Neurotuberculosis

Abstract

Tuberculosis is still one of the leading causes of death worldwide: one-third of the world population is believed to be infected with Mycobacterium tuberculosis. Neurotuberculosis, which affects mainly young patients, is considered the most dangerous complication as it often leads to severe neurological sequelae or death. The clinical presentation of neurotuberculosis can be quite variable and laboratory investigations, e.g. CSF studies, have a limited sensitivity. On the other hand, tuberculostatic therapy is effective and treatment should not be delayed. Imaging, therefore, plays an important role for the workup of this disease. In most cases, a haematogenous spread of the bacteria leads to a meningeal or parenchymal affection, whereby both compartments are commonly affected. Meningeal tuberculosis is characterised by a thick basal exudate most pronounced in the basal cisterns that is best appreciated on contrast-enhanced T1-weighted images. Complications due to this infectious process include cranial nerve affection, hydrocephalus, and ischaemic infarctions. Tuberculous granulomas (tuberculomas) are the most common parenchymal manifestation of neurotuberculosis. They represent circumscriptive, inflammatory lesions affected by mycobacteria that are surrounded by a granulomatous reaction. These mass lesions are usually located at the corticomedullary junction and are hypodense on CT and hypointense on T1-weighted images on native scans. After contrast administration they show, depending on the stage of maturation, a homogenous (non-caseating tuberculoma) or rim enhancement. On T2-weighted images a caseating tuberculoma with solid centre shows characteristically a low signal in the centre. Non-caseating tuberculoma or caseating tuberculoma with a liquid centre is hyperintense. A tuberculous abscess might be indistinguishable from a caseating tuberculoma with liquid centre. Typically, however, an abscess is larger and patients are more severely sick. The differential diagnoses of tuberculous meningitis include other infectious diseases, sarcoidosis and meningeal carcinomatosis. Tuberculomas and tubercular abscesses primarily have to be differentiated from primary and secondary brain tumours and other granulomatous/infectious processes.