Metastatic adenocarcinoma masquerading as basal pontine tuberculoma

Tuberculous infection of the central nervous system is common in Hong Kong. A 39-year-old woman presented with isolated right sixth nerve palsy which was non-progressive for 10 months. Neuro-imaging revealed a right pontine lesion. Cerebrospinal fluid (CSF) examination showed lymphocytic meningitis with negative bacteriological and cytological studies. Empirical antituberculous drugs with initial corticosteroid resulted in improved CSF parameters. A diagnosis of cerebral tuberculoma complicated by meningitis was made. She subsequently deteriorated clinically and radiologically. Despite a number of clinical features which were atypical of leptomeningeal metastasis, adenosquamous carcinoma was found on biopsy. Her relatively indolent clinical course might be due to the initial corticosteroid treatment. This report illustrates the importance of early tissue diagnosis in uncertain cases of chronic lymphocytic meningitis.