Flexible Brainstem Implant May Restore Hearing When Cochlear Implants Can’t
A new flexible auditory brainstem implant may restore better hearing for patients with severe nerve or inner ear damage.
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Researchers co-led by Mass General Brigham have reported a new type of auditory brainstem implant (ABI) that may offer improved hearing for people with deafness caused by neurofibromatosis type 2 (NF2) or severe inner ear abnormalities. These conditions can prevent the use of cochlear implants, the standard treatment for many with hearing loss.
Auditory brainstem implant (ABI)
A device that restores hearing by electrically stimulating the brainstem’s cochlear nucleus when the auditory nerve or inner ear is damaged.
Neurofibromatosis type 2 (NF2)
A genetic disorder that causes benign tumors on nerves responsible for hearing and balance, often resulting in hearing loss.The study, published in Nature Biomedical Engineering, describes a flexible ABI designed to overcome limitations of current devices. This new implant directly stimulates the brainstem’s cochlear nucleus, bypassing damaged auditory pathways to restore auditory signals.
Cochlear nucleus
A brainstem region that processes sound signals received from the cochlea, essential for hearing.The device was developed through a decade-long collaboration between scientists at Mass Eye and Ear, part of Mass General Brigham and researchers at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland. It consists of an elastic multilayer structure containing ultra-thin platinum electrodes embedded in silicone, allowing the implant to closely conform to the curved surface of the brainstem.
In contrast, conventional ABIs use stiff electrodes that do not match the brainstem’s shape well, limiting the effectiveness of stimulation and often causing discomfort. These devices typically provide only basic sound awareness, which can support lip reading but do not restore detailed hearing.
“While cochlear implants are life-changing for many, there remains a group of patients for whom current technology falls short,” said Dr. Daniel J. Lee.
The novel flexible electrodes were created using advanced thin-film processing techniques to enable precise, high-resolution stimulation. Preclinical testing in two macaque monkeys demonstrated that the animals could reliably distinguish different patterns of stimulation over several months of behavioral testing. This indicates the potential for more refined auditory perception compared to current ABIs.
While cochlear implants have transformed hearing for many patients, they are not suitable for all, particularly those with NF2 or other severe inner ear conditions. This new research lays the foundation for an ABI that could improve hearing outcomes and reduce side effects for this group.
Reference: Trouillet A, Revol E, Coen FV, et al. High-resolution prosthetic hearing with a soft auditory brainstem implant in macaques. Nat Biomed Eng. 2025. doi: 10.1038/s41551-025-01378-9
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