Intracranial tuberculous granuloma
Intracranial tuberculous granulomas (also known as CNS tuberculomas) are common in endemic areas, and may occur either in isolation or along with 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, whereas abscesses do not, their center filled with pus 5,6. Not all tuberculomas, however, have a solid granulomatous core and some may undergo liquefaction 4. TB 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 oedema. Either solid or ring enhancement is typical post-contrast. A central focus of enhancement with ring of peripheral enhancement (the "target sign") is described but is not specific to TB.
MRI is the modality of choice in assessing potential tuberculomas which have fairly solid caseous necrosis centrally on the background of granulomatous reaction. In some instances however, liquefactive necrosis centrally can occur, and the imaging appearances are then essentially indistinguishable from a tuberculous abscess, which in turn is similar to pyogenic cerebral abscesses 4.
- isointense to grey-matter 1
- may have central region of hyperintensity representing caseation
- isointense to grey-matter
- may have central region of hypointensity representing gliosis and abundant monocyte infiltration 1
- lesions are surrounded by vasogenic oedema
T1 C+ (Gd)
- usually appears as ring-enhancement
- may appear as a conglomerate enhancing mass
- typically central low signal (i.e. no restricted diffusion) 3 but if liquid necrosis is present centrally may be high signal
- decrease in NAA/Cr
- slight decrease in NAA/Cho
- lipid-lactate peaks are usually elevated (86%) 2
The differential of tuberculomas is essentially is the differential of ring-enhancing lesions, and includes:
- other infection
- cerebral metastases
- CNS lymphoma
Central isointensity or hypointensity compared to grey matter seen centrally on T2 is helpful, as it is not seen in most other causes 1.
- causative agent
- tuberculoma (tuberculous granuloma)
- tuberculous abscess
- miliary tuberculosis
- pulmonary tuberculosis
- cardiac tuberculosis
- intracranial tuberculosis
- tuberculous otomastoiditis
- gastrointestinal tuberculosis
- genitourinary tuberculosis
- skeletal tuberculosis
- tuberculous mastitis
- tuberculous lymphadenopathy
- tuberculous adrenalitis
- 1. Kim TK, Chang KH, Kim CJ et-al. Intracranial tuberculoma: comparison of MR with pathologic findings. AJNR Am J Neuroradiol. 1995;16 (9): 1903-8. AJNR Am J Neuroradiol (abstract) - Pubmed citation
- 2. Khanna PC, Godinho S, Patkar DP et-al. MR spectroscopy-aided differentiation: "giant" extra-axial tuberculoma masquerading as meningioma. AJNR Am J Neuroradiol. 2006;27 (7): 1438-40. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Castillo M. The Core Curriculum. Lippincott Williams & Wilkins. (2002) ISBN:0781736641. Read it at Google Books - Find it at Amazon
- 4. Vidal JE, Oliveira AC, Dauar RF. Cerebral tuberculomas or tuberculous brain abscess: the dilemma continues. Clin. Infect. Dis. 2005;40 (7): 1072. doi:10.1086/428673 - Pubmed citation
- 5. Whitener DR. Tuberculous brain abscess. Report of a case and review of the literature. Arch. Neurol. 1978;35 (3): 148-55. Pubmed citation
- 6. Chatterjee S. Brain tuberculomas, tubercular meningitis, and post-tubercular hydrocephalus in children. J Pediatr Neurosci. 2011;6 (3): S96-S100. doi:10.4103/1817-1745.85725 - Free text at pubmed - Pubmed citation