Central nervous system of a human being consists of brain and spine. Tuberculosis of the central nervous system (CNS) is a form of tuberculosis, which can lead to unimaginable levels of morbidity and mortality. Central nervous system (CNS) tuberculosis (TB) is categorised into three clinical categories namely, Tubercular Meningitis (most common), Intracranial Tuberculoma and Spinal Tubercular Arachnoiditis.
Pathogenesis of CNS tuberculosis
Mycobacterium tuberculosis causes most of CNS TB infections. It is very rarely that other mycobacterium is involved. Doctors believe that the bacterium reaches the CNS through haematogenous route secondary to other infected body organs. Researchers suggested that CNS TB outgrows in two stages. In the initial stage, little tuberculous lesions grow in the CNS either during the stage of bacteraemia of the primary tuberculous infection or shortly afterwards. These lesions may be located in the meninges, the subpial or subependymal surface of the brain or spinal cord and may stay latent for some years after the initial infection. Shortly after, these small tuberculous lesions rupture to produce various types of CNS tuberculosis.
CNS Tuberculosis in a patient may be asymptomatic, have symptoms of pulmonary TB or may present neurologic deficits alone. Usually, CNS TB shows indications of increased intracranial pressure or space-taking lesions in the brain or spine. Patients with TB infection in the brain (Intracranial tuberculomas) usually complain about headache, rigid neck, high body temperature, weight loss, blurred vision, confusion, lethargy, swelling, episodes of vomiting etc. Patients with Intracranial tuberculomas have an examination involving the location of the space-occupying damage in the brain.
Patients with spinal cord lesions or spinal tubercular arsachnoiditis report lower extremity weakness, bowel or bladder symptoms and require getting an examination done of the location of the spinal cord lesion.
Signs and symptoms of CNS tuberculosis such as altered mental status, fever, seizure, cranial nerve deficits, papilloedema (optic disc swelling) or meningismus point towards the occurrence of tubercular meningitis.
Even after the development of some reliable molecular diagnostic techniques, detection of CNS tuberculosis depends largely on microbiological methods that are difficult to conduct; therefore, CNS tuberculosis remains an awful diagnostic challenge. Due to difficult clinical diagnosis, imaging has a crucial role in establishing the diagnosis. The most preferred method for initial analysis of CNS TB is magnetic resonance imaging (MRI) with gadolinium enhancement. Tubercular Meningitis is diagnosed by examining cerebrospinal fluid (CSF) collected by lumbar puncture diagnostic technique. Intracranial Tuberculoma and Spinal Tubercular Arachnoiditis are diagnosed by taking MRI of the brain and spine respectively.
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