Although tuberculomas still constitute an important cause of mass lesions in underdeveloped countries (20% in India), they are now rare in Britain. The lesions may be single or multiple. They often lie in the cerebellum, especially in children.
Clinical features are those of any intracranial mass; alternatively tuberculoma may present in conjunction with tuberculous meningitis.
CT scan clearly demonstrates an enhancing lesion - but this often resembles astrocytoma or metastasis; tuberculomas have no distinguishing features. MRl is even more sensitive and may show additional lesions.
Other investigations: ESR, chest X-ray often fail to confirm the diagnosis. A Mantoux (PPD) test is usually positive but a negative test does not eliminate the diagnosis.
Management: When tuberculoma is suspected, a trial of antituberculous therapy is worthwhile. Follow up CT scans should show a reduction in the lesion size. Other patients require an exploratory operation and biopsy followed by long-term drug treatment.
Sarcoidosis is a systemic disease of unknown aetiology characterised by noncaseating epithelioid cell tubercles. Nervous system involvement occurs in 8% and may dominate the presentation.
When sarcoid infiltrates the central nervous system it usually involves the meninges. In some patients mass lesions may arise from the dura, but more commonly signs and symptoms relate to an adhesive arachnoiditis involving the skull base, cranial nerves and pituitary stalk. Mass lesions may occasionally arise within the brain and spinal cord without obvious meningeal involvement.
Investigation: MRI (T] weighted) shows either a hyperintense mass or multiple periventricular foci. A definitive diagnosis is based on clinical and radiological evidence of multisystem disease confirmed by characteristic histology.
The diagnosis is often elusive and suggested by clinical presentation supported by some of the following.
- elevated serum and CSF angiotensin converting enzyme (ACE),
- elevated serum immunoglobulins,
- elevated serum calcium,
- elevated CSF cell count (monocytes) and immunoglobulins. The Kveim test is not specific and is rarely used.
Management: Long-term steroids. Or in resistant cases, azathioprine or cyclophosphamide.
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