Auditory Brainstem Implant by Prof. Dr. Thomas Lenarz

The auditory brainstem implant (ABI) by Prof. Dr. Thomas Lenarz represents the final frontier in hearing restoration, specifically designed for those with a non-functional or absent inner ear or auditory nerve. While a cochlear implant requires a functioning nerve to carry signals to the brain, the ABI bypasses the ear entirely. During this highly complex neurosurgical procedure, Prof. Lenarz places a micro-electrode array directly onto the cochlear nucleus in the brainstem. This allows electrical sound signals to be transmitted directly to the brain's processing center, providing a sense of sound to patients with conditions such as neurofibromatosis type II (NF2) or severe congenital malformations where no other hearing technology can help. Performing this procedure requires dual expertise in advanced otology and neurosurgery, a hallmark of Prof. Lenarz’s practice at Hannover Medical School. The surgical approach involves intraoperative electrophysiological monitoring to map the brainstem in real time. Because the cochlear nucleus is located near vital centers that control breathing and heart rate, this monitoring is essential to ensure the electrodes are placed with surgical exactness. Clinical data from one of the world’s largest ABI cohorts shows that while the primary goal is often environmental sound awareness and lip-reading support, a significant percentage of patients, especially those without NF2, can achieve varying levels of open-set speech recognition, a milestone once thought impossible for this technology. The diagnostic journey for an auditory brainstem implant includes functional MRI (fMRI) and diffusion tensor imaging (DTI) to visualize the neural pathways leading to the auditory cortex. These scans allow the specialist to assess whether the brain's hearing center is ready to receive and interpret new electrical stimuli. Post-operatively, the package proceeds to a specialized tuning phase, during which the implant's electrodes are meticulously programmed to match the patient’s unique neurological responses.