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Radiation sensitivity of visual and oculomotor pathways
K A Leber1, J Berglöff, G Langmann
1Department of Neurosurgery, Karl-Franzens-University of Graz, Austria.
Stereotactic and Functional Neurosurgery
|January 1, 1995
Summary
Stereotactic radiosurgery for skull base tumors can affect cranial nerves. The visual pathways are more vulnerable to radiation damage, especially if function is already compromised.
Area of Science:
- Neurosurgery
- Radiation Oncology
- Ophthalmology
Background:
- Adverse effects of stereotactic radiosurgery on cranial nerves are not fully understood.
- Benign skull base tumors often require radiation impacting nearby cranial nerves.
Purpose of the Study:
- To evaluate the neuro-ophthalmological adverse effects of Gamma Knife radiosurgery on cranial nerves.
- To correlate radiation dose with neuro-ophthalmological findings in patients with skull base tumors.
Main Methods:
- Retrospective review of 29 patients undergoing Gamma Knife radiosurgery for benign skull base tumors.
- Correlation of radiation dose (Gy) to cranial nerves (III, IV, VI, trigeminal, optic pathways) with neuro-ophthalmological outcomes.
- Follow-up period of 6-24 months.
Main Results:
- Cranial nerves III, IV, VI, and trigeminal nerve tolerated doses of 4.5-30 Gy and 5-20 Gy, respectively, without neuropathy.
- Visual pathways tolerated 7.5-15 Gy in patients with normal pre-treatment neuro-ophthalmological findings.
- 31% of patients with pre-existing visual deficits experienced deterioration after receiving 6-16.6 Gy to visual fibers.
Conclusions:
- Visual pathways are more susceptible to radiation damage from stereotactic radiosurgery than other cranial nerves in the middle cranial fossa.
- Pre-existing visual deficits may increase the vulnerability of visual pathways to radiation-induced injury.