Introduction
Background
Diskitis is an inflammation of the vertebral disk space often related to infection. Infection of the disk space must be considered with vertebral osteomyelitis, as these conditions are almost always present together and share much of the same pathophysiology, symptoms, and treatment. Although diskitis and associated vertebral osteomyelitis are uncommon conditions, they are often the causes of debilitating neurologic injury. Unfortunately, morbidity can be exacerbated by a delay in diagnosis and treatment of this condition. The lumbar region is most commonly affected, followed by the cervical spine and, lastly, the thoracic spine.1,2,3,4,5
Axial CT scan in a patient with diskitis demonstrates extensive destruction of the vertebral endplate. Note the preservation of the posterior elements, including facet joints, lamina, and spinous process. This is characteristic for pyogenic diskitis and less common in tuberculosis (Pott disease).
Sagittal T1-weighted MRI of the lumbar spine in a 74-year-old man, revealing diskitis of the L4-L5 disk space. Note extensive destruction of the endplates of the adjacent vertebral bodies. No compression of the thecal sac is present, which is an important consideration when contemplating surgical intervention.
Contrast-enhanced sagittal T1-weighted MRI image in a 55-year-old woman shows thoracic diskitis with an associated epidural abscess and spinal cord compression. Because of the significant cord compression, this patient underwent surgical decompression.
Trajectory of a needle in a biopsy of the infected disk space guided by CT scan. Care is taken to avoid the thecal sac and nerve roots.
Recent studies
Sharma et al reported on the severe complication of diskitis following diskography. They found that based on the available clinical evidence, IV or intradiskal antibiotics during diskography have not been conclusively shown to decrease the rate of diskitis over sterile technique alone. Animal model research supports prophylactic antibiotic use when used before iatrogenic inoculation of intervertebral disks. Both single- and double-needle techniques when used with stylettes are superior to nonstyletted techniques, according to the authors.6
Maus et al studied procalcitonin (PCT) as a diagnostic tool and monitoring parameter for spondylodiskitis and for discrimination between bacterial infection and aseptic inflammation of the spine. A total of 17 patients with spondylodiskitis and 18 patients with disk herniation used as controls were included in this study. The findings showed, however, that PCT is not useful as diagnostic tool or monitoring parameter for spondylodiskitis, nor was it useful for the discrimination between a bacterial infection and an aseptic inflammation of the spine.7
Karadimas et al retrospectively analyzed the outcome of a large series of patients treated either nonoperatively or surgically for spondylodiskitis. The patients were divided into 3 groups: (A) 70 patients who had nonoperative treatment, (B) 56 patients who underwent posterior decompression alone, and (C) 37 patients who underwent decompression and stabilization. At 12-month follow-up, nonoperative treatment (group A) had failed in 8/70 patients. In 24 of 56 group B patients and in 6 of 37 group C patients, reoperation was necessary. Group A patients had no neurologic symptoms; in group B, 11 had neurologic deficits, and surgery was beneficial for 5 of them; and in group C, 11 patients had altered neurologic deficits.8
Pathophysiology
An infection does not ordinarily originate in the vertebra or disk space, but rather, it spreads there from other sites via the bloodstream. Spinal arteries form 2 lateral anastomotic chains and 1 median anastomotic chain along the posterior surface of the vertebral bodies. The spinal arteries are the origins of the periosteal arteries, which in turn give rise to metaphyseal arteries.
In the child, anastomoses between metaphyseal arteries are made by the intermetaphyseal arteries; however, in the adult, these intermetaphyseal arteries degenerate, causing direct diffusion from the adjacent endplate to be the only source of nutrients for the disk. Septic emboli travelling through this 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. Infection can then spread to the epidural space or paraspinal soft tissues.
The other anastomotic vascular system of the spine is the venous system. The venous system of the spine, like the arterial system, also forms an anastomotic plexus (ie, Batson plexus) in the epidural space. 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 has been postulated to allow the spread of infection from the pelvic organs. Support for this hypothesis comes from the observation that pelvic disease is one of the most common primary sites of infection in patients with diskitis. Other authors take issue with this hypothesis, citing animal studies that show retrograde flow through the epidural venous plexus only at extremely high intra-abdominal pressures that are not physiologic.
Frequency
United States
Incidence ranges from 1 in 100,000 population to 1 in 250,000 population.
International
In other developed nations, the incidence of diskitis is similar to that in the United States; however, in less developed nations, infectious diskitis is much more common. In some areas of Africa, it has been reported that 11% of all patients seen for back pain were diagnosed with diskitis.
Mortality/Morbidity
Mortality associated with diskitis occurs from the spread of infection, either through the nervous system or through other organs. Mortality has been reported to be 2-12%.
Race
No specific racial predilection has been noted.
Sex
The predominance of diskitis in males is more pronounced in adults, with 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.
Age
A bimodal distribution of ages occurs with diskitis. Childhood diskitis affects patients with a mean age of 7 years. The incidence of diskitis then decreases until middle age, when a second peak in incidence is observed at approximately 50 years of age. Some authors argue that childhood diskitis is a separate disease entity and should be considered independently.
Clinical
History
- Unfortunately, adult diskitis has a slow, insidious onset, which can cause diagnosis to be delayed for months. Neck or back pain with localized tenderness is the initial presenting complaint. Movement exacerbates these symptoms, which are not alleviated with conservative treatment (eg, analgesics, bed rest).
- In patients who are chronically ill, 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 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, which consists of pain without neurologic abnormality. Limited movement and localized tenderness also occur; however, superficial signs of infection are rare (only 10% of cases). Diagnosis is rarely delayed in postoperative patients, which is the main reason that neurologic deficit is uncommon in these cases.
- The disease has a more acute course in children. A sudden onset of back pain, refusal to walk, and irritability are the most common symptoms. Fever is often present, accompanied by local tenderness and limited back motion.
Physical
Localized tenderness over the involved area with concomitant paraspinal muscle spasm is the most common physical sign. If the cervical or lumbar segments are involved, restricted mobility secondary to pain occurs. Reported rates of neurologic deficit (eg, radiculopathy, myelopathy) vary widely from 2% to 70%. Cervical disease is associated with a much higher rate of neurologic deficit.
Causes
- Diskitis is thought to spread to the involved intervertebral disk via hematogenous spread of a systemic infection (eg, urinary tract infection [UTI]). Many sites of origin have been implicated, but UTI, pneumonia, and soft-tissue infection seem to be the most common. Direct trauma has not been conclusively shown to be related to diskitis. Intravenous drug use with contaminated syringes offers direct access to the bloodstream for a variety of organisms. Often, no other site of infection is discovered.
- Staphylococcus aureus is the organism most commonly found; however, Escherichia coli and Proteus species are more common in patients with UTIs. Pseudomonas aeruginosa and Klebsiella species are other gram-negative organisms observed in intravenous drug abusers, although they are not seen as commonly as S aureus. Not surprisingly, medical conditions that predispose patients to infections elsewhere in the body are associated with diskitis. Diabetes, AIDS, steroid use, cancer, and chronic renal insufficiency are common comorbidities.1
- Although rare, infection of the disk space can also occur following surgical intervention at the site. The rate of infection following anterior cervical diskectomy has been quoted at 0.5% of cases. The rate of infection for lumbar diskectomy is half of that. In such cases, infection is transmitted through direct inoculation of the operative site. As in spontaneous diskitis, the most common organism is S aureus, but Staphylococcus epidermidis and Streptococcus species also should be considered.
- Childhood diskitis has not been consistently associated with an initial causative infection elsewhere in the body. S aureus is the most common organism found.
More on Diskitis |
 Overview: Diskitis |
| Differential Diagnoses & Workup: Diskitis |
| Treatment & Medication: Diskitis |
| Follow-up: Diskitis |
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| References |
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References
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Further Reading
Related eMedicine topics
Lumbar Disc Disease
Cervical Disc Disease
Spondylodiskitis
Clinical trials
Comparison of Two Antimicrobial Therapy Duration for Spondylodiscitis
Keywords
diskitis, spondylodiskitis, spondylodiscitis, discitis, disk disease, disc disease
