Tuberculosis

*Pott Disease (Tuberculous Spondylitis)**Emedicine*

Pott disease, also known as tuberculous spondylitis, is one of the oldest demonstrated diseases of humankind, having been documented in spinal remains from the Iron Age and in ancient mummies from Egypt and Peru.1 In 1779, Percivall Pott, for whom Pott disease is named, presented the classic description of spinal tuberculosis.2

Since the advent of antituberculous drugs and improved public health measures, spinal tuberculosis has become rare in developed countries, although it is still a significant cause of disease in developing countries. Tuberculous involvement of the spine has the potential to cause serious morbidity, including permanent neurologic deficits and severe deformities. Medical treatment or combined medical and surgical strategies can control the disease in most patients.

Pathophysiology

Pott disease is usually secondary to an extraspinal source of infection. The basic lesion involved in Pott disease is a combination of osteomyelitis and arthritis that usually involves more than one vertebra. The anterior aspect of the vertebral body adjacent to the subchondral plate is area usually affected. Tuberculosis may spread from that area to adjacent intervertebral disks. In adults, disk disease is secondary to the spread of infection from the vertebral body. In children, because the disk is vascularized, it can be a primary site.3

Progressive bone destruction leads to vertebral collapse and kyphosis. The spinal canal can be narrowed by abscesses, granulation tissue, or direct dural invasion, leading to spinal cord compression and neurologic deficits. The kyphotic deformity is caused by collapse in the anterior spine. Lesions in the thoracic spine are more likely to lead to kyphosis than those in the lumbar spine. A cold abscess can occur if the infection extends to adjacent ligaments and soft tissues. Abscesses in the lumbar region may descend down the sheath of the psoas to the femoral trigone region and eventually erode into the skin.

Clinical

History

The presentation of Pott disease depends on the following: o Stage of diseaseo Affected siteo Presence of complications such as neurologic deficits, abscesses, or sinus tracts

The reported average duration of symptoms at diagnosis is 4 months7 but can be considerably longer, even in most recent series.11,9 This is due to the nonspecific presentation of chronic back pain.

Back pain is the earliest and most common symptom. o Patients with Pott disease usually experience back pain for weeks before seeking treatment.o The pain caused by Pott disease can be spinal or radicular.

Potential constitutional symptoms of Pott disease include fever and weight loss. Neurologic abnormalities occur in 50% of cases and can include spinal cord compression with paraplegia, paresis,

impaired sensation, nerve root pain, and/or cauda equina syndrome. Cervical spine tuberculosis is a less common presentation but is potentially more serious because severe

neurologic complications are more likely. o This condition is characterized by pain and stiffness.o Patients with lower cervical spine disease can present with dysphagia or stridor.

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Tuberculosis

o Symptoms can also include torticollis, hoarseness, and neurologic deficits. The clinical presentation of spinal tuberculosis in patients infected with the human immunodeficiency virus (HIV)

is similar to that of patients who are HIV negative; however, spinal tuberculosis seems to be more common in persons infected with HIV.12

Physical

The examination should include the following: o Careful assessment of spinal alignmento Inspection of skin, with attention to detection of sinuseso Abdominal evaluation for subcutaneous flank masso Meticulous neurologic examination

Although both the thoracic and lumbar spinal segments are nearly equally affected in persons with Pott disease, the thoracic spine is frequently reported as the most common site of involvement. Together, they comprise 80-90% of spinal tuberculosis sites. The remaining cases correspond to the cervical spine.

Almost all patients with Pott disease have some degree of spine deformity (kyphosis). Large cold abscesses of paraspinal tissues or psoas muscle may protrude under the inguinal ligament and may

erode into the perineum or gluteal area. Neurologic deficits may occur early in the course of Pott disease. Signs of such deficits depend on the level of

spinal cord or nerve root compression. Pott disease that involves the upper cervical spine can cause rapidly progressive symptoms.

o Retropharyngeal abscesses occur in almost all cases.o Neurologic manifestations occur early and range from a single nerve palsy to hemiparesis or quadriplegia.

Many persons with Pott disease (62-90% of patients in reported series6,7 ) have no evidence of extraspinal tuberculosis, further complicating a timely diagnosis.

Information from imaging studies, microbiology, and anatomic pathology should help establish the diagnosis.

Differential Diagnoses

Actinomycosis Multiple Myeloma

Blastomycosis Mycobacterium Avium-Intracellulare

Brucellosis Mycobacterium Kansasii

Candidiasis Nocardiosis

Cryptococcosis Paracoccidioidomycosis

Histoplasmosis Septic Arthritis

Metastatic Cancer, Unknown Primary Site Spinal Cord Abscess

Miliary Tuberculosis Tuberculosis

Other Problems to Be Considered

Spinal tumors

Workup

Laboratory Studies

Tuberculin skin test (purified protein derivative [PPD]) results are positive in 84-95% of patients with Pott disease who are not infected with HIV.

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The erythrocyte sedimentation rate (ESR) may be markedly elevated (>100 mm/h). Microbiology studies are used to confirm diagnosis. Bone tissue or abscess samples are obtained to stain for acid-

fast bacilli (AFB), and organisms are isolated for culture and susceptibility. CT-guided procedures can be used to guide percutaneous sampling of affected bone or soft-tissue structures. These study findings are positive in only about 50% of the cases.

Imaging Studies

Radiography Radiographic changes associated with Pott disease present relatively late. The following are radiographic

changes characteristic of spinal tuberculosis on plain radiography:13

Lytic destruction of anterior portion of vertebral body Increased anterior wedging Collapse of vertebral body Reactive sclerosis on a progressive lytic process Enlarged psoas shadow with or without calcification

Additional radiographic findings may include the following: Vertebral end plates are osteoporotic. Intervertebral disks may be shrunk or destroyed. Vertebral bodies show variable degrees of destruction. Fusiform paravertebral shadows suggest abscess formation. Bone lesions may occur at more than one level.

CT scanning14

o CT scanning provides much better bony detail of irregular lytic lesions, sclerosis, disk collapse, and disruption of bone circumference.

o Low-contrast resolution provides a better assessment of soft tissue, particularly in epidural and paraspinal areas.

o CT scanning reveals early lesions and is more effective for defining the shape and calcification of soft-tissue abscesses.

o In contrast to pyogenic disease, calcification is common in tuberculous lesions. MRI

o MRI is the criterion standard for evaluating disk-space infection and osteomyelitis of the spine and is most effective for demonstrating the extension of disease into soft tissues and the spread of tuberculous debris under the anterior and posterior longitudinal ligaments. MRI is also the most effective imaging study for demonstrating neural compression.15,16

o MRI findings useful to differentiate tuberculous spondylitis from pyogenic spondylitis include thin and smooth enhancement of the abscess wall and well-defined paraspinal abnormal signal, whereas thick and irregular enhancement of abscess wall and ill-defined paraspinal abnormal signal suggest pyogenic spondylitis. Thus, contrast-enhanced MRI appears to be important in the differentiation of these two types of spondylitis.17

Other Tests

Radionuclide scanning findings are not specific for Pott disease. Gallium and Tc-bone scans yield high false-negative rates (70% and up to 35%, respectively).18

Procedures

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Use a percutaneous CT-guided needle biopsy of bone lesions to obtain tissue samples. o This is a safe procedure that also allows therapeutic drainage of large paraspinal abscesses.o Obtain a tissue sample for microbiology and pathology studies to confirm diagnosis and to isolate

organisms for culture and susceptibility. Some cases of Pott disease are diagnosed following an open drainage procedure (eg, following presentation with

acute neurologic deterioration).

Histologic Findings

Because microbiologic studies may be nondiagnostic of Pott disease, anatomic pathology can be significant. Gross pathologic findings include exudative granulation tissue with interspersed abscesses. Coalescence of abscesses results in areas of caseating necrosis.

Treatment

Medical Care

Before the advent of effective antituberculosis chemotherapy, Pott disease was treated with immobilization using prolonged bed rest or a body cast. At the time, Pott disease carried a mortality rate of 20%, and relapse was common (30%).

The duration of treatment, surgical indications, and inpatient care have since evolved. Studies performed by the British Medical Research Council indicate that tuberculous spondylitis of the

thoracolumbar spine should be treated with combination chemotherapy for 6-9 months.4

According to the most recent recommendations issued in 2003 by the US Centers for Disease Control and Prevention, the Infectious Diseases Society of America, and the American Thoracic Society, a 4-drug regimen should be used empirically to treat Pott disease.1  

Isoniazid and rifampin should be administered during the whole course of therapy. Additional drugs are administered during the first 2 months of therapy. These are generally chosen among the first-line drugs, which include pyrazinamide, ethambutol, and streptomycin. The use of second-line drugs is indicated in cases of drug resistance.

Regarding the duration of therapy, the British Medical Research Council studies did not include patients with multiple vertebral involvement, cervical lesions, or major neurologic involvement. Because of these limitations, many experts still recommend chemotherapy for 9-12 months.

Opinions differ regarding whether the treatment of choice should be conservative chemotherapy or a combination of chemotherapy and surgery. The treatment decision should be individualized for each patient. Routine surgery does not to seem to be indicated. Most common indications for surgical procedures are discussed below.

Surgical Care

Indications for surgical treatment of Pott disease generally include the following:22,23

o Neurologic deficit (acute neurologic deterioration, paraparesis, paraplegia)o Spinal deformity with instability or paino No response to medical therapy (continuing progression of kyphosis or instability)o Large paraspinal abscesso Nondiagnostic percutaneous needle biopsy sample

Resources and experience are key factors in the decision to use a surgical approach. The lesion site, extent of vertebral destruction, and presence of cord compression or spinal deformity determine

the specific operative approach (kyphosis, paraplegia, tuberculous abscess). Vertebral damage is considered significant if more than 50% of the vertebral body is collapsed or destroyed or a

spinal deformity of more than 5° exists.4

Tuberculosis

The most conventional approaches include anterior radical focal debridement and posterior stabilization with instrumentation.24,10

In Pott disease that involves the cervical spine, the following factors justify early surgical intervention: o High frequency and severity of neurologic deficitso Severe abscess compression that may induce dysphagia or asphyxiao Instability of the cervical spine

Contraindications: Vertebral collapse of a lesser magnitude is not considered an indication for surgery because, with appropriate treatment and therapy compliance, it is less likely to progress to a severe deformity.

Consultations

Orthopedic surgeons Neurosurgeons Rehabilitation teams

Activity

Despite questionable efficacy, prolonged recumbence and the use of frames, plaster beds, plaster jackets, and braces are still used.

Cast or brace immobilization was a traditional form of treatment but has generally been discarded. Patients with Pott disease should be treated with external bracing.

Medication

A 4-drug regimen should be used empirically to treat Pott disease. Treatment can be adjusted when susceptibility information becomes available. 

Isoniazid and rifampin should be administered during the whole course of therapy. Additional drugs are administered during the first 2 months of therapy. These are generally chosen among the first-line drugs, which include pyrazinamide, ethambutol, and streptomycin.

A 3-drug regimen usually includes isoniazid, rifampin, and pyrazinamide. The use of second-line drugs is indicated in cases of drug resistance. The duration of treatment is somewhat controversial. Although some studies favor a 6- to 9-month course,

traditional courses range from 9 months to longer than 1 year. The duration of therapy should be individualized and based on the resolution of active symptoms and the clinical stability of the patient.

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Tuberculosis

MRI of a 31-year-old man with tuberculosis of the spine. Images show the thoracic spine before and after an infusion of intravenous gadolinium contrast. The abscess and subsequent destruction of the T11-T12 disc interspace is marked with arrowheads. Vertebral body alignment is normal. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

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MRI of the T11 in a 31-year-old man with tuberculosis of the spine (the same patient as in picture 1). Extensive bone destruction consistent with tuberculous osteomyelitis is evident. The spinal cord has normal caliber and signal. No evidence of spinal cord compression or significant spinal stenosis is distinguishable. Courtesy of Mark C. Diamond, MD, and J. Antonio Bouffard, MD, Detroit, Mich.

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