Other investigations used in patients with suspected TBM
include the tuberculin skin test, but this is subject to both
false positive and false negative results. The chest x ray may
show a miliary appearance in a small proportion of cases.
Brain imaging by CT or magnetic resonance (MR) may reveal
hydrocephalus or basal meningeal enhancement in TBM but
the appearances are non-specific, being shared by other
subacute and chronic meningitides. A significant proportion
of patients with TBM will have normal imaging.
Tuberculomas are seen only in a minority. Taken together
with the imperative of early treatment to reduce the chance
of a fatal outcome or severe complications, all these
considerations mean that it is better generally to start
treatment without delay in a patient with suspected TBM,
diagnostic confirmation coming later.