Auris Nasus Larynx 41 (2014) 313–316
Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Stapes fixation accompanied with abnormal facial nerve pathway Taro Inagaki *, Atsushi Kawano, Yasuo Ogawa, Masaaki Shimizu, Miho Negishi, Yuri Kawada, Mamoru Suzuki Department of Otolaryngology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 31 January 2013 Accepted 12 December 2013 Available online 25 February 2014
The patient was a 52-year-old woman. She had been aware of her bilateral hearing loss since she was 20 years old. The hearing in her left ear started to deteriorate at the age of 49. Pure-tone audiometry showed a bilateral mixed hearing loss. The hearing levels for the right ear and the left ear were 52 dB and 68 dB, respectively. There were no remarkable findings in a computed tomography (CT) scan of the temporal bone. We suspected that she had otosclerosis, and an operation was performed on her left ear. When the incudostapedial joint (I-S joint) was exposed to investigate the movement of the stapes, a soft white band that ran under the superstructure of the stapes was noted. By using a nerve monitoring system, we confirmed that the white band was the bare facial nerve. The ossicular chain was normal, except for a malformed stape due to the facial nerve, and the footplate of the stapes was fixed. Therefore, she was diagnosed as having otosclerosis with an abnormal facial nerve pathway. The malformed superstructure of the stapes was removed carefully. When the ectopic facial nerve was shifted to anteroinferior side, the oval window could be seen. Stapedotomy using a Teflon piston prosthesis was performed with no complications. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Abnormal facial nerve pathway Otosclerosis Stapes surgery
1. Introduction Embryologically, the facial nerve is derived from the second branchial arch, and the middle and external ear are derived from the first and second branchial arches. It has been reported that an abnormal facial nerve pathway usually occurs in conjunction with congenital malformation of the middle and/or external ear, because they are formed at almost the same time [1]. In this report, we describe a case with an abnormal facial nerve pathway that we encountered during surgery for otosclerosis. 2. Case report The patient was a 52-year-old woman. She had been aware of her bilateral hearing loss since the age of 20, but had not received any treatment. The hearing in her left ear started to deteriorate at the age of 49, and she visited a clinic at the age of 52. She was diagnosed with bilateral conductive hearing loss and was referred to our hospital. The external ear and tympanic membrane were normal. Puretone audiometry showed bilateral mixed hearing loss. Her average
* Corresponding author. Tel.: +81 3 3342 6111; fax: +81 3 3346 9275. E-mail address: [email protected] (T. Inagaki). 0385-8146/$ – see front matter ß 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.anl.2013.12.010
hearing levels (500, 1 k, 2 kHz) were 52 and 68 dB in the right ear and the left ear, respectively (Fig. 1a). No laterality was observed in the tympanometry and the stapedial reflex (SR) tests. The tympanogram was identified type A, and an inversive reflex to the ipsilateral stimulus (500 Hz) was seen in the SR test. There was no remarkable finding in the computed tomography (CT) scan of the temporal bone before the operation (Fig. 2), and we suspected that she had otosclerosis. An operation was performed on her left ear with postauricular methods under general anesthesia. When the incudostapedial joint (I-S joint) was exposed to investigate the movement of the stapes, a soft white band that ran under the superstructure of the stapes was noted (Fig. 3a and b). Using a nerve monitoring system, we confirmed that the white band was the bare facial nerve. The prominence of the facial canal could be seen above the stapes, but there was no response to stimulation of the canal. The ossicular chain was normal, except for a malformed stape due to the facial nerve (Fig. 3c and d). While reviewing the temporal bone CT scan, the facial nerve seemed to lie below the oval window niche (Fig. 2f). The mobility of the malleus and incus was normal and the footplate of the stapes was fixed. After dividing the I-S joint, the malformed superstructure of the stapes was removed carefully. Fortunately, the facial nerve could be sufficiently moved to the anteroinferior side for the footplate to be visualized. The stapedotomy using drills (1 0.4, 0.6 and
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Fig. 1. Pure-tone audiogram. (a) Before surgery: the average hearing levels were 52 dB and 68 dB in the right ear and the left ear, respectively. There was an air-bone gap mainly at low frequencies. (b) After surgery (1 year): the average hearing level was 35 dB in the left ear (bold line). The narrow line shows the preoperative hearing level (68 dB).
Fig. 2. Temporal bone CT (left ear). There were no remarkable findings in the temporal bone CT (a)–(e). Facial nerve was seen below the oval window niche (f). (a)–(c) horizontal CT; (d)–(f) coronal CT; single arrow-head, facial nerve; double arrow-head, stapes.
0.8 mm) and the insertion of a Teflon piston prosthesis (1 0.6 mm 5.5 mm) were performed as planned (Fig. 4). From the above findings, she was diagnosed as having otosclerosis with an abnormal facial nerve pathway. We made the diagnosis of otosclerosis based on her progress of hearing, although there were no objective evidences of otosclerosis. One year after the surgery, the averaged hearing level improved to 35 dB in the left ear (Fig. 1b). There were no complications, such as delayed facial palsy, sensorineural hearing loss, or vertigo. 3. Discussion The development of the facial nerve, which is derived from the second branchial arch, begins at the fourth gestational week (gw). The facial nerve already exists in the temporal bone at the
beginning of the sixth gw, though it still runs straight without forming the geniculate. The stapes primordium pushes the facial nerve posteriorly at the sixth gw, and thus the vertical and horizontal portions of the facial nerve are formed. The course of the facial nerve is almost determined by the eighth gw [2]. In brief, abnormal facial nerve pathway is caused not by the facial nerve itself but by the abnormal development of the structure of the middle ear. Gerhardt and Otto [3] reported that malposition of the nerve may be caused by an underdevelopment of the mandibular arch, which is a part of the first branchial arch, leading to the shifting of the facial nerve in the anterior or lateral direction. At the eighth gw, the medial wall of the facial canal derived from the otic capsule is already formed, but the tympanic cavity side is not yet covered. The tympanic cavity side is finally completely covered with the bony wall derived from the
T. Inagaki et al. / Auris Nasus Larynx 41 (2014) 313–316
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Fig. 3. Endoscopic findings and the malformed stapes (left ear). The right figure (b) is a diagram of the endoscopic findings (a). The bare facial nerve runs through under the superstructure of the stapes and outside the facial canal. The upper (c) and lower (d) views of the malformed superstructure of the stapes are shown. The impression caused by the ectopic facial nerve can be seen.
Fig. 4. Microscopic findings. The right figure is a diagram of the microscopic findings. The stapedotomy was performed. Teflon piston prosthesis was put into the footplate between the facial canal and the facial nerve, and was attached to the incus.
connective tissue at the 18th gw [2]. This means that the bony wall does not influence the course of the facial nerve. Dickinson et al. [4] reported that a facial nerve lying on the promontory was injured during an operation. Only some cords, not including the facial nerve, were found inside the facial canal. In other words, the presence of the facial canal prominence does not guarantee the presence of the facial nerve within the canal. At the same time that the course of the facial nerve is determined, the superstructure of the stapes adheres to the otic capsule [5]. A malformation of the stapes is thought to be caused by the ectopic facial nerve lying on the oval window [3]. In the current case, the facial nerve ran through the oval window, and all the other structures were normal, except for the malformed stapes. Ectopic facial nerves covering the oval window were seen in 0.2–2% of stapes operations [6,7], and dehiscence of the facial canal and ectopic facial nerves was reported as a non-specific finding in otosclerosis [8,9]. The ectopic facial nerves were also
seen in the ears with congenital round window anomaly [10] and anomalous facial nerve may cause congenital conductive hearing loss [11]. Therefore, surgeons should be aware that an abnormal facial nerve pathway can be encountered during the ear surgery of the conductive hearing loss, even if it is congenital or acquired. Stapes surgery had been performed to improve the hearing even in patients with an ectopic facial nerve covering the oval window. In those cases, the facial nerve was moved to ensure the location of the oval window and the placement of the prosthesis [12,13]. There was no risk of the bare nerve pressing against the prosthesis causing facial paralysis [12]. In the current case, the stapes surgery was performed successfully without delayed facial paralysis. Though the current case was clinically diagnosed as otosclerosis, there were no objective evidences. We expect that the objective evidence will be found at the surgery on the right ear.
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4. Conclusion During stapes surgery for otosclerosis, we incidentally encountered an abnormal facial nerve pathway. An abnormal facial nerve pathway can exist even if there is no significant ossicular anomaly. Stapes surgery can be performed even if the round window is covered by the ectopic facial nerve. References [1] Hasegawa J, Kawase T, Hidaka H, Oshima T, Kobayashi T. Surgical treatment for congenital absence of the oval window with facial nerve anomalies. Auris Nasus Larynx 2011;39:249–55. [2] Matsumura M. Developmental study on the facial nerve and canal in man. Otol Jpn 1981;84:815–25. [3] Gerhardt HJ, Otto HD. The intratemporal course of the facial nerve and its influence on the development of the ossicular chain. Acta Otolaryngol 1981;91:567–73. [4] Dickinson JT, Srisomboon P, Kamerer DB. Congenital anomaly of the facial nerve. Arch Otolaryngol 1968;88:357–9.
[5] Anson BJ, editor. Morris’ human anatomy. 12th ed., New York: McGraw-Hill; 1966. [6] Li D, Cao Y. Facial canal dehiscence: a report of 1,465 stapes operations. Ann Otol Rhinol Laryngol 1996;105:467–71. [7] Neff BA, Lippy WH, Schuring AG, Rizer FM. Stapedectomy in patients with a prolapsed facial nerve. Otolaryngol Head Neck Surg 2004;130:597–603. [8] Tange RA, de Bruijn AJ. Dehiscences of the horizontal segment of the facial canal in otosclerosis. ORL J Otorhinolaryngol Relat Spec 1997;59: 277–9. [9] Japaridze Sh, Lomidze L, Jashi M, Kekelidze I, Gegenava Kh. Otosclerosis surgery: approaches, profits and complications. Georgian Med News 2009;170: 17–9. [10] Thomeer H, Kunst H, Verbist B, Cremers C. Congenital oval or round window anomaly with or without abnormal facial nerve course: surgical results for 15 ears. Otol Neurotol 2012;33:779–84. [11] Al-Mazrou KA, Alorainy IA, Al-Dousary SH, Richardson MA. Facial nerve anomalies in association with congenital hearing loss. Int J Pediatr Otorhinolaryngol 2003;67:1347–53. [12] Jahrsdoerfer RA. The facial nerve in congenital middle ear malformations. Laryngoscope 1981;91:1217–25. [13] Rothholtz VS, Djalilian HR. Complete obstruction of the stapes footplate by a dehiscent facial nerve in stapedectomy. Ear Nose Throat J 2009;88: 1192–3.
Contents lists available at ScienceDirect
Auris Nasus Larynx journal homepage: www.elsevier.com/locate/anl
Stapes fixation accompanied with abnormal facial nerve pathway Taro Inagaki *, Atsushi Kawano, Yasuo Ogawa, Masaaki Shimizu, Miho Negishi, Yuri Kawada, Mamoru Suzuki Department of Otolaryngology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan
A R T I C L E I N F O
A B S T R A C T
Article history: Received 31 January 2013 Accepted 12 December 2013 Available online 25 February 2014
The patient was a 52-year-old woman. She had been aware of her bilateral hearing loss since she was 20 years old. The hearing in her left ear started to deteriorate at the age of 49. Pure-tone audiometry showed a bilateral mixed hearing loss. The hearing levels for the right ear and the left ear were 52 dB and 68 dB, respectively. There were no remarkable findings in a computed tomography (CT) scan of the temporal bone. We suspected that she had otosclerosis, and an operation was performed on her left ear. When the incudostapedial joint (I-S joint) was exposed to investigate the movement of the stapes, a soft white band that ran under the superstructure of the stapes was noted. By using a nerve monitoring system, we confirmed that the white band was the bare facial nerve. The ossicular chain was normal, except for a malformed stape due to the facial nerve, and the footplate of the stapes was fixed. Therefore, she was diagnosed as having otosclerosis with an abnormal facial nerve pathway. The malformed superstructure of the stapes was removed carefully. When the ectopic facial nerve was shifted to anteroinferior side, the oval window could be seen. Stapedotomy using a Teflon piston prosthesis was performed with no complications. ß 2014 Elsevier Ireland Ltd. All rights reserved.
Keywords: Abnormal facial nerve pathway Otosclerosis Stapes surgery
1. Introduction Embryologically, the facial nerve is derived from the second branchial arch, and the middle and external ear are derived from the first and second branchial arches. It has been reported that an abnormal facial nerve pathway usually occurs in conjunction with congenital malformation of the middle and/or external ear, because they are formed at almost the same time [1]. In this report, we describe a case with an abnormal facial nerve pathway that we encountered during surgery for otosclerosis. 2. Case report The patient was a 52-year-old woman. She had been aware of her bilateral hearing loss since the age of 20, but had not received any treatment. The hearing in her left ear started to deteriorate at the age of 49, and she visited a clinic at the age of 52. She was diagnosed with bilateral conductive hearing loss and was referred to our hospital. The external ear and tympanic membrane were normal. Puretone audiometry showed bilateral mixed hearing loss. Her average
* Corresponding author. Tel.: +81 3 3342 6111; fax: +81 3 3346 9275. E-mail address: [email protected] (T. Inagaki). 0385-8146/$ – see front matter ß 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.anl.2013.12.010
hearing levels (500, 1 k, 2 kHz) were 52 and 68 dB in the right ear and the left ear, respectively (Fig. 1a). No laterality was observed in the tympanometry and the stapedial reflex (SR) tests. The tympanogram was identified type A, and an inversive reflex to the ipsilateral stimulus (500 Hz) was seen in the SR test. There was no remarkable finding in the computed tomography (CT) scan of the temporal bone before the operation (Fig. 2), and we suspected that she had otosclerosis. An operation was performed on her left ear with postauricular methods under general anesthesia. When the incudostapedial joint (I-S joint) was exposed to investigate the movement of the stapes, a soft white band that ran under the superstructure of the stapes was noted (Fig. 3a and b). Using a nerve monitoring system, we confirmed that the white band was the bare facial nerve. The prominence of the facial canal could be seen above the stapes, but there was no response to stimulation of the canal. The ossicular chain was normal, except for a malformed stape due to the facial nerve (Fig. 3c and d). While reviewing the temporal bone CT scan, the facial nerve seemed to lie below the oval window niche (Fig. 2f). The mobility of the malleus and incus was normal and the footplate of the stapes was fixed. After dividing the I-S joint, the malformed superstructure of the stapes was removed carefully. Fortunately, the facial nerve could be sufficiently moved to the anteroinferior side for the footplate to be visualized. The stapedotomy using drills (1 0.4, 0.6 and
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Fig. 1. Pure-tone audiogram. (a) Before surgery: the average hearing levels were 52 dB and 68 dB in the right ear and the left ear, respectively. There was an air-bone gap mainly at low frequencies. (b) After surgery (1 year): the average hearing level was 35 dB in the left ear (bold line). The narrow line shows the preoperative hearing level (68 dB).
Fig. 2. Temporal bone CT (left ear). There were no remarkable findings in the temporal bone CT (a)–(e). Facial nerve was seen below the oval window niche (f). (a)–(c) horizontal CT; (d)–(f) coronal CT; single arrow-head, facial nerve; double arrow-head, stapes.
0.8 mm) and the insertion of a Teflon piston prosthesis (1 0.6 mm 5.5 mm) were performed as planned (Fig. 4). From the above findings, she was diagnosed as having otosclerosis with an abnormal facial nerve pathway. We made the diagnosis of otosclerosis based on her progress of hearing, although there were no objective evidences of otosclerosis. One year after the surgery, the averaged hearing level improved to 35 dB in the left ear (Fig. 1b). There were no complications, such as delayed facial palsy, sensorineural hearing loss, or vertigo. 3. Discussion The development of the facial nerve, which is derived from the second branchial arch, begins at the fourth gestational week (gw). The facial nerve already exists in the temporal bone at the
beginning of the sixth gw, though it still runs straight without forming the geniculate. The stapes primordium pushes the facial nerve posteriorly at the sixth gw, and thus the vertical and horizontal portions of the facial nerve are formed. The course of the facial nerve is almost determined by the eighth gw [2]. In brief, abnormal facial nerve pathway is caused not by the facial nerve itself but by the abnormal development of the structure of the middle ear. Gerhardt and Otto [3] reported that malposition of the nerve may be caused by an underdevelopment of the mandibular arch, which is a part of the first branchial arch, leading to the shifting of the facial nerve in the anterior or lateral direction. At the eighth gw, the medial wall of the facial canal derived from the otic capsule is already formed, but the tympanic cavity side is not yet covered. The tympanic cavity side is finally completely covered with the bony wall derived from the
T. Inagaki et al. / Auris Nasus Larynx 41 (2014) 313–316
315
Fig. 3. Endoscopic findings and the malformed stapes (left ear). The right figure (b) is a diagram of the endoscopic findings (a). The bare facial nerve runs through under the superstructure of the stapes and outside the facial canal. The upper (c) and lower (d) views of the malformed superstructure of the stapes are shown. The impression caused by the ectopic facial nerve can be seen.
Fig. 4. Microscopic findings. The right figure is a diagram of the microscopic findings. The stapedotomy was performed. Teflon piston prosthesis was put into the footplate between the facial canal and the facial nerve, and was attached to the incus.
connective tissue at the 18th gw [2]. This means that the bony wall does not influence the course of the facial nerve. Dickinson et al. [4] reported that a facial nerve lying on the promontory was injured during an operation. Only some cords, not including the facial nerve, were found inside the facial canal. In other words, the presence of the facial canal prominence does not guarantee the presence of the facial nerve within the canal. At the same time that the course of the facial nerve is determined, the superstructure of the stapes adheres to the otic capsule [5]. A malformation of the stapes is thought to be caused by the ectopic facial nerve lying on the oval window [3]. In the current case, the facial nerve ran through the oval window, and all the other structures were normal, except for the malformed stapes. Ectopic facial nerves covering the oval window were seen in 0.2–2% of stapes operations [6,7], and dehiscence of the facial canal and ectopic facial nerves was reported as a non-specific finding in otosclerosis [8,9]. The ectopic facial nerves were also
seen in the ears with congenital round window anomaly [10] and anomalous facial nerve may cause congenital conductive hearing loss [11]. Therefore, surgeons should be aware that an abnormal facial nerve pathway can be encountered during the ear surgery of the conductive hearing loss, even if it is congenital or acquired. Stapes surgery had been performed to improve the hearing even in patients with an ectopic facial nerve covering the oval window. In those cases, the facial nerve was moved to ensure the location of the oval window and the placement of the prosthesis [12,13]. There was no risk of the bare nerve pressing against the prosthesis causing facial paralysis [12]. In the current case, the stapes surgery was performed successfully without delayed facial paralysis. Though the current case was clinically diagnosed as otosclerosis, there were no objective evidences. We expect that the objective evidence will be found at the surgery on the right ear.
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T. Inagaki et al. / Auris Nasus Larynx 41 (2014) 313–316
4. Conclusion During stapes surgery for otosclerosis, we incidentally encountered an abnormal facial nerve pathway. An abnormal facial nerve pathway can exist even if there is no significant ossicular anomaly. Stapes surgery can be performed even if the round window is covered by the ectopic facial nerve. References [1] Hasegawa J, Kawase T, Hidaka H, Oshima T, Kobayashi T. Surgical treatment for congenital absence of the oval window with facial nerve anomalies. Auris Nasus Larynx 2011;39:249–55. [2] Matsumura M. Developmental study on the facial nerve and canal in man. Otol Jpn 1981;84:815–25. [3] Gerhardt HJ, Otto HD. The intratemporal course of the facial nerve and its influence on the development of the ossicular chain. Acta Otolaryngol 1981;91:567–73. [4] Dickinson JT, Srisomboon P, Kamerer DB. Congenital anomaly of the facial nerve. Arch Otolaryngol 1968;88:357–9.
[5] Anson BJ, editor. Morris’ human anatomy. 12th ed., New York: McGraw-Hill; 1966. [6] Li D, Cao Y. Facial canal dehiscence: a report of 1,465 stapes operations. Ann Otol Rhinol Laryngol 1996;105:467–71. [7] Neff BA, Lippy WH, Schuring AG, Rizer FM. Stapedectomy in patients with a prolapsed facial nerve. Otolaryngol Head Neck Surg 2004;130:597–603. [8] Tange RA, de Bruijn AJ. Dehiscences of the horizontal segment of the facial canal in otosclerosis. ORL J Otorhinolaryngol Relat Spec 1997;59: 277–9. [9] Japaridze Sh, Lomidze L, Jashi M, Kekelidze I, Gegenava Kh. Otosclerosis surgery: approaches, profits and complications. Georgian Med News 2009;170: 17–9. [10] Thomeer H, Kunst H, Verbist B, Cremers C. Congenital oval or round window anomaly with or without abnormal facial nerve course: surgical results for 15 ears. Otol Neurotol 2012;33:779–84. [11] Al-Mazrou KA, Alorainy IA, Al-Dousary SH, Richardson MA. Facial nerve anomalies in association with congenital hearing loss. Int J Pediatr Otorhinolaryngol 2003;67:1347–53. [12] Jahrsdoerfer RA. The facial nerve in congenital middle ear malformations. Laryngoscope 1981;91:1217–25. [13] Rothholtz VS, Djalilian HR. Complete obstruction of the stapes footplate by a dehiscent facial nerve in stapedectomy. Ear Nose Throat J 2009;88: 1192–3.
