Comparison of Blood Perfusion Parameters in the Ipsilateral and Contralateral Sides of the Brain in Known Cases of Mesial Temporal Lobe Epilepsy

Abstract

Background: Temporal lobe epilepsy (TLE) is the most common form of focal seizures. To localize the epileptic site for surgery, different neuroimaging tools are used. Perfusion magnetic resonance imaging (MRI) is one of the modalities used to evaluate the cerebral hemodynamics and localize intracranial neoplasia and cerebrovascular events. Two contrast-based perfusion imaging sequences are described, including dynamic susceptibility contrast-enhanced MRI (DSC-MRI) and dynamic contrast-enhanced MRI (DCE-MRI). The most commonly measured parameters include the relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and mean transit time (MTT). Objectives: This study aimed to evaluate the blood perfusion parameters, such as rCBV and rCBF, in patients diagnosed with mesial temporal lobe epilepsy (MTLE), using DSC-perfusion MRI to determine whether there is a change in these parameters and if this modality can be used to diagnose and localize the epileptic side. Patients and Methods: Twenty-two patients, who were diagnosed with TLE clinically and electrophysiologically by a neurologist, were investigated in this study. The patients were examined for the presence of any other lesions, such as tumors or cerebrovascular disease as the exclusion criteria. Perfusion images were processed by the Siemens perfusion software, and the rCBV and rCBF maps were generated based on the gamma variate fit. For qualitative analysis, coronal reconstruction of rCBV and rCBF maps was performed. For quantitative analysis, a single neuroradiologist placed the region of interest (ROI) on the hippocampus and the parahippocampal gyrus on T1W images at the same level of DSC images. After determining the CBV and CBF values relative to the ROI of each side, the asymmetry index (AI) was calculated. Results: In patients with unilateral epilepsy, the blood perfusion parameters in the ipsilateral side of the brain were significantly lower than the contralateral side (P < 0.0001); the mean values of both parameters were significantly lower in the affected side as compared to the opposite side. Conclusion: In patients with TLE, significantly lower blood perfusion parameters in the affected side of the brain can help radiologists and neurologists to lateralize the MTLE side.