trumpeted internal acoustic meatus sign

A trumpeted internal acoustic meatus (IAM) is an indirect sign of a vestibular schwannoma and is useful in helping to differentiate between one and other cerebellopontine angle entities, especially from a meningioma which typically does not extend into the meatus and is more often associated with hyperostosis .

It is characterized by widening of the medial end of the internal acoustic canal and porus acusticus resulting in an appearance reminiscent of a trumpet.

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