Some people who undergo organ transplants lose their hearing as a side-effect of the antibiotics and immunosuppressive drugs they have to take. And while cochlear implants that restore hearing can raise the risk of getting ear infections and are thus not normally considered for patients with weakened immune systems, Kenneth Charles Iverson and Brian John McKinnon, of the Medical College of Georgia (MCG) at Georgia Health Sciences University in Augusta, suggest that under certain conditions they may be safe and effective for kidney transplant patients.
They write about their study in the January issue of the American Journal of Otolaryngology.
The inner ear contains a finite number of dark cells. These produce the tiny amounts of fluid that help transform sound vibrations into neural signals that can be processed by the brain.
These dark cells have a very active metabolism: something that antibiotics are designed to target in bacteria.
When a recipient patient receives a donated organ, they have to keep taking antibiotics and other drugs to stop their immune system rejecting it.
So long term use of these drugs can result in deafness, because destruction of the dark cells also destroys the ability to make the fluid, and any sound entering the ear is then likely to be incomprehensible.
But not many trasplant patients have cochlear implants because they can increase the risk of infection in the inner ear, and an immune system already weakened by drugs is only likely to increase that risk. (The electrode that connects the cochlear device to the inner ear is a highway not just for sound vibrations but also for viruses and bacteria.)
In fact, people who are not transplant patients who receive cochlear implants usually also have vaccinations to boost their immune response to common infections.
But you can’t do this with transplant patients:
“If you do make the immune system work better, they may reject their organ,” McKinnon, an otologist and neurotologist at the MCG, told the press.
So McKinnon and Iverson, who is Chief Resident in otolaryngology at MCG, conducted a small retrospective study to find out if there was any way that transplant patients could benefit from cochlear implants without raising these risks.
And what they found was that if the patient waits at least six months after the transplant, and takes the correct antibiotics before and after receiving the cochlear implant, then they may be able to restore their hearing without raising the health risk.
The study focuses on two patients who had cochlear implants after receiving new kidneys.
One patient was a 47-year-old woman who became very deaf after being treated in intensive care with several powerful antibiotics for an infection that set in after receiving a kidney from a living family member.
She received her cochlear implant 18 months after the infection and 6 years after her kidney transplant. Before the cochlear implant surgery she received an intravenous antibiotic, and afterwards she took an oral antibiotic for a week. She stayed on her usual transplant medication throughout.
13 months after the cochlear implant surgery, her hearing was essentially back to normal. Unfortunately, she died two years after her implant, from health problems not related to it.
The other patient was a 50-year-old man who received his kidney from a deceased donor. He lost his hearing six weeks after a severe brain infection. He had surgery to fit a cochlear implant 7 months after the kidney transplant, and underwent similar antibiotic treatment as the female patient. 14 months later, around 75% of his hearing was restored.
Iverson and McKinnon write that the “study adds to the growing evidence that successful cochlear implantation can be achieved in appropriately selected renal transplant patients”.
Written by Catharine Paddock PhD