3.4.1. TB Meningitis (TBM)

TBM most commonly presents between six months to four years of age but can occur at any age. It is the most severe form of TB in children and uniformly leads to mortality if not treated timely and effectively. The clinical presentation is divided into three stages. The disease usually progresses over several weeks from stage one to three and may progress rapidly over days in infants and young children. The stage at which treatment begins predicts the prognosis. 

 

 

Table 1. Stages of TB Meningitis

 

Cerebrospinal fluid (CSF) tap is mostly clear, and CSF leukocyte count usually ranges from 10 to 500 cells /mm3 (occasionally higher), and the majority are usually lymphocytes. CSF glucose usually remains below 40mg/dl (CSF glucose / blood glucose below 0.5, protein is elevated (often more than 100 mg/dl). Rapid NAAT may be positive in about 30-40% of cases. Tuberculin Skin Test may not be reactive in 50% of cases. Chest X-ray may show abnormality in 20-50% of cases. Not uncommonly, the aetiological diagnosis may come from concomitant extra-neural disease.

The CECT head is the initial modality of diagnosis. It may have one or more of the following: basal meningeal enhancement, hydrocephalus, tuberculoma, infarcts in different areas, especially the basal ganglia and pre-contrast basal hyperdensity. It sometimes is even found normal. Contrast MRI has higher sensitivity than CECT for abnormalities such as meningeal enhancements, infarcts, and tuberculoma, especially of brain stem lesions.

Usually, Magnetic Resonance Imaging (MRI) is preferred when CT is inconclusive, and suspicion is high. Cryptococcal meningitis, Cytomegalovirus encephalitis, toxoplasmosis, sarcoidosis, meningeal metastases, and lymphoma can result in similar radiological findings.

 

 

Figure 4. Algorithm for diagnosis of TBM

 

3.4.2. CNS tuberculosis other than TBM - Tuberculoma

Tuberculoma in the brain presents an intracranial space-occupying lesion (ICSOL). Its location, size and peri-lesional oedema predisposes the manifestations like seizures, headache and focal neurological deficits. Neurocysticercosis (NCC) is an important differential diagnosis.

The table below describes the differentiating features of these two entities on neuroimaging.

 

 

 

Table 2.  Differences Between Tuberculoma and Neurocysticercosis