F. Hoppe

Given our limited scope, this chapter offers only a brief overview of implantable hearing aids. This type of surgery is usually reserved for specialized centers.

Surgical Principle

Sound is transmitted to the inner ear by bone conduction through an osseointegrated titanium post in the temporal squama, which is connected directly to an external hearing aid with an electromagnetic transducer.

Indications

Inoperable congenital aural atresia.

Conductive hearing loss with intractable otorrhea in the setting of chronic otitis media.

Sensorineural hearing loss in a patient with persistent otitis externa.

Surgical Technique

The surgery is usually performed under local anesthesia. A titanium post is implanted into a hole 3–4 mm deep that has been drilled into the temporal squama. The surrounding scalp is thinned and depilated. The procedure may be performed in one or two stages. In a two-stage procedure, a titanium abutment is screwed onto the post after a healing period of 8–12 weeks, and the sound processor is attached to the abutment.

Surgical Principle

Sound is transmitted directly to an intact, mobile ossicular chain by an electromagnetic vibrator. The amplifier is implanted in a postauricular bone bed, and the receiver is worn externally behind the ear. Three different systems are currently available on the market.

Indications

Sensorineural hearing loss not correctible with conventional hearing aids (e. g., severe recurrent otitis externa, anatomic obstacles to wearing a hearing aid in the ear canal). Different indications apply to different implants, depending on the level of inner ear function.

Surgical Technique

A vibrator (active or passive) is coupled to the ossicular chain (long process of the incus, body of incus) through a mastoidectomy. The chordofacial angle may also be drilled open.

The amplifier is implanted in a postauricular bone bed.

Surgical Principle

A multichannel electrode is positioned into the cochlea through a mastoidectomy, and a processor is implanted behind the ear.

Indications

Congenital or acquired bilateral deafness in cases where the auditory nerve is responsive to electrical stimulation (promontory test) and the inner ear is anatomically normal. Cochlear implantation can be done in patients as young as 4 months of age.

Contraindications