Complications Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
Facial Nerve Palsy Munetaka Ushio a · Kimitaka Kaga b
a
Department of Otolaryngology, Social Insurance Central General Hospital, and b National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
In patients with congenital aural atresia, the risk of facial nerve injury is always present because of malformations of the external and middle ear. Mastoid cells, the ossicular chain, and the position of the facial nerve are useful landmarks for tympanoplasty. However, the anatomy of such structures differs in each patient with microtia/ atresia of the external auditory canal (EAC). This is why canal plasty and surgery for improving auditory acuity are difficult in patients with congenital aural atresia [1]. Moreover, there is a risk of damaging the surrounding structures. Facial nerve palsy is a particularly significant complication that affects postoperative quality of life.
The facial nerve enters the temporal bone from the bottom of the internal auditory canal. It forms the geniculate ganglion at the upper anterior region of the vestibule, and bends backward and progresses in a lower posterior direction between the lateral semicircular duct and the vestibular window (horizontal portion). The facial nerve then bends downward at the upper posterior tympanic cavity (the second genu), descends inside the mastoid (vertical portion), and exits to the face from the stylomastoid foramen. In patients with congenital aural atresia, the temporal bone is often poorly developed [2] and the facial nerve is displaced and positioned anteriorly and laterally [3, 4] or anteriorly only [5, 6] due to insufficient growth of the second genu (fig. 1). Imaging diagnostics play an important role in preoperative evaluation of EAC atresia. Helical CT, which enables detailed identification of the facial nerve, is particularly useful. Altmann-Cremers classification [7] and the grading system of Jahrsdoerfer et al. [1] are used for case evaluation. This is explained in more detail in the imaging diagnosis section. Based on the authors’ investigations, important factors responsible for facial palsy include positional anomalies in the facial nerve, absence of
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Abnormal Position of the Facial Nerve and Preoperative Evaluation
Incus
Malleus
Lateral semicircular canal
Geniculate ganglion
Mastoid
Stapes
Eustachian tube
Round window Styloid process
Mastoid process Facial nerve
Fig. 1. Anatomy of middle ear and facial nerve.
Table 1. Mean score on Jahrsdoerfer’s grading system comparing patients with transient facial palsy and nonfacial palsy Parameter
Transient facial palsy after surgery yes (n = 6)
no (n = 93)
Stapes present Oval window open Middle ear space Facial nerve Malleus/incus complex Mastoid pneumatized Incus-stapes connection Round window Appearance external ear
0.67 0.67 0.83 0 0.67 0.67 0.33 0.83 0.17
1.5 0.85 0.92 0.73 0.91 0.77 0.71 0.93 0.15
Total available points
4.83
7.52
the stapes, and low total score among the items of Jahrsdoerfer’s grading system [8] (table 1). If a positional anomaly is present in the facial nerve, surgical procedures approaching the nerve carry greater risk. Trying to identify the indistinct stapes increases the risk of damaging the facial nerve because a surgeon has to manipulate close to the facial nerve [3–6].
Facial Nerve Palsy Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
107
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Mean score on Jahrsdoerfer’s grading system for cases in which facial palsy did or did not occur following surgery (* p < 0.05).
Table 2. Time of appearance for nerve tests after surgery in 6 patients with transient facial palsy Case No.
1 2 3 4 5 6
Initial examination after surgery, days
Time of appearance after surgery, days ENoG
NET
blink reflex
7 7 14 7 20 7
71 77 – 7 20 70
91 7 94 – 20 100
107 77 94 – 20 100
– = No response.
Surgical Approaches and Facial Nerve Palsy
The greatest risk to the facial nerve is in patients whose temporal bone is poorly developed. According to Jahrsdoerfer et al. [8], the facial nerve is likely to be damaged at the following stages of surgery for atresia of the EAC: (1) during creation of the skin incision; (2) during dissection of the glenoid fossa; (3) during canal plasty; (4) during transposition of the facial nerve, and (5) during dissection of the preauricular soft tissue. The posterior (transmastoid method) [9], anterior (one-tunnel method) [9], and combined methods [10] are employed as the surgical approaches to the tympanic cavity of patients with congenital aural atresia. With the posterior method, relatively numerous anatomical landmarks can be used as indices by opening mastoid cells. There is less risk of facial nerve injury but more risk of postoperative infection of mastoid cells [10]. With the anterior method, postoperative morphology is relatively physiological, but anatomical landmarks are fewer and the risk of facial nerve injury would be higher in cases with an abnormal position of the facial nerve, especially at the mastoid section [11]. Although the atretic plate should be removed wider to improve hearing acuity, it should be operated on carefully because there may be cases with an abnormal position of the facial nerve inside the plate.
The incidence of facial nerve palsy due to surgery for microtia/atresia of the EAC was reported to be 8% (5/62 patients) by Schuknecht [12], 1% (10/1,000 patients) by Jahsdoerfer et al. [2], and 2% (2/92 patients) by Chandrasekhar et al. [13]. The authors experienced transient facial nerve palsy in 6 of 99 ears (6%) in 87 patients with nonsymptomatic atresia of the EAC, but all recovered [8] (table 2). The risks of facial nerve palsy resulting from injury are drilling, compression, stretching, or manipulation [2].
108
Ushio · Kaga Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Incidence and Mechanism of Facial Nerve Palsy
The friction of a rotating burr is also sufficient to cause thermal damage to nerves [14]. When the facial nerve is directly injured, complete recovery of facial movement would not be expected.
Prevention of Facial Nerve Palsy
Avoiding irreversible facial nerve palsy would be possible through sufficient preoperative examination and careful manipulation using a facial nerve stimulator during surgery [2]. The use of three-dimensional images enables preoperative examination of the three-dimensional relationship between the ossicles and the position of the facial nerve. A navigation system has gradually become more popular in recent years and it is also applied for congenital aural atresia [15].
References 8 Ushio M, Takeuchi N, Kaga K: Evaluation of recovery from transient facial plasty following canalplasty and tympanoplasty for the treatment of congenital aural atresia. Ann Otol Laryngol 2006;115:749–753. 9 De la Cruz A, Linthicum FH Jr, Luxford WM: Congenital atresia of the external auditory canal. Laryngoscope 1985;95:421–472. 10 Molony TB, de la Cruz A: Surgical approaches to congenital atresia of the external auditory canal. Otolaryngol Head Neck Surg 1990;103:991–1001. 11 Benton C, Bellet PS: Imaging of congenital anomalies of the temporal bone. Neuroimaging Clin N Am 2000;10:35–53. 12 Schuknecht HF: Congenital aural atresia. Laryngoscope 1989;99:908–917. 13 Chandrasekhar SS, De la Cruz A, Garrido E: Surgery of congenital aural atresia. Am J Otol 1995; 16: 713– 717. 14 Call WH: Thermal injury from mastoid bone burrs. Am Otol Rhinol Laryngol 1978;87:43–49. 15 Nishizaki K, Masuda Y, Nishioka S, Akagi H, Takeda Y, Ohkawa Y: A computer-assisted operation for congenital aural malformations. Int J Pediatr Otorhinolaryngol 1996;36:31–37.
Munetaka Ushio Department of Otolaryngology, Social Insurance Central General Hospital 3-22-1 Hyakunincho, Shinjuku-Ku Tokyo 169-0073 (Japan) E-Mail [email protected]
Facial Nerve Palsy Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
109
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1 Jahrsdoerfer RA, Yeakley JW, Aguilar EA, Cole RR, Gray LC: Grading system for the selection of patients with congenital aural atresia. Am J Otol 1992; 13: 6– 12. 2 Jahsdoerfer RA, Lambert PR: Facial nerve injury in congenital aural atresia surgery. Am J Otol 1998; 19: 283–287. 3 Swartz JD, Wolfson RJ, Marlowe FI, Popky GL, Vernose GV, Maueirllo AJ 2nd, Hampel A: External auditory canal dysplasia: CT evaluation. Laryngoscope 1985;95:841–845. 4 Mehra YN, Dubey SP, Mann SB, Suri S: Correlation between high-resolution computed tomography and surgical findings in congenital aural atresia. Arch Otolaryngol Head Neck Surg 1988;114:137–141. 5 Yeakley JW, Jahrsdoerfer RA: CT evaluation of congenital aural atresia: what the radiologist and surgeon need to know. J Comput Assist Tomogr 1996; 20:724–731. 6 Takegoshi H, Kaga K: Difference in facial canal anatomy in terms of severity of microtia and deformity of middle ear in patients with microtia. Laryngoscope 2003;113:635–639. 7 Cremers CW, Oudenhoven JM, Marres EH: Congenital aural atresia: a new subclassification and surgical management. Clin Otolaryngol Allied Sci 1984; 9:119–127.
Facial Nerve Palsy Munetaka Ushio a · Kimitaka Kaga b
a
Department of Otolaryngology, Social Insurance Central General Hospital, and b National Institute of Sensory Organs, National Tokyo Medical Center, Tokyo, Japan
In patients with congenital aural atresia, the risk of facial nerve injury is always present because of malformations of the external and middle ear. Mastoid cells, the ossicular chain, and the position of the facial nerve are useful landmarks for tympanoplasty. However, the anatomy of such structures differs in each patient with microtia/ atresia of the external auditory canal (EAC). This is why canal plasty and surgery for improving auditory acuity are difficult in patients with congenital aural atresia [1]. Moreover, there is a risk of damaging the surrounding structures. Facial nerve palsy is a particularly significant complication that affects postoperative quality of life.
The facial nerve enters the temporal bone from the bottom of the internal auditory canal. It forms the geniculate ganglion at the upper anterior region of the vestibule, and bends backward and progresses in a lower posterior direction between the lateral semicircular duct and the vestibular window (horizontal portion). The facial nerve then bends downward at the upper posterior tympanic cavity (the second genu), descends inside the mastoid (vertical portion), and exits to the face from the stylomastoid foramen. In patients with congenital aural atresia, the temporal bone is often poorly developed [2] and the facial nerve is displaced and positioned anteriorly and laterally [3, 4] or anteriorly only [5, 6] due to insufficient growth of the second genu (fig. 1). Imaging diagnostics play an important role in preoperative evaluation of EAC atresia. Helical CT, which enables detailed identification of the facial nerve, is particularly useful. Altmann-Cremers classification [7] and the grading system of Jahrsdoerfer et al. [1] are used for case evaluation. This is explained in more detail in the imaging diagnosis section. Based on the authors’ investigations, important factors responsible for facial palsy include positional anomalies in the facial nerve, absence of
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Abnormal Position of the Facial Nerve and Preoperative Evaluation
Incus
Malleus
Lateral semicircular canal
Geniculate ganglion
Mastoid
Stapes
Eustachian tube
Round window Styloid process
Mastoid process Facial nerve
Fig. 1. Anatomy of middle ear and facial nerve.
Table 1. Mean score on Jahrsdoerfer’s grading system comparing patients with transient facial palsy and nonfacial palsy Parameter
Transient facial palsy after surgery yes (n = 6)
no (n = 93)
Stapes present Oval window open Middle ear space Facial nerve Malleus/incus complex Mastoid pneumatized Incus-stapes connection Round window Appearance external ear
0.67 0.67 0.83 0 0.67 0.67 0.33 0.83 0.17
1.5 0.85 0.92 0.73 0.91 0.77 0.71 0.93 0.15
Total available points
4.83
7.52
the stapes, and low total score among the items of Jahrsdoerfer’s grading system [8] (table 1). If a positional anomaly is present in the facial nerve, surgical procedures approaching the nerve carry greater risk. Trying to identify the indistinct stapes increases the risk of damaging the facial nerve because a surgeon has to manipulate close to the facial nerve [3–6].
Facial Nerve Palsy Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
107
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Mean score on Jahrsdoerfer’s grading system for cases in which facial palsy did or did not occur following surgery (* p < 0.05).
Table 2. Time of appearance for nerve tests after surgery in 6 patients with transient facial palsy Case No.
1 2 3 4 5 6
Initial examination after surgery, days
Time of appearance after surgery, days ENoG
NET
blink reflex
7 7 14 7 20 7
71 77 – 7 20 70
91 7 94 – 20 100
107 77 94 – 20 100
– = No response.
Surgical Approaches and Facial Nerve Palsy
The greatest risk to the facial nerve is in patients whose temporal bone is poorly developed. According to Jahrsdoerfer et al. [8], the facial nerve is likely to be damaged at the following stages of surgery for atresia of the EAC: (1) during creation of the skin incision; (2) during dissection of the glenoid fossa; (3) during canal plasty; (4) during transposition of the facial nerve, and (5) during dissection of the preauricular soft tissue. The posterior (transmastoid method) [9], anterior (one-tunnel method) [9], and combined methods [10] are employed as the surgical approaches to the tympanic cavity of patients with congenital aural atresia. With the posterior method, relatively numerous anatomical landmarks can be used as indices by opening mastoid cells. There is less risk of facial nerve injury but more risk of postoperative infection of mastoid cells [10]. With the anterior method, postoperative morphology is relatively physiological, but anatomical landmarks are fewer and the risk of facial nerve injury would be higher in cases with an abnormal position of the facial nerve, especially at the mastoid section [11]. Although the atretic plate should be removed wider to improve hearing acuity, it should be operated on carefully because there may be cases with an abnormal position of the facial nerve inside the plate.
The incidence of facial nerve palsy due to surgery for microtia/atresia of the EAC was reported to be 8% (5/62 patients) by Schuknecht [12], 1% (10/1,000 patients) by Jahsdoerfer et al. [2], and 2% (2/92 patients) by Chandrasekhar et al. [13]. The authors experienced transient facial nerve palsy in 6 of 99 ears (6%) in 87 patients with nonsymptomatic atresia of the EAC, but all recovered [8] (table 2). The risks of facial nerve palsy resulting from injury are drilling, compression, stretching, or manipulation [2].
108
Ushio · Kaga Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
Incidence and Mechanism of Facial Nerve Palsy
The friction of a rotating burr is also sufficient to cause thermal damage to nerves [14]. When the facial nerve is directly injured, complete recovery of facial movement would not be expected.
Prevention of Facial Nerve Palsy
Avoiding irreversible facial nerve palsy would be possible through sufficient preoperative examination and careful manipulation using a facial nerve stimulator during surgery [2]. The use of three-dimensional images enables preoperative examination of the three-dimensional relationship between the ossicles and the position of the facial nerve. A navigation system has gradually become more popular in recent years and it is also applied for congenital aural atresia [15].
References 8 Ushio M, Takeuchi N, Kaga K: Evaluation of recovery from transient facial plasty following canalplasty and tympanoplasty for the treatment of congenital aural atresia. Ann Otol Laryngol 2006;115:749–753. 9 De la Cruz A, Linthicum FH Jr, Luxford WM: Congenital atresia of the external auditory canal. Laryngoscope 1985;95:421–472. 10 Molony TB, de la Cruz A: Surgical approaches to congenital atresia of the external auditory canal. Otolaryngol Head Neck Surg 1990;103:991–1001. 11 Benton C, Bellet PS: Imaging of congenital anomalies of the temporal bone. Neuroimaging Clin N Am 2000;10:35–53. 12 Schuknecht HF: Congenital aural atresia. Laryngoscope 1989;99:908–917. 13 Chandrasekhar SS, De la Cruz A, Garrido E: Surgery of congenital aural atresia. Am J Otol 1995; 16: 713– 717. 14 Call WH: Thermal injury from mastoid bone burrs. Am Otol Rhinol Laryngol 1978;87:43–49. 15 Nishizaki K, Masuda Y, Nishioka S, Akagi H, Takeda Y, Ohkawa Y: A computer-assisted operation for congenital aural malformations. Int J Pediatr Otorhinolaryngol 1996;36:31–37.
Munetaka Ushio Department of Otolaryngology, Social Insurance Central General Hospital 3-22-1 Hyakunincho, Shinjuku-Ku Tokyo 169-0073 (Japan) E-Mail [email protected]
Facial Nerve Palsy Kaga K, Asato H (eds): Microtia and Atresia – Combined Approach by Plastic and Otologic Surgery. Adv Otorhinolaryngol. Basel, Karger, 2014, vol 75, pp 106–109 (DOI: 10.1159/000350975)
109
Downloaded by: University of South Australia 198.143.35.1 - 8/3/2015 10:27:07 AM
1 Jahrsdoerfer RA, Yeakley JW, Aguilar EA, Cole RR, Gray LC: Grading system for the selection of patients with congenital aural atresia. Am J Otol 1992; 13: 6– 12. 2 Jahsdoerfer RA, Lambert PR: Facial nerve injury in congenital aural atresia surgery. Am J Otol 1998; 19: 283–287. 3 Swartz JD, Wolfson RJ, Marlowe FI, Popky GL, Vernose GV, Maueirllo AJ 2nd, Hampel A: External auditory canal dysplasia: CT evaluation. Laryngoscope 1985;95:841–845. 4 Mehra YN, Dubey SP, Mann SB, Suri S: Correlation between high-resolution computed tomography and surgical findings in congenital aural atresia. Arch Otolaryngol Head Neck Surg 1988;114:137–141. 5 Yeakley JW, Jahrsdoerfer RA: CT evaluation of congenital aural atresia: what the radiologist and surgeon need to know. J Comput Assist Tomogr 1996; 20:724–731. 6 Takegoshi H, Kaga K: Difference in facial canal anatomy in terms of severity of microtia and deformity of middle ear in patients with microtia. Laryngoscope 2003;113:635–639. 7 Cremers CW, Oudenhoven JM, Marres EH: Congenital aural atresia: a new subclassification and surgical management. Clin Otolaryngol Allied Sci 1984; 9:119–127.
