There is a conglomeration
of lesions in the right temporo-parieto-occipital and left
frontal lobes. These are hypointense on the T2W images and
reveal a whorl or bunch of grapes type of enhancement. Note is
made of perilesional edema.
On plain MRI, granulomas usually appear isointense to gray
matter on the T1W images and may have a slightly hyperintense
rim (probably due to the presence of paramagnetic substances).
On T2W images, the tuberculomas exhibit variable signal. They
are often isointense or hypointense to brain parenchyma and it
is postulated that this relative hypointensity is related to T2
shortening by paramagnetic free radicals produced by
macrophages, which are heterogeneously distributed throughout
the caseous granuloma. The diminished signal on T2W images may
also be due to the mature tuberculoma being of greater cellular
density than brain. Granulomas may also be hyperintense to brain
on T2-weighted images; this is likely due to a greater degree of
central liquefactive necrosis in these lesions. Edema
surrounding tuberculomata is relatively more prominent in the
early stages of granuloma formation.
Post contrast (gadolinium) images of TB granulomas demonstrate
intense nodular and ring-like enhancement. Healed tuberculomas
may calcify in up to 20% of cases and these are usually more
evident on CT than MRI. On MRI, the calcifications are more
evident on gradient-echo than on spin-echo imaging. Atrophy is
frequently a long-term sequelae of tuberculous CNS infection.
Full resolution of cerebral tuberculomas requires months to
years of medical therapy. The length of time required is related
more to the size of the original lesion than to any other single
Meningeal disease and non-enhancing lesions are commonly
encountered in HIV positive patients.