[How I investigate...difficult cases of tuberculous meningitis].

To formally document the presence of the bacillus of Koch in meninges still remains difficult and depends on many variables. We report two cases where the diagnosis proved difficult. The presentation of tuberculous meningitis can take several aspects. Mantoux reaction is frequently negative. The BK cultures, which demonstrate the diagnosis, depend on the volume of CSF and on the importance of BK dissemination. It, unfortunately, remains difficult to make the diagnosis of tuberculous meningitis even though this pathology can have extremely deleterious consequences.