The pre-chorda and post-chorda tympani approach in endoscopic stapes surgery based on the chorda tympani nerve classification.

Abstract

In most stapes surgeries, the posterior ear canal is enlarged and a piston is inserted posterior to the chorda tympani nerve (post-chorda tympani approach; Post C). Although reports vary, some indicate that more than 60% of the patients experience lingual symptoms following surgery. Endoscopic surgery may permit an anterior approach to the nerve (pre-chorda tympani approach; Pre C). Herein, we propose a suitable approach for endoscopic stapes surgery based on the classification of the chorda tympani nerve. We retrospectively reviewed the medical records of 23 patients who underwent endoscopic stapes surgery at our institution between 2019 and 2021. The nerve classification previously reported, the modified nerve classification (attached long type is divided into Category 1: lenticular process is visible with 0° endoscope and Category 2: not visible), selected approach (Pre C or Post C), use of a 30° endoscope, and manipulation of the nerve (number of contacts and traction, with or without suction, with or without malposition or extension and amputation, and damage score) were evaluated. The damage score was significantly lower in the Pre C group (p < 0.05); however, using this approach for all cases is not desirable owing to the high risk of damage to the nerve during posterior malpositioning. The Post C should be used for the detached and attached long 1 types, while the Pre C with a 30° endoscope should be used for the attached long 2, attached short, ultrashort, and external auditory canal types.