|Year : 2020 | Volume
| Issue : 3 | Page : 197-198
Aberrant course of facial nerve in the middle ear cavity
Seyed Basir Hashemi1, Reza Jahangiri1, Milad Hosseinialhashemi2, Maryam Naghmachi2
1 Department of Otorhinolaryngology-Head and Neck Surgeries, Shiraz Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
2 Department of Otorhinolaryngology-Head and Neck Surgeries; Student Research Committee, Shiraz Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
|Date of Submission||14-Mar-2020|
|Date of Decision||17-May-2020|
|Date of Acceptance||18-May-2020|
|Date of Web Publication||22-Dec-2020|
Dr. Reza Jahangiri
Khalili Street, Khalili Hospital, Shiraz
Source of Support: None, Conflict of Interest: None
Facial nerve (FN) course anomaly is often found in patients with congenital aural atresia or other ear anomaly, but in this case report, we report an abnormal FN course with dehiscent facial canal found in a patient with congenital conductive hearing loss without any accompanying auricular deformity or cholesteatoma.
Keywords: Aberrant course of facial nerve, congenital ear anomaly, middle ear exploration
|How to cite this article:|
Hashemi SB, Jahangiri R, Hosseinialhashemi M, Naghmachi M. Aberrant course of facial nerve in the middle ear cavity. Indian J Otol 2020;26:197-8
| Introduction|| |
Facial nerve (FN) course anomaly is often found in patients with congenital aural atresia., The most common anomalous portion of the FN is the tympanic portion overlying the oval window. Facial canal dehiscence of the tympanic portion may be the cause for the deviant course of FN. Facial canal dehiscence is usually found in patients with cholesteatomas. Herein, we report an abnormal FN course with dehiscent facial canal found in a patient with congenital conductive hearing loss (CHL) without any accompanying auricular deformity or cholesteatoma.
| Case Report|| |
A 15-year-old girl presented with bilateral nonprogressive hearing loss since childhood. She had a negative history for any other problem such as vertigo, tinnitus, otorrhae, and otalgia. Her medical and surgical history was not significant. Physical examination revealed no facial palsy or auricular deformity. Otoscopic examination of the ears was normal and the tympanic membranes were intact. Weber test was not lateralizing. Rinne test was negative for both ears. Other examinations were normal except for minimal low-set-ear. Tympanometry was A-type for both sides. Pure tone audiometry showed bilateral CHL with a wide gap (70 dB, 55 dB, and 30 dB at 500 Hz, 1000 Hz, and 2000 Hz, respectively). SRT (speech reception threshold) was 60 dB, SDS (speech discrimination score) was 100% and MCL (most comfortable level) was 80 dB, respectively. High-resolution computed tomography (HRCT) of the temporal bone showed normal pneumatization of mastoid, normal inner ear anatomy, and no obvious facial course anomaly. The patient was scheduled for middle ear exploration and ossiculoplasty if possible. In middle ear exploration, after elevating tympanomeatal flap, FN was over promontory between oval and round window niche and under malleus. The FN covered more than 70% of footplate. It was dehiscent in the tympanic portion. Incus bone was absent and stapes bone was jointed to malleolus neck [Figure 1] and [Figure 2]. Due to FN route anomaly and hazard of injury to the FN, the operation was terminated.
|Figure 1: Middle ear exploration. white arrow: chorda tympani nerve black arrow: facial nerve|
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|Figure 2: Deviant facial nerve. Black arrow: Malleus bone, green arrow: Stapes bone, white arrow: Chorda tympani nerve, blue arrow: Facial nerve|
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| Discussion|| |
Deviant FN route is a rare anomaly that often presents with congenital CHL due to ossicular disruptions. It may be associated with or without congenital auricular deformities such as microtia or atresia., In addition, microscopic otoscopic examination (MOE) may reveal a bundle-like structure behind the eardrum. In our case report, no significant auricular deformity or abnormal MOE was noted. HRCT imaging may or may not help the surgeon to locate the FN course prior to surgery. In previous case reports of anomalous FN,, like our report, the FN course is more anterolaterally in the middle ear cavity than in normal patients. Therefore, physicians should suspect the mass located in the posterior middle ear cavity as a variation of the FN pathway. In our case, CT scan seemed normal and showed no obvious abnormality. Hence, FN route anomaly and dehiscence should always be in consideration in patients with congenital CHL even if examination or imaging is normal.
| Conclusion|| |
Congenital CHL may be the only presentation in patients with FN course anomaly. Physical examination and imaging may be normal in such patients. Hence, the last and most accurate step to locate FN course is middle ear exploration. Due to high risk of injury to FN, surgeons should be more careful during otologic surgeries in such patients.
Informed consent was obtained from patient that included in the study. And, our investigation and case report was accepted in Ethics Committee of Shiraz University of Medical Sciences with code: IR.sums.med.rec.1398.640.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that name and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]