Figure 1: The most common intracranial location of schwannoma is in the cerebellopontine angle, as in this patient. Cystic change is quite common in larger schwannomas on T2WI (left). Schwannomas are also typically avidly enhancing on postcontrast T1WI (right). This schwannoma can be differentiated from meningioma based on this cystic change and on the clearly delineated extension into the internal auditory canal. IAC remodeling and widening may also be present. The lack of a meningioma's "dural tail" is also helpful.
Figure 2: Axial T1 post-contrast images demonstrate bilateral vestibular schwannomas (top row left) and meningiomas (top row right and middle row left). Sagittal T1 post-contrast (middle row right) and T2 (bottom row) images demonstrate enhancing, expansile, centrally located intramedullary lesions within the spinal cord compatible with ependymomas in this patient with Neurofibromatosis Type II (NF-2).
Figure 3: Post-contrast T1 images (top row left – axial, top row right – coronal) demonstrate an avidly enhancing tiny in the apex of the left internal auditory canal. Heavily T2-weighted CISS sequence (bottom row) also shows this nodule and can show the nerve from which it arises. This appearance is typical for a tiny IAC schwannoma.
- Benign peripheral nerve sheath tumor arising from Schwann cells of CN 8 (vestibular portion) within the CPA-IAC
- WHO grade 1
- Originates from Schwann cells surrounding CN 8 vestibular segment
- CN 8 inferior vestibular branch > superior branch
- CN 5 and CN 7 schwannomas not uncommon
- Origin in CN 8 cochlear portion is rare
- Bilateral VS hallmark of Neurofibromatosis type 2 (NF-2)
- Mutations in NF2 tumor suppressor gene in majority of sporadic and familial cases
- Associated abnormality: arachnoid cyst or “CSF cap” (7-10% of cases)
- Variable hypercellular (Antoni A) and more hypocellular (Antoni B) areas are characteristic microscopic features
- ± Intratumoral cysts, microhemorrhage
- Most common during adulthood (ages 40-60)
- Uncommon in children unless associated with NF-2
- Majority of cases exhibit slow growth over time
- Common presenting signs/symptoms: unilateral sensorineural hearing loss
- Treatment: surgical resection
- Prognosis: size >2 cm and involvement of IAC fundus and/or cochlear aperture are negative prognosticators for hearing preservation
- Well-marginated, enhancing mass within the CPA or CPA-IAC with “ice cream on cone” morphology
- Expansion of the IAC (in contrast to meningiomas)
- Small lesions may be entirely intracanalicular
- Calcification, cystic degeneration may be seen; hemorrhage rare
- Small lesions may be entirely intracanalicular and nonvisible on CT
- Enhancement on contrast-enhanced CT
- T1WI: usually hypo- to isointense
- T2WI: high resolution sequences (SPACE, CISS, or FIESTA) optimize visualization; appears as a hypo- to isointense CPA-IAC filling defect (ovoid if small, “ice cream on cone” if larger); ± hyperintense tumoral cysts
- T2*GRE: ± signal blooming from foci of microhemorrhage
- T1WI+C: avid enhancement
- MRI without and with IV contrast including high-resolution T2-weighted sequences through the CPA-IAC (SPACE, CISS, or FIESTA); serial MR imaging for small lesions to ensure stability
For more information, please see the corresponding chapter in Radiopaedia.
Contributor: Rachel Seltman, MD; Jacob A. Eitel, MD
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Thamburaj K, et al. Intratumoral microhemorrhages on T2*-weighted gradient-echo imaging helps differentiate vestibular schwannoma from meningioma. AJNR Am J Neuroradiol. 2008;29:552-557.
Woodruff JM, et al. Schwannoma, in Kleihues P et al (eds): Tumours of the Nervous System. Lyon: IARC Press, 2000; 164-166.
Zealley IA, et al. MRI screening for acoustic neuroma: a comparison of fast spin echo and contrast enhanced imaging in 1233 patients. Br J Radiol. 2000;73:242-247.
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