What Is Pott's Disease?
Pott's disease is also known as tuberculosis spondylitis or spinal tuberculosis. It is a rare infectious disease of the spine that is typically caused by a tuberculosis infection from another site. This disease presents as a combination of osteomyelitis and arthritis involving multiple vertebrae. It typically involves the anterior part of the vertebral body and occurs most frequently involving the lower thoracic vertebrae. This disease causes vertebral collapse, and when it occurs anteriorly, the anterior wedging leads to a deformity of the spine known as kyphosis (hunched back). The other effects include compression fractures, deformities of the spine, and neurological manifestations, including paraplegia. The disease was named after the person who discovered the condition in the 1700s, Dr. Percivall Pott.
What Causes Pott's Disease?
Tuberculosis is caused by the infectious bacteria Mycobacterium tuberculosis, which primarily affects the lungs. If timely treatment is not provided, it may quickly progress to the spine and cause arthritis. When the infection spreads to two adjacent joints and treatment is not given, it can result in deterioration as the spinal disc receives fewer nutrients.
The disc collapse leads to damage to the spinal cord. If treatment is not given, it results in damage to nerves, paralysis, and deformities of the spine. Only one to two percent of patients develop Pott's disease after contracting pulmonary (lung) tuberculosis.
What Are the Symptoms of Pott's Disease?
The lower thoracic vertebrae are the most commonly involved (40% to 50%), followed by the lumbar vertebra (35% to 45%), cervical spine (10%), and atlantoaxial region (1%).
Primary Symptoms:
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Tenderness and pain in the affected region.
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Spasm of the associated muscles.
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The spinal motion may become restricted.
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Deformity of the spine.
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Neurological defects.
The first and foremost symptom of Pott disease is back pain. The back pain lasts for weeks, if not months before the patient seeks treatment and presents as either spinal or radicular pain. The thoracic and lumbar spinal areas are affected almost equally, involving 80% to 90% of spinal tuberculosis sites. However, the thoracic area of the spine is more frequently reported as the common site of involvement.
Neurologic defects occur in about 50% of cases and include compression of the spinal cord accompanied by:
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Impaired sensation.
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Nerve root pain.
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Cauda equina syndrome.
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Paresis.
Spinal deformity is seen in almost all patients with Pott's disease. The most common spinal deformity is thoracic kyphosis.
Other Associated Symptoms:
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Weight loss.
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Night sweats.
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Malaise.
The less common variant, cervical spine tuberculosis, occurs in approximately 10% of cases. However, this variant is relatively more severe because of the severe neurological complications, cervical pain and stiffness, torticollis, and hoarseness. In upper cervical spine involvement, the symptoms are rapidly progressive and may occur early. The neurologic manifestations range from a single nerve palsy to hemiparesis or quadriplegia accompanied by a retropharyngeal abscess. In lower cervical spine injuries, the patient can present with dysphagia or stridor.
Pott's Disease in People With HIV Infection:
Spinal tuberculosis is more common in people infected with the human immunodeficiency virus (HIV), and the clinical presentation is similar to that of HIV negative population.
Asymptomatic Population:
Pott's disease is asymptomatic in 62% to 90% of the population with the disease and shows no evidence of extraspinal tuberculosis as well. This complicates timely diagnosis and worsens the prognosis.
How Is Pott's Disease Diagnosed?
The following tests aid in the diagnosis of Pott's disease:
1) The Tuberculin Skin Test (Mantoux Test):
It is a skin test that is used to diagnose tuberculosis that involves the injection of a purified protein derivative (PPD).
2) Erythrocyte Sedimentation Rate (ESR):
The erythrocyte sedimentation rate may be markedly increased (greater than 100 mm/h).
3) Bacterial Isolation:
The samples are collected from bone tissue to stain for acid-fast bacilli (AFB). The organisms are then isolated for culture and tested for susceptibility. However, the samples tested positive for the organism in only about 50% of the cases.
4) Radiographic Changes:
The radiographic changes are usually present much later compared to the other symptoms. On plain radiography, the following changes can be noted:
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Lytic destruction of the anterior portion of the vertebral body.
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Reactive sclerosis on a progressive lytic process.
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Increased anterior wedging.
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The collapse of the vertebral body.
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Vertebral endplates may be osteoporotic.
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Enlarged psoas shadow with or without calcification.
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Vertebral bodies show variable degrees of destruction.
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Intervertebral disks may be shrunk or destroyed.
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Bone lesions may occur at more than one level.
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Fusiform paravertebral shadows suggest abscess formation.
5) Computed Tomography (CT) Scanning:
CT scanning with low contrast resolution provides a better assessment of the epidural and paraspinal soft tissues. CT scan also shows bony detail of disk collapse, irregular lytic lesions, disruption of bone circumference, and sclerosis.
6) Magnetic Resonance Imaging (MRI):
Disk-space infections, neural compression, tuberculosis spondylitis (differentiates from pyogenic spondylitis), and spinal osteomyelitis are best diagnosed by MRI, as it is the gold standard criterion. It is the most effective for demonstrating the extension of tuberculosis into the soft tissue space. It also demonstrates the spread of tuberculosis under the anterior and posterior longitudinal ligaments.
7) Biopsy:
A CT-guided needle biopsy can be used to drain large paraspinal abscesses and obtain tissue samples from bone lesions.
8) Polymerase Chain Reaction (PCR):
PCR techniques rapidly detect and diagnose several strains of Mycobacterium without the need for prolonged culture and are used to identify discrete genetic mutations in deoxyribonucleic acid (DNA) sequences associated with drug resistance.
How Is Pott's Disease Treated?
The treatment of Pott's disease varies for each individual and is based on the doctor's discretion. The course of treatment is usually from six months to one year. The medications prescribed aim at inhibiting the growth and proliferation of Mycobacterium tuberculosis. The first line of drugs is Isoniazid and Rifampin. These drugs are administered throughout the course of treatment. Other drugs that may be given during the first two months of treatment are Pyrazinamide, Ethambutol, and Streptomycin. If there is drug resistance, the second line of drugs is avoided. Although pharmacologic treatment is effective, certain cases require surgical management to prevent further progression of the disease and to correct any deformities.
Conclusion:
The progress of the disease is often slow and persists for months or years. Prognosis is better if the symptoms are noted early and the latest regimes of drugs are administered. However, the symptoms are often identified at a later stage. Preventive measures like getting the BCG (bacillus Calmette-Guerin) vaccine are ideal for people who are at high risk.