Superficial parotidectomy
When parotidectomy is performed on the face, there are two important concerns for the surgeon and the patient: the facial surgical scar and the functional damage to the facial nerve. If the close relationship between the facial nerve and the parotid gland were in place, removal of superficial parotid lobe tumors would be an extremely simple and easy procedure. However, because of the close relationship between the branches of the facial nerve and the parotid tissue, superficial parotidectomy with dissection and preservation of the facial nerve becomes a very delicate procedure.
Indications
1, Benign tumors located in the superficial lobe of the parotid gland, low grade malignant tumors that are small in size and not closely related to the facial nerve.
2.Chronic parotiditis, extensive salivary fistulas that have failed with conservative treatment.
3, nodular type of qualified Len syndrome, eosinophilic lymphogranuloma and other tumor-like lesions.
Surgical methods
1.Position and anesthesia
The patient is placed in a supine position, with shoulder pads and head tilted to the opposite side. 1% procaine or lidocaine is used for local infiltration anesthesia, or the following nerves are blocked respectively to improve the anesthetic effect.
(1) The auriculotemporal nerve emanating from the anterior part of the ear screen and the posterior edge of the condyle.
(2) The posterior border of the sternocleidomastoid muscle and the superficial traveling auricular nerve.
2. Incision
Generally, an “S” shaped incision is made, with the upper end starting from the root of the zygomatic arch in front of the ear screen, and the incision is made along the longitudinal skin line, bypassing the earlobe posteriorly and following the posterior edge of the inferior frontal ascending branch in the direction of the mandibular angle forward to the plane of the greater horn of the hyoid bone (Figure 1). The skin, subcutaneous tissues, and the cervical muscle in the subcollar region are incised.
3.Flap
Flap the parotid chewing muscle fascial surface or deep surface until the superior, anterior and inferior margins of the parotid gland are exposed, completely revealing the superficial part of the parotid gland.
4.Exposure of facial nerve and gland excision
The process of anatomical separation of the facial nerve is the process of superficial parotidectomy. There are two main methods to expose the facial nerve: one is to follow the dissection method from the trunk to the tip. The other is a retrograde dissection that traces the nerve from the tip to the trunk. Both methods have their advantages and disadvantages. The trunk of the facial nerve is in a more constant position with clear anatomical landmarks, but it is deeper, narrower, and has a restricted field of view, which increases the chance of trunk damage. Doctors in Europe and the United States mostly use this method. When the tumor is far away from the main trunk of facial nerve, the trunk can not be revealed, so as to reduce the damage to the trunk. This method is mostly used by domestic surgeons. As a surgeon, you should master these two anatomical methods, but the choice of specific cases depends on the location of the tumor and the operator’s habit.
(1) Retrograde dissection method: It is especially suitable for tumors located in the deep lobe of parotid gland and posterior collar area, which can be dissected from the inferior frontal margin branch, buccal branch or frontal branch.
Sistrunt (1921), Adson and Gt (1923) were the first to advocate dissecting the facial nerve from the inferior frontal marginal branch. The posterior vein in the inferior frontal horn can be used as a marker to find the inferior collateral branch, thus the inferior collateral branch crosses the posterior facial vein at this location. In addition, the inferior collateral branch can also be found at the anterior inferior border of the parotid gland, above the angle of the mandible, on the surface of the chewing muscle, and where the inferior collateral branch leaves the parotid gland.
Bailey (1947) advocated a method of dissecting the facial nerve starting from the buccal branch of the facial nerve using the parotid duct as a landmark. This method is also customary in our institution. The flap is lifted and pulled with a hook to reveal the most prominent part of the anterior border of the parotid gland, where the parotid duct emanates. The parotid gland is often visible on the anterior side of the flap. The parotid duct is separated bluntly in the direction of its course, and the buccal branch of the nerve can be seen on its surface or above and below. After confirming the parotid duct, two treatments can be used according to the position of the duct in relation to the buccal branch of the facial nerve: if the buccal branch is located on the deep side of the parotid duct and the parotid duct is blocking the separation of the facial nerve, the parotid duct can be ligated and cut off as close as possible to the oral mucosa, and then the other branches of the facial nerve can be separated and dissected backwards along the buccal branch of the facial nerve. This is also the traditional way of treatment. If the buccal branch is located on the surface of the parotid duct and is largely unobstructed by the parotid duct during dissection of the facial nerve, the parotid duct may be preserved.
When dissecting the facial nerve from the zygomatic branch, the zygomatic arch is used as a marker to find the zygomatic branch anteriorly above the parotid gland, 1 cm below the zygomatic arch, using a blunt separation method. The zygomatic branch is thicker and in a constant, but deeper position.
After finding any of the ventrolateral nerves, the branches are separated along the nerve branches toward the parotid gland, and each branch is found to reach the temporal facial trunk and the cervical facial trunk bifurcation. During the separation process, the method of “comprehensive advancement” should be adopted, and it is not advisable to “isolate the deep man” and separate too deeply at a certain point to avoid bleeding on the deep side and accidental injury to the facial nerve due to the small field of view when stopping bleeding. After exposing the temporal facial trunk, cervical facial trunk and the branches, the rest of the superficial lobe of the parotid gland is separated and removed from the sternocleidomastoid muscle and the mastoid process in front, under the external auditory canal and behind the joint.
(2) Parallel dissection method: In 1940, Canadian surgeon Janes advocated dissecting the facial nerve by separating it from the trunk, which has been improved since then. It is particularly suitable for parotid tumors located in the anterior part of the superficial lobe. In the case of parotid malignant tumors, the facial nerve can be dissected more conveniently from the trunk because the sternocleidomastoid muscle and the biceps muscle have been dissociated during the cervical dissection.
The facial nerve trunk is divided equally between its upper edge and the angle formed by the tympanic plate (in front of the mastoid process) (Figure 2). The stem mammary foramen is located at about 1 cm on the deep surface of the diastasis. The facial nerve trunk can also be found by separating the cartilage along the external auditory canal to the deep side and revealing the triangular process of the external auditory canal cartilage, with its tip pointing anteriorly and inferiorly at 1｛n (Figure 3). After showing the facial nerve trunk, the posterior border of the parotid gland can be separated from the posterior belly of the sternocleidomastoid muscle and the biceps muscle under the protection of the index finger, and the trunk can be dissected forward to the temporal and cervical facial trunk bifurcations, and then separated to each branch to remove the superficial lobe of the parotid gland and the tumor. When dissecting the facial nerve trunk, the adjacent posterior auricular artery and vein may be touched and bleeding, which should be promptly pressed with fingers and then attracted with suction device, releasing the finger pressure while attracting, and then accurately clamped to stop bleeding after seeing the bleeding point to avoid accidental injury to facial nerve.
When dissecting the posterior lower pole of the parotid gland, the auricular nerve can be seen to enter the chewing muscle fascia of the parotid gland. If it is a benign tumor in the preauricular region, the anterior branch of the auricular nerve can be separated and cut into the parenchyma of the parotid gland, and the small branches distributed in the earlobe and posterior side can be preserved to avoid numbness and discomfort in the earlobe after surgery. If the tumor is malignant and the facial nerve may be sacrificed and a facial nerve graft is needed, the branches of the auricular nerve can be separated and the distal end of the nerve can be cut off one by one, and the free auricular nerve can be protected by saline gauze so that it can be used as a donor for nerve graft after facial nerve resection.
(3) Wound treatment: After removal of the superficial lobe of the parotid gland and tumor, the residual gland should be sutured on the broken surface to stop bleeding on the one hand and prevent the formation of salivary fistula on the other. However, if the parotid ducts are preserved and the function of the residual gland is to be preserved, the sutures should not be too deep and too many, so as not to tie the interlobular ducts of the residual normal gland and affect the function of the gland. Rinse the wound and stop the bleeding thoroughly. Check the integrity of each branch of the facial nerve. In case of inadvertent severance, end-to-end anastomosis should be performed immediately. Place rubber drainage strips or negative pressure drainage tubes on the wound surface. In the latter case, care should be taken to avoid the facial nerve that has been separated and exposed to avoid damage to the nerve by continuous negative pressure suction. The flap is repositioned and the broad cervical muscle and subcutaneous tissue are sutured. After suturing, the incision should be laminated in a linear fashion and the skin interrupted with 1 to 3 “0” silk sutures to minimize scarring. If rubber strips are used for drainage, all residual blood within the trauma day should be squeezed out with gauze so that the flap is tightly attached to the trauma surface. Apply pressure bandage so that there is no dead cavity or blood accumulation under the flap, compress to stop bleeding, reduce exudation, and promote wound healing.
(4) Postoperative treatment: The traditional method is that the drainage strip is removed in 24-28 hours, if the wound oozes more blood within a short period of time after surgery, the dressing that has been soaked is dried and hard, it should be replaced with a fresh and soft dressing, otherwise the patient feels very uncomfortable. 6-7 days later, the stitches are removed. After removal of the stitches, the dressing is still applied with pressure for 1 week to promote atrophy of the remaining gland and to prevent the formation of salivary fistula. In recent years, we have switched to negative pressure drainage, which is withdrawn after 48 hours and is no longer applied with pressure dressing, and only a small piece of muslin cloth is used to cover the wound.
This has the following advantages compared to the traditional method.
(i) The duration of pressure dressing is greatly reduced and the patient feels comfortable.
(ii) If the function of the residual gland is desired to be preserved, the desired purpose can be achieved.
③If the wound is properly treated, it does not increase the incidence of salivary fistula.
Surgical techniques
1.Anesthesia
In addition to the aforementioned auriculotemporal or auricular nerve block anesthesia to improve the anesthetic effect, when the superficial part of the parotid gland is exposed by flap ← before cutting the glandular tissue, the anatomical feature of the parotid chewing muscle fascia closely wrapping the superficial part of the parotid gland is used to inject anesthetic into the entire superficial part of the parotid gland, at this time, the drug can evenly penetrate into the glandular tissue without spillage, and the anesthetic effect is good. If the parotid tissue is cut and then injected with anesthetic, the drug will easily leak out and spill over, affecting the anesthetic effect.
2.Flap
There are two ways to flap: the more traditional is to do it on the surface of the parotid chewing muscle fascia. If the gland is injected with 1% methylene blue through the parotid duct before surgery, the surface of the fascia is transparently blue, which makes it easier to identify. The flap is lifted from the fascial surface, and in the mandibular angle and subcollar region, the cervical muscle is included in the flap. This method has the advantage of less bleeding and a clear operative field. The other flap is performed on the deep surface of the parotid chewing muscle fascia, directly exposing the blue-stained glandular vesicles and containing the fascia intact within the flap. This fascia has the potential to prevent the development of gustatory sweating syndrome by blocking the vagal regeneration between the nerve fibers distributed between the gland and the sweat gland. The authors used this approach to flap reversal in some cases, but its exact effect remains to be further observed. The disadvantage is that there is relatively more bleeding, but if the flap is turned with an electric knife and small vessels are seen connecting the fascia to the gland, then electrocoagulation is used first, followed by cutting with the electric knife, which can also be done with almost no bleeding.
3.Protection of facial nerve
In the process of revealing the facial nerve and glandular excision, in order to minimize mechanical damage to the facial nerve, the following points should be noted.
(1) When turning the skin flap in front of the ear, sharp peeling is commonly used. However, when the flap is lifted to the anterior edge of the gland, blunt peeling is recommended, because the facial nerve branches penetrate the anterior edge of the gland and enter the chewing muscle, the site is superficial and easily damaged.
(2) When separating the facial nerve, the facial nerve should be separated gradually on its superficial side along its course, and the parotid gland should be removed while separating it, and not on the deep side of the facial nerve. Although there is no complete anatomical plane separating the parotid gland from the facial nerve, there is often a layer of fibrous connective tissue that can be easily separated.
(3) After exposing the gland, saline gauze should be used instead of dry gauze to stop the bleeding, and the bleeding should be “dipped” instead of “rubbed” to avoid friction and damage to the nerve. The isolated facial nerve should be covered with saline gauze to avoid damage by exposure to air and drying.
(4) When there is a lot of bleeding, the bleeding should be stopped by compression rather than easy clamping, because the blood vessels are often accompanied by the facial nerve, the facial nerve may be damaged when clamping. Capillary bleeding can often be stopped by pressure. When pressure is applied to stop bleeding, other parts can be replaced to continue the separation.
(5) The posterior facial vein is often involved when separating the temporal and cervical facial trunks. The posterior facial vein has several small branches, which should be carefully ligated one or two times. If there is an active bleeding point, apply the suction device to attract it and clamp it accurately after seeing the bleeding point to avoid damaging the facial nerve.
(6) The branch ducts of the parotid gland and the facial nerve should be carefully distinguished. The facial nerve is a myelinated fiber, the axon is surrounded by myelin sheath, the chemical composition of myelin sheath is mainly lipid and protein, called myelin phosphorus old purpose, which is high in lipid content, accounting for about 80%, the myelin sheath is shiny white when fresh, so there is no degeneration of the facial nerve is silvery white, shiny, there are parotid branch ducts are gray, no luster.
4. Preservation of parotid ducts
Traditionally, the superficial lobectomy of the parotid gland is often performed by ligating the parotid ducts so that the remaining parotid tissue atrophies on its own. According to the report of Zhao Kun et al. and the authors’ own experience, the facial nerve travels on the surface of the dominant parotid duct (including the intraglandular segment of the dominant duct) in a significant number of patients, so it is possible to preserve the parotid duct by separating the superficial parotid lobe from the surface of the facial nerve. The advantage is that the saliva secreted by the deep lobe of the parotid gland can be drained through the parotid duct, and the remaining deep lobe of the parotid gland still maintains some function. However, intraoperative care should be taken to ligate the ducts visible to the naked eye (interlobular ducts) – to prevent the formation of salivary fistulae.
Accidental treatment
1. Facial nerve injury
According to the aforementioned precautions of surgical operation, most of the mechanical injuries to facial nerve can be avoided. However, when the benign tumor is large in size and obviously pushes and squeezes the facial nerve, or when the tumor is small in size but closely related to the facial nerve, in order to keep the facial nerve intact and not to rupture the tumor and cause tumor cell implantation, the action of separating the facial nerve should be very gentle, and the amplitude of the vascular clamp should not be too large, so as not to cause pressure on the tumor and make it rupture, or make the facial nerve overstretch or even rupture. For recurrent parotid tumors, especially for those who have already dissected the facial nerve, the surgical scar makes the identification of the facial nerve difficult, so the separation should be started at the terminal end of the facial nerve, i.e. the normal facial nerve, and the separation should follow the direction of the fibers to the trunk. If necessary, a combination of the two can be used in conjunction with the paracentral dissection method of finding the trunk first to eventually free the most significant scar adhesions. The facial nerve can be damaged to varying degrees in these cases, but recovery is generally expected within 3 to 6 months as long as the nerve is not severed. This period can be supplemented with intramuscular injections of vitamin B1 and B12, etc., and with functional training of the expression muscles. In selective cases, if the patient is young and has a high occupational demand, and the patient strongly requests to preserve the facial nerve, careful separation of the facial nerve can be considered and preserved, together with intraoperative liquid nitrogen freezing and postoperative radiation therapy to kill possible residual tumor cells, and the function of the facial nerve can be gradually restored. If the facial nerve is penetrated by a tumor or a highly malignant tumor, the facial nerve often needs to be sacrificed, unless the malignant tumor is not excised, then facial nerve repair should be performed immediately. If the facial nerve is inadvertently sacrificed or cut off during surgery, end-to-end facial nerve anastomosis should also be performed immediately. See “facial nerve repair” for details.
2.Secondary bleeding
Secondary hemorrhage in superficial parotidectomy is usually caused by improper treatment of the rupture of the posterior facial vein and its branches. When this procedure is performed, most of the posterior facial veins can be preserved. This vein drains the superficial temporal vein and the internal maxillary vein, and its preservation can appropriately reduce the postoperative reactive swelling of the face. The posterior facial vein has many small branches in its course in the parotid gland and should be ligated to avoid secondary postoperative bleeding. In case of rupture of the main trunk of the posterior facial vein, it should be reliably ligated at its upper and lower ends. In case of serious secondary bleeding, the wound should be opened, the clot should be removed, the wound should be flushed with saline, and the active bleeding point should be found and clamped and ligated to stop the bleeding.
3. Local effusion and salivary fistula
The residual gland continues to secrete and poor drainage is the cause. If negative pressure drainage is placed, the negative pressure tube is blocked and the drainage is not smooth, resulting in local effusion. Therefore, the drainage tube chosen should not be too thin, and the drainage should be checked regularly after surgery to see if it is clear. When blockage is found, 10rn1 saline can be instilled from the drainage tube outside the field to flush the blood clot out of the drainage tube hole, and then connected to the negative pressure, then the drainage can be smooth. Intraoperative suture ligation of residual glands, timely and good postoperative pressure bandaging can prevent the occurrence of effusion and salivary fistula. If the amount of fluid is large, it can be re-pressurized after aspiration, and the duration of the dressing should be extended appropriately. Patients are advised to avoid acidic food after surgery and to take atropine 0.3 mg daily half an hour before eating to reduce salivary secretion.