Middle Ear Implants (MEI)

Middle Ear Implants Overview

Middle ear implants are hearing aids which are surgically implanted into the middle ear and either attaches onto one of the middle ear bones or to the round window between the middle ear and the cochlea. The attachment enhances the transmission of the sound waves to the cochlea without the need for ear moulds. Middle ear implants can be fully implantable or semi-implantable.

Working Principle

A middle ear implant consists of two components: an external part (which is the Processor) and the internal part, which is implanted surgically. The function of the processor is to transmit sound to the internal part of the hearing implant. This contains a receiver just below the skin to collect the sound from the processor, together with the implant, which is surgically implanted to one of the bones in the middle ear, or attached near to the oval window of the cochlea.

Middle Ear Implant Working
Fig 1: Middle Ear Implant
The implant functions by moving the bones of the middle ear, or by vibrating the oval window of the cochlea. In both the case, the purpose is to amplify sounds by adding extra movement into the natural hearing pathway. The middle ear implant depends on a working cochlea and hearing nerve.

  1. The sound processor captures sound, processes it and transmits it to the implant.
  2. The implant sends the digital sound to the actuator.
  3. The actuator converts the digital signal to mechanic vibrations.
  4. Mechanical vibrations then stimulate the cochlea via the ossicular chain or round window.,

Who will benefit from middle ear implant?

A middle ear implant is offered to individuals who present with a hearing loss but who are unable to manage with conventional hearing aids. A patient can present with a stable sensorineural hearing loss or have a conductive or mixed hearing loss. Some of the medical issues that present can be:

  • Chronic otitis externa
  • Eczema of the ear
  • Psoriasis
  • Allergies
  • Absence of a pinna
  • Partial or complete stenosis of the ear canal
  • Exostoses (external ear bone growth closing the ear canal)
  • Furunculosis
  • Excessive wax production or perspiration which affect hearing aid usage