Development and Evaluation of a Novel Transcanal Catheter for Delivery of Hypothermia to the Inner Ear.

Mild therapeutic hypothermia (MTH) has demonstrated neuroprotective effects in the cochlea, particularly against noise-induced and electrode insertion trauma, by reducing inflammation and oxidative stress. Prior cadaveric studies have shown that localized cochlear cooling can be achieved using a probe placed on the promontory or a surface cooling device placed on the mastoid. While the effects of MTH on the vestibular system remain unstudied, its proximity and physiological similarity to the cochlea suggest potential benefits. We aimed to develop the first noninvasive, localized MTH device for use in the clinical environment, capable of targeting both cochlear and vestibular structures without obstructing the surgical field. A custom-designed, saline-filled cooling catheter with a balloon tip was designed to be positioned in the ear canal adjacent to the tympanic membrane. Temperature measurements were recorded from the round window, oval window, and all three semicircular canals, and compared to whole-head temperature fluctuations measured via the nasopharynx in human cadaver samples. Thermistors recorded an average temperature reduction of 4-6°C during a 30-minute protocol in cadaver heads. Nasopharyngeal temperature remained stable throughout. Furthermore, a numerical model was used to evaluate the theoretical temperature reduction achieved through ear canal cooling. The computational model further validated the experimental measurements from the cochlea. In conclusion, these findings demonstrate that cochlear and vestibular hypothermia can be effectively induced using an external cooling system positioned in the ear canal, supporting the development of a more accessible and practical clinical approach to protect the inner ear during invasive procedures.