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Redalyc.Deviant Facial Nerve Course in the Middle Ear Cavity Brazilian Journal of Otorhinolaryngology ISSN: 1808-8694 [email protected] Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico- Facial Brasil Cho, Jungkyu; Choi, Nayeon; Hwa Hong, Sung; Moon, Il Joon Deviant facial nerve course in the middle ear cavity Brazilian Journal of Otorhinolaryngology, vol. 81, núm. 6, 2015, pp. 681-683 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial São Paulo, Brasil Available in: http://www.redalyc.org/articulo.oa?id=392442695018 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Document downloaded from http://bjorl.elsevier.es day 25/11/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited. Braz J Otorhinolaryngol. 2015;81(6):681---683 Brazilian Journal of OTORHINOLARYNGOLOGY www.bjorl.org CASE REPORT ଝ Deviant facial nerve course in the middle ear cavity Trajeto anômalo do nervo facial na cavidade da orelha média ∗ Jungkyu Cho, Nayeon Choi, Sung Hwa Hong, Il Joon Moon Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea Received 27 December 2014; accepted 17 March 2015 Available online 7 September 2015 Introduction (Fig. 1A). Other physical exams showed no facial nerve palsy or auricular anomaly (Fig. 1B). Pure-tone average Anomalous facial nerve (FN) course can be found in a sig- (0.5, 1, 2, and 3 kHz) showed air-bone gap of 58 dB nificant number of cases with aural anomalies. The most (average bone-conduction threshold = 3.75 dB, average air- common anomaly of the FN involves the tympanic portion conduction threshold = 62.5 dB) (Fig. 1C). Accordingly, 1 --- 3 overlying the oval window. Facial canal dehiscence of computed tomography (CT) scan of the temporal bone was the tympanic portion may be responsible for the anomalous performed for evaluation of the middle ear cavity along with course of FN over the oval window. The incidence of facial ossicular structures. CT revealed a hypoplastic middle ear canal dehiscence found during otologic surgery is relatively cavity, incudostapedial joint separation, and lateralization 4,5 frequent and is usually related with cholesteatomas. of the tympanic segment of the facial nerve, which was Aberrant FN course in a patient without accompanying observed behind the tympanic membrane (Fig. 1D and E). anomaly or cholesteatoma has been demonstrated in a pre- Internal auditory canal MRI demonstrated no anomalies in 6 vious case report. However, the patient had not undergone the inner ear (Fig. 1F and G). Since aberrant course of the imaging evaluation. Herein, the authors report an abnor- tympanic segment of facial nerve was identified, further mal FN course in the tympanic portion, without any other surgical exploration was deferred. associated anomalies. Discussion Case report Most patients with FN anomaly do not have any clin- An 18-year-old male presented to the outpatient clinic ical symptoms. Conductive hearing loss, mainly due to with left-sided non-progressive hearing loss since child- associated ossicular disruption, may be the only clinical hood. Otoscopic examination revealed bundle-like structure presentation. Therefore, it is difficult to suspect middle behind the posterior portion of the tympanic membrane ear mass as an unusual presentation of the FN course or even as a structural or passage anomaly, especially when other associated anomalies are not noted. Furthermore, ଝ cases of FN dehiscence shown in previous studies were Please cite this article as: Cho J, Choi N, Hong SH, Moon IJ. Deviant facial nerve course in the middle ear cavity. Braz J Otorhi- mainly associated with cholesteatomas or congenital aural 2,3,5 nolaryngol. 2015;81:681---3. atresias. ∗ Corresponding author. However, aberrant course of FN lateral to the ossicles E-mail: [email protected] (I.J. Moon). without accompanying auricular anomaly was reported in a http://dx.doi.org/10.1016/j.bjorl.2015.03.011 1808-8694/© 2015 Associac¸ão Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved. Document downloaded from http://bjorl.elsevier.es day 25/11/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited. 682 Cho J et al. C –10 A B 0 10 20 30 40 Left (Bone) P 50 A Left (Air) 60 70 Right (Air) 80 90 100 110 120 250 500 1k 2k 4k 8k Frequency, Hz D E F G Figure 1 (A) Otoscopic examination reveals streak-like structure (asterisk) behind the eardrum. Yellowish bundle-like structure is placed at postero-superior quadrant. P, posterior canal wall; A, anterior canal wall. (B) External ear shows normal structure without anomaly. (C) Pure tone audiometry shows conductive hearing loss; air-bone conduction gap of 58 dB in the left ear. (D) Facial nerve dehiscence of tympanic segment, which is seen behind the tympanic membrane (white arrow). (E) Incudostapedial dislocation (white arrow) with lateralized facial nerve (white arrow head). (F) Intermediate signal intensity of the aberrant facial nerve course. (G) Well-delineated facial and vestibulocochlear nerve in internal auditory canal. 6 prior case. Hence, it is advisable not to exclude aberrant Final comments FN pathway in patients without accompanying anomaly or other middle ear disease. In the previous report of aber- Unusual structure seen through the tympanic membrane rant FN course without other anomalies, imaging evaluation should be evaluated by imaging before definitive treatment. was not performed preoperatively. Surgical exploration CT is especially useful for this purpose, because the tym- with electrical stimulation monitoring was used to confirm panic segment of the FN lying lateral to the ossicles can 6 the middle ear mass as the FN. However, these surgi- be easily identified. If aberrant course of the FN is sus- cal procedures in the middle ear cavity could lead to FN pected by symptoms and clinical findings, physicians should damage. Thus, if anomalous FN is suspected, preoperative be cautious in determining surgical interventions, such as imaging evaluation is mandatory. In the present case, radio- ventilation tube insertion or explorative tympanotomy. logic evaluation was performed before planning surgical exploration. Conflicts of interest CT imaging provides precise prediction of the FN course, coinciding with surgical findings in most cases of congeni- 2 The authors declare no conflicts of interest. tal aural atresia. Therefore, the primary imaging modality for evaluation of the FN course should include high resolu- tion CT. In previous studies of anomalous FN of the tympanic References portion, the FN runs more anterolaterally in the middle ear cavity than in normal patients. 1. Fu Y, Zhang T. Facial nerve lying lateral to ossicles in one Therefore, physicians should suspect the mass located case of congenital aural atresia. Int J Pediatr Otorhinolaryngol. in the posterior middle ear cavity as a variation of the FN 2011;75:597---9. pathway and perform imaging evaluation before planning 2. Yu Z, Han D, Gong S, Wang Z, Dai H, Zhao S, et al. 1,2,4,6 interventions. Facial nerve course in congenital aural atresia --- identified by Document downloaded from http://bjorl.elsevier.es day 25/11/2015. This copy is for personal use. Any transmission of this document by any media or format is strictly prohibited. Deviant facial nerve course in the middle ear cavity 683 preoperative CT scanning and surgical findings. Acta Otolaryngol. 5. Di Martino E, Sellhaus B, Haensel J, Schlegel JG, Westhofen 2008;128:1375---80. M, Prescher A. Fallopian canal dehiscences: a survey of clinical 3. Huang BR, Juan CJ, Wang CH. Infantile facial nerve course in an and anatomical findings. Eur Arch Otorhinolaryngol. 2005;262: adult patient with congenital aural dysplasia. Otolaryngol Head 120---6. Neck Surg. 2008;139:470---1. 6. Kuo CY, Wang CH. Aberrant facial nerve exposed behind the 4. Selesnick SH, Lynn-Macrae AG. The incidence of facial nerve eardrum. Otolaryngol Head Neck Surg. 2012;147:1158---9. dehiscence at surgery for cholesteatoma. Otol Neurotol. 2001;22:129---32..
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