Vestibular Schwannoma
– Centered in IAC
– Smooth scalloping of the IAC
– Spherical or ovoid, occasionally lobulated; Acute bone-tumor angle.
– Mostly isodense, a few slightly hypodense or hyperdense.
– CT Enhancement: Moderate to marked, often inhomogenous.
– T1W signal : GM > VS > CSF
– T2W signal : VS < CSF
– MR Enhancement : Marked ; Cystic changes maybe present
Meningioma
– Along posterior petrous wall; Most are eccentric to IAC
– Occasional hyperostosis
– Hemispherical, rarely plaque-like; may herniate ; Obtuse bone-tumor angle.
– Isodense or mostly slightly hyperdense; Some calcified
– CT Enhancement: Marked and homogenous
– T1 signal : GM > M > CSF
– T2 Signal : Variable
– MR enhancement: Moderate to Avid
Epidermoid
– Anterolateral or posterolateral to brainstem
– Occasional erosion
– Variable shape, with tendency to insinuate to middle cranial fossa and the contralateral CPA
– Mostly about CSF density, rarely denser than brain, occasional peripheral calcification
– Non-enhancing on CT
– T1 signal: GM > E > CSF
– T2 signal: </= CSF
– Non-enhancing on MR
Contributed by – Dr. Varun Tyagi, Mumbai
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