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A Rare Origin of Chorda Tympani Nerve (Need to Assess Facial Nerve Anatomy during Facial Recess Approach for Cochlear Implantation)

Shraddha Jain*
Department of Otorhinolaryngology and Head and Neck Surgery, Jawaharlal Nehru Medical College, Datta Meghe Institute of Medical Sciences (DMIMSU), India


*Corresponding author: Shraddha Jain, Department of Otorhinolaryngology and Head and Neck Surgery, Jawaharlal Nehru Medical College, DMIMSU, Sawangi, Wardha, Maharashtra, India 442004


Published: 02 Nov, 2017
Cite this article as: Jain S. A Rare Origin of Chorda Tympani Nerve (Need to Assess Facial Nerve Anatomy during Facial Recess Approach for Cochlear Implantation). Ann Clin Otolaryngol. 2017; 2(4): 1024.

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We encountered one rare case of origin of chorda tympani nerve at the level of lateral semi-circular canal, during cadaveric temporal bone dissection. In 1955, Haynes had observed considerable variation in the point where chorda tympani nerve (CTN) joins the facial nerve [1]. He contradicted the popular belief that the chorda tympani joins the facial nerve at a fixed distance above the stylomastoid foramen. In one specimen, he found origin of the chorda tympani almost outside the stylomastoid foramen (SMF), whereas in others it joined the trunk almost at the level of the semicircular canal. Gray’s Anatomy describes the chorda tympani nerve arising at a fixed distance of 6mm from the SMF [2]. In 1967, Durcan et al. also reported distance of CTN from SMF to be 6 mm [3]. Kullman GL et al. [4] (1971), in their 100 temporal bone dissections, noted great variability in the origin of CTN nerve, from 1.2mm distal to 10.9mm proximal to SMF ( mean of 5.3 mm).


Figure 1

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Figure 1
Variation in origin of chorda tympani nerve at the level of lateral semicircular canal. CTN, chorda tympani nerve; VFN, vertical facial nerve; HFN, horizontal facial nerve; LSC, lateral semicircular canal; S, Stapes.

References

  1. Haynes DR. The relations of the facial nerve in the temporal bone. Ann R Coll Surg Engl. 1955;16(3):175-85.
  2. Davies DV and Coupland RE, In Gray’s Anatomy, Davies DV, Ed, p. 1161, Longmans, Green, and Co, London, UK, 34th edition, 1967.
  3. Durcan DJ, Shea JJ, Sleeckx JP. Bifurcation of the facial nerve. Arch Otolaryngol. 1967;86(6):619-631.
  4. Kullman GL, Dyck PJ, Cody DT. Anatomy of the mastoid portion of the facial nerve. Arch Otolaryngol. 1971;93(1):29-33.