Pott disease, also known as tuberculous spondylitis, is a classic presentation of extrapulmonary tuberculosis (TB). It is associated with significant morbidity and can lead to severe functional impairment.
The diagnosis tends to be delayed because of a nonspecific initial early manifestations and/or low degree of suspicion. The diagnostic approach needs to be based on chronic pain or deformity, epidemiological considerations, imaging, and adequate procedures to obtain samples for bacteriological, pathological, or molecular confirmation.
Treatment requires several months of medical therapy according to current recommendations and consideration for surgical procedures, when indicated.
Pott disease is one of the oldest demonstrated diseases of humankind, having been documented in spinal remains from the Iron Age in Europe and in ancient mummies from Egypt and the Pacific coast of South America.[1, 2] In 1779, Percivall Pott, for whom the disease is named, presented the classic description of spinal tuberculosis. (See the image below.)[3]
View Image | 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 contras.... |
Since the advent of antituberculous drugs and improved public health measures, spinal tuberculosis has become rare in industrialized countries, although it is still a significant cause of disease in developing nations. 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.[4, 5]
Pott disease usually results from an extraspinal source of infection and hematogenous dissemination. Pott disease manifests as a combination of osteomyelitis and arthritis that usually involves more than 1 vertebra. The anterior aspect of the vertebral body adjacent to the subchondral plate is 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, the disk, because it is vascularized, can be the primary site.[6]
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.
Globally, extrapulmonary tuberculosis (TB) represented 14% of the 6.4 million TB cases reported in 2017, ranging from 8% in the WHO Western Pacific Region to 24% in the WHO Eastern Mediterranean Region.[7] The global relative frequencies of different TB presentations are not more detailed than pulmonary/extrapulmonary. In the United States, the proportion of extrapulmonary cases in 2017 was 20.8% (1,887 cases). Of these, bone and joint involvement was the third most common, comprising 9.8% of cases, after lymphatic and pleural disease.[8]
Between 2002 and 2011, a total of 75,858 cases of TB were reported in the United States. Of these, 2,789 cases (3.7%) involved the spine. The median age among affected individuals was 51 years; 61% of cases involved males, and 11% had diabetes mellitus. Twenty percent required surgery, most commonly of the thoracic-lumbar segments.[9]
Although the incidence of tuberculosis increased in the late 1980s to early 1990s, the total number of cases has decreased in recent years. The frequency of extrapulmonary tuberculosis has remained stable. Bone and soft-tissue tuberculosis accounts for approximately 10-15% of extrapulmonary tuberculosis cases and between 1% and 2% of total cases. Tuberculous spondylitis is the most common manifestation of musculoskeletal tuberculosis, accounting for approximately 40-50% of cases. These figures are roughly similar for North American and international series.[10, 11]
Approximately 1-2% of total tuberculosis cases are attributable to Pott disease. In the Netherlands, between 1993 and 2001, tuberculosis of the bone and joints accounted for 3.5% of all tuberculosis cases (0.2-1.1% in patients of European origin, and 2.3-6.3% in patients of non-European origin).[12]
Data from Los Angeles and New York show that musculoskeletal tuberculosis affects primarily African Americans, Hispanic Americans, Asian Americans, and foreign-born individuals.
As with other forms of tuberculosis, the frequency of Pott Disease is related to socioeconomic factors and historical exposure to the infection.
Although some series have found that Pott disease does not have a sexual predilection, the disease is more common in males (male-to-female ratio of 1.5-2:1).
In the United States and other developed countries, Pott disease occurs primarily in adults. In countries with higher rates of Pott disease, involvement in young adults and older children predominates.[13, 14]
Current treatment modalities are highly effective against Pott disease if the disorder is not complicated by severe deformity or established neurologic deficit.
Deformity and motor deficit are the most serious consequences of Pott disease and continue to be a serious problem when diagnosis is delayed or presentation of the patient is in advanced stages of the disease.[15]
Therapy compliance and drug resistance are additional factors that significantly affect individual outcomes.
Paraplegia resulting from cord compression caused by the active disease usually responds well to chemotherapy. However, paraplegia can manifest or persist during healing because of permanent spinal cord damage.
Operative decompression can greatly increase the recovery rate, offering a means of treatment when medical therapy does not bring rapid improvement.
Careful long-term follow up is also recommended, since late-onset complications can still occur (disease reactivation, late instability or deformity).[16]
Pott disease is the most dangerous form of musculoskeletal tuberculosis because it can cause bone destruction, deformity, and paraplegia.
Pott disease most commonly involves the thoracic and lumbosacral spine. However, published series have shown some variation.[17, 18, 19, 20] The lower thoracic vertebrae make up the most common area of involvement (40-50%), followed closely by the lumbar spine (35-45%). In other series, proportions are similar but favor lumbar spine involvement.[21] Approximately 10% of Pott disease cases involve the cervical spine.
Patients with Pott disease should be instructed on the importance of therapy compliance. For patient education information, see the Infections Center, as well as Tuberculosis.
The presentation of Pott disease depends on the following[22] :
Patients with Pott disease may have history of pulmonary tuberculosis or concomitant disease. A large 2019 series reported that 26.6% of patients had concomitant pulmonary tuberculosis.[23]
Potential constitutional symptoms of Pott disease include fever and weight loss. The reported average duration of symptoms at diagnosis is 4 months[18] but can be considerably longer.[20, 24] This is due to the nonspecific presentation of chronic back pain.
Back pain is the earliest and most common symptom of Pott disease, with patients usually experiencing this problem for weeks before seeking treatment. The pain caused by Pott disease can be spinal or radicular.
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. This condition is characterized by pain and stiffness. Patients with lower cervical spine disease can present with dysphagia or stridor. 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.[25]
The physical examination in Pott disease should include the following:
Although 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, these segments make up 80-90% of spinal tuberculosis sites, with the remaining cases of Pott disease occurring in the cervical spine.[19, 20, 22] Almost all patients with Pott disease have some degree of spine deformity (kyphosis).
Examination should reveal local pain related to the affected area or radicular pain. Muscle spasm and rigidity can also be associated.
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. Retropharyngeal abscesses occur in almost all cases affecting this part of the spine. Neurologic manifestations occur early and range from a single nerve palsy to hemiparesis or quadriplegia.
A large proportion of patients with Pott disease do not present with extraskeletal disease. In reported series, only 10-38% of cases of Pott disease are associated with extraskeletal tuberculosis.
Laboratory studies used in the diagnosis of Pott disease include the following:
With regard to the above-mentioned microbiologic studies, bone tissue or abscess samples are obtained to stain for acid-fast bacilli (AFB), culture and susceptibility, and DNA amplification. Procedures guided by computed tomography (CT) scanning 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. A 2015 multicentric, multinational study involving 35 centers and 314 cases reported that the causative agent was identified in 41% of cases.[28] Surgical biopsies can also be considered for tissue sampling.
Nonculture methods (DNA amplification) using skeletal tissue samples offer a high diagnostic yield and high specificity (96%), high sensitivity (95%), and rapid results (2 days).[29, 30, 31] An additional potential advantage is simultaneously identifying drug resistance and improving outcomes.[32]
Percutaneous, CT scan ̶ guided needle biopsy of bone lesions is a safe procedure that also allows therapeutic drainage of large paraspinal abscesses. Obtain a tissue sample for microbiologic and pathologic studies to confirm diagnosis and to isolate organisms for culture and susceptibility. Positive culture yield of percutaneous is 50-83% and appears to be influenced by technical details, such as decontamination of specimens prior to culture.[33]
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.
Some cases of Pott disease are diagnosed following an open drainage procedure (eg, following presentation with acute neurologic deterioration).
Radionuclide scanning findings are not specific for Pott disease. Gallium and technetium bone scans yield high false-negative rates (70% and up to 35%, respectively).[34]
Radiographic changes associated with Pott disease present relatively late. The following are radiographic changes characteristic of spinal tuberculosis on plain radiography:[35]
Additional radiographic findings may include the following:
CT scanning provides much better bony detail of irregular lytic lesions, sclerosis, disk collapse, and disruption of bone circumference.[36]
Low-contrast resolution provides a better assessment of soft tissue, particularly in epidural and paraspinal areas.
CT scanning reveals early lesions and is more effective for defining the shape and calcification of soft-tissue abscesses. In contrast to pyogenic disease, calcification is common in tuberculous lesions.
Magnetic resonance imaging (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.[37] MRI is also the most effective imaging study for demonstrating neural compression.[38, 39]
Contrast-enhanced MRI findings are useful in differentiating tuberculous spondylitis from pyogenic spondylitis. MRI findings in Pott disease include thin and smooth enhancement of the abscess wall and a well-defined paraspinal abnormal signal. Thick and irregular enhancement of the abscess wall and an ill-defined paraspinal abnormal signal suggest pyogenic spondylitis.[40] The images below are studies of a man aged 31 years with spinal tuberculosis.
Involvement of the disk is typically a characteristic of infectious spondylitis; however, this may not always be the case, and Pott disease can present with atypical features resembling neoplastic lesions. Findings of an intradural extramedullary mass at the lower end of the spinal cord associated with holocord T2 hyperintensities of the choroid has been described in intramedullary tubercular abscesses ”precipitation sign."[41, 42, 43, 44]
Three MRI parameters have been found to be strongly suggestive of spinal tuberculosis: subligamentous spread of abscess, vertebral body collapse, and large abscess collection with thin abscess wall. A combination of these MRI findings has a higher predictive value, an odds ratio of 16.3 when comparing a group of patients with spinal tuberculosis versus a group of patients evaluated for spondylodiscitis with a different diagnosis.[45]
View Image | 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 contras.... |
View Image | MRI of the T11 in a 31-year-old man with tuberculosis of the spine. Extensive bone destruction consistent with tuberculous osteomyelitis is evident. T.... |
Before the advent of effective antituberculosis chemotherapy, Pott disease was treated with immobilization using prolonged bed rest or a body cast. At the time, the disease carried a mortality rate of 20%, and relapse was common (30%).
The duration of treatment, surgical indications, and inpatient care for Pott disease have since evolved. 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, although routine surgery does not seem to be indicated.[46]
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.
Once the diagnosis of Pott disease is established and treatment is started, the duration of hospitalization depends on the need for surgery and the clinical stability of the patient.
Patients with Pott disease should be closely monitored to assess their response to therapy and compliance with medication. Directly observed therapy may be required.
The development or progression of neurologic deficits, spinal deformity, or intractable pain should be considered evidence of poor therapeutic response. This raises the possibility of antimicrobial drug resistance, as well as the necessity for surgery.
Because of the risk of deformity exacerbations, children with Pott disease should undergo long-term follow-up until their entire growth potential is completed.[47] Older patients can also present with late-onset complications such as reactivation, instability, or deformity. Observation is warranted in all groups of patients.
Consultations in Pott disease can include the following:
Practice guidelines issued in 2016 by the US Centers for Disease Control and Prevention (CDC), the Infectious Diseases Society of America, and the American Thoracic Society continue to recommend a 4-drug regimen for empirical treatment of Pott disease.[48] Identifying the susceptibility pattern of the particular strain, if possible, is important in order to adjust the treatment regimen and duration accordingly.
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 from among the first-line drugs, which include pyrazinamide, ethambutol, and streptomycin. The use of second-line drugs is indicated in cases of drug resistance.[49]
Treatment duration
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.[50]
However, the research council’s 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.[48]
For selected cases with surgical indication that allows complete debridement of the lesion, a combination of surgery and ultra-shortened course of therapy (4.5 mo), appears to show comparable outcomes of a combination of surgery and 9 months of drug therapy.[51]
While most patients should respond to medical treatment, a surgical approach needs to be evaluated and considered. Indications for surgical treatment of Pott disease generally include the following:[52, 53]
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).[54, 55, 56]
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.
The most conventional approaches include anterior radical focal debridement and posterior stabilization with instrumentation. Several variations of this approach have been described. The specific advantages and limitations of surgical techniques vary.[57] Individualization of the case is of greatest importance.[21, 58, 59, 60, 61] Newer modalities and techniques are being reported, such as thoracoscopic decompression.[62]
In Pott disease that involves the cervical spine, the following factors justify early surgical intervention:
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.
Tubercular epidural abscess may produce spinal cord and nerve root compression leading to significant deficits. The American Spinal Injury Association impairment scale (ASIA) is useful to document neurological recovery from Pott disease. A designation of ASIA A indicates the most severe neurological compromise, ASIA E the least. At the beginning of treatment, most individuals are characterized as ASIA D. Large epidural abscesses correlated with a poor prognosis in terms of recovery from neurological deficits.[63]
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 and are generally chosen from among the first-line drugs, such as pyrazinamide, ethambutol, and streptomycin. (A 3-drug regimen usually includes isoniazid, rifampin, and pyrazinamide.) In cases of drug resistance, the use of second-line medications is indicated.
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.[64, 65]
Clinical Context: Isoniazid is highly active against Mycobacterium tuberculosis. It has good gastrointestinal (GI) absorption and penetrates well into all body fluids and cavities.
Clinical Context: Rifampin is for use in combination with at least 1 other antituberculous drug. It inhibits deoxyribonucleic acid (DNA) ̶ dependent bacterial (but not mammalian) ribonucleic acid (RNA) polymerase. Cross resistance may occur.
Clinical Context: Pyrazinamide is bactericidal against M tuberculosis in an acid environment (macrophages). It has good absorption from the GI tract and penetrates well into most tissues, including the cerebrospinal fluid (CSF).
Clinical Context: Ethambutol has bacteriostatic activity against M tuberculosis. The drug has good GI absorption. CSF concentrations remain low, even in the presence of meningeal inflammation.
Clinical Context: Streptomycin is bactericidal in an alkaline environment. Because it is not absorbed from the GI tract, the drug must be administered parenterally. Streptomycin exerts action mainly on extracellular tubercle bacilli. Only about 10% of the drug penetrates cells that harbor organisms. Streptomycin enters the CSF only in the presence of meningeal inflammation. Excretion is almost entirely renal.
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.
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.
MRI of the T11 in a 31-year-old man with tuberculosis of the spine. 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.
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.
MRI of the T11 in a 31-year-old man with tuberculosis of the spine. 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.