The reasons for performing an auditory brainstem implant, the stages of the procedure, all the complications that may occur, in addition to the expectations of success, and the best centers to perform it in Turkey.
What is an auditory brainstem implant (ABI)?
Auditory brainstem implant is a surgically implanted device that provides a better sense of sound. Auditory brainstem implant is a treatment option for people with severe hearing loss due to damage to the inner ear (cochlear) and the auditory nerve.
Patients’ response to the auditory brainstem implant varies widely, with many achieving better phonemic awareness and improved lip-reading ability, and others may be able to recognize a sound, word, or sentence.
Who is a good candidate for an auditory brainstem implant?
An auditory brainstem implant was first developed for people with neurofibromatosis type 2 (NF2) who have lost their hearing as a result of auditory nerve damage (sensorineural hearing loss).
Neurofibromatosis (NF2) is a rare genetic disorder in which tumors form along the auditory nerve.
These tumors are called acoustic neuromas (also known as vestibulocochlear nerve tumors).
These tumors are treated with surgical removal/radiation treatments that may cause permanent damage to the auditory nerves and deafness in both ears.
In this case, the patient does not benefit from the use of hearing aids or electronic cochlear implants.
Since auditory brainstem transplantation was first used in people with neurofibromatosis (NF2), a group of people have found benefit from the procedure.
This category includes:
- For babies born without a functioning auditory nerve in one ear (aplasia) or an improperly developed auditory nerve (hypoplasia).
- People with deafness caused by an abnormal shape of the inner ear (cochlea), incomplete development of the inner ear (hypoplasia), lack of inner ear structures (cochlear aplasia), or overgrowth of bone in the inner ear (otosclerosis or cochlear ossification).
- Trauma and damage to the auditory nerve caused by fractures of the temporal bone (the skull bone above the ear) on both sides of the head.
- Have other causes of severe deafness that do not improve with hearing aids or cochlear implants.
How does an auditory brainstem implant work?
An auditory brainstem implant consists of two separate parts. One part, which is worn on top of the ear, is called the processor.
This part contains a microphone that picks up ambient sounds.
The processor converts the sounds into an electrical signal and sends the signals to the implant, which consists of a receiver implanted just under the skin on the side of the head and terminating in an electronic receiver.
This receiver is placed on the surface of the brain stem in an area called the cochlear nerve.
The electrodes on it stimulate different types of neurons in the brain stem, creating acoustic sensations in response to this stimulation.
Auditory brainstem implants use a similar technology to that used in cochlear implants.
The main difference is where and what the electrodes stimulate.
With a cochlear implant, the electrodes stimulate the auditory nerve in the cochlea.
With an auditory brainstem device, the electrodes are attached directly to the brainstem, bypassing the cochlea and the auditory nerve altogether.
What tests are done before an auditory brainstem implant?
Before an auditory brainstem transplant, specialized medical teams make sure it is an appropriate option for the case.
First, doctors collect a complete medical history (medical history, audiogram, etc.) and take x-rays to examine the condition of the cochlea, auditory nerve, and surrounding structures. These tests include CT scans and MRIs.
MRIs help visualize the anatomy of soft tissues such as the auditory nerve.
Behavioral testing is also used to determine hearing ability.
A language-communication assessment is performed to examine language development and communication style.
Electrophysiological testing is used to assess the extent and location of hearing loss. A neuropsychological assessment examines the person’s level of brain function (thought, learning and memory, language development, motor abilities, organizational/planning skills, and concentration).
How is auditory brainstem implant surgery performed?
An auditory brainstem implant is a complex surgical procedure performed by a team that typically includes a neurosurgeon, an anesthesiologist, and a neurologist. In addition, an electrophysiologist and audiologist perform extensive testing during the procedure to confirm function and help adjust the position of the implant.
An auditory brainstem implant (ABI) is often performed during acoustic neuroma removal for patients with neurofibromatosis (NF2) who are not expected to preserve their hearing after surgery.
It can also be performed as a separate surgery in some cases, such as previous surgery or radiation therapy.
Or in cases of inner ear abnormalities, after accidents, and other causes of hearing loss that are not candidates for cochlear implant surgery.
What happens after an auditory brainstem transplant?
The typical hospital stay after an auditory brainstem implant is 2 to 4 days.
The stay is longer for patients with neurofibromatosis.
The programming of the device begins in the operating room while the implant is placed in the brainstem.
Auditory brainstem implants (ABI) are usually activated 4 to 6 weeks after surgery.
The programming of the device continues to be adjusted over several days, then monthly for the first year.
Does an auditory brainstem implant restore hearing? What results can be expected?
First, knowing that an auditory brainstem implant does not restore normal hearing is important. But it can provide the following:
- Helps improve vocal awareness.
- Improve the ability to detect and differentiate between sounds (e.g., female vs. male; child vs. adult).
- Improved ability to identify environmental sounds (e.g., barking dogs vs. ringing phones).
- Improve face-to-face communication by improving the ability to read lips.
When examining the results of studies of auditory brainstem implant recipients, those without neurofibromatosis (NF2) showed improved word recognition and had better auditory outcomes than those with NF2.
They achieved proper environmental awareness and developed their language, including simple words and sentences.
The tests showed that the children’s hearing abilities continued to improve in the years following the brainstem transplant.
It’s important to know that results vary widely.
Researchers are still exploring possible causes, which include the cause of the hearing loss, surgical approach, surgeon experience, device design, signal processing, software issues with the device system, and other factors.
It is also important to carefully discuss the expected outcomes with each patient and family before deciding on surgery.
What are the complications of auditory brainstem implant surgery?
Complications of this procedure include cerebrospinal fluid leakage, facial nerve palsy (loss of facial movement due to nerve damage), wound infection, meningitis, incomplete removal of the tumor, and transplant failure (failure to provide useful auditory sensations or movement). As brain stem transplantation is performed under general anesthesia, complications of surgery may include anesthetic complications.
However, the rate of serious complications is considered low, especially when the surgery is performed in a medical facility with experienced staff.
There can also be minor complications that can be easily managed if they arise and usually heal completely.
Is an auditory brainstem implant a type of cochlear implant?
Although the design and function of ear implants are similar, devices implanted in the brainstem are different.
Cochlear implants are typically used in individuals who have cochlear damage but still have an intact auditory nerve.
Cochlear implants bypass and repair damaged areas of the inner ear.
Where a set of electrodes are used to stimulate the auditory nerve directly, the auditory nerve transmits the impulses generated by the implant to the brain, and the brain in turn interprets the incoming signals as sound.
A brain stem implant bypasses the auditory nerve and connects the device to the brain stem and is therefore considered more complex.
Cost of auditory brainstem implant in Turkey
The cost of an auditory brainstem implant varies depending on the type used, the manufacturer, the doctor who will perform the procedure, and the quality of the hospital, but in general, the cost ranges between 30,000 and 55,000 USD.
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