of the intervertebral disk and destruction of the adjacent endplate and bone, with surrounding edema.
The most sensitive and specific test is MRI with T1-weighted images showing narrowing of the disk space and edema in the marrow of adjacent vertebral bodies and T2-weighted images show increased signals in both the disk space and the surrounding vertebral bodies.
Disk space involvement suggests the presence of infection, as it only is involved late in tuberculosis and very rarely in neoplasia.
With the use of intravenous contrast in CT or MRI can detect paraspinal disease.
Antibiotic treatment is directed at theisolated organism and any other sites of infection, but broad-spectrum antibiotics must be used if no organism is isolated.
Tuberculosis) must be considered in the face of persistently negative cultures.
Parenteral antibiotic treatment is usually administered for 6-8 weeks and continued until ESR has dropped by 1/3-1/2, pain has resolved and no neurologic deficits are present.
Clinical or laboratory evidence for continues infection requires rebiopay and continued antiobitoic treatment.
Bed rest to allow verebral fusion should be followed by external immobilization with a brace when the patient gets out of bed.
Bracing is used for 3-6 months following initiation of treatment to prevent collapse of the vertebral segments and kyphos formation.
Patients must be monitored to rule out progressive neurologic deficit.
Mortality associated with diskitis occurs from the spread of infection, either through the nervous system or through other organs and has been reported to be 2-12%.
Cancer is the second most common cause.
Metastatic disease is most common cause of cancer of the spine.
Approximately 70% of sbpinal lesions involve the thoracic spine.
Approximately 10% of cancers initially manifest as metastatic spinal disease.
Metastatic spinal metastases back pain usually occurs at night.
Lung cancer is the most common cause of spinal metastases.
Systemic inflammatory disease can cause diskitis.
Inflammatory back pains diminishes with activity.
Spondyloarthropathies include: psoriatic arthritis, reactive arthritis, ankylosing spondylitis, inflammatory bowel disease
Sarcoidosis can rarely manifest as diskitis.