Diskitis

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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] See images below.


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Axial CT scan in a patient with diskitis demonstrates extensive destruction of the vertebral endplate. Note the preservation of the posterior elements....


View Image

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 endpl....


View Image

Contrast-enhanced sagittal T1-weighted MRI image in a 55-year-old woman shows thoracic diskitis with an associated epidural abscess and spinal cord co....


View Image

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.

Epidemiology

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.

History

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

Laboratory Studies

Imaging Studies

Other Tests

Procedures

Histologic Findings

The histologic findings of diskitis are similar to those of any bacterial pyogenic infection. Local destruction of the disk and endplates occurs with infiltration of neutrophils in the early stages. Later, a lymphocytic infiltrate predominates.

Medical Care

Surgical Care

Indications for surgery beyond open biopsy include neurologic deficit, spinal deformity, disease progression, noncompliance, and antibiotic toxicity. The goal of surgery is to remove diseased tissue, decompress neural structures, and ensure spinal stability. Although in most cases the vertebrae fuse spontaneously following diskitis and osteomyelitis, operative fusion can be a useful adjunct by allowing earlier mobilization of the patient. Despite early concerns, use of a fusion plug and metallic instrumentation in an infected field has not been shown to impede successful treatment.

Consultations

Diet

No particular diet has been shown to have a clinical benefit in patients with diskitis.

Activity

Many authors believe that 2 weeks of bed rest with initial treatment helps prevent the development of a kyphotic deformity. Use of an orthotic brace to help stabilize the spine while spontaneous fusion takes place is recommended for 3-6 months. Ambulation is recommended only if the patient has neither pain nor radiographic signs of instability.

Medication Summary

Parenteral narrow-spectrum antibiotics should be prescribed according to the organism isolated. If cultures are consistently negative, administer broad-spectrum antibiotics for several weeks.

Vancomycin (Lyphocin, Vancocin, Vancoled)

Clinical Context:  Potent antibiotic that is directed against gram-positive organisms and is active against Enterococcus species. Useful in the treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or have failed to respond to penicillins or cephalosporins or who have infections with resistant staphylococci. For abdominal penetrating injuries, it is combined with an agent active against enteric flora and/or anaerobes.

To avoid toxicity, the current recommendation is to assay vancomycin trough levels after the third dose is drawn and a half an hour prior to the next dose. Use CrCl to adjust the dosage in patients diagnosed with renal impairment.

Used in conjunction with gentamicin for prophylaxis in patients who are allergic to penicillin and are undergoing gastrointestinal or genitourinary procedures.

Nafcillin (Unipen, Nallpen, Nafcil)

Clinical Context:  Initial therapy for suspected penicillin-G–resistant streptococcal or staphylococcal infections. Use parenteral therapy initially for severe infections. Change to oral therapy as condition warrants.

Due to thrombophlebitis, particularly in the elderly, administer parenterally only for short term (1-2 d); change to oral route as clinically indicated.

Ceftazidime (Tazidime, Tazicef, Ceptaz, Fortaz)

Clinical Context:  Third-generation cephalosporin with broad-spectrum, gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding proteins.

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.

Further Inpatient Care

Further Outpatient Care

Inpatient & Outpatient Medications

Transfer

Deterrence/Prevention

Complications

Prognosis

Author

Alvin Marcovici, MD, Consulting Staff, Southcoast Neurosurgery

Disclosure: Nothing to disclose.

Coauthor(s)

George I Jallo, MD, Professor of Neurosurgery, Pediatrics, and Oncology, Director, Clinical Pediatric Neurosurgery, Department of Neurosurgery, Johns Hopkins University School of Medicine

Disclosure: Codman (Johnson & Johnson) Grant/research funds Consulting; Medtronic Grant/research funds Consulting

Specialty Editors

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

William O Shaffer, MD, Professor, Vice-Chairman and Residency Program Director, Department of Orthopedic Surgery, University of Kentucky at Lexington

Disclosure: DePuySpine 1997-2007 (not presently) Royalty Consulting; DePuySpine 2002-2007 (closed) Grant/research funds SacroPelvic Instrumentation Biomechanical Study; DePuyBiologics 2005-2008 (closed) Grant/research funds Healos study just closed; DePuySpine 2009 Consulting fee Design of Offset Modification of Expedium

Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital

Disclosure: Nothing to disclose.

Chief Editor

Mary Ann E Keenan, MD, Professor, Vice Chair for Graduate Medical Education, Department of Orthopedic Surgery, University of Pennsylvania School of Medicine; Chief of Neuro-Orthopedics Program, Department of Orthopedic Surgery, Hospital of the University of Pennsylvania

Disclosure: Nothing to disclose.

References

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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.

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.

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.