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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May 25, 2015
Arachnoid Cyst with Accessory Nerve Palsy
- Background:
- Injuries to the accessory nerve are rare and may cause unpredictable motor defects in the neck, including trapezius muscle weakness/atrophy.
- In the absence of prior trauma or surgery, a space-occupying posterior fossa or upper cervical lesion should be sought.
- Key DiagnosticFeatures:
- Muscle denervation: Signal increase on STIR is earliest MR sign (precedes atrophy).
- Arachnoid cyst: Extra-axial lesion following CSF signal on all MR sequences (imperceptible wall, no enhancement or restricted diffusion). Remodeling of adjacent bone may be present.
- DDx:
- Epidermoid cyst
- Neurenteric cyst
- Cystic schwannoma
- Treatment options: Neurosurgical decompression of the cyst may be indicated in symptomatic cases; however, the outcome is uncertain.