耳鼻科ジャーナル

Anatomical Variation-Notch in Long Process of Incus Due to Chorda Tympani Nerve in Two Cases

Dalmia D, Behera SK and Bhatia JS

Introduction: The chorda tympani nerve takes origin from the mastoid portion of the facial nerve.Then it separates from the main trunk of facial nerve approximately 4 mm proximal to the stylomastoid foramen.Among the three ear ossicles present in middle ear, Incus is most stable ossicle showing least number morphological variation. Our aim is to describe a rare anatomical variation of incus i.e. a notch in the long process of incus which fits the chorda tympani nerve. This study will help otologic surgeons while performing operative procedures in a better way by understanding the anatomical details of middle ear and preventing chorda tympani nerve to iatrogenic trauma.

Method: We performed 1500 tymapnoplasties and tympanomastoid surgeries and about 500 exploratory tympanotomies for last 10 years for various otological problems in our institution Dr BAM Central Railway Hospital. Any morphological variations were noted during surgeries.

Case report: We found a rare anatomical variation of chorda tympani nerve in two cases where the nerve was found to be buried into the long process of Incus. Out of different middle ear surgeries we performed in last 10 years, Incus had minimum morphological variations in the ossicles. Although there are few studies which shows the presence of notch in the short process of incus but no study shows presence of notch in long process of incus so far.

Conclusion: The knowledge of these anatomical variations of incus and course of chorda tympani will help in dealing with difficulties encountered during performing the surgical procedures and thereby it will help to preserve chorda tympani nerve.