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Comparison of facial nerve injury and recovery rates after antegrade and retrograde nerve dissection in parotid surgery for benign disease: prospective study over 4 years
Available online at www.sciencedirect.com
British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
Comparison of facial nerve injury and recovery rates after antegrade and retrograde nerve dissection in parotid surgery for benign disease: prospective study over 4 years Barry O’Regan ∗ , Girish Bharadwaj Maxillofacial Unit, Queen Margaret Hospital, Dunfermline, United Kingdom Accepted 19 May 2010 Available online 15 June 2010
Abstract The facial nerve can be dissected using an antegrade or retrograde approach. Antegrade dissection is the established technique and retrograde dissection is used less often. Recent publications have drawn attention to the potential value of the retrograde technique particularly if direct identification of the nerve trunk is difficult, and in revision procedures. We prospectively studied 43 consecutive procedures in 40 patients who had parotidectomy over a 4-year period, and evaluated and compared rates of temporary and permanent nerve injury, and nerve recovery after antegrade and retrograde dissection in operations for benign parotid disease. Each patient was allocated randomly to the antegrade (n = 20) or retrograde (n = 20) groups. Three patients were excluded. All patients had peroperative nerve monitoring and were followed up at 1 week, 1 month, 3 months, or to full recovery of the nerve. The House-Brackmann (HB) grading system was used to assess the degree of injury to the nerve. A high rate of serious nerve injury (HBIII or above) was associated with retrograde dissection at 1 week. Serious nerve injuries (HBIII or above) were slow to recover after the antegrade technique at 3 months. There was no difference between groups in the rates of full nerve recovery at 6 months. © 2010 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Parotidectomy; Antegrade nerve dissection; Retrograde nerve dissection; Nerve injury rate; Nerve recovery rate; Facial nerve monitoring
Introduction One of the main aims of parotidectomy is to minimise injury to the facial nerve and maximise the rate at which it recovers. Two techniques are used for dissection of the facial nerve in parotid surgery. In the antegrade technique the nerve trunk is identified as it leaves the stylomastoid foramen and dissection then proceeds peripherally, and in retrograde technique the peripheral nerve branches are identified initially and dissection proceeds towards the nerve trunk.1 Antegrade dissection is used most commonly. In a national cross specialty questionnaire survey in 2007,2 it was used
∗ Corresponding author at: Maxillofacial Unit, Queen Margaret Hospital, Whitefield Road, Dunfermline, Fife KY12 0SU, United Kingdom. Tel.: +44 1383 623623; fax: +44 1383 674044. E-mail address: [email protected] (B. O’Regan).
routinely by 87% of responding surgeons. Almost half the surgeons combined both techniques in revision parotid surgery, indicating their familiarity with both approaches. In some clinical situations such as in obese patients with large tumours it may be difficult to identify the nerve trunk directly, and the retrograde technique provides a useful alternative. Many factors affect the rate that the facial nerve recovers after parotid gland surgery.3–9 They include age, sex, disease, location (superficial or deep lobe involvement), tumour size, recurrent disease, type and duration of operation, and the total length of nerve dissected. We know of no published prospective studies that compare rates of injury to the facial nerve and its recovery across both techniques. In a recent retrospective comparative study of the techniques, no difference was found in the incidence of postoperative nerve morbidity, although the study did not describe how the injury was measured.10 We measured rates of injury
0266-4356/$ – see front matter © 2010 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2010.05.013
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
287
Fig. 1. Data collection form – nerve dissection technique prospective study.
at 1 week after operation using the House-Brackmann (HB) system,11,12 and documented the rates at which the nerve recovered for both techniques at 1 month, 3 months, 6 months, or until recovery was complete.
Method Over 4 years 40 consecutive patients were recruited and randomly allocated into two groups of 20, antegrade (4 men, 16
women, age range 40–73, mean age 52 years) and retrograde (6 men, 14 women, age range 36–81, mean age 56 years). Male to female ratio overall was 1:3. All patients were advised that they would be included in the study on the assumption that there would be no difference in outcome after operation whichever technique was used. They were made aware that the choice of technique was random, and were also advised that the default technique in the event of exclusion would be the retrograde method. No patient asked to be excluded. Forty-three operations were done; 21
288
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
in the antegrade group and 22 in the retrograde group. One patient with malignant disease was excluded from the antegrade group, and two were excluded from the retrograde group. All patients were operated on by a single surgeon, and continuous intraoperative monitoring of the facial nerve was done in all cases. Technique Antegrade dissection is done by identifying the facial nerve trunk using the tragal pointer method. A modified Blair incision is used for access to the parotid gland. After initial identification of the nerve trunk, dissection proceeds towards the peripheral branches with simultaneous mobilisation of parotid tissue anteriorly and laterally. The length and number of branches dissected depends on the disease that necessitated removal of the parotid gland. In a retrograde dissection a modified Blair incision is used and the skin flap raised. Blunt dissection extends to the anterior border of the gland where the parotid duct is used as a landmark to identify the buccal branch of the facial nerve. The duct is routinely ligated and divided. The retromandibular vein is used to identify the marginal mandibular branch, and the zygomatic branches are located below the lower border of the zygomatic arch. The preferred order in which to expose the branches is buccal, mandibular, cervical, zygomatic, and temporal for diffuse disease. For benign tumours the number and sequence in which the branches are exposed is decided by the site and size of the tumour. We continue the dissection to identify the bifurcation and trunk of the facial nerve. We used the House-Brackmann grading system to assess nerve function. This system has six grades: grade I is normal nerve function; grade II indicates mild nerve dysfunction not detectable at rest; and grades III–VI indicate progressively severe paresis of the nerve in function and at rest. Examination at each stage in the study was carried out either by the
Table 1 Histological diagnoses across the groups. Diagnosis Pleomorphic salivary adenoma Warthin tumour Sialadenitis Sialosis Other
Antegrade (n = 20)
Retrograde (n = 20)
Combined (n = 40)
5
10
15
1 11 2 1
1 9 0 0
2 20 2 1
Table 2 Operations in each group. Operation
Antegrade (n = 20)
Retrograde (n = 20)
Superficial parotidectomy Total parotidectomy Lobectomy
13 7 0
15 4 1
authors or by one of the senior clinicians in the unit to reduce bias. All patients were followed up at 1 week, 1 month, 3 months, or at full recovery. The most affected branch was used for the purpose of analysis. The data collection form is shown in Fig. 1. An Excel database was used to collate and analyse the data. Results The disease profile of the patients is shown in Table 1, and the operations carried out in both groups are shown in Table 2. Initial nerve injury The initial nerve injury was recorded at 1 week after operation. Any injury equivalent to HBIII or more was considered serious. Half the patients in the antegrade group and 60% in the retrograde group had such injuries at week 1 (Table 3, Fig. 2).
Fig. 2. Bar chart showing initial nerve injury rates in both groups at week 1.
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291 Table 3 Nerve injury 1 week after operation (n = 20 in both groups). Data are number. House-Brackmann scale
Antegrade Retrograde
I
II
III
IV
V
1 1
9 7
8 11
1 1
1 0
Table 4 Recovery of facial nerve after operation in both groups (n = 20 in both groups). Data are number. House-Brackmann scale I
II
III
IV
V
Antegrade Week 1 Month 1 Month 3 Month 6
1 7 13 17
9 6 4 2
8 7 3 1
1 0 0 0
1 0 0 0
Retrograde Week 1 Month 1 Month 3 Month 6
1 4 10 18
7 11 10 2
11 5 0 0
1 0 0 0
0 0 0 0
289
Table 5 Number of patients with full recovery of the facial nerve (n = 20 in both groups). Time after operation
Antegrade Retrograde
1 week
1 month
3 months
6 months
12 months
1 1
4 7
10 13
18 16
20 20
Table 5 shows recovery of the nerve in both groups. Patients in the retrograde group seemed to recover from serious nerve injury faster than in the antegrade group. Proportionately more had fully recovered in the retrograde group than in the antegrade group at 1 month and 3 months. Almost all the nerves had recovered fully at 6 months. All patients in both groups had recovered fully at 12 months (Figs. 3–5).
Discussion
Nerve recovery (Table 4) In the antegrade group half the patients had no nerve injury or mild injury (HB I–II) at week 1. A third of the remaining patients with serious nerve injuries (HBIII or above) had fully recovered by 3 months, and nerves in 85% of the whole group had fully recovered at 6 months. In the retrograde group 40% of patients had mild or no nerve injury at week 1 and 60% had a serious nerve injury. Half the whole group had fully recovered nerves at 3 months, and all who had had a serious nerve injury had fully recovered at this time.
Two basic techniques are used for facial nerve dissection in parotid surgery. Antegrade dissection is the more widely used technique, and in a recent national questionnaire survey,2 87% of the responding surgeons used it routinely. By comparison, the retrograde approach was used by 4% routinely, and a combined technique by 9% routinely. We know of no published prospective studies that compare the techniques with respect to nerve injury and recovery. We applied a low threshold to the identification and assessment of any weakness in the nerve branch, which may be reflected in the high initial rate of injury to the nerve that we documented in both groups compared with other studies. There are numerous published studies of temporary and permanent weakness of the facial nerve after parotidectomy for benign disease.3–9 Methods used to assess facial nerve function vary considerably and grading of facial paresis is not standardised. Often no distinction is made between the
Fig. 3. Bar chart showing nerve recovery rates for the antegrade technique.
290
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
Fig. 4. Bar chart showing nerve recovery rates for the retrograde technique.
degree of nerve injury and the site of paresis or paralysis. The application of the HB system enables the comparison of nerve morbidity across techniques and specialties. Although there were more initial serious (HBIII or above) nerve injuries (60%) in the retrograde group than in the antegrade group, recovery was faster in the retrograde group. This raises interesting questions about the pathophysiology of motor nerve injury. Weakness of the facial nerve in the postoperative phase is related to the length of dissection and the degree of ischaemia during operation.8 Similar postoperative results have been noted in other motor nerves, but we know of no data on the direct effects of intraoperative trauma on the facial nerve and its recovery. It is also not known whether
initial direct exposure of the facial nerve trunk contributes to the degree of postoperative weakness. It is possible that a more severe ischaemic pattern is associated with different dissection techniques. This does not seem to affect long-term recovery of the nerve as permanent recovery was complete in both groups. In a number of clinical situations the retrograde technique may provide an adjunctive or alternative approach. These include large tumours, obese patients, or where revision parotidectomy is necessary. Variability in the anatomy of the nerve branch and the diameter of the peripheral branch compared with the nerve trunk may concern surgeons who wish to consider using a retrograde approach. The landmarks
Fig. 5. Bar chart showing a comparison of full nerve recovery rates in both groups.
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
of the peripheral branches are relatively easy to identify. The buccal branch is the most reliable branch to locate initially and is closely related to the parotid duct, which is relatively constant in position and easily identified. The location of the marginal mandibular nerve may be more difficult as its position is not constant.13 The relation of the nerve branch to the retromandibular vein is not always reliable and its identification is made easier by using a nerve stimulator. The lower border of the zygomatic arch is a reliable bony landmark for the zygomatic branches. Retrograde nerve dissection also has some possible advantages. Selective or individual exposure of branches of the nerve is possible and helps to avoid unnecessary exposure of the trunk, which may reduce the risk of nerve injury across the face.14 A wider operative field allows easier dissection with safer haemostasis.4 The position of the facial nerve trunk may make it difficult to locate, particularly when the tumour is large or when the main trunk is displaced by the tumour.15,16 We found a higher rate of serious nerve injury associated with the retrograde group at week 1, and serious nerve injuries were slower to recover in the antegrade group than in the retrograde group at 3 months, but there was no difference between the groups in the rates of full recovery at 6 months, which indicates that the rate of permanent nerve injury in our study was not affected by the choice of dissection technique.
2.
3. 4.
5.
6.
7. 8. 9. 10.
11. 12.
Conflict of interest
13.
The authors have no conflict of interest. 14.
References 1. O’Regan B, Bharadwaj G, Bhopal S, Cook V. Facial nerve morbidity after retrograde nerve dissection in parotid surgery for benign disease:
15. 16.
291
a 10-year prospective observational study of 136 cases. Br J Oral Maxillofac Surg 2007;45:101–7. O’Regan B, Bharadwaj G, Elders A. Techniques for dissection of the facial nerve in benign parotid surgery: a cross specialty survey of oral and maxillofacial and ear nose and throat surgeons in the UK. Br J Oral Maxillofac Surg 2008;46:564–6. Bron LP, O’Brien CJ. Facial nerve function after parotidectomy. Arch Otolaryngol Head Neck Surg 1997;123:1091–6. Mehle ME, Kraus DH, Wood BG, Benninger MS, Eliachar I, Levine HL, et al. Facial nerve morbidity following parotid surgery for benign disease: the Cleveland Clinic Foundation experience. Laryngoscope 1993;103:386–8. Laccourreye H, Laccourreye O, Cauchois R, Jouffre V, Ménard M, Brasnu D. Total conservative parotidectomy for primary benign pleomorphic adenoma of the parotid gland: a 25-year experience with 229 patients. Laryngoscope 1994;104:1487–94. Watanabe Y, Ishikawa M, Shojaku H, Mizukoshi K. Facial nerve palsy as a complication of parotid gland surgery and its prevention. Acta Otolaryngol Suppl 1993;504:137–9. Witt RL. The significance of the margin in parotid surgery for pleomorphic adenoma. Laryngoscope 2002;112:2141–54. Cannon CR, Replogle WH, Schenk MP. Facial nerve in parotidectomy: a topographical analysis. Laryngoscope 2004;114:2034–7. Reilly J, Myssiorek D. Facial nerve stimulation and postparotidectomy facial paresis. Otolaryngol Head Neck Surg 2003;128:530–3. Anjum K, Revington PJ, Irvine GH. Superficial parotidectomy: antegrade compared with modified retrograde dissections of the facial nerve. Br J Oral Maxillofac Surg 2008;46:433–4. House JW. Facial nerve grading systems. Laryngoscope 1983;93:1056–69. Brackmann DE, Barrs DM. Assessing recovery of facial function following acoustic neuroma surgery. Otolaryngol Head Neck Surg 1984;92:88–93. Bramley PA. Surgical access and its applied anatomy. In: Norman JE, de B, Bramley PA, editors. Textbook and colour atlas of the temporomandibular joint: diseases, disorders, surgery. Chicago: Mosby; 1990. p. 26–51. Zhao K, Qi DY, Wang LM. Functional superficial parotidectomy. J Oral Maxillofac Surg 1994;52:1038–41. Wang DZ, Liu SJ, Donoff RB, Guralnick W. A modified centripetal approach to parotidectomy. J Oral Maxillofac Surg 1985;43:14–9. Wong DS. Surface landmarks of the facial nerve trunk: a prospective measurement study. ANZ J Surg 2001;71:753–6.
British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
Comparison of facial nerve injury and recovery rates after antegrade and retrograde nerve dissection in parotid surgery for benign disease: prospective study over 4 years Barry O’Regan ∗ , Girish Bharadwaj Maxillofacial Unit, Queen Margaret Hospital, Dunfermline, United Kingdom Accepted 19 May 2010 Available online 15 June 2010
Abstract The facial nerve can be dissected using an antegrade or retrograde approach. Antegrade dissection is the established technique and retrograde dissection is used less often. Recent publications have drawn attention to the potential value of the retrograde technique particularly if direct identification of the nerve trunk is difficult, and in revision procedures. We prospectively studied 43 consecutive procedures in 40 patients who had parotidectomy over a 4-year period, and evaluated and compared rates of temporary and permanent nerve injury, and nerve recovery after antegrade and retrograde dissection in operations for benign parotid disease. Each patient was allocated randomly to the antegrade (n = 20) or retrograde (n = 20) groups. Three patients were excluded. All patients had peroperative nerve monitoring and were followed up at 1 week, 1 month, 3 months, or to full recovery of the nerve. The House-Brackmann (HB) grading system was used to assess the degree of injury to the nerve. A high rate of serious nerve injury (HBIII or above) was associated with retrograde dissection at 1 week. Serious nerve injuries (HBIII or above) were slow to recover after the antegrade technique at 3 months. There was no difference between groups in the rates of full nerve recovery at 6 months. © 2010 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Parotidectomy; Antegrade nerve dissection; Retrograde nerve dissection; Nerve injury rate; Nerve recovery rate; Facial nerve monitoring
Introduction One of the main aims of parotidectomy is to minimise injury to the facial nerve and maximise the rate at which it recovers. Two techniques are used for dissection of the facial nerve in parotid surgery. In the antegrade technique the nerve trunk is identified as it leaves the stylomastoid foramen and dissection then proceeds peripherally, and in retrograde technique the peripheral nerve branches are identified initially and dissection proceeds towards the nerve trunk.1 Antegrade dissection is used most commonly. In a national cross specialty questionnaire survey in 2007,2 it was used
∗ Corresponding author at: Maxillofacial Unit, Queen Margaret Hospital, Whitefield Road, Dunfermline, Fife KY12 0SU, United Kingdom. Tel.: +44 1383 623623; fax: +44 1383 674044. E-mail address: [email protected] (B. O’Regan).
routinely by 87% of responding surgeons. Almost half the surgeons combined both techniques in revision parotid surgery, indicating their familiarity with both approaches. In some clinical situations such as in obese patients with large tumours it may be difficult to identify the nerve trunk directly, and the retrograde technique provides a useful alternative. Many factors affect the rate that the facial nerve recovers after parotid gland surgery.3–9 They include age, sex, disease, location (superficial or deep lobe involvement), tumour size, recurrent disease, type and duration of operation, and the total length of nerve dissected. We know of no published prospective studies that compare rates of injury to the facial nerve and its recovery across both techniques. In a recent retrospective comparative study of the techniques, no difference was found in the incidence of postoperative nerve morbidity, although the study did not describe how the injury was measured.10 We measured rates of injury
0266-4356/$ – see front matter © 2010 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2010.05.013
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
287
Fig. 1. Data collection form – nerve dissection technique prospective study.
at 1 week after operation using the House-Brackmann (HB) system,11,12 and documented the rates at which the nerve recovered for both techniques at 1 month, 3 months, 6 months, or until recovery was complete.
Method Over 4 years 40 consecutive patients were recruited and randomly allocated into two groups of 20, antegrade (4 men, 16
women, age range 40–73, mean age 52 years) and retrograde (6 men, 14 women, age range 36–81, mean age 56 years). Male to female ratio overall was 1:3. All patients were advised that they would be included in the study on the assumption that there would be no difference in outcome after operation whichever technique was used. They were made aware that the choice of technique was random, and were also advised that the default technique in the event of exclusion would be the retrograde method. No patient asked to be excluded. Forty-three operations were done; 21
288
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
in the antegrade group and 22 in the retrograde group. One patient with malignant disease was excluded from the antegrade group, and two were excluded from the retrograde group. All patients were operated on by a single surgeon, and continuous intraoperative monitoring of the facial nerve was done in all cases. Technique Antegrade dissection is done by identifying the facial nerve trunk using the tragal pointer method. A modified Blair incision is used for access to the parotid gland. After initial identification of the nerve trunk, dissection proceeds towards the peripheral branches with simultaneous mobilisation of parotid tissue anteriorly and laterally. The length and number of branches dissected depends on the disease that necessitated removal of the parotid gland. In a retrograde dissection a modified Blair incision is used and the skin flap raised. Blunt dissection extends to the anterior border of the gland where the parotid duct is used as a landmark to identify the buccal branch of the facial nerve. The duct is routinely ligated and divided. The retromandibular vein is used to identify the marginal mandibular branch, and the zygomatic branches are located below the lower border of the zygomatic arch. The preferred order in which to expose the branches is buccal, mandibular, cervical, zygomatic, and temporal for diffuse disease. For benign tumours the number and sequence in which the branches are exposed is decided by the site and size of the tumour. We continue the dissection to identify the bifurcation and trunk of the facial nerve. We used the House-Brackmann grading system to assess nerve function. This system has six grades: grade I is normal nerve function; grade II indicates mild nerve dysfunction not detectable at rest; and grades III–VI indicate progressively severe paresis of the nerve in function and at rest. Examination at each stage in the study was carried out either by the
Table 1 Histological diagnoses across the groups. Diagnosis Pleomorphic salivary adenoma Warthin tumour Sialadenitis Sialosis Other
Antegrade (n = 20)
Retrograde (n = 20)
Combined (n = 40)
5
10
15
1 11 2 1
1 9 0 0
2 20 2 1
Table 2 Operations in each group. Operation
Antegrade (n = 20)
Retrograde (n = 20)
Superficial parotidectomy Total parotidectomy Lobectomy
13 7 0
15 4 1
authors or by one of the senior clinicians in the unit to reduce bias. All patients were followed up at 1 week, 1 month, 3 months, or at full recovery. The most affected branch was used for the purpose of analysis. The data collection form is shown in Fig. 1. An Excel database was used to collate and analyse the data. Results The disease profile of the patients is shown in Table 1, and the operations carried out in both groups are shown in Table 2. Initial nerve injury The initial nerve injury was recorded at 1 week after operation. Any injury equivalent to HBIII or more was considered serious. Half the patients in the antegrade group and 60% in the retrograde group had such injuries at week 1 (Table 3, Fig. 2).
Fig. 2. Bar chart showing initial nerve injury rates in both groups at week 1.
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291 Table 3 Nerve injury 1 week after operation (n = 20 in both groups). Data are number. House-Brackmann scale
Antegrade Retrograde
I
II
III
IV
V
1 1
9 7
8 11
1 1
1 0
Table 4 Recovery of facial nerve after operation in both groups (n = 20 in both groups). Data are number. House-Brackmann scale I
II
III
IV
V
Antegrade Week 1 Month 1 Month 3 Month 6
1 7 13 17
9 6 4 2
8 7 3 1
1 0 0 0
1 0 0 0
Retrograde Week 1 Month 1 Month 3 Month 6
1 4 10 18
7 11 10 2
11 5 0 0
1 0 0 0
0 0 0 0
289
Table 5 Number of patients with full recovery of the facial nerve (n = 20 in both groups). Time after operation
Antegrade Retrograde
1 week
1 month
3 months
6 months
12 months
1 1
4 7
10 13
18 16
20 20
Table 5 shows recovery of the nerve in both groups. Patients in the retrograde group seemed to recover from serious nerve injury faster than in the antegrade group. Proportionately more had fully recovered in the retrograde group than in the antegrade group at 1 month and 3 months. Almost all the nerves had recovered fully at 6 months. All patients in both groups had recovered fully at 12 months (Figs. 3–5).
Discussion
Nerve recovery (Table 4) In the antegrade group half the patients had no nerve injury or mild injury (HB I–II) at week 1. A third of the remaining patients with serious nerve injuries (HBIII or above) had fully recovered by 3 months, and nerves in 85% of the whole group had fully recovered at 6 months. In the retrograde group 40% of patients had mild or no nerve injury at week 1 and 60% had a serious nerve injury. Half the whole group had fully recovered nerves at 3 months, and all who had had a serious nerve injury had fully recovered at this time.
Two basic techniques are used for facial nerve dissection in parotid surgery. Antegrade dissection is the more widely used technique, and in a recent national questionnaire survey,2 87% of the responding surgeons used it routinely. By comparison, the retrograde approach was used by 4% routinely, and a combined technique by 9% routinely. We know of no published prospective studies that compare the techniques with respect to nerve injury and recovery. We applied a low threshold to the identification and assessment of any weakness in the nerve branch, which may be reflected in the high initial rate of injury to the nerve that we documented in both groups compared with other studies. There are numerous published studies of temporary and permanent weakness of the facial nerve after parotidectomy for benign disease.3–9 Methods used to assess facial nerve function vary considerably and grading of facial paresis is not standardised. Often no distinction is made between the
Fig. 3. Bar chart showing nerve recovery rates for the antegrade technique.
290
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
Fig. 4. Bar chart showing nerve recovery rates for the retrograde technique.
degree of nerve injury and the site of paresis or paralysis. The application of the HB system enables the comparison of nerve morbidity across techniques and specialties. Although there were more initial serious (HBIII or above) nerve injuries (60%) in the retrograde group than in the antegrade group, recovery was faster in the retrograde group. This raises interesting questions about the pathophysiology of motor nerve injury. Weakness of the facial nerve in the postoperative phase is related to the length of dissection and the degree of ischaemia during operation.8 Similar postoperative results have been noted in other motor nerves, but we know of no data on the direct effects of intraoperative trauma on the facial nerve and its recovery. It is also not known whether
initial direct exposure of the facial nerve trunk contributes to the degree of postoperative weakness. It is possible that a more severe ischaemic pattern is associated with different dissection techniques. This does not seem to affect long-term recovery of the nerve as permanent recovery was complete in both groups. In a number of clinical situations the retrograde technique may provide an adjunctive or alternative approach. These include large tumours, obese patients, or where revision parotidectomy is necessary. Variability in the anatomy of the nerve branch and the diameter of the peripheral branch compared with the nerve trunk may concern surgeons who wish to consider using a retrograde approach. The landmarks
Fig. 5. Bar chart showing a comparison of full nerve recovery rates in both groups.
B. O’Regan, G. Bharadwaj / British Journal of Oral and Maxillofacial Surgery 49 (2011) 286–291
of the peripheral branches are relatively easy to identify. The buccal branch is the most reliable branch to locate initially and is closely related to the parotid duct, which is relatively constant in position and easily identified. The location of the marginal mandibular nerve may be more difficult as its position is not constant.13 The relation of the nerve branch to the retromandibular vein is not always reliable and its identification is made easier by using a nerve stimulator. The lower border of the zygomatic arch is a reliable bony landmark for the zygomatic branches. Retrograde nerve dissection also has some possible advantages. Selective or individual exposure of branches of the nerve is possible and helps to avoid unnecessary exposure of the trunk, which may reduce the risk of nerve injury across the face.14 A wider operative field allows easier dissection with safer haemostasis.4 The position of the facial nerve trunk may make it difficult to locate, particularly when the tumour is large or when the main trunk is displaced by the tumour.15,16 We found a higher rate of serious nerve injury associated with the retrograde group at week 1, and serious nerve injuries were slower to recover in the antegrade group than in the retrograde group at 3 months, but there was no difference between the groups in the rates of full recovery at 6 months, which indicates that the rate of permanent nerve injury in our study was not affected by the choice of dissection technique.
2.
3. 4.
5.
6.
7. 8. 9. 10.
11. 12.
Conflict of interest
13.
The authors have no conflict of interest. 14.
References 1. O’Regan B, Bharadwaj G, Bhopal S, Cook V. Facial nerve morbidity after retrograde nerve dissection in parotid surgery for benign disease:
15. 16.
291
a 10-year prospective observational study of 136 cases. Br J Oral Maxillofac Surg 2007;45:101–7. O’Regan B, Bharadwaj G, Elders A. Techniques for dissection of the facial nerve in benign parotid surgery: a cross specialty survey of oral and maxillofacial and ear nose and throat surgeons in the UK. Br J Oral Maxillofac Surg 2008;46:564–6. Bron LP, O’Brien CJ. Facial nerve function after parotidectomy. Arch Otolaryngol Head Neck Surg 1997;123:1091–6. Mehle ME, Kraus DH, Wood BG, Benninger MS, Eliachar I, Levine HL, et al. Facial nerve morbidity following parotid surgery for benign disease: the Cleveland Clinic Foundation experience. Laryngoscope 1993;103:386–8. Laccourreye H, Laccourreye O, Cauchois R, Jouffre V, Ménard M, Brasnu D. Total conservative parotidectomy for primary benign pleomorphic adenoma of the parotid gland: a 25-year experience with 229 patients. Laryngoscope 1994;104:1487–94. Watanabe Y, Ishikawa M, Shojaku H, Mizukoshi K. Facial nerve palsy as a complication of parotid gland surgery and its prevention. Acta Otolaryngol Suppl 1993;504:137–9. Witt RL. The significance of the margin in parotid surgery for pleomorphic adenoma. Laryngoscope 2002;112:2141–54. Cannon CR, Replogle WH, Schenk MP. Facial nerve in parotidectomy: a topographical analysis. Laryngoscope 2004;114:2034–7. Reilly J, Myssiorek D. Facial nerve stimulation and postparotidectomy facial paresis. Otolaryngol Head Neck Surg 2003;128:530–3. Anjum K, Revington PJ, Irvine GH. Superficial parotidectomy: antegrade compared with modified retrograde dissections of the facial nerve. Br J Oral Maxillofac Surg 2008;46:433–4. House JW. Facial nerve grading systems. Laryngoscope 1983;93:1056–69. Brackmann DE, Barrs DM. Assessing recovery of facial function following acoustic neuroma surgery. Otolaryngol Head Neck Surg 1984;92:88–93. Bramley PA. Surgical access and its applied anatomy. In: Norman JE, de B, Bramley PA, editors. Textbook and colour atlas of the temporomandibular joint: diseases, disorders, surgery. Chicago: Mosby; 1990. p. 26–51. Zhao K, Qi DY, Wang LM. Functional superficial parotidectomy. J Oral Maxillofac Surg 1994;52:1038–41. Wang DZ, Liu SJ, Donoff RB, Guralnick W. A modified centripetal approach to parotidectomy. J Oral Maxillofac Surg 1985;43:14–9. Wong DS. Surface landmarks of the facial nerve trunk: a prospective measurement study. ANZ J Surg 2001;71:753–6.