Intracranial tuberculous granuloma

Last revised by Travis Fahrenhorst-Jones on 21 Aug 2022

Intracranial tuberculous granulomas, also known as CNS tuberculomas, are common in endemic areas and may occur either in isolation or along with tuberculous meningitis.

The epidemiology of patients with tuberculomas is the same as that of other CNS manifestations of tuberculosis (TB) (see CNS tuberculosis).

A tuberculoma is distinct from a tuberculous abscess in that it demonstrates evidence of granulomatous reaction and caseous necrosis histologically. In contrast, abscesses do not display a granulomatous reaction and their centers are filled with pus 5,6. Not all tuberculomas, however, have a solid granulomatous core and some may undergo liquefaction 4.  Tuberculous organisms may not necessarily be identified in tuberculomas, whereas they are necessary to make the diagnosis of tuberculous abscess 6.

On CT, tuberculomas may appear as a round or lobulated nodule with moderate to marked edema.  Either solid or ring enhancement is typical post-contrast.  A central focus of calcification with a ring of peripheral enhancement (the "target sign") is described but is not specific to tuberculosis 7. When calcification is present (the minority of cases) it tends to be larger than that calcification seen in neurocysticercosis. 

MRI is the modality of choice in assessing potential tuberculomas. Although the appearance can be classical and highly suggestive of the diagnosis (central low T2 signal, surrounding enhancement and edema) it does, however, vary with the stage of disease 1,3,8,9. In some instances, when liquefactive necrosis occurs central, the imaging appearances are essentially indistinguishable from a tuberculous abscess, which in turn is similar to pyogenic cerebral abscesses 4.

  • T1: iso- to- hypointense
  • T2: hyperintense
  • FLAIR: no suppression
  • DWI/ADC: no restricted diffusion
  • T1 C+ (Gd): homogeneous enhancement
  • T1: iso- to- hypointense with hyperintense rim
  • T2:
    • hypointense representing gliosis and abundant monocyte infiltration 1
    • surrounded by vasogenic edema
  • FLAIR: no suppression
  • DWI/ADC: no restricted diffusion
  • T1 C+ (Gd): homogeneous or ring-enhancement
  • MR spectroscopy
    • decrease in NAA/Cr
    • slight decrease in NAA/Cho
    • lipid-lactate peaks are usually elevated (86%) 2
  • T1: iso- to- hypointense with hyperintense rim
  • T2:
    • hypointense rim with central hyperintensity
    • surrounded by vasogenic edema
  • FLAIR: partial suppression
  • DWI/ADC: variable diffusion restriction
  • T1 C+ (Gd): ring enhancement
  • T1: iso- to- hypointense
  • T2: hypointense
  • FLAIR: no suppression
  • DWI/ADC: no restriction
  • T1 C+ (Gd): no enhancement

The differential of tuberculomas is primarily the differential of ring-enhancing lesions and includes:

Central isointensity or hypointensity compared to grey matter seen centrally on T2 is helpful, as it is not seen in most other causes 1.

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