MRI in Cerebellopontine angle and internal auditory canal lesions

Background: A large variety of inflammatory and neoplastic lesions are known to occur within internal auditory canal and cerebellopontine angle. Imaging techniques are now available to guide the search for the underlying cause of most patient complaints. The advent of MRI has revolutionized the medical diagnostic imaging because it allowed tissue characterization of many lesions. High resolution MRI scan is highly sensitive in detecting lesions of internal auditory canal and cerebellopontine angle. More recently, diffusion imaging is playing a substantial role in evaluation of CPA masses. High ADC values of solid vestibular schwannomas were in conformity with increased diffusion rates, indicating the presence of increased amounts of extracellular water (a relatively loose tissue in tumor matrix). This study was undertaken with purpose to present MRI findings in cases of CPA and IAC lesions and to assess the impact of MRI on the diagnosis management and follow up, after treatment, of these lesions with an attempt to compare MRI findings with operative and H/P findings in the cases where surgery was done. Materials and methods: The present study was conducted in Post Graduate Department of Radiodiagnosis, Government Medical College, Srinagar on patients presenting with otoneurological signs and symptoms suggestive of CP angle and IAC lesions referred for MR imaging by various departments of GMC Hospital Srinagar during the one year period of study. Results: Majority of lesions found in this study were tumors (33 lesions), next common in our series were inflammatory lesions and vascular lesions (4 each case). Among all lesions and tumors most common MR diagnosis in our study was acoustic neuroma 20 of 41 lesions (48.78%) and 20of 33 tumors (60.60%) respectively. Next common among tumors was meningiomas 3 out of 33 cases (9.09%). Conclusion: The results of the present study concluded that, MRI has particular advantages over CT for study of internal auditory canal and cerebellopontine lesions because it is non-ionizing investigation, better soft tissue contrast and resolution, multiplanar capability permits more reliable distinction of lesions, better identification of structures involved by lesions, tissue characterization of lesions and absence of beam hardening artifacts makes MR imaging superior ion evaluating the lesions in CP angle and IAC. The radiological features of various lesions are often sufficiently distinctive to permit a specific diagnosis to be made. MR imaging due to its multiplanar capability helps in knowing the exact site and extent of these lesions. MRI shows inflammatory and vascular lesions with exquisite detail and is better for detection of such lesions as compared to CT. MRI allows a confident perspective pathologic diagnosis to be made (Using FSE T2 weighted images, diffusion imaging, SE images, thin section post gadolinium scans) and this predictive value far exceeded the CT.