Role of MRI in the evaluation of acoustic schwannoma and its comparison to histopathological findings

Abstract

Magnetic Resonance Imaging (MRI) has been the primary imaging modality and has revolutionized the imaging of brain tumors. MRI can display accurate multi planer imaging without interfering of adjacent structures specially for posterior fossa mass lesion. MRI is the imaging modality of choice for cerebollo-pontine (CP) angle Schwannoma. The study was performed to determine, the diagnostic accuracy of MRI in the evaluation of intracranial extra axial CP angle Schwannoma. MRI scan of brain was done on 42 consecutively selected patients referred for the evaluation of CP Acoustic Schwannoma. The age range from 21-60 years and the mean age was 42.85(+9.5) years. Highest incidence of cerebollo-pontine angle (CPA) mass were found 42.86% in 41-50 age group of patients. Male and Female ratio was 1.083:1. The most common presenting feature of the patients with CP angle Acoustic Schwannoma were headache 90.48%. Acoustic Schwannoma is T1 hypointense 100%, T2 hyper intense 84.61% and heterogeneously hyper intense 92.30% in FLAIR image. After giving contrast agents, homogeneous enhancement 57.69% and heterogeneous 42.31% cases of Acoustic Schwannoma. Overall 61.54% Acoustic Schwannoma strong contrast enhancement was observed. Dural tail was observed in 26.92% cases. Perilesional edema was observed 38.46% cases. Mass effect was observed in 76.92%. After complete MRI evaluation 61.9% had Acoustic Schwannoma. Histopathologicaly proved cases showed out of all patients Acoustic Schwannoma 59.52%. The overall sensitivity of MRI to diagnose Acoustic Schwannoma were found, Sensitivity- 96%, Specificity- 88.2%, PPV-92.31%, NPV-93.75% and Acceuracy 92.86%. Test is significant with p<0.0001 level. It is conceivable that MRI is a highly accurate, sensitive and Gadolinium enhanced MRI is more sensitive in detection of acoustic Schwannoma. MR imaging is the study of choice for the examination of the patient of cerebellopontine angle Schwannoma because of its high sensitivity specially after use of contrast material. DOI: http://dx.doi.org/10.3329/bmrcb.v37i3.9120 BMRCB 2011; 37(3): 92-96