Role of diffusion weighted imaging in differentiation of intracranial tuberculoma and tuberculous abscess from cysticercus granulomas-a report of more than 100 lesions

Abstract

Restricted diffusion is noted in a large number of non-stroke conditions including tuberculoma. The purpose of this study was to demonstrate spectrum of diffusion weighted imaging (DWI) abnormalities in tuberculomas and tuberculous abscess and to distinguish these from degenerating neurocysticercosis. Seventy tuberculomas and tuberculous abscesses in 30 patients were categorized in three groups depending on the intensity in the core of the lesion on T2 weighted images. Mean apparent diffusion coefficient (ADC) was calculated from the core as well as from the wall of the lesions. Forty-five lesions of neurocysticercosis in different stage of evolution in 12 patients were also included for comparison. The mean ADC value from the core of the T2 hypointense lesions was significantly higher compared to the wall ((1.24 ± 0.32) × 10⁻³ and (1.06 ± 0.15) × 10⁻³ mm²/s, respectively), while mean ADC value from the core of mildly T2 hyperintense lesions was significantly lower compared to the wall ((0.80 ± 0.08) × 10⁻³ and (1.08 ± 0.13) × 10⁻³ mm²/s, respectively). Truly T2 hyperintense lesions were divided into two subgroups, tuberculomas and tuberculous abscesses; ADC values from the core and the wall of these lesions were (0.74 ± 0.13) × 10⁻³, (0.61 ± 0.08) × 10⁻³ and (1.03 ± 0.14) × 10⁻³, (1.08 ± 0.14) × 10⁻³ mm²/s, respectively, and was significantly lower in core as compared to the wall. However, there was no significant difference between ADC values of the tuberculous abscess and the hyperintense tuberculomas. Vesicular and degenerating stages of cysticercus cysts from the core showed ADC values of (1.66 ± 0.29) × 10⁻³ and (1.51 ± 0.23) × 10⁻³ mm²/s, respectively, and were significantly higher than the core of all groups of tuberculomas and tuberculous abscess. We conclude that addition of DWI to routine imaging protocol may help in differentiation of tuberculous lesions from degenerating cysticercus granuloma.

Introduction

Intracranial tuberculoma is still the commonest cause of intracranial space occupying lesion in the developing countries. It is also on the rise in industrialized nations with the endemicity of AIDS and increasing use of immunosuppressive agents for the management of organ transplantation [1], [2]. Though CT and conventional MRI features have been described for the diagnosis of tuberculomas and tuberculous abscess, these are not very specific of the disease in a number of patients [2]. Addition of proton MR spectroscopy and magnetization transfer MRI to the brain infection protocol has improved the tissue characterization of tuberculomas and tuberculous abscesses considerably [3], [4], [5], [6], [7], [8]. However, there are a small number of patients where it may not always be possible to differentiate these lesions from degenerating neurocysticercosis (NCC).

Currently, a large number of non-stroke neurological conditions have been investigated with DWI, like tumors, abscess, epidermoids, and encephalitis where a restricted diffusion with low ADC may be noted [9], [10]. Recently, few reports have described diffusion changes in patients with intracranial tuberculoma with variable ADC values [11], [12], [13]. We describe spectrum of diffusion abnormalities in patients with tuberculomas and tuberculous abscess with an aim to further understand the pathology of the disease process and to look for its possible role in assisting the current MR techniques in differentiation of these lesions from degenerating cysticercus granuloma.