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EDITORIAL
Year : 2019  |  Volume : 67  |  Issue : 6  |  Page : 1402--1404

Spinal Tuberculosis: Still a Great Mimic

Ravindra Kumar Garg, Hardeep Singh Malhotra, Neeraj Kumar 
 Department of Neurology, King George's Medical University, Lucknow, Uttar Pradesh, India

Correspondence Address:
Dr. Ravindra Kumar Garg
Department of Neurology, King George's Medical University, Lucknow - 226 003, Uttar Pradesh
India




How to cite this article:
Garg RK, Malhotra HS, Kumar N. Spinal Tuberculosis: Still a Great Mimic.Neurol India 2019;67:1402-1404


How to cite this URL:
Garg RK, Malhotra HS, Kumar N. Spinal Tuberculosis: Still a Great Mimic. Neurol India [serial online] 2019 [cited 2020 Apr 7 ];67:1402-1404
Available from: http://www.neurologyindia.com/text.asp?2019/67/6/1402/273618


Full Text



Approximately 10 million people fell ill with tuberculosis in 2018 worldwide. Eight countries accounted for two-thirds of the global burden of tuberculosis, of which India tops the list with 27% of all cases. Spinal tuberculosis is the most common form of extrapulmonary tuberculosis and accounts for 1%–2% of all cases with tuberculosis.[1]

Spinal tuberculosis may be regarded as one of the oldest malady known to the human race with its detection and molecular characterisation dating back to almost 9000 years, or more.[2] Even though it is an affliction of the skeletal system, secondary or indirect involvement of parts of the nervous system and other soft tissues may result in various neuromuscular disabilities in addition to the skeletal ones.

As a disease per se tuberculosis is a great masquerader, and spinal tuberculosis is no exception to this rule. Of the several types of skeletal tuberculosis, spinal tuberculosis is the most disabling type of tuberculosis that necessitates that the disease to be detected early and treated effectively. It is inherently a destructive disease, and in the early stages, clinical manifestations, laboratory findings, and imaging abnormalities may not be distinct enough to accurately distinguish it from its close mimics, particularly, pyogenic and malignant (primary as well as metastases) involvement of the spinal cord. Consequently, spinal tuberculosis may be misdiagnosed. It is equally important to acknowledge the fact that over-diagnosing tuberculosis can erroneously subject someone to unnecessary drugs, having their own adverse effects.

A combination of factors, namely, anatomical (based on vascular pattern), pathophysiological (with or without infection/inflammation), and radiological (X-Ray, CT, and MRI), in the light of a suitable clinical setting help in the correct diagnosis of spinal tuberculosis. The dissection of features become important in an individual patient than what is defined in a trial or a composite analysis. Results of a given study only provide the likelihood of a particular disease, but to what extent these would be applicable to a patient may purely be suppositional. This also brings to the fore the aspect of breaking the news appropriately to the patient stating that “in the given circumstances, in the absence of histopathology, and with the current epidemiology, the probability of spinal tuberculosis is so-and-so,” as an example.

Kumaran et al. present an intriguing single-center retrospective experience of etiologies that may mimic spinal tuberculosis and lay stress on various features that can help a physician to differentiate or at least detect a red flag based on their presentation.[3] Some of these look-alikes are of serious concern such as pyogenic spondylitis, spinal cord metastasis, and lymphomatous spread to the spinal cord. Breast, prostate, and lung cancer are the most common malignancies metastasising to the spinal cord. Non-Hodgkin's lymphoma and Hodgkin's Lymphoma can rarely lead to spinal cord compression. Such lesions usually involve the vertebral body and epidural compartment.[4] Another common group of disorders that the authors discuss are those that are degenerative, traumatic, or metabolic in nature, like, old spinal cord trauma, degenerative disk disease, and osteoporotic involvement. They also describe some cases, inflammatory in nature, like ankylosing spondylitis and rheumatoid arthritis.

The most crucial differential diagnosis is with spinal cord metastasis and lymphomatous spread to the spinal cord. Misdiagnosis is frequent.[5],[6] Clinically, both tuberculous and malignant spinal cord diseases present with similar subacute myelopathy with backache, except the patients with spinal tuberculosis much younger than that of metastatic spine. This point always needs to be kept in mind while considering this differential diagnosis.[7] A chest X-ray in a patient with spinal tuberculosis can be of great help in the initial assessment. [Figure 1] Plain X-rays of the spine can show owl-eye erosion of the pedicles, which is quite characteristic of metastatic disease from spinal cord disease. A chest X-ray may detect an unsuspected lung malignancy or can detect a lesion consistent with pulmonary tuberculosis.[5] Search for an additional site of involvement, for example, in the brain, can clinch the diagnosis of metastasis. [Figure 1] In addition, ultrasound of the abdomen can aid in the diagnosis by either detecting a malignancy or a distant focus of tuberculosis.{Figure 1}

MRI is the imaging modality of choice in such circumstances. Characteristically, in spinal tuberculosis, thoracic spine involvement, affection of 2 or more adjacent vertebral bodies, severe destruction of the vertebral body, subligamentous spread, vertebral collapse, and large paraspinal abscess.[8]

Spinal deformities, like, kyphosis and gibbus are common in spinal tuberculosis. In spinal cord metastasis, posterior elements of the vertebral bodies are predominantly involved. Intervertebral disc and disc space are spared till late. Paraspinal soft tissue pus collection is uncommon. Lymphomatous metastasis commonly involves the cauda equina. In addition, multiple vertebral involvements are common. Fluorine-18-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG PET-CT) can help in differentiating spinal tuberculosis from spinal metastasis. FDG PET/CT demonstrates multiple FDG-avid lymph nodes and bone lesions in spinal cord metastasis. In spinal tuberculosis, para-discal FDG avid lesions and cold abscess are common.[9],[10]

In the series by Kumaran et al., brucellar spondylitis was demonstrated in one patient while pyogenic spondylitis was seen in 15 patients. It is possible that several patients who in fact have brucella get treated in the garb of spinal tuberculosis; they may improve completely because of rifampicin and frequent use of quinolones as an additional drug in the anti-tuberculosis regime. Both brucellar spondylitis and pyogenic spondylitis affect the lumbar spine. Sacroiliitis is present in many cases of brucellosis. Soft-tissue lesions are usually small in size, and large cold abscesses are rare. In pyogenic spondylitis, fever is less commonly noted and occurs in only 20% of patients.

Unfortunately, none of the imaging modalities are reliable enough to clearly distinguish between spinal tuberculosis and spinal metastasis. Hence, histopathological evaluation is mandatory to confirm the diagnosis. CT-guided needle biopsy is an effective and safe procedure for diagnosing spinal lesions. The Xpert MTB/RIF assay is a widely available modality for rapid identification of Mycobacterium tuberculosis in aspirated pus or biopsied material. In addition, the Xpert MTB/RIF assay detects rifampicin drug resistance as well.[11] Xpert Ultra is a better technology that, confirms more number of spinal tuberculosis cases than Xpert or culture, making it a useful tool for the rapid diagnosis of spinal tuberculosis. These newer molecular tests demonstrated an excellent initial diagnostic method that greatly improves the proportion of confirmed cases.[12] The major limitation with this test is that in more than 50% of cases results are negative. Therefore, in such conditions, only biopsy and histopathological evaluation remain the gold standard. A confirmed diagnosis of pyogenic spondylitis requires microscopic or bacteriological examination and culture of the infected tissues.

Thus, it may be understood that the ultimate gold standard in conclusively labeling a patient with spinal tuberculosis is the histopathology specimen demonstrating Mycobacterium tuberculosis; all of the other cues just point toward the possibility of tuberculosis as an etiology.

References

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