Aug 2016 Univ of Miami Medicine News
A team of researchers in the Department of Otolaryngology led by Dr Suhrud Rajguru, assistant professor of biomedical engineering and otolaryngology, has developed a novel system for delivering therapeutic hypothermia locally to the inner ear to conserve residual hearing following cochlear implant surgical trauma. Their approach has the potential to ensure that the sensory structures in the cochlea are left undamaged, enabling patients to benefit from future technologies and therapies. Rajguru and his colleagues reported on the safety and efficacy of the procedure in a recently published article in the journal Hearing Research.
While various therapeutic approaches have been studied to prevent implant-induced residual hearing loss, they have shown limited success. “Long-term preservation of a patient’s residual hearing and sensitive neural structures post-implantation is critical,” said Rajguru. “We knew that mild therapeutic hypothermia, exposing nerve cells to low temperatures after trauma and injury, could protect them from damage.” To develop a device to deliver hypothermia that does not require any modifications to the cochlear implant or the surgical procedure, Rajguru and Ilmar Tamames, a doctoral student in his lab, collaborated with Lucent Medical Systems and other Miller School researchers. Once the technology was created, they tested the “cool approach” by delivering localised hypothermia to the middle turn of the cochlea in animal models for 20 minutes before and after implantation using a custom-designed probe perfused with cooled fluorocarbon.
Auditory brainstem responses were recorded to assess the hearing function before and after cochlear implantation, up to 30 days following the procedure. At the conclusion of the trials, inner ears were harvested for histology and cell count. The team discovered a significant loss of residual hearing in the normothermic implant group. By contrast, the residual hearing in the cochleae receiving therapeutic hypothermia was significantly conserved. Histology confirmed a significant loss of outer hair cells in normothermic cochleae receiving the surgical trauma when compared to the hypothermia treated group.
To test the potential for clinical translation, the approach was extended to cadaver temporal bones to study the potential surgical approach and efficacy of the device. In this case, the hypothermia probe was placed next to the round window niche via the facial recess or a myringotomy.
“We successfully achieved a controlled and effective cooling of the cochleae using our approach,” Rajguru said. These results suggest that therapeutic hypothermia during cochlear implantation may reduce traumatic effects of electrode insertion and improve conservation of residual hearing, and can be extended to all inner ear related surgeries.