Pott's Disease

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Original Editors - David Pieschel & Craig Satterley from Bellarmine University's Pathophysiology of Complex Patient Problems project.

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Definition/Description

Pott’s Disease, also known as tuberculosis spondylitis, is a rare infectious disease of the spine which is typically caused by an extraspinal infection. Pott’s Disease is a combination of osteomyelitis and arthritis which involves multiple vertebrae. (3) The typical site of involvement is the anterior aspect of the vertebral body adjacent to the subchondral plate and occurs most frequently in the lower thoracic vertebrae. A possible effect of this disease is vertebral collapse and when this occurs in this aspect of the vertebrae, anterior wedging results leading to kyphotic deformity of the spine. (2,3) Other possible effects can include compression fractures, spinal deformities and neurological insults, including paraplegia. (3,4)

Prevalence

Incidence
In 2005, there were 8.8 million new patients with tuberculosis (TB) all over the world, and of these, there were 7.4 million in Asia and sub-Saharan Africa (5). Involvement of the spine reportedly occurs in less than 1-2% of patients who contracted TB. Although the incidence of tuberculosis increased in the late 1980’s to early 1990’s, the total number of cases has decreased in recent years. In the United States, bone and soft tissue tuberculosis accounts for approximately 10% of extrapulmonary TB cases and between 1% and 2% of total cases. Of these cases, Pott’s disease is the most common manifestation of musculoskeletal TB, accounting for approximately 40-50% (3).Internationally, approximately 1-2% of total tuberculosis cases are attributable to Pott’s disease.

Ethnicity
Data from the United States show that musculoskeletal tuberculosis primarily affects African Americans, Hispanic Americans, Asian Americans, and foreign-born individuals (3). The number of patients with TB spondylitis in Japan also declined to 233 in 2005 from 734 in 1978 and 276 in 2001 [10, 21].

Gender
Although some series have found that Pott’s disease does not have sexual predilection, the disease is more common in males. The male to female ratio is reportedly 1.5-2:1.

Age
In the United States and other developed countries, Pott’s disease occurs primarily in adults. In underdeveloped countries which have higher rates of Pott’s disease, involvement in young adults and older children predominates (3).

Characteristics/Clinical Presentation

Spinal Involvement

• Lower thoracic vertebrae is the most common area of involvement (40-50%), followed by the Lumbar spine (35-45%) (3)
• Approximately 10% of Pott's disease cases involve the cervical spine. (3)
• The thoracic spine is involved in about 65% of cases, and the lumbar, cervical and thoracolumbar spine in about 20%, 10% and 5%, respectively (2)
• The atlanto-axial region may also be involved in less than 1% of cases (2)

Physical Findings

• Localized Tenderness
• Muscle Spasms
• Restricted Spinal Motion
• Spinal Deformity
• Neurological Deficits

Back Pain

Back pain is the earliest and most common symptom. Patients with Pott’s disease usually experience back pain for weeks before seeking treatment and the pain caused by spinal TB can present as spinal or radicular. Although both the thoracic and lumbar spinal segments are nearly equally affected, the thoracic spine is frequently reported as the most common site of involvement. Together, thoracic and lumbar involvement comprise of 80-90% of spinal TB sites(3).

Neurological Signs

Neurologic abnormalities occur in 50% of cases and can include spinal cord compression with the following: 

• Paraplegia
• Paresis
• Impaired sensation
• Nerve root pain
• Cauda equina syndrome(3).

Spinal Deformities

Almost all patients with Pott’s disease have some degree of spine deformity with thoracic kyphosis being the most common (3).

Constitutional Symptoms

Potential constitutional symptoms include fever, night sweats, weight loss and malaise(7,8,11).

Cervical Spinal TB

Cervical spine TB is a less common presentation occurring in approximately 10% of cases, but is potentially more serious because severe neurological complications are more likely. This condition is characterized by cervical pain and stiffness and symptoms can also include torticollis, hoarseness, and neurological deficits. Upper cervical spine involvement can cause rapidly progressive symptoms and neurologic manifestations occur early and range from a single nerve palsy to hemiparesis or quadriplegia. Retropharyngeal abscesses occur in almost all cases. In lower cervical spine insults, the patient can present with dysphagia or stridor(3).

Presentation in People Infected with HIV

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 TB seems to be more common in persons infected with HIV(3).

Asymptomatic Presentation

Many persons with Pott’s disease (62-90%) of patients reported series have no evidence of extraspinal tuberculosis, further complicating a timely diagnosis.(3)

Associated Co-morbidities

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Medications

The duration of treatment is somewhat controversial. Although some studies favor 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.
The main drug class consists of agents that inhibit growth and proliferation of the causative bacteria. Isoniazid and rifampin should be administered during the whole course of therapy. Additional drugs are administered during the first two months of therapy and 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.

Isoniazid (Laniazid, Nydrazid)
View full drug information: http://reference.medscape.com/drug/isoniazid-342564
Highly active against Mycobacterium tuberculosis. Has good GI absorption and penetrates well into all body fluids and cavities.

Rifampin (Rifadin, Rimactane)
View full drug information: http://reference.medscape.com/drug/rifadin-rimactane-rifampin-342570
For use in combination with at least one other antituberculous drug; inhibits DNA-dependent bacterial but not mammalian RNA polymerase. Cross-resistance may occur.

Pyrazinamide
View full drug information: http://reference.medscape.com/drug/pyrazinamide-342678
Bactericidal against M tuberculosis in an acid environment (macrophages). Has good absorption from the GI tract and penetrates well into most tissues, including CSF.

Ethambutol (Myambutol)
View full drug information: http://reference.medscape.com/drug/myambutol-ethambutol-342677
Has bacteriostatic activity against M tuberculosis. Has good GI absorption. CSF concentrations remain low, even in the presence of meningeal inflammation.

Streptomycin
View full drug information: http://reference.medscape.com/drug/streptomycin-342682
Bactericidal in an alkaline environment. Because it is not absorbed from the GI tract, must be administered parenterally. Exerts action mainly on extracellular tubercle bacilli. Only about 10% of the drug penetrates cells that harbor organisms. Enters the CSF only in the presence of meningeal inflammation. Excretion is almost entirely renal. (3)

Diagnostic Tests/Lab Tests/Lab Values

Tuberculosis Skin Test
Injection of a purified protein derivative (PPD). Results are positive in 84-95% of patients with Pott’s disease who are not infected with HIV. 

Erythrocyte Sedimentation Rate (ESR)
ESR may be markedly elevated (>100 mm/h)

Microbiology Studies
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; however, these study findings are positive in only about 50% of the cases.

Radiography
Radiographic changes associated with Pott’s disease present relatively late. The following are radiographic changes characteristics of spinal tuberculosis on plain radiography:

• 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
• Vertebral end plates may be 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 Scanning
CT scanning provides much better bony detail of irregular lytic lesions, sclerosis, disk collapse, and disruption of bone circumference. 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 which is common in TB lesions.

MRI
MRI is the criterion gold standard for evaluating disk-space infection and osteomyelitis of the spine and is most effective for demonstrating the extension of disease into soft tissue and the spread of tuberculous debris under the anterior and posterior longitudinal ligaments. MRI is also called the most effective imaging study for demonstrating neural compression. MRI findings useful to differentiate tuberculosis 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.

Biopsy
Use of a percutaneous CT-guided needle biopsy of bone lesions to can be used to obtain tissue samples. This is a safe procedure that also allows therapeutic drainage of large paraspinal abscesses.

 

Etiology/Causes

The organism that has been identified as causing Pott’s disease is mycobacterium tuberculosis. The primary mode of transmission the bacteria travels to the spine is hematogenously from an extraspinal site of infection. It is common to travel from the lungs in adults but the primary site of infection is often unknown in children.  (8, 9) The infection has also been found to spread through the lymphatic system. (6) Once being spread, the infection can target vertebrae, intervertebral discs, the epidural or intradural space within the spinal canal and adjacent soft tissue. (7)

If a single vertebra is affected, the surrounding intervertebral discs will remain normal. However, if two adjacent vertebrae are affected, the intervertebral disc between them will also collapse and become avascular. (8) Due to the vascularity of intervertebral discs in children, the discs can become a primary site of infection rather than spreading from the vertebrae. (3)

Spinal cord compression in Pott’s disease is usually caused by paravertebral abscesses which can also develop calcifications or sequestra within them. (2) If the infection reaches adjacent ligaments and soft tissues, a cold abscess can also form. Abscesses in the lumbar region may descend down the sheath of the psoas to the femoral trigone region and eventually erode into the skin. (3) Other causes of neurological involvement include dural invasion from granulation tissue, sequestrated bone, intervertebral disc collapse or a dislocated vertebra. (2,3,8) Neurological symptoms can occur at any point, including years later as a result of stretching of the spinal cord within the vertebral foramen of the deformed spine. (2)

Systemic Involvement

The severity of Pott’s disease varies from one person to another, resulting in different clinical presentations. Possible signs and symptoms that may present are depicted in Table 1 by system.

Table 1. Systemic Signs and Symptoms of Pott's Disease

Musculoskeletal	Neurological	Cardiovascular	Integumentary	Urogenital	Constitutional Symptoms
Vertebral Fractures	Paresthesia	Spinal Artery Infarction	Pressure Ulcers (Secondary)	Bowel Dysfunction	Fever
Vertebral Collapse	Paralysis	Avascularity of Intervertebral Discs	Sinus (Secondary to Abscess Rupture)	Bladder Dysfunction	Night Sweats
Spinal Ligament Destruction	Paresis	Thrombosis			Malaise
Intervertebral Disc Destruction	Abnormal Muscle Tone				Fatigue
Paravertebral Abscess	Abnormal Reflexes				Weight Loss
Osteopenia/Osteoporosis	Cauda Equina Syndrome
Bone Sequestrations	Myelomalacia
Dislocated Vertebrae	Gliosis
Kyphotic Deformity	Syringomyelia
Muscle Atrophy
Torticollis

 

Medical Management (current best evidence)

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Physical Therapy Management (current best evidence)

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Alternative/Holistic Management (current best evidence)

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Case Reports/ Case Studies

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Resources

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Recent Related Research (from Pubmed)

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References

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