Decoding CNS granulomas: cracking the imaging mystery in tuberculosis and neurocysticercosis endemic zones

Central nervous system (CNS) granulomas present formidable diagnostic challenges in tuberculosis and neurocysticercosis-endemic regions, where empirical therapy based on imaging alone frequently results in misclassification and suboptimal outcomes.

To evaluate the diagnostic accuracy of conventional and multiparametric MRI in differentiating CNS granulomas, correlate imaging findings with histopathological diagnoses, and assess 3-6 month clinical and radiological outcomes in a prospectively enrolled cohort.

We conducted a prospective observational study (February 2016-August 2017) of 30 consecutive patients with MRI-diagnosed CNS granulomas at a tertiary referral center. Comprehensive clinical assessment, multisequence MRI including diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) mapping, and selective MR spectroscopy were performed. Stereotactic biopsy was undertaken for lesions demonstrating treatment failure or accessible progression. Primary endpoints included imaging-histopathology concordance and clinical/radiological response at 3-6 months.

The cohort comprised 22 females and 8 males (mean age 24.8 years, range 11-56). Presenting features included headache (96.7%) and seizures (86.7%). Baseline MRI demonstrated lesions < 2 cm in 86.7%, ring enhancement in 80.0%, central T2 hypointensity in 66.7%, and conglomerate morphology in 53.3%. Initial radiological assessment favored tuberculoma in 63.3% and neurocysticercosis in 20.0% of cases. Seven patients underwent stereotactic biopsy, revealing tuberculous pathology in 6 (85.7%) and neurocysticercosis in 1 (14.3%). Critically, among four patients with worsening lesions initially treated as neurocysticercosis, three (75.0%) proved tuberculous on histopathology. At 3-6 month follow-up, 76.7% demonstrated clinical improvement, while 30.0% showed radiological worsening despite appropriate therapy.

Conventional MRI features of CNS granulomas demonstrate substantial overlap across etiologies, with significant potential for misdiagnosis in endemic settings. Multiparametric imaging enhances diagnostic confidence but cannot eliminate misclassification. Early tissue diagnosis of treatment-resistant or progressing lesions frequently alters management and is essential for optimal patient outcomes. These findings support a combined approach incorporating advanced imaging, serial clinical assessment, and timely biopsy when clinically indicated.