The artful dodger: capturing elusive spinal tuberculosis aka Potts disease

Spinal tuberculosis (TB) can be devastating if left unchecked, but its ability to mimic other diseases makes early detection challenging. Here, Dr Alpaslan Şenköylü explains the increased incidence of spinal TB, outlines diagnostic clues, patient risk factors, and sets out the treatment options that can prevent and correct spine deformity. Early intervention may avoid surgery and disability.

Spinal tuberculosis—or Potts disease—is an interesting disease because it is both very fragile and very good at hiding its tracks. Often, patients will present at a clinic with symptoms such as back pain and night fever, but of course these symptoms are common across many other diseases too. Spinal tuberculosis often forms a ‘cold abscess’—a lump or swelling, that is not accompanied by a secondary inflammatory response such as inflammation, heat and local tenderness. With TB, it’s often just a mass, so it mimics many kinds of tumors, especially in the musculoskeletal system. This creates a challenge in terms of early diagnosis.

An additional issue is that the people who are most at risk of spinal tuberculosis are often vulnerable, and not well tracked by medical professionals. The mycobacterium behind tuberculosis is very fragile, so it is difficult to get infected with TB if you are relatively young, fit and healthy. In most cases, our very powerful immune system will destroy the mycobacterium. However, people who are very young, such as less than three years old, or people who are over around 70, are more susceptible. The risk increases if you add in comorbidities such as diabetes or intravenous drug use. Often, IV drug users with HIV infections also have tuberculosis.

War and poverty increase incidences of spinal tuberculosis

In developing countries, there are widespread childhood vaccination programs to help protect the population against diseases such as TB. This is often not the case in the developing world, and coupled with low general health and malnutrition, we are seeing increased incidences of the illness. That is not to say this is a disease only of third world countries. Immigration and war have also brought a rise in cases in the developed world. 

I am from Turkiye and the conflict in the Middle East over the past 20 years, particularly in Syria and Iraq, has brought many immigrants from those countries. Of course, the circumstances of war are not easy. It compromises basic health services, like vaccination and pregnancy aftercare, and there’s a lack of basics such as money for food and availability of clean water. All these issues mean that immigrants and homeless people are accessing health services at a very late stage, often when the disease has already started to present.

Tuberculosis can sit in the body and develop slowly over a period of years before we start to see the symptoms I outlined such as abscess or spinal deformity. Because tuberculosis is very fragile, it favors well perfused organs with high levels of oxygen, most commonly the lungs. This is why tuberculosis is most commonly understood by people as a lung disease. However, it also often presents in the kidneys. From these primary focuses, the disease travels through the blood into the spine and may develop spinal-TB as a secondary tuberculosis. It is attracted to metaphyseal part of long bones, such as the humerus, tibia and femur, as well as the extremities. It is able to take a strong hold where patients are immunosuppressed.

MRI with contrast: crucial tool in diagnosis 

Early treatment greatly improves the prognosis for the patient and surgery can even be avoided, but the difficulties associated with diagnosis mean spinal-TB is often accompanied by high mortality rates. The important thing is for medics treating patients with abscess and no secondary inflammatory response to consider that spinal-TB may be the cause. 

Diagnosis can come from a PCR test, which detects the presence of mycobacterium tuberculosis from a sample such as sputum, blood or fluid. However, it is difficult to gather a culture from the spine and lab analysis is not easy, and often time consuming.

On the other hand, an MRI with a gadolinium contrast injection is really helpful in identifying the contrast media uptake around damaged tissue so called rim enhancement. Protection of disc space is another MRI finding of the spinal TB. For patients with late diagnosed Potts, you will often see epidural abscess formation together with the destruction of the vertebral bodies, which TB tends to attack because of its very strong blood perfusion. 

S Rajasekaran—one of the prominent surgeons in the field—has developed useful “spine at risk” criteria for the young spinal-TB patient. If they have facet joint dislocation, retropulsion, lateral translation or toppling, this is likely to develop into post-TB kyphosis, which can result in the tethering of the spinal cord at the apex, leading to myelopathy and paraparesis or paraplegia of the patient at the end. Morbidity levels are high because treatment involves a very extensive surgery from the posterior approach.