Diffusion Tensor Imaging Parameters in Patients with Meningitis: A Case-control Study

Introduction: Neuroimaging plays an important role in the assessment of meningitis, but conventional Magnetic Resonance Imaging (MRI) is insensitive for early and specific diagnosis. Diffusion Tensor Imaging (DTI) can illustrate disturbances in white matter integrity before they become obvious on conventional MRI. Aim: To determine DTI parameters, specifically Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC), in patients with meningitis and compare them with controls. Materials and Methods: This case-control study was conducted over a period of 18 months at Teerthanker Mahaveer Medical College and Research Centre in Moradabad, Uttar Pradesh, India. The study included a total of 61 clinically diagnosed meningitis patients, aged 18 years and above, who were referred to the Department of Radiodiagnosis for an MRI Brain. Additionally, 61 controls were included. Conventional MRI images were obtained followed by DTI. FA and ADC values were calculated by placing Regions Of Interest (ROI) at different levels for both groups. DTI parameters for different causative organisms (bacterial, viral, tubercular, and fungal) were compared. Data was analysed using Statistical Package for the Social Sciences (SPSS) software version 24.0, and Analysis of Variance (ANOVA) test was used to identify significant differences. The p-value <0.05 was considered as statistically significant. Results: FA values were significantly lower in cases compared to controls at all levels in the brain (mean whole brain FA value of 0.30±0.036 in cases vs 0.43±0.030 in controls). ADC values were significantly higher in cases at the cerebellum, brainstem, and whole brain levels compared to controls (mean whole brain ADC value of 0.812±0.095 in cases vs 0.758±0.026 in controls) (p-value<0.05 considered statistically significant). These differences were evident in patients with clinically proven meningitis who had a normal appearance on conventional MRI, demonstrating the superiority of DTI over conventional MRI for the diagnosis of meningitis. Statistically significant differences were also found among different aetiological agents, highlighting the potential utility of DTI in the differential diagnosis of meningitis cases (mean whole brain FA of 0.31±0.038 in bacterial cases, 0.029±0.037 in viral cases, 0.299±0.034 in tubercular cases, and 0.27±0.00 in fungal cases vs. 0.43±0.030 in controls (p-value <0.01) and mean whole brain ADC values of 0.80±0.051 in bacterial, 0.85±0.14 in viral, 0.79±0.058 in tubercular, 1.03±0.00 in fungal cases vs. 0.758±0.026 in controls (p-value <0.01)). Conclusion: DTI is more sensitive than conventional MRI and is a useful early indicator of inflammatory process in patients with meningitis.