Middle ear implant

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A middle ear implant is a hearing device that is surgically implanted into the middle ear. They help people with conductive, sensorineural or mixed hearing loss to hear. [1]  

Contents

Middle ear implants work by improving the conduction of sound vibrations from the middle ear to the inner ear. There are two types of middle ear devices: active and passive. Active middle ear implants (AMEI) consist of an external audio processor and an internal implant, which actively vibrates the structures of the middle ear. [2] Passive middle ear implants (PMEIs) are sometimes known as ossicular replacement prostheses, TORPs or PORPs. They replace damaged or missing parts of the middle ear, creating a bridge between the outer ear and the inner ear, so that sound vibrations can be conducted through the middle ear and on to the cochlea. Unlike AMEIs, PMEIs contain no electronics and are not powered by an external source.

PMEIs are the usual first-line surgical treatment for conductive hearing loss, due to their lack of external components and cost-effectiveness. However, each patient is assessed individually as to whether an AMEI or PMEI would bring more benefit. This is especially true if the patient has already had several surgeries with PMEIs.

Active middle ear implant

Parts

An active middle ear implant (AMEI) has two parts: an internal implant and an external audio processor. The microphone of the audio processor picks up sounds from the environment. The processor then converts these acoustic signals into digital signals and sends them to the implant through the skin. The implant sends the signals to the Floating Mass Transducer (FMT): a small vibratory part that is surgically fixed either on one of the three ossicles or against the round window of the cochlea. The FMT vibrates and sends sound vibrations to the cochlea. The cochlea converts these vibrations into nerve signals and sends them to the brain, where they are interpreted as sound. [3]

Indications

AMEIs are intended for patients with mild-to-severe sensorineural hearing loss, as well as those with conductive or mixed hearing loss. They can be used by adults and children over the age of 5. [2]

Sensorineural hearing loss

An AMEI can be beneficial for patients with mild-to-severe sensorineural hearing loss who have an intact ossicular chain and healthy middle ear, but who either cannot wear hearing aids or who do not get sufficient benefit from them. [2] Reasons for not being able to wear hearing aids include earmold allergies, skin problems, narrow, collapsed or closed ear canals, or malformed ears. [1] In cases of sensorineural hearing loss, the FMT is usually attached to the incus. [2]

Conductive or mixed hearing loss

An AMEI is also indicated for patients with conductive or mixed hearing loss with bone conduction thresholds from 45 dB in the low frequencies to 65 dB in the high frequencies. In these cases, the FMT can be coupled to various parts of the middle ear, depending on the patient's pathology:

  • The oval window, causing stimulation of the cochlea in patients without an ossicular chain.
  • The round window, causing reverse stimulation of the cochlea in patients without an ossicular chain.
  • The mobile stapes in patients with absence or fixation of other ossicles, usually in cases of chronic otitis media or malformations. [2]

Efficacy

AMEIs have been shown by several studies to be equal or superior to both hearing aids and bone conduction implants. Lee et al used the PBmax test to study speech intelligibility in patients before and after receiving an AMEI. All patients had used hearing aids pre-implantation. The researchers found that speech intelligibility improved with the AMEI, particularly in patients with a down-sloping hearing loss. [4] These findings were supported by Iwasaki et al, who found that both speech intelligibility and quality of life improved after implantation with an AMEI, applied to the round window. [5]

AMEIs can also offer improved hearing performance over bone conduction implants for patients with mixed hearing loss. Mojallal et al found that patients whose mixed hearing loss was treated with an AMEI experienced both better word recognition and speech understanding in noise than those who received a bone conduction implant, providing that their bone conduction pure-tone average (0.5 to 4 kHz) was poorer than 35 dB HL. [6]

Passive middle ear implant

Parts

Passive middle ear implants (PMEI) are ossicular replacement prostheses designed to replace some or all of the ossicular chain in the middle ear.  They create a bridge between the outer ear and the inner ear, so that sound vibrations can be conducted through the middle ear and on to the cochlea

There are two types of PMEIs: tympanoplasty implants and stapes implants.  Tympanoplasty implants (also known as PORPs or TORPs) are suitable for patients with a mobile stapes footplate, ie. a stapes footplate that moves in the normal way. Either a partial or a total tympanoplasty implant can be used, depending on the condition of the stapes. If the stapes is fixed and cannot transfer vibrations to the inner ear, then a stapes implant would be used. [7]

PMEIs are made from different materials including titanium, teflon, hydroxylapatite, platinum, and nitinol, all of which are suitable for use within the human body.  Titanium implants can safely undergo MRIs of up to 7.0 Tesla. [7]

Indications

Tympanoplasty implant

The tympanoplasty implant is indicated in cases of congenital or acquired defects of the ossicular chain, due to e.g.:

It can also be used to treat patients with inadequate conductive hearing from previous middle ear surgery.

Stapes implant

The stapesplasty prosthesis is indicated in cases of congenital or acquired defects of the stapes due to e.g.:

  • Otosclerosis
  • Congenital fixation of the stapes
  • Traumatic injury
  • Malformation of the ossicular chain/middle ear

It can also be used to treat patients with inadequate conductive hearing from previous stapes surgery.

See also

Related Research Articles

<span class="mw-page-title-main">Middle ear</span> Portion of the ear internal to the eardrum, and external to the oval window of the inner ear

The middle ear is the portion of the ear medial to the eardrum, and distal to the oval window of the cochlea.

<span class="mw-page-title-main">Otosclerosis</span> Condition characterized by an abnormal bone growth in the middle ear

Otosclerosis is a condition of the middle ear where portions of the dense enchondral layer of the bony labyrinth remodel into one or more lesions of irregularly-laid spongy bone. As the lesions reach the stapes the bone is resorbed, then hardened (sclerotized), which limits its movement and results in hearing loss, tinnitus, vertigo or a combination of these. The term otosclerosis is something of a misnomer: much of the clinical course is characterized by lucent rather than sclerotic bony changes, so the disease is also known as otospongiosis.

Stapedectomy is a surgical procedure in which the stapes bone is removed from the middle ear and replaced with a prosthesis.

<span class="mw-page-title-main">Hearing test</span> Evaluation of the sensitivity of a persons sense of hearing

A hearing test provides an evaluation of the sensitivity of a person's sense of hearing and is most often performed by an audiologist using an audiometer. An audiometer is used to determine a person's hearing sensitivity at different frequencies. There are other hearing tests as well, e.g., Weber test and Rinne test.

Bone conduction is the conduction of sound to the inner ear primarily through the bones of the skull, allowing the hearer to perceive audio content even if the ear canal is blocked. Bone conduction transmission occurs constantly as sound waves vibrate bone, specifically the bones in the skull, although it is hard for the average individual to distinguish sound being conveyed through the bone as opposed to the sound being conveyed through the air via the ear canal. Intentional transmission of sound through bone can be used with individuals with normal hearing — as with bone-conduction headphones — or as a treatment option for certain types of hearing impairment. Bones are generally more effective at transmitting lower-frequency sounds compared to higher-frequency sounds.

<span class="mw-page-title-main">Ear</span> Organ of hearing and balance

An ear is the organ that enables hearing and body balance using the vestibular system. In mammals, the ear is usually described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear consists of the pinna and the ear canal. Since the outer ear is the only visible portion of the ear in most animals, the word "ear" often refers to the external part alone. The middle ear includes the tympanic cavity and the three ossicles. The inner ear sits in the bony labyrinth, and contains structures which are key to several senses: the semicircular canals, which enable balance and eye tracking when moving; the utricle and saccule, which enable balance when stationary; and the cochlea, which enables hearing. The ear is a self cleaning organ through its relationship with earwax and the ear canals. The ears of vertebrates are placed somewhat symmetrically on either side of the head, an arrangement that aids sound localization.

<span class="mw-page-title-main">Conductive hearing loss</span> Medical condition

Conductive hearing loss (CHL) occurs when there is a problem transferring sound waves anywhere along the pathway through the outer ear, tympanic membrane (eardrum), or middle ear (ossicles). If a conductive hearing loss occurs in conjunction with a sensorineural hearing loss, it is referred to as a mixed hearing loss. Depending upon the severity and nature of the conductive loss, this type of hearing impairment can often be treated with surgical intervention or pharmaceuticals to partially or, in some cases, fully restore hearing acuity to within normal range. However, cases of permanent or chronic conductive hearing loss may require other treatment modalities such as hearing aid devices to improve detection of sound and speech perception.

<span class="mw-page-title-main">Weber test</span> Screening test for hearing

The Weber test is a screening test for hearing performed with a tuning fork. It can detect unilateral (one-sided) conductive hearing loss and unilateral sensorineural hearing loss. The test is named after Ernst Heinrich Weber (1795–1878). Conductive hearing ability is mediated by the middle ear composed of the ossicles: the malleus, the incus, and the stapes. Sensorineural hearing ability is mediated by the inner ear composed of the cochlea with its internal basilar membrane and attached cochlear nerve. The outer ear consisting of the pinna, ear canal, and ear drum or tympanic membrane transmits sounds to the middle ear but does not contribute to the conduction or sensorineural hearing ability save for hearing transmissions limited by cerumen impaction.

The Rinne test is used primarily to evaluate loss of hearing in one ear. It compares perception of sounds transmitted by air conduction to those transmitted by bone conduction through the mastoid. Thus, one can quickly screen for the presence of conductive hearing loss.

Unilateral hearing loss (UHL) is a type of hearing impairment where there is normal hearing in one ear and impaired hearing in the other ear.

<span class="mw-page-title-main">Bone-anchored hearing aid</span>

A bone-anchored hearing aid (BAHA) is a type of hearing aid based on bone conduction. It is primarily suited for people who have conductive hearing losses, unilateral hearing loss, single-sided deafness and people with mixed hearing losses who cannot otherwise wear 'in the ear' or 'behind the ear' hearing aids. They are more expensive than conventional hearing aids, and their placement involves invasive surgery which carries a risk of complications, although when complications do occur, they are usually minor.

<span class="mw-page-title-main">Round window</span> Opening in the ear

The round window is one of the two openings from the middle ear into the inner ear. It is sealed by the secondary tympanic membrane, which vibrates with opposite phase to vibrations entering the inner ear through the oval window. It allows fluid in the cochlea to move, which in turn ensures that hair cells of the basilar membrane will be stimulated and that audition will occur.

Hearing loss with craniofacial syndromes is a common occurrence. Many of these multianomaly disorders involve structural malformations of the outer or middle ear, making a significant hearing loss highly likely.

<span class="mw-page-title-main">Pure-tone audiometry</span> Medical test

Pure-tone audiometry is the main hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss and thus providing a basis for diagnosis and management. Pure-tone audiometry is a subjective, behavioural measurement of a hearing threshold, as it relies on patient responses to pure tone stimuli. Therefore, pure-tone audiometry is only used on adults and children old enough to cooperate with the test procedure. As with most clinical tests, standardized calibration of the test environment, the equipment and the stimuli is needed before testing proceeds. Pure-tone audiometry only measures audibility thresholds, rather than other aspects of hearing such as sound localization and speech recognition. However, there are benefits to using pure-tone audiometry over other forms of hearing test, such as click auditory brainstem response (ABR). Pure-tone audiometry provides ear specific thresholds, and uses frequency specific pure tones to give place specific responses, so that the configuration of a hearing loss can be identified. As pure-tone audiometry uses both air and bone conduction audiometry, the type of loss can also be identified via the air-bone gap. Although pure-tone audiometry has many clinical benefits, it is not perfect at identifying all losses, such as ‘dead regions’ of the cochlea and neuropathies such as auditory processing disorder (APD). This raises the question of whether or not audiograms accurately predict someone's perceived degree of disability.

Geoffrey R. Ball (born 1964) is an American physiologist specializing in Biomechanics and the inventor of the VIBRANT SOUNDBRIDGE active middle ear implant – a medical device designed to treat his own hearing loss.

Bone-conduction auditory brainstem response or BCABR is a type of auditory evoked response that records neural response from EEG with stimulus transmitted through bone conduction.

SoundBite Hearing System is a non-surgical bone conduction prosthetic device that transmits sound via the teeth. It is an alternative to surgical bone conduction prosthetic devices, which require surgical implantation into the skull to conduct sound.

In medicine, an ossicular replacement prosthesis is a device intended to be implanted for the functional reconstruction of segments of the ossicles and facilitates the conduction of sound waves from the tympanic membrane to the inner ear. There are two common types of ossicular replacement prostheses, the total ossicular replacement prosthesis (TORP) and partial ossicular replacement prosthesis (PORP). A TORP replaces the entire ossicular chain while a PORP replaces only the incus and malleus but not the stapes. Indications for use of an ossicular replacement prosthesis include:

A direct acoustic cochlear implant - also DACI - is an acoustic implant which converts sound in mechanical vibrations that stimulate directly the perilymph inside the cochlea. The hearing function of the external and middle ear is being taken over by a little motor of a cochlear implant, directly stimulating the cochlea. With a DACI, people with no or almost no residual hearing but with a still functioning inner ear, can again perceive speech, sounds and music. DACI is an official product category, as indicated by the nomenclature of GMDN.

<span class="mw-page-title-main">Diagnosis of hearing loss</span> Medical testing

Identification of a hearing loss is usually conducted by a general practitioner medical doctor, otolaryngologist, certified and licensed audiologist, school or industrial audiometrist, or other audiometric technician. Diagnosis of the cause of a hearing loss is carried out by a specialist physician or otorhinolaryngologist.

References

  1. 1 2 "What is a Middle Ear Implant?". Hearing Link. Retrieved 2021-12-13.
  2. 1 2 3 4 5 Lassaletta, Luis; Sánchez-Cuadrado, Isabel; Espinosa, Juan Manuel; Batuecas, Ángel; Cenjor, Carlos; Lavilla, María José; Cavallé, Laura; Huarte, Alicia; Nuñez, Faustino; Manrique, Manuel; Ramos, Ángel (2019-03-01). "Active Middle Ear Implants". Acta Otorrinolaringologica (English Edition). 70 (2): 112–118. doi:10.1016/j.otoeng.2019.03.006. ISSN   2173-5735. PMID   29555078. S2CID   196458327.
  3. ↑ "Middle ear implant - What is a middle ear implant?". www.hear-it.org. Retrieved 2021-12-13.
  4. ↑ Lee, Hyun-Jin; Lee, Jeon Mi; Choi, Jae Young; Jung, Jinsei (October 2017). "Evaluation of Maximal Speech Intelligibility With Vibrant Soundbridge in Patients With Sensorineural Hearing Loss". Otology & Neurotology. 38 (9): 1246–1250. doi:10.1097/MAO.0000000000001537. ISSN   1537-4505. PMID   28806311. S2CID   4879849.
  5. ↑ Iwasaki, Satoshi; Usami, Shin-Ichi; Takahashi, Haruo; Kanda, Yukihiko; Tono, Tetsuya; Doi, Katsumi; Kumakawa, Kozo; Gyo, Kiyofumi; Naito, Yasushi; Kanzaki, Sho; Yamanaka, Noboru (July 2017). "Round Window Application of an Active Middle Ear Implant: A Comparison With Hearing Aid Usage in Japan". Otology & Neurotology. 38 (6): e145–e151. doi:10.1097/MAO.0000000000001438. ISSN   1537-4505. PMC   5470858 . PMID   28481780.
  6. ↑ Mojallal, Hamidreza; Schwab, Burkard; Hinze, Anna-Lena; Giere, Thomas; Lenarz, Thomas (June 2015). "Retrospective audiological analysis of bone conduction versus round window vibratory stimulation in patients with mixed hearing loss". International Journal of Audiology. 54 (6): 391–400. doi:10.3109/14992027.2014.986690. ISSN   1708-8186. PMID   25735204. S2CID   27767414.
  7. 1 2 "Passive Middle Ear Implants | MED-EL Pro". www.medel.pro. Retrieved 2021-12-13.
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