superficial parotidectomy through retrograde facial nerve dissection

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HOW I DO IT

Superficial parotidectomy through retrograde facial nerve

dissection

G.Y. YU Department of Oral and Maxillofacial Surgery, Peking University School of Stomatology, Beijing,100081, P. R. China

Introduction

Indications

Procedure

Complications

References

Keywords: Facial nerve, operation, parotid tumour, superficial parotidectomy

J.R.Coll.Surg.Edinb., 46, February 2001, 104-107

INTRODUCTION

The surgical procedure of superficial parotidectomy is commonly used in the treatment of superficial parotid tumours. It is essential that, where possible, the facial nerve should be preserved, so itsidentification and careful dissection is of paramount importance.

There are two basic techniques for the identification and dissection of the facial nerve. One is the forward

or anterograde dissection, where the approach to the main trunk is taken as an early step, tracing it to the bifurcation and peripheral branches. The other technique is the retrograde dissection, where the peripheral branches are identified first, then proximally to the bifurcation or main trunk. This retrograde dissectionof the facial nerve is the more popular in China. In the past 40 years, we have used this technique inaround 2000 cases, presenting with superficial parotid tumour, in the Peking University School of Stomatology, with encouraging results.

INDICATIONS

The indications for superficial parotidectomy are as follows:

Benign tumours or low-grade malignant tumours of small size and without involvement of thefacial nerve in the superficial lobe of the parotid gland.Chronic inflammation of the parotid gland, resistant to conservative treatment.Tumour-like lesions in the parotid, such as nodular Sjögrens syndrome; oxyphiliclymphogranuloma.

PROCEDURE

Anaesthesia

Local anaesthesia with 1% Lidocain (containing adrenaline if possible) is satisfactory and used in mostcases. Subcutaneous injection of the anaesthetic is administered over the whole operative field. After elevation of the skin flap, anaesthetic is injected into the superficial gland before the gland is incised. In

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this way the anaesthetic infiltrates the gland evenly without gland spillage as the periparotid fascia formsa snug envelope and encompasses the gland. If the anaesthetic is injected after gland incision, theanaesthetic will spill out of the gland, lessening the anaesthetic effect.

Incision

A modified Blair incision is used (Figure 1). The preauricular incision is made in the preauricular crease.

The skin flap is raised to the superior, anterior and inferior borders of the gland. There are two techniquesthat can be utilised to raise the skin flap. One is to raise the flap over the periparotid fascia. The advantageof this technique is less bleeding and a clear operating field. The other technique is to raise the flap under the periparotid fascia. The fascia is included in the skin flap and the gland tissues are exposed. The periparotid fascia can then act as a barrier to the parasympathetic fibres innervating the salivary and sweatglands, thereby, reducing the incidence of Frey’s syndrome. The disadvantage of this technique, however,is more bleeding peri-operatively. The latter may be overcome if the flap is raised by using cuttingdiathermy. Blunt dissection with a haemostat should be used when the anterior border of the gland is to beexposed because the distal branches of the facial nerve emanate from the gland on to the masseter muscle.

Figure 1: The modified Blair incision

Dissection of the facial nerve and resection of the gland

The posterior branch of the great auricular nerve should be preserved unless the tumour involves the nerveor the nerve adheres to the tumour. The great auricular nerve, therefore, is identified and its posterior

branch is preserved before the dissection of the facial nerve is commenced (Figure 2). This approachserves to diminish the loss of sensation to the earlobe.

Figure 2: The posterior branch of great auricular nerve (arrow) is preserved





The procedure of dissection of the facial nerve is the same as that used in the resection of the gland.Stensen’s Duct is used as a landmark for the identification of the buccal branches of the facial nerve. Theskin flap is pulled by a retractor to expose the protrusion of the anterior border of the gland, whereStensen’s duct emanates from the gland onto the masseter muscle. The accessory gland may be foundsuperior to the duct (Figure 3). There are two ways of handling the duct. The facial nerve lies across theduct in most cases, and the duct should be preserved during the dissection of the nerve; the duct, however,

is ligated and cut if the facial nerve is below the duct. The duct is then traced towards the direction of themouth in order to remove the remnants.

Figure 3: Relationship among (1) the buccal branch of the facial nerve, (2) the accessory gland and (3) parotid duct





The retromandibular vein is used as a landmark for the identification of the marginal mandibular branch,and the zygomatic arch for the zygomatic branch of the facial nerve.

Once a nerve branch is identified, dissection proceeds using fine-tipped haemostats to create tunnels in the parotid tissue immediately above the nerve. The bridges of parotid tissue over-lying the nerve are gentlycut with a size 14 # scalpel. The cutting should stop immediately if suspected nerve or blood vessels are

found in the bridges. The dissection should displace the parotid upwards and downwards, and hence,avoiding too deep and narrow tunnelling. Great care should be exercised to avoid inadvertent entry intothe tumour during preservation of the facial nerve. As the bifurcation and main trunk of the facial nerve isexposed, the gland is resected at the posterior border. The parotidectomy should be excised with thetumour ‘en bloc’ (Figure 4).

Figure 4: (left) The superficial lobe is removed; (right) The specimen of superficial lobe and tumour





Several points should be emphasised to avoid mechanical damage to the facial nerve:

Dissection of the facial nerve should be done just above the nerve to show it clearly. To dissect below the nerve is inadvisable. However, the sheath of the facial nerve should not be opened toavoid damage to the nerve fibres.When gauze is used for haemostasis, wet rather than dry gauze is preferable. Clearing of the

operative field of blood should be performed by mild pressure or absorption of the blood rather thanscrubbing. The dissected nerve should be covered by wet gauze to avoid exposure to the air.Bleeding from capillary vessels should be stopped by the pressure of wet gauze, as some bloodvessels are distributed along with the nerve. The facial nerve is readily damaged if artery forcepsare used for haemostasis. The dissection may be continued in the other areas of the gland whilstattaining this haemostasis.The bifurcation of the nerve is close to the retromandibular vein, and any fine branches of the veinshould be ligated and carefully sectioned. Suction is suggested to ensure a clear operational field.Any bleeding vessel should be carefully clipped with a haemostat to avoid damage to the nerve.The branching ducts of the gland must be distinguished from the facial nerve. In general, the nerveis white and shiny, while the duct is grey and dull.

Preservation of the parotid duct

The parotid duct is resected by the traditional technique of superficial parotidectomy. The parotid remnantatrophies spontaneously. It is reported and found in our own experience, that the facial nerve is above the

parotid duct in most cases.2 It is possible, therefore, to preserve the duct during resection of the superficiallobe of the parotid gland. The advantage of this is that the saliva secreted from the parotid remnant will bedischarged into the mouth through the duct and partial function of the gland may be preserved. It should be emphasized that the interlobular ducts, encountered during the dissection, should be ligated carefully inorder to prevent the establishment of a salivary fistula (Figure 5).

Figure 5: Ligation of interlobular duct





Completion of the procedure

After removal of the superficial parotid gland and the tumour, the cut surface of the parotid remnantshould be sutured by absorbable sutures. This achieves haemostasis, and also prevents the development of a salivary fistula. If the duct and function of the parotid remnant are to be preserved, deep sutures should be avoided in order to prevent obstruction of the duct. The wound is irrigated with saline and the integrityof the facial nerve is checked. If the nerve has been disrupted, an end to end anastomosis of the nerve iscarried out. Closed suction drainage is advisable, and the suction tube should be placed away from thedissected facial nerve to prevent damage to the nerve. Further anaesthetic is injected into both sides of theincision. The skin flap is replaced; the platysma muscle and subcutaneous tissues are closed withabsorbable sutures. Finally, the skin incision is closed using 5-0 non-absorbable sutures.

Post-operative management

Closed suction drainage with external pressure by gauge is maintained for 48 or 72 hours and, thereafter,a thin layer of gauze is placed on the wound. The sutures are removed one week after operation.

COMPLICATIONS

Facial nerve weakness

Mechanical damage to the facial nerve should be avoided in most cases if the aforementioned proceduresare followed. The facial nerve may be compressed by a large tumour, or be in close proximity to atumour. In these cases, the facial nerve will inevitably be damaged (to a variable degree) if the nerve is peeled from the capsule of the tumour. In general, the function of the damaged facial nerve will recover inthree months if the nerve itself is not disrupted. During this period, treatment, including injection of Vitamin B1, B12, and the functional training of facial muscles, may serve to accelerate the recovery of facial nerve weakness.

Secondary bleeding

This is a rare complication. In most cases the secondary bleeding is from the damaged retromandibular vein or its branches. The postoperative swelling of the face will be diminished if the retromandibular veinis reserved. The branches of the vein should be li ated carefull to revent secondar bleedin . If the





retromandibular vein is damaged, the upper and lower ends of the damaged vein should be ligated. If significant secondary bleeding occurs, the wound should be reopened, the haematoma removed, thewound irrigated with saline, the active bleeding point identified and the damaged vein ligated.

Local saliva accumulation or salivary fistula

This is caused by continuous secretion of the parotid remnant and obstruction to the outflow of the

secretions. The obstruction of the suction tube may be one of the causes so a regular check of the suctiondrainage system is necessary. If the drainage tube is obstructed irrigation with saline from the outport of the tube into the wound may clean the blood clots obstructing the holes of the inner tube. Suction is thenreconnected and checked for flow. Should there be a large collection of saliva in the wound it can beeliminated by aspiration with a syringe and the wound is then compressed with gauze. Spicy and acidicfoods should be avoided. Administration of atropine, 0.3 mg three times a day, is suggested 30 minutes before meals to decrease saliva secretion.

Loss of sensation to the earlobe

This is generally due to damage to the great auricular nerve. If possible, the nerve should be preserved.The patient will gradually adapt to the situation and the peripheral sensory nerve fibres will regenerate.The loss of earlobe sensation will gradually improve.

Frey’s syndrome

Frey’s syndrome, also termed gustatory sweating syndrome, results from damage to the parasympatheticfibres, which regenerate in a misdirected manner to innervate the sweat glands in the skin overlying thenerve. Stimuli that normally promote parotid gland secretion result in facial sweating. The transfer of thesternocleidomastoid muscle, to preserve the periparotid fascia within the skin flap, might prevent thiscomplication. Most patients with Frey’s syndrome require nothing more than education about the

pathophysiology and reassurance that it is a not unusual side-effect of parotidectomy.3 No specialtreatment is necessary for most patients though application of topical glycopyrrolate is reported to be

effective.4

REFERENCES

1. Bailey H. Treatment of tumors of parotid gland with special reference to total parotidectomy. BMJ 1941; 28: 336-49

2. Zhao K, QI DY, Wang LM. Functional superficial parotidectomy. J Oral Maxillofac Surg 1994; 52:

1038-41

3. Hoffman H, Funt G, Endres D. Evaluation and surgical treat-ment of tumors of the salivary glands.In: Thawley SE, Panje WR, Batsakis JG, Lindberg RD (eds). Comprehensive management of head and neck tumors, 2nd ed. 1999, Philadelphia: W.B. Saunders Co.

4. Hays LL, Novack AJ, Worsham JC. The Frey’s syndrome: a simple, effective treatment.Otolaryngol Head Neck Surg 1982; 90: 419-25

Copyright date: 17th February 2001

Correspondence: Professor Guangyan Yu, Department of Oral and Maxillofacial Surgery, Peking University School of Stomatology, Beijing, 100081, P. R. China

E-mail: [email protected]

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superficial parotidectomy through retrograde facial nerve dissection

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