Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 12, 2018
Hemorrhagic Vestibular Schwannoma
- Background:
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Clinically significant intratumoral hemorrhage occurs in only a small fraction of vestibular schwannomas (VSs), fewer than 1% of patients.
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Hemorrhage in cystic VS seems to be the major mechanism of fluid‑fluid level formation.
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The abnormal vascularity and dilated, thin-walled vessels found in VS are thought to be the causes of hemorrhages.
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Identification of hemorrhages may indicate a potentially aggressive biologic behavior of VS and therefore influence management.
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Advances in MRI sequences (gradient-echo and SWI) suggest that intratumoral microhemorrhages, on the other hand, are far more common than previously believed and might represent an aspect of the natural history of VS.
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- Clinical Presentation:
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Macrohemorrhage may induce a significant and sudden increase in the overall size of the mass, with subsequent clinical signs and symptoms (unilateral sensorineural hearing loss, headache, facial nerve weakness, gait disturbance, trigeminal nerve dysfunction, dizziness, etc.) resulting from an acute mechanical conflict with the adjacent cranial nerves. It may also double the risk of hearing loss at presentation.
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Death occurs much more frequently in patients with hemorrhagic (10.0%) than nonhemorrhagic (0.2%) VS.
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Large intratumoral hemorrhage may occur in conjunction with subarachnoid hemorrhage at times, with adverse outcomes.
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- Key Diagnostic Features:
- Fluid-fluid levels can be identified in CT or MRI scans. A thin-slice, heavily T2-weighted 3D sequence is considered more sensitive for detecting small fluid-fluid levels.
- Differential Diagnoses:
- Meningiomas: calcified, dural-based mass eccentric to the porus acusticus; presence of hyperostosis, formation of an obtuse angle with the petrous temporal bone, homogeneous contrast enhancement, and a dural tail; typically no microhemorrhages seen on T2*-weighted GRE.
- Ependymoma: centered on the fourth ventricle and does not extend into the internal acoustic canal (IAC); usually younger patients
- Epidermoid cyst: may mimic rare cystic VS; nonenhancing mass with restricted diffusion; does not widen the IAC
- Aneurysm in cerebellopontine angle (CPA): ovoid to fusiform complex signal
- Facial nerve schwannoma: when confined to CPA-IAC may mimic VS; look for labyrinthic segment “tail” to differentiate
- Metastases: may have bilateral meningeal involvement; usually does not remodel the IAC
- Treatment:
- Urgent surgery may be needed in cystic VS to avoid the risks for a large hemorrhage.
- Radiosurgery is not recommended, as the expansion of the cystic components and possible hemorrhage following the procedure may result in sudden deterioration.
- Cystic VSs with fluid-fluid levels more frequently adhere tightly to surrounding neurovascular structures and have a less favorable surgical outcome.
- It is essential that total resection is performed during the initial surgical procedure due to the tendency for accelerated regrowth of residual cystic VS.
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