POTT`S DISEASE

Pott's spine, commonly known as spinal tuberculosis (TB), is an extrapulmonary form of TB caused by Mycobacterium TB. Pott’s disease starts in your lungs before it moves to your spine affecting the intervertebral disks and bony vertebrae in the spine. It is also known as Pott’s spine or tuberculosis spondylitis. 

How common is Pott`s disease?

In 2021, 10.6 million people were infected with TB, equating to 134 cases per 100000 people. Human immunodeficiency virus (HIV)-positive individuals accounted for 6.7% of all TB cases. Geographically, the WHO areas of South-East Asia (45%), Africa (23%), and the Western Pacific (18%) had the highest percentages of TB cases in 2021, while the Eastern Mediterranean (8.1%), the Americas (2.9%), and Europe (2.2%) had the lowest percentages. 

What areas of the spine are commonly affected by TB?

According to several retrospective studies, the lower thoracic and upper lumbar vertebrae account for 90% of individuals with spinal TB. Overall, the thoracolumbar junction is most frequently affected, followed by the lumbar, and cervical areas. 

What are the causes of Pott`s disease?

The bacterium Mycobacterium tuberculosis causes Pott’s disease. The infection is contagious and starts in the lungs and moves to the bones in your spine via your bloodstream.

TB bacteria often migrate from a primary location, such as the lungs or genitourinary system, to the vertebral body via a hematogenous pathway. Each vertebra has a rich vascular plexus in the subchondral region, which makes it easier for TB bacteria to spread to the paradisiacal area. Two neighbouring vertebrae are supplied by the same segmental artery, so often both are affected. (https://pmc.ncbi.nlm.nih.gov/articles/PMC10251269/) 

What are the symptoms of Pott`s disease?

• Back pain (specially at night) 
• Neck pain
• Arm and leg weakness
• Loss of appetite
• Unexplained weight loss
• Fever 

Who is at risk of getting Pott`s disease?

You may be more at risk of developing Pott’s disease if you have exposure to someone who has TB, live in a crowded area (high population density) or have limited access to healthcare. People with certain health conditions have an increased Pott’s disease risk, including:

• Malnutrition
• Substance use disorder
• Conditions that compromise immune system like HIV

What are the complications of Pott`s disease?

If left untreated, Pott`s disease bacteria create inflammation (swelling) and pus-filled pockets (abscesses) in the spinal column. This weakens the vertebrae leading to compression and collapse. Pott’s disease can also lead to the following complications:

• Difficulty moving or walking.
• Nerve compression (weakness, numbness, loss of bladder or bowel control).
• Paralysis 
• Infection spreading to other parts of body for e.g. to the brain and kidneys. (https://my.clevelandclinic.org/health/diseases/potts-disease-spinal-tuberculosis) 

How is Pott`s disease diagnosed?

Spinal TB is diagnosed based on clinical and radiographic cues, as well as microbiological and histological markers. Early identification of mycobacterium from clinical samples is critical for both diagnostic confirmation and drug susceptibility testing. 

Imaging

• A Computed tomography (CT) scan can help in the diagnosis at a much earlier stage than plain x-rays. The types of vertebral destructive lesions by CT in spinal TB include fragmentary, osteolytic, subperiosteal, and localized sclerosis. CT scans can also aid in image-guided biopsy for establishing the diagnosis.
• Magnetic resonance imaging (MRI) scans best detects the extent of soft tissue enhancement, the location of the abscess and spinal canal compromise. Gadolinium-enhanced MRI may provide additional information regarding the diagnosis. Screening sequences involving the whole spine can also help us in identifying non-contiguous vertebral involvement. MRI can also assess response to treatment.

Laboratory testing

• C-reactive protein (CRP) (71% sensitivity) is preferred, as it is more specific than Erythrocyte Sedimentation Rate.
• Molecular testing and polymerase chain reaction (PCR) (75% sensitivity and 97% specificity): This technique requires only a concentration of 1 to 10 bacilli/ ml. This is a very useful technique in paucibacillary, extrapulmonary TB infections. 
• Gene Xpert MTB/RIF: This is a fully automated test, which yields results within 90 minutes (82.9% sensitivity and 98% specificity). This test also helps in diagnosing resistance to rifampicin. WHO, in March 2017 recommended Xpert MTB/RIF Ultra (87.8% sensitivity and 94.8% specificity) as an investigation with good yield in pediatric and extrapulmonary patients.
• Histopathological evaluation: Characteristic findings including caseating necrosis, epithelioid cell granuloma, and Langhans giant cells can be found in 72% to 97% of patients. (https://www.ncbi.nlm.nih.gov/books/NBK538331/) 

Acid-fast bacilli (AFB) staining (25% to 75% sensitivity and 99% specificity): Using the Ziehl-Neelsen technique, tubercle bacillus presents with a bright red stain. At least, a concentration of 1 to 10 bacteria/ ml is necessary for detection.

How is Pott`s disease treated?

Treatment for Pott’s disease happens in stages by taking certain medications over several months. Your healthcare provider might recommend taking the following chemotherapy medications: 

• Isoniazid, rifampicin, pyrazinamide, ethambutol and/or streptomycin for 2 months.
• Continuing isoniazid and rifampicin for 4 to 12 months or longer. 

Always follow your provider’s instructions to take medications for TB as directed. Stopping medications early can make treatments less effective. In case of drug-resistant TB, your provider might recommend the following medications: 

• Kanamycin
• Capreomycin
• Pyrazinamide 
• Amikacin
• Fluoroquinolone 

There are potential side-effects to TB medicine which may need to be discussed with your healthcare provider. In some cases, surgery might be necessary to repair your spine, reduce symptoms and prevent complications of Pott’s disease. Types of surgeries may include:

• Debridement: Cleaning or removing damaged tissue around your spine.
• Drainage: Removing or draining the pus-filled abscesses collected in your spinal column.
• Stabilization and alignment: TB can destroy or damage vertebrae. A surgeon may remove and/or repair broken bones and disks and add plates and screws to hold your bones in place.
• Fusion: A surgeon may permanently join two vertebrae together to limit their movement, which can prevent pain and other complications. Your surgeon may use a piece of bone from another part of your body (a bone graft) to help the two vertebrae fuse together. (https://my.clevelandclinic.org/health/diseases/potts-disease-spinal-tuberculosis)