Acoustic neuroma MRI
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Acoustic neuroma Microchapters | |
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Case Studies | |
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Acoustic neuroma MRI On the Web | |
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American Roentgen Ray Society Images of Acoustic neuroma MRI | |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Gadolinium-enhanced MRI scan is definitive diagnostic test of acoutic neuroma and can identify tumors as small as 1-2 millimeter in diameter. On brain MRI, acoustic neuroma characterized by hypointense mass on T1-weighted MRI, and hyperintense mass on T2-weighted MRI.
MRI
- Gadolinium-enhanced magnetic resonance imaging (MRI) is the preferred diagnostic test for identifying acoustic neuromas and can identify tumors as small as 1-2 millimeter in diameter.
- Most vestibular schwannomas have an intracanalicular component, and often result in widening of the porus acusticus resulting in the trumpeted IAM sign, which is present in up to 90% of cases.
- In a minority of cases (~20%) they are purely extracanalicular, only abutting the porus acousticus.
- Usually there is a small CSF cap between intracanalicular portion and the cochlea; occasionally, these tumors grow laterally through the cochlea (transmodiolar) or vestibule (transmacular) into the middle ear. Rarely they are small and confined to the vestibule (intravestibular) or to the cochlea (intracochlear) or both (vestibulocochlear).
- Extracanalicular extension into cerebellopontine angle (path of least resistance) can lead to "ice-cream-cone" appearance. Small tumors tend to be solid whereas cystic degeneration seen commonly in larger tumors. Haemorrhagic areas may also be seen. Calcification is typically not present.
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Post-op MRI: Linear enhancement may not indicate tumor, but if there is nodular enhancement suspect tumor recurrence (needs follow up MRI).[1]
References
- ↑ Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015
- ↑ Image courtesy of Dr Frank Gaillard. Radiopaedia (original file here).[http://radiopaedia.org/licence Creative Commons BY-SA-NC
- ↑ Image courtesy of Dr. Roberto Schubert Radiopaedia (original file here).[http://radiopaedia.org/licence Creative Commons BY-SA-NC