Skip to content

Hearing Preservation

Cochlear hearing preservation

The cochlea sits behind two thin windows. Middle-ear surgery works next to them, and sometimes through them. Protecting the hair cells inside is the first duty of the surgeon.

Line illustration of the ear showing the outer ear, eardrum, ossicles and cochlea

Why the cochlea is at risk

The inner ear is sealed fluid. Middle-ear surgery threatens it in several ways: mechanical energy transmitted through the ossicles (drilling on a mobile chain, manipulating a fixed one), direct opening of the oval or round window during stapes surgery or after erosion, loss of perilymph, infection reaching the inner ear, and, more subtly, the noise of surgical drills and suction. Hair cells damaged by any of these do not recover.

The clinical result ranges from a small high-frequency loss the person never notices, through a measurable drop in bone conduction, to a profound loss in the operated ear.

Where the risk concentrates

  • Stapedotomy opens the inner ear deliberately. Small-fenestra technique, gentle handling, correct prosthesis length and sealing of the fenestra reduce the risk to well under 1% for a profound loss, with smaller high-frequency shifts more common.
  • Revision stapes surgery carries a several-fold higher risk because of scar and a previously opened window.
  • Ossiculoplasty onto the footplate, and removal of disease from the oval-window niche, risk the inner ear when the footplate is disturbed.
  • Cholesteatoma eroding the lateral semicircular canal or the footplate creates a fistula that must be managed with great care.
  • Drilling near an intact chain transmits energy to the cochlea; the chain is disconnected or the drill kept clear.

Selection matters as much as technique

Some ears should not be operated because the cochlear risk outweighs any gain: an only-hearing ear, an ear where bone conduction has already deteriorated, a third-window lesion mimicking otosclerosis, an ear where the person could not tolerate the outcome of a rare complication. Recognising these is as much a part of cochlear preservation as anything done in theatre.

Technique and evidence

In stapes surgery, small-fenestra stapedotomy shows fewer sensorineural complications than total stapedectomy in comparative series. Laser fenestration avoids mechanical footplate trauma, but randomised trials have not consistently shown a difference in bone-conduction outcome versus micro-drill or perforator in experienced hands. Avoid suction over the open vestibule; seal the fenestra; choose prosthesis length to avoid utricular contact; consider local anaesthesia in selected cases so that the patient can report vertigo. Perioperative corticosteroids are used by some surgeons with limited high-quality evidence. Drill-induced noise exposure is real; disarticulate the chain before drilling the attic in canal-wall-up procedures where feasible. In labyrinthine fistula, matrix over the fistula may be left and removed at a second stage, or removed with immediate sealing, depending on size and the contralateral ear.

Verifying preservation

The marker is bone conduction: thresholds before surgery, and again once the ear has settled. A change of more than 10 dB in the average, or a new high-frequency loss, is a preservation failure even if the air-bone gap has closed beautifully. Speech discrimination should be unchanged. And the person should be asked whether tinnitus or sound quality has changed. Preservation that is not measured has not been demonstrated.

This page provides general educational information. It cannot replace an individual assessment, which depends on a full history, examination, audiometry and, where relevant, imaging. If you have sudden hearing loss, severe pain, facial weakness, severe dizziness or discharge with fever, seek medical care promptly.