Intratympanic Gentamicin

Your doctor has recommended intratympanic gentamicin procedure for you. Below are some common questions and answers about this procedure. 

What is intratympanic gentamicin?

Gentamicin is an antibiotic that is usually given intravenously (through the vein). However, it does have a unique property of being ototoxic – which means that it is harmful to the inner ear, specifically to the balance hair cells and less so the hearing hair cells.

Intratympanic means through the ear drum into the middle ear.  Medicines that are placed  into the middle ear space can be absorbed into the inner ear structures such as the cochlear or balance organ.

So we can give gentamicin through the ear drum, to specifically allow it to get into the inner ear and destroy the balance hair cells.

Why have you been offered intratympanic gentamicin?

When patients have surgery for vestibular schwannoma (also known as acoustic neuroma) the balance nerve is sacrificed. This means they suffer an immediate loss of balance and have spinning vertigo for many days after. To help them recover good long term balance we need to mobilise them, which is difficult immediately after surgery.

We have found that if patients have lost their balance function slowly beforehand and perform rehabilitation exercises before surgery then they do significantly better in the immediate post operative period and have better long term balance adaptation.   

Sometimes we also offer this to patients with small non-operative tumours who have significant balance issues, and to patients with recurrent vertigo due to Meniere’s Disease.

What to expect during the procedure

Local anaesthetic is injected into the ear. It feels like a bee-sting lasting a few seconds.

Gentamicin is then injected through the drum into the middle ear, filling it entirely. You may feel pressure and the hearing will decrease temporarily.  You may also feel some medicine going down the back of the nose and throat area as it drains down the Eustachian tube.

At this point, it is important that you try not to swallow or talk; each time you do this, some of the gentamicin drains down the Eustachian tube.

You will be asked to lie for 15-20 minutes with the injected ear facing the ceiling.

The intention is to allow the gentamicin to be in the middle ear so it gets absorbed as much as possible into the inner ear.

What to expect after the procedure

Most patients feel very little difference after the injection other than a numb and blocked ear that resolves after 24 hours. However, some patients may have some burning or stinging sensation for 1-2 days after. Paracetamol or simple non-steroidals are usually enough.

Most people are well enough to drive afterwards, although occasionally patients can have no more than a few hours of bad spinning vertigo. It is best to have a driver with you at least for your first injection.

Balance starts getting affected usually after 1-2 weeks. Most people complain of a “drunk” feeling.

It is very important during this period to challenge your balance system; walking on uneven surfaces, moving the head quickly and lots of motions and movements. This will help your balance adapt quickly.

Why does it sometimes hurt?

We cannot inject local anaesthetic directly into the ear drum, so we rely on the local to trickle down towards the ear drum. You won’t feel a sharp pain, but you may still feel pressure and some discomfort.  Also not commonly, some people do experience some pain from the gentamicin itself in the middle ear or down the Eustachian tube.

Why are different temperatures of gentamicin used?

Intratympanic gentamicin is usually given as a series of 2-3 injections in total to ensure that as many as possible balance hair cells are destroyed.

Sometimes the last dose is given as an “ice cold” injection.  If there is residual balance function remaining, then during the ice-cold injection you will experience spinning. This then lets us know that you require to lie for a further 20 minutes. If however there is no reaction, then we know your balance has been completely obliterated on that side and you can get up and leave immediately.

Occasionally we bring the gentamicin to body temperature if there has been a previous painful reaction to the gentamicin.

Will I get hearing loss?

10% of patients receiving Intratympanic gentamicin can get a hearing loss. However, your doctor would have weighed up the benefit of the procedure and your residual hearing. With vestibular schwannoma surgery you will have complete hearing loss anyway.