Categorization of Chorda Tympani

By June 7, 2019

Matsumoto, Yu1; Uranaka, Tsukasa1; Hoshi, Yujiro1; Kashio, Akinori1; Iwasaki, Shinichi1; Yamasoba, Tatsuya1
1 Department of Otorhinolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.

Anatomical study of chorda tympani is rare. Wide field of view of transcanal endoscopic ear surgery can depict the chorda tympani running through the middle ear.

– Study Design: Retrospective case review.
– Setting: Tertiary referral center.
– Patients: Among 192 cases of 162 patients who underwent transcanal endoscopic ear surgery from August 2013 to June 2018, middle ear malformations, revision surgeries, myringoplasty cases, cholesteatoma that involved the chorda tympani nerve, were excluded.
– Intervention(s): An intraoperative photo that depicts chorda tympani was selected for each patient. The pictures were classified into five groups. Preoperative CT scans were also analyzed to match the classification.

– Main Outcome Measure(s): 101 patients, 128 ears were enrolled in this study. The tympanic segment of the chorda tympani could be classified into five groups such as External Auditory Canal (EAC) type, Separate type, Adjunct long type, Adjunct short type, and Rivinus type.
– Results: The number of patients who had their chorda tympani classified as EAC type, Separate type, Adjunct long type, Adjunct short type, and Rivinus type was 7 (5.5%), 6 (4.7%), 84 (65.6%), 18 (14.0%), 13 (10.2%), respectively. Preoperative CT scans could distinguish between the EAC type, Separate and Adjunct long types, and Adjunct short and Rivinus types.
Conclusion: Tympanic segment of the chorda tympani can be classified into five groups, and these groups can be partially predicted with preoperative CT.