Images below require Macromedia's Flash Player to view

Neuroradiology Case of the Week

Case 293

Balasubramanya Kolar, MD, Henry Z. Wang, MD, PhD,
and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 25-year-old male patient who presented with numbness in the right side of face and right half of body.He also had an episode of cataplectic posturing.Past medical history was significant for being treated for pulmonary tuberculosis and he had also undergone ventriculoperitoneal shunting for hydrocephalus following tubercular meningitis two years back.

Imaging Findings: T2-weighted MR images of brain showed highly hypointense lesions in the left sided pons (Fig. 1), midbrain (Fig. 2) and left perisylvian areas. These lesions showed peripheral, ring enhancement and were found to be coalescent and conglomerate lesions on the post-contrast images (Figs. 3-5). Similar lesions were also noted in the suprasellar and interpeduncular cistern (Fig. 6).

Diagnosis: Intracranial tuberculomas

Discussion: Tuberculomas are a common form of central nervous system (CNS) tuberculosis presenting as intracranial space-occupying lesions. They usually present with seizures, focal neurological deficits, and/or raised intracranial pressure.
They vary in size, from smaller lesions of about a centimeter to larger lesions confused with mass lesions [1]. MR imaging characterizes these lesions and is valuable in making the diagnosis. Hypointensity on T2-weighted images is considered to be a strong indicator in the appropriate clinical setting which helps in the diagnosis. However, signal intensity varies with the stage of tuberculoma [2]. In the non-caseous stage, the granuloma is hypointense in short TR and hyperintense in long TR sequences, with homogeneous enhancement. Whereas, the solid caseating tuberculoma is isointense in short TR and hypointense in long TR sequences, with ring enhancement. T2 shortening is ascribed to a combination of factors—caseation, macrophages and their byproducts (free radicals), fibrosis/gliosis, and inflammatory infiltrate [3]. The hypointensity or isointensity on T2-weighted images may reflect restricted mobile protons within high protein contents in organized caseation, cellular and collagenous layers, the presence of heterogeneously distributed free radicals produced by macrophages during active phagocytosis, and/or highly immobile saturated fatty acids [4]. The conglomerate or coalescent ring enhancement correlated histologically with both the layers of inner collagenous fibers and outer inflammatory cellular infiltrates [3].
     In addition, the characteristic location of the lesion in the basal cisterns and along the middle cerebral artery distribution in the Sylvian fissures aid in further characterizing the lesions as possibly tuberculomas.

References:

1. Brismar J, Hugosson C, Larsson SG, Lundstedt C, Nyman R. Imaging of tuberculosis. III. Tuberculosis as a mimicker of brain tumour. Acta Radiol. 1996 Jul;37(4):496-505. [Medline]
2. Gupta RK, Prakash M, Mishra AM, Husain M, Prasad KN, Husain N. Role of diffusion weighted imaging in differentiation of intracranial tuberculoma and tuberculous abscess from cysticercus granulomas-a report of more than 100 lesions. Eur J Radiol. 2005 Sep;55(3):384-92. [Medline]
3. Kim TK, Chang KH, Kim CJ, Goo JM, Kook MC, Han MH. Intracranial tuberculoma: comparison of MR with pathologic findings. AJNR Am J Neuroradiol. 1995 Oct;16(9):1903-8. [Medline]
4. Gupta RK, Pandey R, Khan EM, Mittal P, Gujral RB, Chhabra DK. IIntracranial tuberculomas: MRI signal intensity correlation with histopathology and localised proton spectroscopy. Magn Reson Imaging. 1993;11(3):443-9. [Medline]