Acoustic Neuromas

Hearing Preservation up to 3 Years After Gamma Knife Radiosurgery for Gardner-Robertson Class I Patients With Vestibular Schwannomas

BACKGROUND:

Vestibular schwannoma patients with Gardner-Robertson (GR) class I hearing seek to maintain high-level hearing whenever possible.

OBJECTIVE:

To evaluate hearing outcomes at 2 to 3 years in GR class I patients who underwent Gamma Knife radiosurgery (GKRS).

METHODS:

Sixty-eight patients with GR class I hearing were identified between 2006 and 2009. Twenty-five patients had no subjective hearing loss (group A) and 43 patients reported subjective hearing loss (group B) before GKRS. The median tumor volume (1 cm3) and tumor margin dose (12.5 Gy) were the same in both groups.

RESULTS:

Serviceable hearing retention rates (GR grade I or II) were 100% for group A compared with 81% at 1 year, 60% at 2 years, and 57% at 3 years after GKRS for group B patients. Group A patients had significantly higher rates of hearing preservation in either GR class I (P < .001) or GR class II (P < .001). Patients with a pure tone average (PTA) <15 dB before GKRS had significantly higher rates of preservation of GR class I or II hearing.

CONCLUSION:

At 2 to 3 years after GKRS, patients without subjective hearing loss or a PTA <15 dB had higher rates of grade I or II hearing preservation. Modification of the GR hearing classification into 2 groups of grade I hearing (group A, those with no subjective hearing loss and a PTA <15 dB; and group B, those with subjective hearing loss and a PTA >15 dB) may be useful to help predict hearing preservation rates at 2 to 3 years after GKRS.

Auditory rehabilitation of patients with neurofibromatosis Type 2 by using cochlear implants

OBJECT

The aim of this study was to determine whether patients with neurofibromatosis Type 2 (NF2) who have intact ipsilateral cochlear nerves can have open-set speech discrimination following cochlear implantation.

METHODS

Records of 7 patients with documented NF2 were reviewed to determine speech discrimination outcomes following cochlear implantation. Outcomes were measured using consonant-nucleus-consonant words and phonemes; Hearing in Noise Test sentences in quiet; and City University of New York sentences in quiet and in noise.

RESULTS

Preoperatively, none of the patients had open-set speech discrimination. Five of the 7 patients had previously undergone excision of ipsilateral vestibular schwannoma (VS). One of the patients who received a cochlear implant had received radiation therapy for ipsilateral VS, and another was undergoing observation for a small ipsilateral VS. Following cochlear implantation, 4 of 7 patients with NF2 had open-set speech discrimination following cochlear implantation during extended follow-up (15-120 months). Two of the 3 patients without open-set speech understanding had a prolonged period between ipsilateral VS resection and cochlear implantation (120 and 132 months), and had cochlear ossification at the time of implantation. The other patient without open-set speech understanding had good contralateral hearing at the time of cochlear implantation. Despite these findings, 6 of the 7 patients were daily users of their cochlear implants, and the seventh is an occasional user, indicating that all of the patients subjectively gained some benefit from their implants.

CONCLUSIONS

Cochlear implantation can provide long-term auditory rehabilitation, with open-set speech discrimination for patients with NF2 who have intact ipsilateral cochlear nerves. Factors that can affect implant performance include the following: 1) a prolonged time between VS resection and implantation; and 2) cochlear ossification.

Preservation of functional hearing after gamma knife surgery for vestibular schwannoma

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 intra-canalicular 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.