Auditory Nerve Test System During Vestibular Schwannoma Resection

The Auditory Nerve Test System (ANTS) is a novel device that stimulates the auditory nerve much like a cochlear implant. The purpose of this study is to demonstrate feasibility of the ANTS during translabyrinthine surgery for vestibular schwannoma resection. If the auditory nerve is kept intact, then the patients will also receive a cochlear implant at the same time potentially alleviating the morbidities caused by a vestibular schwannoma and asymmetric sensorineural hearing loss.

Many patients diagnosed with a vestibular schwannoma (also called acoustic neuroma) eventually lose hearing in the afflicted ear. Improvements in magnetic resonance imaging (MRI) have led to tumors being diagnosed at smaller sizes, however, this has not changed the eventual demise in hearing for most patients. Hearing loss leads to tinnitus, poor sound localization, difficulty hearing in background noise, and imbalance all of which contribute to the decreased quality of life associated with a vestibular schwannoma diagnosis.

Some tumors may be resected while maintaining the integrity of the auditory nerve. When a patient has hearing, the health of the auditory nerve can be monitored during the surgery through auditory-evoked (sound) measurements. When a patient has already lost their hearing or the surgical approach sacrifices all residual hearing, then auditory-evoked measurements can no longer be used and there is no way to monitor the auditory nerve aside from visual inspection.

The Auditory Nerve Test System (ANTS) is a novel device designed to facilitate electrically-evoked auditory nerve monitoring. The ANTS is comprised of three parts: a test electrode, connector cable, and stimulator box. The test electrode functions like a mini-cochlear implant placed within the cochlea during a translabyrinthine surgery. During tumor resection the test electrode electrically stimulates the auditory nerve allowing surgeons to monitor electrophysiologic data on the health of the auditory nerve. The primary goal of this study is to assess the ANTS during translabyrinthine vestibular schwannoma resections.

If patient are able to maintain an intact auditory nerve following vestibular schwannoma resection then a cochlear implant will be placed during the same surgery. Secondary outcomes measures will investigate cochlear implant outcomes and patient quality of life following this procedure and over the first year of using their cochlear implant. These secondary outcomes will be measured at 3-months, 6-months, and 12-months following cochlear implant activation. The test will assess how well the cochlear implant is working, the cochlear implant's impact on sound localization and hearing in background noise, and finally various aspects relevant to the patient's quality of life (tinnitus, balance, hearing, and overall quality of life).

Eligibility Criteria:
Inclusion Criteria:

* Vestibular schwannoma (sporadic or Neurofibromastosis Type-2)
* 12 years of age or older
* Tumor size \< 2.5 cm
* Non-serviceable ipsilateral hearing
* No prior cochlear implant or auditory brainstem implant use
* No prior microsurgery or stereotactic radiation for this tumor
* Patient decision and medical clearance for a translabyrinthine approach for tumor resection
* Willingness to comply with research protocol
* Reasonable expectations of cochlear implant performance
* Auditory nerve integrity visually confirmed following tumor resection

Exclusion Criteria:

* Pathology/tumors other than a vestibular schwannoma
* Younger than 12 years of age
* Tumor size \> 2.5 cm
* Serviceable hearing in the tumor ear
* Prior cochlear implant use in either the contralateral or ipsilateral ear
* Prior microsurgery or stereotactic radiation for this tumor
* Unwilling to comply with research protocol
* Auditory nerve integrity cannot be visually confirmed after tumor resection