Preservation of Functional Hearing
Object: The goal of this retrospective study was to define the rates of preservation of functional hearing and growth control of vestibular schwannomas (VS) treated by gamma knife surgery (GKS) involving a consistent 12-Gy prescription dose.
Methods: One hundred thirty-four patients with unilateral VS underwent GKS between 1994 and 2000. The mean magnetic resonance (MR) imaging follow-up period was 31.7 months (maximum 72 months), and the mean audiometry follow-up interval was 26.3 months (maximum 60 months). The mean marginal dose was 12 ± 0.6 Gy. The mean maximum dose delivered to the tumor center was 25.4 Gy (range 17.4–34.3 Gy). The tumor control rate, defined as no change or a reduction in size at last follow up, was 96.7%. Of the patients studied, 97.7% remained free from the need to undergo tumor resection. Overall functional hearing preservation was 61.7%; the preservation rate for intracanalicular tumors was 63.6%, for those with an intracranial diameter less than 1.5 cm it was 54.5%, for those between 1.5 and 3 cm it was 68.2%, and for those larger than 3 cm it was 33.3%. Early in the series, three patients (2.2%) developed temporary facial weakness (House–Brackmann Grade II–III) in the posttreatment period, but this resolved within a few weeks. No case of facial weakness occurred after 1996.
Conclusions: The authors demonstrated the efficacy, safety, and in many ways, the advantage of GKS over microsurgery for VS. Patients harboring tumors 3 cm or smaller in intracranial diameter, regardless of their age and medical condition, should be given the option of undergoing GKS as primary treatment.
In recent years, preservation of hearing has become an increasingly important issue in the management of VS. Because complete removal of the lesion and preservation of facial nerve function are routinely expected at centers of excellence, the next important achievement is preservation of functional hearing. In selected series in which small tumors have been resected by experienced surgeons, the authors have demonstrated that hearing, when functional preoperatively, can be preserved in 40 to 70% of the cases. Preservation of functional hearing after excision of medium-sized and large tumors, however, is technically demanding, and the preservation rate is less impressive than that for small lesions. In several studies of GKS for VS investigators have published more promising results.
This retrospective study was undertaken to study the potential of functional hearing preservation and growth control in VS when GKS is administered in a consistent manner with regard to dose level and dosimetry.
Object: The goal of this retrospective study was to define the rates of preservation of functional hearing and growth control of vestibular schwannomas (VS) treated by gamma knife surgery (GKS) involving a consistent 12-Gy prescription dose.
Methods: One hundred thirty-four patients with unilateral VS underwent GKS between 1994 and 2000. The mean magnetic resonance (MR) imaging follow-up period was 31.7 months (maximum 72 months), and the mean audiometry follow-up interval was 26.3 months (maximum 60 months). The mean marginal dose was 12 ± 0.6 Gy. The mean maximum dose delivered to the tumor center was 25.4 Gy (range 17.4–34.3 Gy). The tumor control rate, defined as no change or a reduction in size at last follow up, was 96.7%. Of the patients studied, 97.7% remained free from the need to undergo tumor resection. Overall functional hearing preservation was 61.7%; the preservation rate for intracanalicular tumors was 63.6%, for those with an intracranial diameter less than 1.5 cm it was 54.5%, for those between 1.5 and 3 cm it was 68.2%, and for those larger than 3 cm it was 33.3%. Early in the series, three patients (2.2%) developed temporary facial weakness (House–Brackmann Grade II–III) in the posttreatment period, but this resolved within a few weeks. No case of facial weakness occurred after 1996.
Conclusions: The authors demonstrated the efficacy, safety, and in many ways, the advantage of GKS over microsurgery for VS. Patients harboring tumors 3 cm or smaller in intracranial diameter, regardless of their age and medical condition, should be given the option of undergoing GKS as primary treatment.
In recent years, preservation of hearing has become an increasingly important issue in the management of VS. Because complete removal of the lesion and preservation of facial nerve function are routinely expected at centers of excellence, the next important achievement is preservation of functional hearing. In selected series in which small tumors have been resected by experienced surgeons, the authors have demonstrated that hearing, when functional preoperatively, can be preserved in 40 to 70% of the cases. Preservation of functional hearing after excision of medium-sized and large tumors, however, is technically demanding, and the preservation rate is less impressive than that for small lesions. In several studies of GKS for VS investigators have published more promising results.
This retrospective study was undertaken to study the potential of functional hearing preservation and growth control in VS when GKS is administered in a consistent manner with regard to dose level and dosimetry.