Efficacy of Three Dimensional Fast Imaging Employing Steady State Acquisition Combined with Conventional MRI in Evaluation of Patients with Cerebellopontine Angle Lesions

Abstract

Introduction: The Three Dimensional Fast Imaging Employing Steady state Acquisition (3D FIESTA) has higher spatial resolution between the Cerebrospinal Fluid (CSF) and cranial nerves with accurate identification of Cerebellopontine Angle (CPA) and internal auditory canal tumours and takes shorter acquisition imaging time than conventional Magnetic Resonance Imaging (MRI) scan. Aim: To evaluate the efficacy of 3D FIESTA imaging as a screening tool for CPA lesions, hence to depict the fine anatomy of the cisternal and canalicular segments of the facial nerve and vestibulocochlear nerves in order to elucidate the aetiopathogenesis of unexplained inner ear symptoms. Materials and Methods: The present study was a hospital based cross-sectional study which was done in Department of Radiodiagnosis, Chettinad Hospital and Research Institute, Chennai, Tamil Nadu, India. The study was conducted on 30 patients, who were referred for MRI Brain to the department and diagnosed with cerebellopontine angle lesion from August 2018 to October 2019. A 1.5 Tesla, MRI scanner was used to scan all patients with a 8 channel Neurovascular (NV) radiofrequency coil. Along with routine conventional MRI sequences, 3D FIESTA sequence was also performed. All the data was collected and analysed by Statistical Package for Social Sciences (SPSS) software version 23.0. Data for descriptive statistics i.e. frequency and percentage analysis, mean±Standard Deviation (SD), sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) were calculated. Results: On Histopathological Examination (HPE), 63.3% were schwannoma, 16.7% meningioma, 10% epidermoid cyst and 3.3% intracanalicular lipoma. In 6.7% of patients, imaging features were in favour of CPA arachnoid cyst. The size of the intracanalicular part of tumour was underestimated in T2 weighted images (T2WI). 3D FIESTA gave a better estimated tumour area, even though slightly less but almost equivalent to that in post-contrast imaging. In this study, post-contrast imaging was considered as the gold standard. It was proven that conventional sequences like T2WI showed a sensitivity of 85.71% and specificity of 100% whereas 3D FIESTA sequence showed 100% sensitivity and specificity in assessing the CPA tumour extent and cranial nerve involvement. Conclusion: 3D FIESTA imaging is a sensitive technique for the diagnosis of retrocochlear and CPA lesions without contrast administration. 3D FIESTA imaging can be considered as a useful screening tool for patients presenting with inner ear symptoms.