1 Auditory Rehabilitation in Sporadic Vestibular Schwannoma

10.1055/b-0039-169215

61 Auditory Rehabilitation in Sporadic Vestibular Schwannoma

Brendan P. O’Connell, David S. Haynes, and George B. Wanna

61.1 Introduction

Hearing loss in patients with sporadic vestibular schwannoma (VS) can occur either as part of the natural history of the disease or secondary to intervention by way of surgery or stereotactic radiation. Patients with minimal or no hearing loss in the tumor ear and good hearing in the contralateral ear generally fair well and do no pursue amplification. For patients with greater degrees of hearing loss, conventional hearing amplification is successful in most patients with a word recognition score greater than 60% and pure-tone thresholds better than 80 dB HL.

In patients with more advanced unilateral hearing loss, or single-sided deafness (SSD), the loss of binaural hearing can have the following audiologic consequences: decreased perception of sound coming from the affected side, reduced ability to localize sound, difficulty with speech perception in noise, and increased listening effort. The level of hearing loss, of course, must be evaluated in the context of the patient. For example, a person who works in a quiet office may be only minimally impacted by SSD, while a police officer that relies heavily on accurate sound localization or a waitress who works in a noisy restaurant may encounter significant difficulty. Furthermore, many patients are more bothered by their hearing loss if lost abruptly from sudden hearing loss or immediately following surgery. In these cases, we generally advise that the patient not pursue surgical treatments until at least 6 months, as a significant number of patients adjust to the loss and ultimately do not pursue additional treatments.

Depending on the patient and their daily environment, advanced unilateral hearing loss can cause psychological and social impairment; therefore, it is important for clinicians to be cognizant of the potential quality-of-life implications that profound unilateral hearing loss can have on patients with VS. Furthermore, specialists caring for patients with VS should be knowledgeable about the available auditory rehabilitation options.

61.2 Impact of Hearing Loss on Patients with Sporadic Vestibular Schwannoma

Despite our best efforts at hearing preservation, the majority of patients eventually experience significant unilateral hearing loss following diagnosis and/or treatment.s. Literatur Studies that retrospectively survey patients after VS treatment demonstrate that hearing loss is indeed bothersome, albeit to variable degrees. In patients with unilateral deafness after translabyrinthine VS removal, 80% of individuals endorsed a subjective hearing handicap of varying severity.s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur When asked to report one’s most disabling symptom, hearing loss is cited by 10 to 61% of patients. Furthermore, when using the World Health Organization (WHO) classification of functional deficits, reported disabilities were attributed to auditory impairment in the majority of cases.s. Literatur Patients with good hearing in the nontumor ear report far less hearing handicap than patients with bilateral hearing impairment.s. Literatur

Studies have also looked at changes in hearing handicap comparing pre- and postoperative time points. While 58% of patients demonstrated no change in their hearing handicap between preoperative and 12-month postoperative follow-up, 25% of patients had significant worsening in their hearing handicap.s. Literatur Not surprisingly, the patients who noted worsening disability were those with a better hearing class preoperatively.

Studies have also assessed the association between hearing loss and overall quality of life using validated health-related quality-of-life instruments. While poor hearing has been shown to be predictive of decreased quality of life when using the validated Penn Acoustic Neuroma Quality of Life Scale (PANQOL), surprisingly no relation between hearing loss and other global measures of health-related quality of life has been demonstrated.s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur Although instruments used in these studies have been validated and are well-established measures, perhaps they are not sensitive enough to detect more subtle changes in hearing handicap that are associated with SSD.

61.3 Auditory Rehabilitation in Cases of Functional Residual Hearing

Amplification with a conventional hearing aid is an option for patients with either treated or untreated VSs so long as hearing remains functional. In most cases, conventional hearing aids provide benefit if ipsilateral word recognition scores are greater than 60% and pure-tone thresholds are better than 80 dB HL. This threshold varies between patients and may also be influenced by hearing status in the opposite ear. Several unique considerations regarding sensorineural hearing loss and hearing aid fitting in patients with VS deserve review. First, patients with retrocochlear hearing loss may experience rollover effects in which speech recognition decreases as presentation level increases. Second, patients often have disproportionally poorer word recognition scores than would be expected from pure-tone levels and may experience abnormal loudness growth functions with reduced dynamic ranges. Finally, patients have a much greater probability of accelerated deterioration of hearing than the average population, which may require more frequent hearing aid adjustments and upgrades. The latter has cost implications, particularly in cases of either untreated or previously radiated tumors that may demonstrate progressive hearing loss over time. Given the aforementioned points, the degree of durable benefit from traditional amplification in patients with VS is less predictable than the general population. Nevertheless, conventional hearing aids may be worthwhile in select patients with benefits including improved word recognition, enhanced sound localization, and perhaps even tinnitus masking.

61.4 Auditory Rehabilitation of Single-Sided Deafness in Vestibular Schwannoma

Traditionally, audiologic rehabilitation of SSD was limited to devices that allow for routing of sound from the affected ear to the hearing ear, thus overcoming the head shadow effect. More recently, cochlear implantation (CI) has emerged as an option for sound restoration in the deaf ear. Both surgical and nonsurgical options for contralateral routing of sound (CROS) are available to patients, and are discussed later.

61.4.1 Contralateral Routing of Sound Hearing Aids

CROS hearing aids collect sound through a microphone placed in the hearing-impaired ear, transferring the signal wirelessly to a receiver placed in the contralateral normal hearing ear. Patients who have aidable hearing loss in the better hearing ear should be fitted with a bilateral contralateral routing of signals (BiCROS) system. In addition to transferring sound from the deaf ear, the BiCROS system delivers amplified sound from both sides to the better hearing ear. Available data support that CROS aids provide modest improvement in speech discrimination in noise when compared to the unaided condition.s. Literatur ^, s. Literatur Historically, CROS hearing aids were not universally accepted, as patients complained of sound distortion, the need to wear devices in both ears with occlusion effect, and discomfort related to occlusion of the better hearing ear.s. Literatur Long-term usage rates in patients treated for VS have been reported to be as low as 32%.s. Literatur With recent advances in hearing aid technology, in particular digital noise reduction and directional microphones, there appears to be an increased acceptance rate of newer generation CROS and BiCROS systems.s. Literatur ^, s. Literatur ^, s. Literatur

61.4.2 Bone-Anchored Implants

Bone-anchored implants (BAIs) are surgically implanted systems that were initially approved for conductive or mixed bilateral hearing loss, but in recent years have been popularized as transcranial cochlear stimulators for rehabilitation of SSD. Currently available BAIs include Baha Attract (Cochlear Corporation, Centennial, CO), Baha Connect (Cochlear Corporation), Ponto (Oticon Medical, Somerset, NJ), and Sophono (Sophono Inc, Boulder, CO). The Baha Connect and Ponto devices are percutaneous bone-conduction hearing implants (Fig. 61‑1 ). Specifically, an osseointegrated screw is implanted into the skull and an abutment is attached that protrudes through the skin. Allowing time for osseointegration, a sound processor is then connected to the abutment weeks to months after surgery. The Baha Attract and Sophono are transcutaneous implants without abutments (Fig. 61‑2 ). Although the design of these particular devices differs slightly, an internal magnet is implanted into the skull beneath the skin. The processor then couples to the internal device via an external magnet. Both percutaneous and transcutaneous devices allow for transmission of sound through bone to the contralateral cochlea (Fig. 61‑3 ). While transcutaneous devices decrease the risk of postoperative crusting and skin overgrowth, cases of pressure necrosis have been reported. In addition, signal gain is reduced secondary to the intervening soft tissue between magnets and the audiologic outcomes remain unclear in the setting of SSD. For this reason, further discussion regarding BAIs will be largely limited to the use of percutaneous devices.

**Fig. 61.1** Schematic of a percutaneous bone-anchored implant. (Image courtesy of Cochlear Americas, © 2016.)

**Fig. 61.2** Schematic of a transcutaneous bone-anchored implant. (Image courtesy of Cochlear Americas, ©2016.)

**Fig. 61.3** In patients with right-sided deafness, a bone-anchored implant placed on the right can transmit sound via bone conduction to the contralateral cochlea. (Image courtesy of Cochlear Americas, ©2016.)

Strong evidence supports that BAIs are associated with improved speech recognition in noise in patients with SSD.s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur In addition, the majority of BAI users report satisfaction and improved hearing-related quality of life with their device, which has been shown to persist at long-term follow-up.s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur Long-term usage rates are generally reported to be around 80 and 95%.s. Literatur ^, s. Literatur ^, s. Literatur Postoperative healing issues should be discussed when counseling patients about implantable bone-conductive devices as the rate of skin reactions around the abutment site with BAIs has been reported to range between 5 and 38%.s. Literatur ^, s. Literatur ^, s. Literatur ^, s. Literatur Of course, it is critical that the patient understands that BAIs will not improve sound localization. In addition, all patients should trial a bone conduction hearing aid for several days before proceeding with BAI placement. Proper patient selection is key to long-term consistent use.