Acoustic neuroma MRI

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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.[1][2]
  • Most acoustic neuroma have an internal acoustic meatus and often result in widening of the medial opening of the internal acoustic canal.
  • 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.
MRI component Features
T1
  • Slightly hypointense cf. adjacent brain (63%)
  • Isointense cf. adjacent brain (37%)
  • May contain hypointense cystic areas
T2
  • Heterogeneously hyperintense cf. to adjacent brain
  • Cystic areas fluid intensity
  • May have associated peritumoural arachnoid cysts
T1 C+ (Gd)
  • Contrast enhancement is vivid
  • But heterogeneous in larger tumors

Post-op MRI: Linear enhancement may not indicate tumor, but if there is nodular enhancement suspect tumor recurrence (needs follow up MRI).[3]

MRI showing Intracanalicular acoustic neuroma[4]
MRI showing Intrameatal vestibularis schwannoma[5]

References

  1. E. P. Lin & B. T. Crane (2017). "The Management and Imaging of Vestibular Schwannomas". AJNR. American journal of neuroradiology. 38 (11): 2034–2043. doi:10.3174/ajnr.A5213. PMID 28546250. Unknown parameter |month= ignored (help)
  2. D. F. Wilson, R. S. Hodgson, M. F. Gustafson, S. Hogue & L. Mills (1992). "The sensitivity of auditory brainstem response testing in small acoustic neuromas". The Laryngoscope. 102 (9): 961–964. doi:10.1288/00005537-199209000-00001. PMID 1518359. Unknown parameter |month= ignored (help)
  3. Acoustic Schwannoma. Radiopedia(2015) http://radiopaedia.org/articles/acoustic-schwannoma Accessed on October 2 2015
  4. Image courtesy of Dr Frank Gaillard. Radiopaedia (original file here).[http://radiopaedia.org/licence Creative Commons BY-SA-NC
  5. Image courtesy of Dr. Roberto Schubert Radiopaedia (original file here).[http://radiopaedia.org/licence Creative Commons BY-SA-NC

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