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Facial nerve morbidity after retrograde nerve dissection in parotid surgery for benign disease: A 10-year prospective observational study of 136 cases
British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
Facial nerve morbidity after retrograde nerve dissection in parotid surgery for benign disease: A 10-year prospective observational study of 136 cases Barry O’Regan ∗ , Girish Bharadwaj, Satwant Bhopal, Victoria Cook Department of Maxillofacial Surgery, Queen Margaret Hospital, Dunfermline, Fife, Scotland, United Kingdom Accepted 13 March 2006 Available online 3 May 2006
Abstract We evaluated the facial nerve function in 136 patients who had had retrograde nerve dissection during parotidectomy for benign disease. One week after the operation 90 patients (66%) had some weakness of the facial nerve. After 1 month 52 (38%) had facial nerve paresis. After 3 months 114 (84%) had recovered fully and 21 (16%) had minor nerve paresis. After 6 months 135 (99%) had normal nerve function. One patient had persistent marginal mandibular nerve paresis. © 2006 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Parotidectomy; Retrograde facial nerve dissection; Antegrade approach; Facial nerve morbidity; House–Brackmann grading; Electromyographic nerve monitoring
Introduction During operations on the parotid it is necessary to identify the facial nerve using either an antegrade1 or a retrograde2 approach. The antegrade approach requires identification of the facial nerve trunk as it leaves the stylomastoid foramen and centrifugal dissection of the peripheral branches. Sistrunk in 1921, and Arson and Ott in 1923, described the retrograde exposure of the marginal mandibular branch of the facial nerve to lead to the nerve trunk, but the technique was not widely practised.3 Janes in 1940 advocated a new direct approach to the nerve trunk,4 and this led to the adoption of antegrade dissection as the preferred technique. A number of recent publications have renewed attention to the retrograde technique.5–7 Bhattacharyya et al.5 reported a series of 45 patients (19 standard and 26 retrograde) who had had parotidectomies. They concluded that the retrograde ∗
Corresponding author. Tel.: +44 1383 623623x6637. E-mail address: [email protected] (B. O’Regan).
approach to the facial nerve was quicker, reduced intraoperative blood loss, and resulted in less normal parotid tissue being removed than the antegrade approach. Wang et al.7 reported no permanent facial paresis in 383 patients after retrograde identification of the facial nerve. The conventional antegrade approach is the standard procedure for a trainee to master, but location of the nerve trunk may challenge even an experienced surgeon who operates on obese patients, those with large tumours, or who does revision operations.8 Retrograde dissection of the nerve is a useful option if the surgeon fails to identify the nerve trunk directly, or in revision surgery where the technique has a more established role.9 Recently many other authors have suggested a more conservative approach to benign parotid tumours.10–12 O’Brien, in a study of 363 parotidectomies, questioned the use of traditional parotidectomy in the surgical treatment of benign tumours.11 He suggested that complete superficial parotidectomy is not necessary in the treatment of localised tumours. In his series, limited superficial parotidectomy was associated with a low incidence of lesions of the facial nerve, and
0266-4356/$ – see front matter © 2006 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2006.03.009
102
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
Table 1 Histological diagnosis of specimens Diagnosis
n = 136
Adenomas Pleomorphic salivary adenoma Adenolymphoma Basal cell adenoma
51 14 2
Tumour-like lesions Sialopathy Benign lymphoepithelial lesion Cystic lesions
11 5 7
Sialadenitis
42
Others Benign lymphadenopathy Fibrolipoma Lipoma
2 1 1
he quoted a transient weakness of the nerve in 27% and permanent weakness in 2.5%. Technological improvements in peroperative monitoring of the facial nerve during the past decade have made the identification of the peripheral branches easier.13
Patients and methods During a period of 10 years, from 1995 to 2005, we examined 136 consecutive patients (86 women and 50 men) who had retrograde dissection of the nerve in parotidectomies for benign disease by a single consultant surgeon. The mean age was 48 years (range 14–83 years). A total of 114 patients (83%) had superficial parotidectomy, 11 (8%) had partial
superficial parotidectomy, and 11 (8%) had total parotidectomy. The histological diagnoses are shown in Table 1. We excluded patients with malignant lesions. We refined the data collection form after consultation with colleagues. Preoperative diagnoses were established by fine needle aspiration cytology and computed tomography or magnetic resonance imaging. The condition of the facial nerve was recorded after the operation. Operation (Figs. 1–4) Local anaesthesia is injected around the parotid to reduce bleeding. The incision is made using a modified Blair approach, and the skin flap rose to the anterior, superior and inferior borders of the gland superficial to the periparotid fascia, which also causes less bleeding. Blunt dissection extends to the anterior border of the gland where the parotid duct is used as a landmark to identify and dissect the buccal branch of the facial nerve. The parotid duct is ligated routinely and divided, except when a limited superficial parotidectomy is indicated. The retromandibular vein is used to identify the marginal mandibular branch, and the zygomatic branches are located inferior to the lower border of the zygomatic arch. Dissection of the facial nerve branches is aided by creating a tunnel within the parotid tissue superficial to the nerve. The preferred order of exposure of branches of the nerve is usually buccal, mandibular, cervical, zygomatic, and temporal for diffuse disease. For benign tumours, the number and sequence of exposure of the branches is decided by the site and size of tumour. We continue the dissection to identify the bifurcation and trunk of the facial nerve, and then
Fig. 1. Surface markings and infiltration of anaesthetic.
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
103
Fig. 2. Identification of buccal (yellow sling), mandibular (arrow), and zygomatic (blue sling) branches.
dissect the posterior border of the gland in the avascular precartilagenous plane using the mastoid process as a landmark. The lower pole and posterolateral margin of the gland are dissected off the anterolateral edge of the sternocleidomastoid muscle to complete its mobilisation. All patients had intraoperative monitoring of the nerve using a MAGSTIM NEUROSIGN® . They were all assessed postoperatively using the House–Brackmann grading system 14–16 (Table 2) at 1 week; 1, 3, and 6 months; or until full recovery of the nerve (Fig. 5). This is the standard for grading recovery of the facial nerve recommended by the American Society of Otolaryngology.16
Results At the end of a week 1, 46 patients (34%) had fully recovered and 90 patients (66%) had some paresis of the facial nerve. Of these, 68 had slight paresis, noticeable on movement, consistent with House–Brackmann grade II, and 21 had grade III shown by obvious but not disfiguring paresis on movement. One patient had obvious paresis and disfiguring asymmetry on movement consistent with grade IV. (Grades II, III, and IV show normal symmetry and tone at rest.) No patient had grade V or VI at week 1. At the end of a month, 84 patients (62%) had recovered fully, 44 patients (32%) had facial nerve paresis consistent
Fig. 3. Cervical branch identified (arrow).
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B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
Fig. 4. Demonstration of temporal (arrow), zygomatic (blue sling), and buccal (yellow sling) branches.
with grade II, and the remaining 8 patients (6%) were graded as House–Brackmann III. At the end of the third month, 114 patients (84%) had recovered fully, 21 patients (15%) had mild weakness consistent with grade II, and 1 patient (1%) had obvious paresis on movement consistent with grade III. At 6 months and 1 year after the operation, one patient had a presumed permanent minor paresis of the marginal mandibular nerve (grade II). The data on lesions of the nerve were also analysed with reference to four histological categories (Table 3), and four arbitrarily selected age groups (Table 4, Fig. 6).
Table 3 summarises the morbidity associated with the facial nerve by histological subtypes. Table 4 gives the morbidity associated with age.
Discussion Assessment methods of nerve function vary considerably, and there is often no distinction made between the degree and the site of paresis or paralysis. The application of the House–Brackmann grading system14–16 facilitates the comparison of morbidities both within and across specialties.
Table 2 House–Brackmann grading Grade
Function
I II
Normal Mild dysfunction
III
Moderate dysfunction
IV
Moderately severe dysfunction
V
Severe dysfunction
VI
Total paralysis
Appearance
Movement
Gross
At rest
Forehead
Eye
Mouth
Normal Slight weakness noticeable on close inspection, may have slight synkinesis Obvious but not disfiguring difference between two sides. Noticeable but not severe synkinesis, contracture or hemifacial spasm. Obvious weakness and disfiguring asymmetry Only barely perceptible movement No movement
Normal Normal symmetry and tone
Normal Moderate to good function
Normal Complete closure with minimum effort
Normal Slight asymmetry
Normal symmetry and tone
Slight to moderate movement
Complete closure with effort
Slightly weak with maximum effort
Normal symmetry and tone
None
Incomplete closure
Asymmetrical with maximum effort
Asymmetry
None
Incomplete closure
Slight movement
No movement
None
None
None
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
105
Table 4 Age and facial nerve morbidity using the House–Brackmann grading postoperatively Time and grade
Age group (years) 10–30 (n = 12)
Fig. 5. Postoperative morbidity of facial nerve. House–Brackmann grade I, open bars; grade II, solid bars; grade III, hatched bars; and grade IV, dotted bars.
Various authors have reported permanent weakness of the facial nerve of 2.5–5% using the antegrade technique.17–21 The rate of permanent nerve weakness (1%) in our study was low and compares favourably with the rate quoted in a retrospective series by Wang et al.7 who described no permanent facial nerve weakness in 383 patients using the retrograde dissection technique. The diameter of the peripheral branches compared with that of the trunk and the variability of their anatomy are of concern to surgeons who may wish to consider the use of a retrograde approach. The soft tissue landmarks of the periphTable 3 Histological diagnosis and morbidity using the House–Brackmann grading postoperatively Time and grade
One week I II III IV One month I II III Three months I II III Six months I II III
Adenoma (n = 67)
Tumour-like lesions (n = 23)
Sialadenitis (n = 42)
Other (n = 4)
22 (33) 35 (52) 10 (15) 0
5 (22) 12 (52) 5 (22) 1 (4)
17 (40) 21 (50) 4 (9) 0
2 0 2 0
39 (58) 26 (39) 2 (3)
9 (39) 11 (48) 3 (13)
34 (81) 6 (14) 2 (5)
2 1 1
56 (84) 10 (15) 1 (1)
17 (74) 6 (26) 0
39 (93) 3 (7) 0
2 2 0
67 (100) 0 0
23 (100) 0 0
41 (98) 1 (2) 0
4 0 0
Data are number (%).
31–50 (n = 55)
51–70 (n = 60)
71–90 (n = 9)
One week I II III IV
5 7 0 0
21 (38) 28 (51) 6 (11) 0
16 (27) 29 (48) 14 (23) 1 (2)
4 4 1 0
One month I II III
9 3 0
40 (73) 14 (25) 1 (2)
30 (50) 23 (38) 7 (12)
5 4 0
Three months I II III
11 1 0
50 (91) 5 (9) 0
45 (75) 14 (23) 1 (2)
8 1 0
Six months I II
12 0
55 (100) 0
59 (98) 1 (2)
9 0
Data are number (%).
eral branches are easier to identify than is commonly thought. The position of the parotid duct is relatively constant and it is easily identified.7,21 The buccal branch is intimately related to the parotid duct, and in our experience it is the most reliable branch to locate initially. Although the position of the marginal mandibular nerve is not constant,22 and its relationship to the retromandibular vein not always reliable, its identification is facilitated by the use of a facial nerve stimulator. The lower border of the zygomatic arch is a reliable bony landmark for the zygomatic branches. The use of electromyographic monitoring of the facial nerve with a stimulating electrode has made the identification of the peripheral branches of the facial nerve much easier.13 We did not find it necessary to convert to an antegrade approach in any patient in this series. There are several possible advantages of the retrograde nerve dissection that deserve comment. Selective exposure of branches of the nerve is possible, and the unnecessary exposure of the trunk may be avoided,21 which reduces the risk of serious damage. A wider operative field allows easier dissection with safer haemostasis, and a shorter operating time reduces morbidity.5 The anatomical position of the trunk of the facial nerve may make it difficult to locate, particularly when the tumour is large, dumbbell-shaped, or when the main trunk is displaced by the tumour.7,23 In such circumstances a retrograde approach to the nerve may be useful. In a recent review of parotid tumours, McGurk24 described a trend towards a more conservative surgical approach to benign parotid tumours. He acknowledged that this approach has been strengthened by two recent publications on benign parotid tumours in which limited superficial parotidectomy was associated with low morbidity and low rates of
106
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Fig. 6. Postoperative morbidity of facial nerve and age. House–Brackmann grade I, open bars; grade II, solid bars; grade III, hatched bars, and grade IV, dotted bars. (A) Age 11–30 years (n = 12); (B) age 31–50 years (n = 55); (C) age 51–70 years (n = 60); and (D) 71–90 years (n = 9).
recurrence.10,12 Snow recommended that partial parotidectomy would preferably entail retrograde nerve dissection of one or more of the peripheral branches of the facial nerve during the removal of pleomorphic adenomas that are situated in the anterior part of superficial lobe, to limit the amount of parotid parenchyma being removed.1
References 1. Snow GB. The surgical approaches to the treatment of parotid pleomorphic adenomas. In: McGurk M, Renehan A, editors. Controversies in the management of salivary gland disease. Oxford: Oxford University Press; 2001. p. 57–63. 2. Chan S, Gunn A. Conservative parotidectomy by the peripheral approach. Br J Surg 1981;68:405–7. 3. Seifert G, Miehlke A, Haubrich J, Chilla R. In: Seifert G, editor. Diseases of the salivary glands—pathology–diagnosis–treatment–facial nerve surgery. New York: Thieme; 1986. p. 329. 4. Janes RM. The treatment of tumours of salivary gland by radical excision. Can Med Assoc J 1940;43:554–9. 5. Bhattacharyya N, Richardson ME, Gugino LD. An objective assessment of the advantages of retrograde parotidectomy. Otolaryngol Head Neck Surg 2004;131:392–6. 6. Yu GY. Superficial parotidectomy through retrograde facial nerve dissection. J R Coll Surg Edin 2001;46:104–7. 7. Wang DZ, Liu SJ, Donoff RB, Guralnick W. A modified centripetal approach to parotidectomy. J Oral Maxillofac Surg 1985;43:14–9.
8. Gunn A. Benign tumours of the parotid and submandibular gland. In: Norman JE, McGurk M, editors. Colour atlas and text of salivary glands. New York: Mosby-Wolfe; 1995. p. 146. 9. Norman JE. Recurrent mixed tumours of the parotid and submandibular glands. In: Norman JE, McGurk M, editors. Colour atlas and text of the salivary glands. New York: MosbyWolfe; 1995. p. 237–9. 10. Ghosh S, Panarese A, Bull PD, Lee JA. Marginally excised parotid pleomorphic adenomas: risk factors for recurrence and management. A 12.5-year mean follow-up study of histologically marginal excisions. Clin Otolaryngol 2003;28:262–6. 11. O’Brien CJ. Current management of benign parotid tumours—the role of limited superficial parotidectomy. Head Neck 2003;25:946–52. 12. Witt RL. Facial nerve function after partial superficial parotidectomy: an 11-year review (1987–1997). Otolaryngol Head Neck Surg 1999;121:210–3. 13. Harner SG, Daube JR, Beatty CW, Ebersold MJ. Intraoperative monitoring of the facial nerve. Laryngoscope 1988;98:209–12. 14. House JW. Facial nerve grading systems. Laryngoscope 1983;93:1056–69. 15. Brackmann DE, Barrs DM. Assessing recovery of facial function following acoustic neuroma surgery. Otolaryngol Head Neck Surg 1984;92:88–93. 16. House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg 1985;93:146–7. 17. Mehle ME, Kraus DH, Wood BG, et al. Facial nerve morbidity following parotid surgery for benign disease: the Cleveland Clinic Foundation experience. Laryngoscope 1993;103:386–8. 18. Laccourreye H, Laccourreye O, Couchois R, Jouffre V, Menard M, Brasnu D. Total conservative parotidectomy for primary benign pleo-
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107 morphic adenoma of the parotid gland: a 25-year experience with 229 patients. Laryngoscope 1994;104:1487–94. 19. O’Brien CJ. Morbidity following surgery for benign parotid disease. In: McGurk M, Renehan A, editors. Controversies in the management of salivary gland disease. Oxford: Oxford University Press; 2001. p. 136. 20. Bron LP, O’Brien CJ. Facial nerve function after parotidectomy. Arch Otolaryngol Head Neck Surg 1997;123:1091–6. 21. Zhao K, Qi DY, Wang LM. Functional superficial parotidectomy. J Oral Maxillofac Surg 1994;52:1038–41.
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22. Bramley PA. Surgical access and its applied anatomy. In: Norman JE, Bramley P, editors. Textbook and colour atlas of temporomandibular joint surgery. London: Wolfe Medical; 1990. p. 26–51. 23. Wong DSY. Surface landmarks of the facial nerve trunk: a prospective measurement study. Aust NZ J Surg 2001;71:753–6. 24. McGurk M. Parotid tumours-pertinent papers 2002–03; A personal view. J Oral Maxillofac Surg 2005;43:350–3.
Facial nerve morbidity after retrograde nerve dissection in parotid surgery for benign disease: A 10-year prospective observational study of 136 cases Barry O’Regan ∗ , Girish Bharadwaj, Satwant Bhopal, Victoria Cook Department of Maxillofacial Surgery, Queen Margaret Hospital, Dunfermline, Fife, Scotland, United Kingdom Accepted 13 March 2006 Available online 3 May 2006
Abstract We evaluated the facial nerve function in 136 patients who had had retrograde nerve dissection during parotidectomy for benign disease. One week after the operation 90 patients (66%) had some weakness of the facial nerve. After 1 month 52 (38%) had facial nerve paresis. After 3 months 114 (84%) had recovered fully and 21 (16%) had minor nerve paresis. After 6 months 135 (99%) had normal nerve function. One patient had persistent marginal mandibular nerve paresis. © 2006 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Parotidectomy; Retrograde facial nerve dissection; Antegrade approach; Facial nerve morbidity; House–Brackmann grading; Electromyographic nerve monitoring
Introduction During operations on the parotid it is necessary to identify the facial nerve using either an antegrade1 or a retrograde2 approach. The antegrade approach requires identification of the facial nerve trunk as it leaves the stylomastoid foramen and centrifugal dissection of the peripheral branches. Sistrunk in 1921, and Arson and Ott in 1923, described the retrograde exposure of the marginal mandibular branch of the facial nerve to lead to the nerve trunk, but the technique was not widely practised.3 Janes in 1940 advocated a new direct approach to the nerve trunk,4 and this led to the adoption of antegrade dissection as the preferred technique. A number of recent publications have renewed attention to the retrograde technique.5–7 Bhattacharyya et al.5 reported a series of 45 patients (19 standard and 26 retrograde) who had had parotidectomies. They concluded that the retrograde ∗
Corresponding author. Tel.: +44 1383 623623x6637. E-mail address: [email protected] (B. O’Regan).
approach to the facial nerve was quicker, reduced intraoperative blood loss, and resulted in less normal parotid tissue being removed than the antegrade approach. Wang et al.7 reported no permanent facial paresis in 383 patients after retrograde identification of the facial nerve. The conventional antegrade approach is the standard procedure for a trainee to master, but location of the nerve trunk may challenge even an experienced surgeon who operates on obese patients, those with large tumours, or who does revision operations.8 Retrograde dissection of the nerve is a useful option if the surgeon fails to identify the nerve trunk directly, or in revision surgery where the technique has a more established role.9 Recently many other authors have suggested a more conservative approach to benign parotid tumours.10–12 O’Brien, in a study of 363 parotidectomies, questioned the use of traditional parotidectomy in the surgical treatment of benign tumours.11 He suggested that complete superficial parotidectomy is not necessary in the treatment of localised tumours. In his series, limited superficial parotidectomy was associated with a low incidence of lesions of the facial nerve, and
0266-4356/$ – see front matter © 2006 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.bjoms.2006.03.009
102
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
Table 1 Histological diagnosis of specimens Diagnosis
n = 136
Adenomas Pleomorphic salivary adenoma Adenolymphoma Basal cell adenoma
51 14 2
Tumour-like lesions Sialopathy Benign lymphoepithelial lesion Cystic lesions
11 5 7
Sialadenitis
42
Others Benign lymphadenopathy Fibrolipoma Lipoma
2 1 1
he quoted a transient weakness of the nerve in 27% and permanent weakness in 2.5%. Technological improvements in peroperative monitoring of the facial nerve during the past decade have made the identification of the peripheral branches easier.13
Patients and methods During a period of 10 years, from 1995 to 2005, we examined 136 consecutive patients (86 women and 50 men) who had retrograde dissection of the nerve in parotidectomies for benign disease by a single consultant surgeon. The mean age was 48 years (range 14–83 years). A total of 114 patients (83%) had superficial parotidectomy, 11 (8%) had partial
superficial parotidectomy, and 11 (8%) had total parotidectomy. The histological diagnoses are shown in Table 1. We excluded patients with malignant lesions. We refined the data collection form after consultation with colleagues. Preoperative diagnoses were established by fine needle aspiration cytology and computed tomography or magnetic resonance imaging. The condition of the facial nerve was recorded after the operation. Operation (Figs. 1–4) Local anaesthesia is injected around the parotid to reduce bleeding. The incision is made using a modified Blair approach, and the skin flap rose to the anterior, superior and inferior borders of the gland superficial to the periparotid fascia, which also causes less bleeding. Blunt dissection extends to the anterior border of the gland where the parotid duct is used as a landmark to identify and dissect the buccal branch of the facial nerve. The parotid duct is ligated routinely and divided, except when a limited superficial parotidectomy is indicated. The retromandibular vein is used to identify the marginal mandibular branch, and the zygomatic branches are located inferior to the lower border of the zygomatic arch. Dissection of the facial nerve branches is aided by creating a tunnel within the parotid tissue superficial to the nerve. The preferred order of exposure of branches of the nerve is usually buccal, mandibular, cervical, zygomatic, and temporal for diffuse disease. For benign tumours, the number and sequence of exposure of the branches is decided by the site and size of tumour. We continue the dissection to identify the bifurcation and trunk of the facial nerve, and then
Fig. 1. Surface markings and infiltration of anaesthetic.
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
103
Fig. 2. Identification of buccal (yellow sling), mandibular (arrow), and zygomatic (blue sling) branches.
dissect the posterior border of the gland in the avascular precartilagenous plane using the mastoid process as a landmark. The lower pole and posterolateral margin of the gland are dissected off the anterolateral edge of the sternocleidomastoid muscle to complete its mobilisation. All patients had intraoperative monitoring of the nerve using a MAGSTIM NEUROSIGN® . They were all assessed postoperatively using the House–Brackmann grading system 14–16 (Table 2) at 1 week; 1, 3, and 6 months; or until full recovery of the nerve (Fig. 5). This is the standard for grading recovery of the facial nerve recommended by the American Society of Otolaryngology.16
Results At the end of a week 1, 46 patients (34%) had fully recovered and 90 patients (66%) had some paresis of the facial nerve. Of these, 68 had slight paresis, noticeable on movement, consistent with House–Brackmann grade II, and 21 had grade III shown by obvious but not disfiguring paresis on movement. One patient had obvious paresis and disfiguring asymmetry on movement consistent with grade IV. (Grades II, III, and IV show normal symmetry and tone at rest.) No patient had grade V or VI at week 1. At the end of a month, 84 patients (62%) had recovered fully, 44 patients (32%) had facial nerve paresis consistent
Fig. 3. Cervical branch identified (arrow).
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Fig. 4. Demonstration of temporal (arrow), zygomatic (blue sling), and buccal (yellow sling) branches.
with grade II, and the remaining 8 patients (6%) were graded as House–Brackmann III. At the end of the third month, 114 patients (84%) had recovered fully, 21 patients (15%) had mild weakness consistent with grade II, and 1 patient (1%) had obvious paresis on movement consistent with grade III. At 6 months and 1 year after the operation, one patient had a presumed permanent minor paresis of the marginal mandibular nerve (grade II). The data on lesions of the nerve were also analysed with reference to four histological categories (Table 3), and four arbitrarily selected age groups (Table 4, Fig. 6).
Table 3 summarises the morbidity associated with the facial nerve by histological subtypes. Table 4 gives the morbidity associated with age.
Discussion Assessment methods of nerve function vary considerably, and there is often no distinction made between the degree and the site of paresis or paralysis. The application of the House–Brackmann grading system14–16 facilitates the comparison of morbidities both within and across specialties.
Table 2 House–Brackmann grading Grade
Function
I II
Normal Mild dysfunction
III
Moderate dysfunction
IV
Moderately severe dysfunction
V
Severe dysfunction
VI
Total paralysis
Appearance
Movement
Gross
At rest
Forehead
Eye
Mouth
Normal Slight weakness noticeable on close inspection, may have slight synkinesis Obvious but not disfiguring difference between two sides. Noticeable but not severe synkinesis, contracture or hemifacial spasm. Obvious weakness and disfiguring asymmetry Only barely perceptible movement No movement
Normal Normal symmetry and tone
Normal Moderate to good function
Normal Complete closure with minimum effort
Normal Slight asymmetry
Normal symmetry and tone
Slight to moderate movement
Complete closure with effort
Slightly weak with maximum effort
Normal symmetry and tone
None
Incomplete closure
Asymmetrical with maximum effort
Asymmetry
None
Incomplete closure
Slight movement
No movement
None
None
None
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
105
Table 4 Age and facial nerve morbidity using the House–Brackmann grading postoperatively Time and grade
Age group (years) 10–30 (n = 12)
Fig. 5. Postoperative morbidity of facial nerve. House–Brackmann grade I, open bars; grade II, solid bars; grade III, hatched bars; and grade IV, dotted bars.
Various authors have reported permanent weakness of the facial nerve of 2.5–5% using the antegrade technique.17–21 The rate of permanent nerve weakness (1%) in our study was low and compares favourably with the rate quoted in a retrospective series by Wang et al.7 who described no permanent facial nerve weakness in 383 patients using the retrograde dissection technique. The diameter of the peripheral branches compared with that of the trunk and the variability of their anatomy are of concern to surgeons who may wish to consider the use of a retrograde approach. The soft tissue landmarks of the periphTable 3 Histological diagnosis and morbidity using the House–Brackmann grading postoperatively Time and grade
One week I II III IV One month I II III Three months I II III Six months I II III
Adenoma (n = 67)
Tumour-like lesions (n = 23)
Sialadenitis (n = 42)
Other (n = 4)
22 (33) 35 (52) 10 (15) 0
5 (22) 12 (52) 5 (22) 1 (4)
17 (40) 21 (50) 4 (9) 0
2 0 2 0
39 (58) 26 (39) 2 (3)
9 (39) 11 (48) 3 (13)
34 (81) 6 (14) 2 (5)
2 1 1
56 (84) 10 (15) 1 (1)
17 (74) 6 (26) 0
39 (93) 3 (7) 0
2 2 0
67 (100) 0 0
23 (100) 0 0
41 (98) 1 (2) 0
4 0 0
Data are number (%).
31–50 (n = 55)
51–70 (n = 60)
71–90 (n = 9)
One week I II III IV
5 7 0 0
21 (38) 28 (51) 6 (11) 0
16 (27) 29 (48) 14 (23) 1 (2)
4 4 1 0
One month I II III
9 3 0
40 (73) 14 (25) 1 (2)
30 (50) 23 (38) 7 (12)
5 4 0
Three months I II III
11 1 0
50 (91) 5 (9) 0
45 (75) 14 (23) 1 (2)
8 1 0
Six months I II
12 0
55 (100) 0
59 (98) 1 (2)
9 0
Data are number (%).
eral branches are easier to identify than is commonly thought. The position of the parotid duct is relatively constant and it is easily identified.7,21 The buccal branch is intimately related to the parotid duct, and in our experience it is the most reliable branch to locate initially. Although the position of the marginal mandibular nerve is not constant,22 and its relationship to the retromandibular vein not always reliable, its identification is facilitated by the use of a facial nerve stimulator. The lower border of the zygomatic arch is a reliable bony landmark for the zygomatic branches. The use of electromyographic monitoring of the facial nerve with a stimulating electrode has made the identification of the peripheral branches of the facial nerve much easier.13 We did not find it necessary to convert to an antegrade approach in any patient in this series. There are several possible advantages of the retrograde nerve dissection that deserve comment. Selective exposure of branches of the nerve is possible, and the unnecessary exposure of the trunk may be avoided,21 which reduces the risk of serious damage. A wider operative field allows easier dissection with safer haemostasis, and a shorter operating time reduces morbidity.5 The anatomical position of the trunk of the facial nerve may make it difficult to locate, particularly when the tumour is large, dumbbell-shaped, or when the main trunk is displaced by the tumour.7,23 In such circumstances a retrograde approach to the nerve may be useful. In a recent review of parotid tumours, McGurk24 described a trend towards a more conservative surgical approach to benign parotid tumours. He acknowledged that this approach has been strengthened by two recent publications on benign parotid tumours in which limited superficial parotidectomy was associated with low morbidity and low rates of
106
B. O’Regan et al. / British Journal of Oral and Maxillofacial Surgery 45 (2007) 101–107
Fig. 6. Postoperative morbidity of facial nerve and age. House–Brackmann grade I, open bars; grade II, solid bars; grade III, hatched bars, and grade IV, dotted bars. (A) Age 11–30 years (n = 12); (B) age 31–50 years (n = 55); (C) age 51–70 years (n = 60); and (D) 71–90 years (n = 9).
recurrence.10,12 Snow recommended that partial parotidectomy would preferably entail retrograde nerve dissection of one or more of the peripheral branches of the facial nerve during the removal of pleomorphic adenomas that are situated in the anterior part of superficial lobe, to limit the amount of parotid parenchyma being removed.1
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