Tuberculosis is a challenging disease even in developed nations with even with advance medical facilities. One of most potentially lethal form is miliary form, which can be either pulmonary or brain. It needs early diagnosed and treatment. Earlier miliary pulmonary TB used to occur mainly in children however lately it's occurrence has significantly increased in younger and elderly population.(1) Endogenous reactivation of TB and massive lymphogenous and hematogenous dissemination is seen in people who are on immunosuppressive, immunomodulating, and cytotoxic drug therapy. The microbiological confirmation of any other form of TB is unsatisfactory in comparison to pulmonary TB. Even in miliary tuberculosis microbiological confirmation on sputum, sensitivity reduced to one third. (2) In our patient sputum and urine both were positive for MTB bacilli. However, her CSF did not show Tubercular bacilli.
Any ring enhancing lesion in brain is a diagnostic challenge for clinicians because most of these patients come with similar clinical syndromes. Contrast MRI brain is one of best investigation in diagnosis of ring enhancing lesion brain. MRI sensitivity is also very high for diagnosing other form of tuberculosis like tubercular exudative leptomeningitis.(3) However, n then even some time it is very difficult in differentiating from other causes ring enhancing lesion like Neurocysticercosis, fungal granuloma, Toxoplasma and even metastatic malignancies on plan MRI Brain when the lesion are very small in size. Closest differential diagnosis of miliary brain tuberculoma is multiple Neurocysticercosis.
Tuberculomas are commonly more than 20 mm in size however in miliary tuberculoma are less than 20 mm in size so difficult to differentiate from Neurocysticercosis on the bases of size. (4) On non contrast CT scan these lesions can easily be missed because of small size. Another important character is that, these lesions have very less perilesional edema as compare to classical tuberculoma which has disproportionate perilesional edma. In tuberculoma restriction diffusion is seen on diffusion weighted MRI images.(5) However, in miliary tuberculoma diffusion restriction are not seen. Tuberculoma are generally conglomerate lesion, but miliary tuberculomas are discrete spreads out lesion. With all these features it is very difficult to differentiate from multiple Neurocysticercosis. In our case, patient had multiple early mild disc enhancing lesions at the level of left temporal lobe, midbrain and right frontal lobe, pons, inferior cerebellar peduncle and bilateral cerebellar hemispheres. There was no significant perilesional edema on T2 and Flair images. Even there was no conglomerate lesion seen.
Magnetic resonance spectroscopy (MRS) is a specific MRI sequence which can help distinguish tubercular lesion from Neurocysticercosis. Elevated lactate (LA) peak, diminish N Acetyl Aspartate (NAA) and creatinine peak, and a choline/creatinine ratio of more than one is seen in tuberculoma.(6) Whereas in NCC these is elevated lactate and proteins such as glutamate, alanine, succinate, glycine levels with some reduction of NAA and creatinine is seen.(7) We have not done MRS sequence since in our patient’s urine and sputum has shown mycobacterium tuberculosis.
Serological markers in CSF are also helpful in case of making diagnosis. Even though CSF of our patient was normal, but ADA was significantly raised. High ADA is also suggestive of CNS tuberculosis. CSF can be normal in tuberculoma brain since there is no inflammatory response at meanings.