**1. Introduction**

Active middle ear implants (AMEI) represents today one of the possible rehabilitative solutions for hearing-impaired individuals. These devices utilize, for their function, a vibratory effect instead of the classical, physiological air-conducted sound stimulation. This natural sound transmission way, if warranting the perfect solution under normal hearing conditions, usually generates several negative issues on a hearing-impaired ear, going from an insufficient stimulation to the presence of distortions when the conventional hearing amplifiers, i.e. hearing aids (HA), are in use. In fact, despite their striking technological improvement over the last decades (advanced miniaturization, open-fitting systems, sophisticated digital signal processing software, and wide connectivity), the latter are rarely showing to be optimal for the patients' auditory needs while generating distorted amplification issues (feedback, occlusion effect, and insufficient high-frequency gain). As a consequence, the number of HA users is far from equaling the purchased devices worldwide. Another playing factor is due to the scarce impact on some quality of life issues (manual difficulty, stigma, pathology, or reduced caliber of the external

auditory canal, earmold allergies, and impossibility to use them during water contact, physical activities, and overnight, while sleeping).

The advent of AMEI with the stimulation pathway different from the normal (or amplified) sound, i.e., the electromechanical one, has paved the way for the possible theoretical resolution of the above-mentioned annoying cHA-related issues. In fact, these devices are directly coupled to middle or inner ear elements (ossicular chain or part of it, round window membrane) for achieving close-field cochlear stimulation, and should theoretically overcome most of the issues deriving from the obligatory acoustic over-stimulation that needs to be delivered by an external amplifier, such as a cHA. Moreover, all of them leave the external ear canal free, so as to improve the auditory and physical occlusion issues, as well as the compatibility with external ear canal or middle ear pathologies.

In relation to the presence of an external component, the AMEI can be distinguished in semi- or fully implantable devices, this latter term inherently meaning that all their components remain completely invisible under the skin. At the present time, only two fully implantable devices are available for the rehabilitation of sensorineural hearing loss (SNHL): the Carina® (Cochlear, Lane Cove, Australia) and the Esteem® (Envoy Medical Corporation, St. Paul, MN, USA). Both devices have in common the complete allocation inside the skull, while carrying at the same time some major differences, as listed in **Table 1**.

This last appealing factor is surely playing an important role for the decisionmaking process while counseling with a possible candidate, but it would not be wise to consider it as primary factor for its choice, and anyhow never replacing a preoperative use or trial with a best-fitted last-generation digital cHA.

At Sant'Andrea University Hospital, Rome, Italy, an extensive rehabilitative program for hearing impairment has been applied since nearly 15 years, mostly aiming at the resolution of different types and severity of conductive, mixed and SNHL. In particular, from 2007, a series of subjects affected by bilateral SNHL have undergone Esteem® surgical application. The Esteem® (Envoy Medical, St Paul, MN, USA) middle ear implant has recently been reported to be beneficial for individuals affected by moderate-to-severe bilateral SNHL, with low morbidity and complication rate [1, 2]. This device works via a piezoelectric vibratory stimulus on the stapes and thereafter to the inner ear fluids, also vibrating the intact eardrum that plays as natural microphone. Following this physiological route, a natural sound quality is likely to be perceived by preserving auricular filtering (at high frequencies) and leaving the ear canal open, thus eliminating the occlusion effect.

The aim of the present report is to highlight specific clinical issues including those that have emerged while following up the Esteem®-implanted patients over several years. In particular, special attention is devoted to the surgical procedure; to the functional outcome, also in comparison with the performance with cHA, and its impact on the quality of life; to the battery, in terms of its variable duration and surgical replacement; and, finally, to the complication occurrence and rate.


**Table 1.**

*Features of the two fully implantable hearing systems available today; FDA: Food and Drug Administration.*

**93**

**Figure 2.**

**Figure 1.**

*and the driver.*

*The Esteem®, Fully Implantable Middle Ear Device DOI: http://dx.doi.org/10.5772/intechopen.89250*

(**Figure 2**).

less of degree of hearing loss [3].

i.e., the sensor and the actuator (driver) (**Figure 1**).

The implantable components of the Esteem® are represented by a sound processor (SP), powered by a nonrechargeable battery, and two piezoelectric transducers,

The SP titanium case is housed in a temporal bone niche and receives the electrical signals from the sensor cemented to the incus body. After being processed, the signals are sent to the driver cemented to the stapes head, with a vibrational movement that generates the perilymphatic wave for cochlear stimulation

The Envoy Medical Company recommendations for candidacy include moderate to severe types of SNHL whilst its application is discouraged in patients with word recognition score (WRS) in quiet inferior to 40%. Nevertheless, recent reports have shown that Esteem® may provide large amplification ranges up to 2–4 kHz, regard-

*The Esteem® middle ear implant. The sound processor is connected to the two transducers, namely the sensor* 

*The two transducers connected to the sound processor (2) are then placed in contact with the ossicular chain:* 

*The sensor (1) to the incus body and the driver (3) to the stapes head.*

*The Esteem®, Fully Implantable Middle Ear Device DOI: http://dx.doi.org/10.5772/intechopen.89250*

*Advances in Rehabilitation of Hearing Loss*

auditory canal, earmold allergies, and impossibility to use them during water

The advent of AMEI with the stimulation pathway different from the normal (or amplified) sound, i.e., the electromechanical one, has paved the way for the possible theoretical resolution of the above-mentioned annoying cHA-related issues. In fact, these devices are directly coupled to middle or inner ear elements (ossicular chain or part of it, round window membrane) for achieving close-field cochlear stimulation, and should theoretically overcome most of the issues deriving from the obligatory acoustic over-stimulation that needs to be delivered by an external amplifier, such as a cHA. Moreover, all of them leave the external ear canal free, so as to improve the auditory and physical occlusion issues, as well as the compatibility

In relation to the presence of an external component, the AMEI can be distinguished in semi- or fully implantable devices, this latter term inherently meaning that all their components remain completely invisible under the skin. At the present time, only two fully implantable devices are available for the rehabilitation of sensorineural hearing loss (SNHL): the Carina® (Cochlear, Lane Cove, Australia) and the Esteem® (Envoy Medical Corporation, St. Paul, MN, USA). Both devices have in common the complete allocation inside the skull, while carrying at the same

This last appealing factor is surely playing an important role for the decisionmaking process while counseling with a possible candidate, but it would not be wise to consider it as primary factor for its choice, and anyhow never replacing a preop-

At Sant'Andrea University Hospital, Rome, Italy, an extensive rehabilitative program for hearing impairment has been applied since nearly 15 years, mostly aiming at the resolution of different types and severity of conductive, mixed and SNHL. In particular, from 2007, a series of subjects affected by bilateral SNHL have undergone Esteem® surgical application. The Esteem® (Envoy Medical, St Paul, MN, USA) middle ear implant has recently been reported to be beneficial for individuals affected by moderate-to-severe bilateral SNHL, with low morbidity and complication rate [1, 2]. This device works via a piezoelectric vibratory stimulus on the stapes and thereafter to the inner ear fluids, also vibrating the intact eardrum that plays as natural microphone. Following this physiological route, a natural sound quality is likely to be perceived by preserving auricular filtering (at high frequencies) and leaving the ear canal open, thus eliminating the occlusion effect. The aim of the present report is to highlight specific clinical issues including those that have emerged while following up the Esteem®-implanted patients over several years. In particular, special attention is devoted to the surgical procedure; to the functional outcome, also in comparison with the performance with cHA, and its impact on the quality of life; to the battery, in terms of its variable duration and

surgical replacement; and, finally, to the complication occurrence and rate.

Carina Yes Daily recharge Electromagnetic No

*Features of the two fully implantable hearing systems available today; FDA: Food and Drug Administration.*

**Microphone Battery Stimulation FDA approval (by** 

Piezoelectric Yes

**June 2019)**

contact, physical activities, and overnight, while sleeping).

with external ear canal or middle ear pathologies.

time some major differences, as listed in **Table 1**.

**Essential features of fully implantable AMEI**

Esteem No Periodic surgical

change

erative use or trial with a best-fitted last-generation digital cHA.

**92**

**Table 1.**

The implantable components of the Esteem® are represented by a sound processor (SP), powered by a nonrechargeable battery, and two piezoelectric transducers, i.e., the sensor and the actuator (driver) (**Figure 1**).

The SP titanium case is housed in a temporal bone niche and receives the electrical signals from the sensor cemented to the incus body. After being processed, the signals are sent to the driver cemented to the stapes head, with a vibrational movement that generates the perilymphatic wave for cochlear stimulation (**Figure 2**).

The Envoy Medical Company recommendations for candidacy include moderate to severe types of SNHL whilst its application is discouraged in patients with word recognition score (WRS) in quiet inferior to 40%. Nevertheless, recent reports have shown that Esteem® may provide large amplification ranges up to 2–4 kHz, regardless of degree of hearing loss [3].

#### **Figure 1.**

*The Esteem® middle ear implant. The sound processor is connected to the two transducers, namely the sensor and the driver.*

#### **Figure 2.**

*The two transducers connected to the sound processor (2) are then placed in contact with the ossicular chain: The sensor (1) to the incus body and the driver (3) to the stapes head.*
