The Role of Magnetic Resonance Imaging (MRI) in Diagnostics of Acoustic Schwannoma

BACKGROUND: Acoustic neuromas are also called vestibular schwannoma, acoustic neurinoma, vestibular neuroma, and acoustic neurofibroma. These are tumors that evolve from Schwann cell sheath and can be either intracranial or extra-axial. They usually occur adjacent to the cochlear or vestibular nerve. Anatomically, acoustic neuromas tend to occupy the cerebellopontine angle. About 20% of internal carotid artery (ICA) tumors are meningiomas and may occur elsewhere in the brain. Bilateral acoustic neuromas also tend to be exclusively in individuals with type 2 neurofibromatosis. OBJECTIVE: The aim was to asses the role of MRI in evaluation of cerebellopontine angle acoustic schwannomas, the role of the cyber knife treatment in eliminating the tumor with a maximum protection of healthy tissue. METHODS: MRI, GE 1.5 Tesla unit and standard protocol: Pre-contrast MRI images of the temporal bones and posterior fossa were obtained using Ax 3D Fiesta T2W Hi-resolution; Ax 3D T1 Fat-Suppressed, Thin-slice (2mm) Coronal T2W, Sag 3D FiestaT2W Hi-resolution images. Post-contrast images were obtained using Ax 3D T1 Fat-Suppressed Cor 3D T1 Fat-suppressed sequences. FLAIR sequence axial). CASE REPORT: A woman 62 years of age, reported sudden tinnitus, dizziness, hearing loss in her left ear. After one years she began to experience vertigo, headache. RESULTS: MRI of brain temporal bone with contrast show acoustic schwannoma measuring 20x9 mm on the left cerebellopontine angle extending into and enlarging the left IAC, solid enhancing component is seen the acoustic meatus and peripheral contrast cystic component in the left cerebellopontine angle, after cyber knife treatment MRI result was the solid component of the mass, filling the left internal acoustic canal shows marked post-contrast enhancement and is measured 10x5x4mm, cystic component of it filling the left cerebellopontine angle cistern is enlarged to 25x19x12mm), it extends down till the left lateral aspect of medullary cistern, abutting the CN-XII at its entrance to left hypoglossal canal. After 5 month control show, a 15mm long and 5mm thick neoplastic soft-tissue in the left internal acoustic canal, with post-contrast enhancement, measured up to 12mm at the level of porus acusticus but cystic component of the mass in left cerebellopontine angle cistern is no longer visible in this MRI exam. CONCLUSION: The sensitivity of MRI for correctly diagnosing acoustic schwannoma was 100 % and specificity was 92.86 % with a positive predictive value of 94.12 % and accuracy of 96.67 %. MRI is considered as an excellent noninvasive investigation for pontocerebral angle Schwannoma’s.