TBAs are very rare. Fifty-nine cases of tuberculous abscess have been reported in the world literature, but only 18 cases fulfil the criteria laid down by Whitener.
3 It is not known why abscesses form instead of the usual tuberculoma, which comprise approximately 20% of all intracranial space occupying lesions in children. Several factors such as the state of the body’s immunity, dose of infecting agent, nature of the involved tissue, and antituberculosis treatment perhaps determine the type of tissue reaction.
2,3 It usually occurs due to haematogenous spread of
Mycobacterium tuberculosis from elsewhere, but can also occur via lymphatic spread from the cervical nodes. Abscess walls are usually devoid of epithelioid and giant cells, which are characteristic of tuberculoma, but if present are not in the form of organised follicles.
4 The abscess wall is composed of a necrotic inner surface and a fibrous outer surface associated with an inflammatory reaction.
3,4 Our patient had a relevant history, a positive tuberculin test, and acid fast bacilli in the aspirate of the pontine abscess.
The presentation of tuberculous abscess is acute, as in our patient. The locations of TBA are mainly supratentorial and rarely in the cerebellum. Patients usually present with focal neurological signs and are associated with histological and laboratory evidence of tuberculosis. Cerebrospinal fluid examination may show pleocytois with increased protein, and PCR may be positive for mycobacteria in a good number of cases.
CT shows a hypodense lesion surrounded by an enhancing ring.
6 There may be associated surrounding oedema. The clinical picture of both types of abscesses—that is, pyogenic and tuberculous—is similar. Abscesses are present frequently in the supratentorial compartment, with focal neurological deficit, fits, and altered level of consciousness. Papilloedema and headache are more common in pyogenic than in tuberculous abscesses. Both types of abscesses produce the ring lesion with peripheral oedema in the CT scan.
6,7 The lower attenuation value in the centre of the lesion than in the brain tissue may be indicative of the presence of pus. Surrounding brain oedema and low gliosis may resemble low grade glioma.
6 A majority of the TBAs have a thicker wall compared with pyogenic abscesses because of their slower evolution, but some pyogenic abscesses may have a thick capsule if they develop over a longer period. Multiplicity is more common in pyogenic than in cold abscesses. Most of the time it is not possible to make a preoperative diagnosis. Intraoperative smear examination of the aspirated pus is the easiest way to determine the diagnosis so that proper chemotherapy can be instituted immediately, thereby minimising postoperative mortality and morbidity as in our case. Acid fast bacilli should be demonstrated on Ziehl-Neelsen stain.
Treatment options include simple puncture, continuous drainage, fractional drainage, repeated aspiration through a burr hole, stereotactic aspiration, and total excision of the abscess. Total excision is usually required in multilocular non-communicating and thick walled abscesses. The development of fulminant tubercular meningitis is sometimes problematic following surgical stereotactic aspiration.
8Learning points
- CNS tuberculosis is a significant cause of morbidity and mortality in Indian children.
- Tuberculous brain abscess is rare.
- Pontine tuberculous abscess is extremely rare and may be life threatening in children.
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