02-27-2008, 08:50 PM
Correct Answer = A)
Key Points
* Differentiating bacterial from mycobacterial infections of the spine generally requires CT-guided needle biopsy of a lesion for histopathologic examination and cultures.
* Almost all immunocompetent patients with spinal tuberculosis have a positive intermediate-strength tuberculin skin test, whereas false-negative test results are more common in immunosuppressed patients.
* In immunosuppressed transplant recipients and other persons at high risk for developing active tuberculosis, a tuberculin skin test result of >5 mm of induration is considered a positive test.
This patient most likely has Mycobacterium tuberculosis infection of the lumbar spine and requires a CT-guided needle biopsy of the lesion to establish the diagnosis and guide therapy. The clinical scenario is compatible with various entities, but some type of spinal infection seems most likely because of the time frame. Distinguishing mycobacterial from bacterial infections of the spine is difficult without tissue for histopathologic examination and culture, as there is some overlap between the presentations of more common bacterial infections and less common mycobacterial infections. Local pain, muscle spasm, and rigidity are the most common presenting symptoms for both types of infection. Fever and other constitutional symptoms are reported by less than 50% of patients.
Almost all immunocompetent patients with spinal tuberculosis have a positive intermediate-strength tuberculin skin test, whereas false-negative test results are more common in immunosuppressed patients. However, a negative tuberculin skin test can never exclude the diagnosis of tuberculosis in any clinical setting. In immunosuppressed transplant recipients and other persons at high risk for developing active tuberculosis (e.g., patients with HIV infection or persons having recent close contact with someone with tuberculosis), a tuberculin skin test result of >5 mm of induration is now considered positive and is a key finding in the patient described in this clinical scenario. Although there is no report of prior tuberculin skin testing in this patient, transplant candidates are routinely tested before transplantation, and therapy is initiated for any candidates with positive test results. This preventive therapy does not need to delay the transplant procedure.
There is no single classic radiographic presentation of spinal tuberculosis. Most series report infection at one spinal level that usually first involves the anterior vertebral body. However, contiguous involvement, including the disk space, is not uncommon. As the disease progresses, a paravertebral abscess may develop that is associated with further destruction of the anterior vertebral body and subsequent collapse and wedging. A recent review of patients with spinal tuberculosis in France described purely osteolytic lesions of the spine without disk involvement. This is probably one of the major distinctions between tuberculous and bacterial osteomyelitis. The latter almost always begins in and involves the intervertebral disk and tends to involve adjacent vertebrae in a œkissing fashion.
More than 50% of patients with spinal tuberculosis have normal chest radiographs. Therefore, a negative chest film does not rule out this infection, but a positive chest radiograph showing active or inactive disease would strongly support the diagnosis. In a patient with a normal chest radiograph, a CT scan of the chest provides no additional useful information.
Spinal cord compression is the most serious complication of spinal tuberculosis and requires emergent MRI and follow-up surgical decompression. However, in a patient without symptoms suggesting compression, a normal neurologic examination, and a CT scan suggesting involvement limited to the anterior vertebral body, imminent spinal cord compression is unlikely, and urgent MRI is not necessary.
Multiple myeloma should always be considered in the differential diagnosis of destructive spinal lesions, but the patient's age, immunosuppressed state, and positive tuberculin skin test make spinal tuberculosis a much more likely diagnosis. Therefore, serum protein electrophoresis and urine immunoelectrophoresis are not needed at this time. Although testicular cancer is the most common solid malignancy in males between 15 and 35 years of age, pelvic and abdominal lymph nodes are usually the first site of metastatic disease. The involvement of contiguous vertebral bodies and the positive tuberculin skin test alsoargue against the possibility of metastatic testicular cancer as the cause of the patient's back pain. In addition, the initial evaluation of suspected testicular cancer would include scrotal ultrasonography, studies for serum markers, and a high-resolution CT scan of the pelvis and abdomen. Positron emission tomography is usually reserved for evaluation of residual masses following curative therapy.
Key Points
* Differentiating bacterial from mycobacterial infections of the spine generally requires CT-guided needle biopsy of a lesion for histopathologic examination and cultures.
* Almost all immunocompetent patients with spinal tuberculosis have a positive intermediate-strength tuberculin skin test, whereas false-negative test results are more common in immunosuppressed patients.
* In immunosuppressed transplant recipients and other persons at high risk for developing active tuberculosis, a tuberculin skin test result of >5 mm of induration is considered a positive test.
This patient most likely has Mycobacterium tuberculosis infection of the lumbar spine and requires a CT-guided needle biopsy of the lesion to establish the diagnosis and guide therapy. The clinical scenario is compatible with various entities, but some type of spinal infection seems most likely because of the time frame. Distinguishing mycobacterial from bacterial infections of the spine is difficult without tissue for histopathologic examination and culture, as there is some overlap between the presentations of more common bacterial infections and less common mycobacterial infections. Local pain, muscle spasm, and rigidity are the most common presenting symptoms for both types of infection. Fever and other constitutional symptoms are reported by less than 50% of patients.
Almost all immunocompetent patients with spinal tuberculosis have a positive intermediate-strength tuberculin skin test, whereas false-negative test results are more common in immunosuppressed patients. However, a negative tuberculin skin test can never exclude the diagnosis of tuberculosis in any clinical setting. In immunosuppressed transplant recipients and other persons at high risk for developing active tuberculosis (e.g., patients with HIV infection or persons having recent close contact with someone with tuberculosis), a tuberculin skin test result of >5 mm of induration is now considered positive and is a key finding in the patient described in this clinical scenario. Although there is no report of prior tuberculin skin testing in this patient, transplant candidates are routinely tested before transplantation, and therapy is initiated for any candidates with positive test results. This preventive therapy does not need to delay the transplant procedure.
There is no single classic radiographic presentation of spinal tuberculosis. Most series report infection at one spinal level that usually first involves the anterior vertebral body. However, contiguous involvement, including the disk space, is not uncommon. As the disease progresses, a paravertebral abscess may develop that is associated with further destruction of the anterior vertebral body and subsequent collapse and wedging. A recent review of patients with spinal tuberculosis in France described purely osteolytic lesions of the spine without disk involvement. This is probably one of the major distinctions between tuberculous and bacterial osteomyelitis. The latter almost always begins in and involves the intervertebral disk and tends to involve adjacent vertebrae in a œkissing fashion.
More than 50% of patients with spinal tuberculosis have normal chest radiographs. Therefore, a negative chest film does not rule out this infection, but a positive chest radiograph showing active or inactive disease would strongly support the diagnosis. In a patient with a normal chest radiograph, a CT scan of the chest provides no additional useful information.
Spinal cord compression is the most serious complication of spinal tuberculosis and requires emergent MRI and follow-up surgical decompression. However, in a patient without symptoms suggesting compression, a normal neurologic examination, and a CT scan suggesting involvement limited to the anterior vertebral body, imminent spinal cord compression is unlikely, and urgent MRI is not necessary.
Multiple myeloma should always be considered in the differential diagnosis of destructive spinal lesions, but the patient's age, immunosuppressed state, and positive tuberculin skin test make spinal tuberculosis a much more likely diagnosis. Therefore, serum protein electrophoresis and urine immunoelectrophoresis are not needed at this time. Although testicular cancer is the most common solid malignancy in males between 15 and 35 years of age, pelvic and abdominal lymph nodes are usually the first site of metastatic disease. The involvement of contiguous vertebral bodies and the positive tuberculin skin test alsoargue against the possibility of metastatic testicular cancer as the cause of the patient's back pain. In addition, the initial evaluation of suspected testicular cancer would include scrotal ultrasonography, studies for serum markers, and a high-resolution CT scan of the pelvis and abdomen. Positron emission tomography is usually reserved for evaluation of residual masses following curative therapy.
