Radiosurgery of lower cranial schwannomas Tumor control and functional outcome

Keywords: gamma knife, radiosurgery, schwannoma, skull base, outcome

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     Lower cranial nerve schwannomas may be managed with radiosurgery.
Long-term follow-up results of stereotactic radiosurgery for lower cranial schwannomas in and around the jugular foramen are reported.
     The subjects of this study were 33 patients with lower cranial schwannomas, 11 males and 22 females, and their mean age was 47.0 years.
      Large tumors in the posterior fossa as well as tumors in the upper cervical region were treated first by surgical resection. In two cases, upper cervical tumors were removed by a transcervical approach, and the residual tumor in and around jugular foramen was currently treated by radiosurgery. The mean diameter of the schwannomas was 25.0 mm (10.3 cc in mean volume), and they were treated with mean maximum dose of 26.1 Gy and mean marginal dose of 13.3 Gy.
     Tumor control was achieved in all cases and the estimated response rate (tumor shrinkage) was 70%. Neurological deficits attributable to motor nerve dysfunction, including hoarseness and swallowing disorders, improved in 16 cases (48.5%) and disappeared in another 5 cases (15%) in the mean follow-up period of 70 months after the radiosurgery. Meanwhile, 12 cases (36%) were unchanged without showing any progression. No clear adverse effects were identified.
     This was a retrospective study.
     From both a radiological and functional standpoint, lower cranial schwannomas can be treated successfully by radiosurgery to achieve an excellent outcome, especially when tumors grow and extend into the jugular foramen. 
     Among intracranial schwannomas, motor nerve ones like lower cranial and facial nerves showed a best response in terms of tumor control as well as functional recovery after radiosurgery, which is much better in quality than that of surgical resection.


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