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Jugular foramen schwannoma – upfront radiosurgery
SKULL BASE REGION
Jugular foramen
HISTOPATHOLOGY
N/A
PRIOR SURGICAL RESECTION
No
PERTINENT LABORATORY FINDINGS
None
Case description
The patient is a 38-year-old female who was evaluated after 3 years of nonspecific disequilibrium and pulsatile tinnitus and was found to have a right jugular foramen mass consistent with schwannoma ( Figure 10.52.1 ). Examination revealed normal cranial nerve function, including normal hearing. Given her age, the location and size of the tumor, and normal cranial nerve function, the decision was made to proceed with stereotactic radiosurgery (SRS) ( Figure 10.52.2 ).
Radiosurgery Machine
Gamma Knife
Radiosurgery Dose (Gy)
14, at the 50% isodose line
Number of Fractions
1
Figure 10.52.1.
A. Initial MRI 1 month prior to stereotactic radiosurgery (SRS): Axial T1-weighted image with gadolinium showing a heterogeneously enhancing mass of the jugular foramen. B. Initial MRI 1 month prior to SRS: Coronal T1-weighted image with gadolinium showing inferior tumor extension into the neck. C. Initial CT scan 1 month prior to SRS: Axial non-contrasted image demonstrating smooth enlargement of the jugular foramen and minimal bony erosion.
Figure 10.52.2.
Imaging of the treatment plan. Yellow line, 50% isodose; outer green line, 30% isodose; inner green line, 80% isodose; blue, cochlea outline.
Critical Structure
Dose Tolerance
Brainstem
15 Gy maximum point dose
Internal carotid artery in canal
Unknown dose tolerance
Cochlea
4 Gy maximum point dose (extrapolated from vestibular schwannoma literature)
Lower cranial nerves in foramen
Unknown dose tolerance
Side Effects/Complications
Frequency
Deteriorating lower cranial neuropathy
3%–7.5% ,
New lower cranial nerve neuropathy
15%–17% at 5 years ,
Malignant transformation (or malignancy within SRS field)
Unknown in jugular schwannoma literature
Vestibular schwannoma literature cites a 0.04% chance within 15 years of treatment
Internal carotid artery stenosis
Unknown in jugular schwannoma literature. Paraganglioma literature suggests risk of clinically significant carotid stenosis is negligible
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