Magnetic Resonance Diffusion, Spectroscopy and Susceptibility Imaging in Evaluation of Cerebellopontine Angle Masses

Abstract

Background: The cerebellopontine angle (CPA) is a triangular subarachnoid space located within the posterior cranial fossa and centered at the level of the internal audiotary canal. Approximately 10%of intracranial tumors arise in the cerebellopontine angle and 80% of these are vestibular schwannomas. The majority of the remaining 20%are meningiomas, with rare incidance of facial or trigeminal schwannomas, epidermoid cysts(primarycholeseatomas), glomus jugular tumors, arachnoid cysts, giant cell tumors, metastatic deposits, and other masses. Objective: To evaluate the role of DWI, susceptibility and specrtroscopy in evaluation of cerebello pontine angle masses. Patients and methods: Our study included thirty cases with CPA masses that were subjected to advanced MRI techniques (DWI, SWi and, MRS) in addition to the conventional MRI techniques to evaluate their role in evaluation of CPA masses. Results: By using DWI in our protocol, we proved that; It can differentiate shwannomas, meningiomas and epidermoid cyst; where meningiomas are always restricted with low ADC values (mean ADC value < 1× 10−3 mm2 /s) while shwannomas have higher ADC values (mean ADC value >1× 10−3 mm2 /s) and epidermoid cysts are restricted with ADC values <1× 10−3 mm2 /s. By using SWI: SWI also proved to has an important value in differentiating meningiomas and shwannomas where in our study no meningiomas showed blooming on SWI while 61.5 % of shwannomas showed blooming (likely due to intra-lesional hemorrhage). Thus the presence
of blooming within a lesion (after exclusion of calcifications) would rather the diagnosis of shwannoma than meningioma. By using MRS: 100% of shwannomas showed myo-inositol peak in our study and 87.5% of meningiomas showed alanine peak and 100% of meningiomas showed glutamate\glutamine peak, proving that MRS can be an accurate technique in differentiating the two
entities. 100% of metastatic lesions showed choline peak in our study so MRS has an important value in the diagnosis of metastatic lesions. Conclusion: Advanced MRI techniques as DWI, susceptibility and spectroscopy have a great value in evaluation of CPA masses.