новая папка / 450-550 operativ

lobe. Drainage area are – temple, side of the scalp, lateral part of ear, external acoustic meatus, middle ear, parotid gland, upper part of cheek, eyelids partly, orbit. E erent from these nodes drain into upper deep neck nodes.

Nerve Supply

Parotid fascia sheath is supplied by great auricular nerve (C2); sensory supply to gland is through auriculotemporal nerve; sympathetic vasomotor bres are from plexus around ECA; parasympathetic supply is through otic ganglion with complex pathway. Inferior salivatory nucleus → Preganglionic bres → glossopharyngeal nerve → tympanic branch → tympanic plexus → lesser petrosal nerve → otic ganglion → post-ganglionic fibres → through auriculotemporal branch of mandibular division of trigeminal nerve → parotid gland (Fig. 17-10).

FACIAL NERVE

It is 7th cranial nerve (2nd branchial arch). It is the ‘queen of the face’. It arises from 4 nuclei at lower pons. Sensory (nervus intermedius) and motor roots run along with 8th cranial vestibulocochlear nerve to enter the internal acoustic meatus with labyrinthine vessels. In the meatus two roots join to lie in the petrous temporal bone. In the canal it has got 2 bends. First bend is called as genu which is related to geniculate ganglion. Nerve leaves the skull through stylomastoid foramen. Stylomastoid foramen is located medial to mastoid tip and lateral to styloid process. Stylomastoid branch of posterior auricular artery (branch of ECA) is just in front of the facial nerve trunk which also enters the stylomastoid foramen. Here facial nerve runs lateral to styloid process to enter the parotid gland; divides into branches behind the neck of the mandible. Branches –in the canal are greater petrosal, nerve to stapedius, chorda tympani; branches immediately after coming out of stylomastoid foramen - are posterior auricular (to post auricular muscles), digastric (to posterior belly) and stylohyoid; terminal branches are - temporal, zygomatic, buccal, marginal mandibular and cervical. Buccal branch is in relation to the parotid duct; marginal mandibular branch crosses over the anterior facial vein. Chorda tympani originates from facial nerve 6 mm above the stylomastoidforamen; entersmiddle ear close totympanic membrane, then petrotympanic ssure to reach infratemporal fossa where it joins

lingual nerve to distribute secretomotor bres to submandibular ganglion (parasympathetic secretomotor) and submandibular and sublingual glands. It also gives taste bres to anterior 2/3rd of the tongue (Figs 17-11 to 17-14).

Greater petrosal nerve pathway is - superior salivatory nucleus → facial nerve → greater petrosal nerve → opening in the petrous temporal bone for greater petrosal nerve → joins sympathetic deep petrosal nerve to

Fig. 17-11: Structures in the internal meatus (Left).

Fig. 17-12: Course of facial nerve to reach face.

Fig. 17-14: Facial nerve – on table look.

form nerve of the pterygoid canal → through canal reaches pterygopalatine ganglion (largest peripheral parasympathetic ganglion) → postganglionic bres supply lacrimal gland and mucous glands of nose, sinuses, palate and pharynx.

PAROTIDECTOMY

Indications

Parotidectomy is done in benign/malignant tumours of parotid including adenolymphoma of parotid. Super cial parotidectomy is done only in benign tumours of super cial lobe. In tumours (benign) involving both super cial or deep lobe and only deep lobe total conservative parotidectomy is done. In malignant tumour invading facial nerve radical parotidectomy is done. Presently evenin malignant parotid tumours, sacri cing only the involved/in ltrated branches of facial nerve and retaining uninvolved branches, with wide clearance and neck dissection is contemplated; as evidence suggests that there is no survival bene t between removing all branches and removing only the involved branches. In aggressive tumour radical parotidectomy is done sacri cing the trunk of facial nerve with nerve graft.

Occasionally super cial parotidectomy is added as part of radical neck dissection in case if primary tumour is in head and neck region

Types of Parotidectomy

Superficial/lateral parotidectomy (Patey) – It is removal of super ciallobe of the parotid in front of the faciovenous plane of Patey.

Total conservative parotidectomy – Here both super cial and deep lobes of the parotid are removed preserving the facial nerve. Dissection along the faciovenous plane is carried out to identify the branches of the facial nerve retaining the isthmus/tumour bearing area. Nerve branches are retracted aside to reach the deep lobe which is removed entirely by dissecting o the branches of facial nerve carefully without injuring them. is is the right technique even though many advocate removing super cial lobe initially then deep lobe separately. Retromandibular vein is ligated here.

Radical parotidectomy – Involves removal of both lobes of parotid with facial nerve, fat, fascia, masseter, pterygoid, buccinator along with neck lymph node dissection. Facial nerve is sacri ced. Its branches whenever possible can be saved as additional advantage of survival not thereby removing uninvolved branches. On table frozen section biopsy of cut ends of nerve are needed. Ends of the cut nerve branches are tagged by ne sutures for eventual nerve grafting using great auricular nerve or sural nerve. Often radical parotidectomy is combined with removal of temporomandibular joint, mastoid process and external auditory meatus with lessadditional bene t. Mastoidectomy is done to visualize the clear proximal part of the facial nerve. Reconstruction of the main trunk, marginal mandibular, temporal and buccal branches are done to maintain eye closure and good oral competence.

Suprafacial parotidectomy is done for benign tumour at lower pole wherein all branches of facial nerve need not be dissected.

TECHNIQUE OF PAROTIDECTOMY

Position and Anaesthesia

Procedure is done under general anaesthesia. Paralytic agents used for intubation purpose are of short acting only as during surgery facial nerve branches are identi ed and con rmed by stimulationto achieve contraction of facial muscles. Neck is extended by placing a sandbag under the shoulder with a head support using a ring. After cleaning, draping is done to expose the face and eyelids to see the contractions of muscles whenever needed. Head is extended with face turning opposite side. Head end of the table is elevated 15° to reduce venous congestion. In many centres of China procedure is done under local anaesthesia also. Nerve monitor device is used. Its electrode tips are placed into orbicularis oculi and orbicularis oris muscles. Nerve either the main trunk or branches are stimulated using nerve stimulator whenever needed.

Incision

Standard incision is ‘Lazy S’ incision (modi ed Blair/Sistrunk incision). It begins in front of tragus closely running vertically to the ear lobule;

curving on the margin of the ear lobule towards middle of the mastoid (mastoid tip) along postauricular part; again curving back downwards along the margin of the sternocleidomastoid muscle in the superior cervical crease 2 cm below the angle of the mandible. Inverted T and modi ed Y incisions are also used. ‘Face lift’ incision’ can be used in benigntumoursofthe tailormiddlepartoftheparotid.It beginsattragus running vertically downwards curving the ear lobule and extending in the postauricular region along the hair line (Figs 17-15 to 17-18).

Fig. 17-15: Modi ed Blair incision for parotidectomy.

Fig. 17-16: Inverted ‘T’ incision for parotidectomy.

Fig. 17-17: Modi ed Y incision for parotidectomy.

Fig. 17-18: Face lift incision for parotidectomy.

Usual plane used is subplatysmal in the neck area. Incidence of Frey’s syndrome and ap necrosis are higher if ap is raised in front of the platysma. Ear lobule is held under traction with suture. Skin ap is raised anteriorly super cial to parotid fascia in face by holding with skin hooks up to the anterior margin of the parotid with visualisation of the masseter muscle. While elevating the ap anteriorly close to the masseter, branches of facial nerve will be close to skin ap and care should be taken not to injure them. Posterior skin ap is raised to expose the anterior border of the sternocleidomastoid muscle and mastoid process (Fig. 17-19).

Even though great/greater auricular nerve has to be cut, it is cut close to the parotid gland or after it gives the posterior branch (it is the largest branch of cervical plexus). Adequate length of the great auricular nerve is dissected for the possible need of nerve graft in case of facial nerve injury. External jugular vein with its tributaries is visible which can be retained or transected. Fascia along the anterior border of the sternocleidomastoid muscle is incised to expose the upper part of the muscle. After retracting sternocleidomastoid, once posterior belly of digastric muscle is identi ed; both muscles are retracted; dissection is done in front of the mastoid along the tragal cartilage. Dissection begins from the posterior part of the gland near tail of the parotid. Gland is freed of the brous attachments and with blunt dissection bony cartilaginous junction of the auditory canal, tympanomastoid suture/ ssure (groove between mastoid tip and tympanic portion of the temporal bone) and tragal pointer is felt and identi ed. Parotid tissue between superior border of posterior belly of digastric muscle and tympanomastoid ssure is dissected and separated carefully layer by layer by blunt and sharp dissection. Temporoparotid fascia from tympanomastoid ssure to parotid is cut to visualize facial nerve. Facial nerve is 1 cm below and medial (or anterior and inferior) to tip of the tragal cartilage (Fig. 17-20).

Identi cation of Facial Nerve

Facial nerve trunk is identi ed by di erent techniques – (1) Facial nerve is 5 – 10 mm deep and below from the tip of the cartilaginous canal – Conley’s point. (2) Sternocleidomastoid muscle is retracted behind, gland is retracted front; posterior belly of digastric is identi ed where nerve is anterior to this. (3) Nerve is lateral to styloid process. (4) Tracing branch from distal to proximal – Hamilton–Bailey technique through buccal branch or marginal

Fig. 17-19: Incision and subplatysmal plane for parotidectomy.

Fig. 17-20: Venous anatomy of face is important in parotidectomy.

mandibular branch. (5) Using Faradic or mechanical stimulation (pinching tissues) muscle movements/twitching can be observed.

(6) Stylomastoid branch of posterior auricular artery is just in front of the facial nerve trunk which also enters the stylomastoid foramen. Facial nerve after coming out of stylomastoid foramen travels for 1 cm forward and below between mastoid process and membranous portion of external auditory canal and divides into temporofacial/ temporozygomatic and cervicofacial branches behind the neck of the mandible. is bifurcation may be often distal or often proximal before coming out of the stylomastoid foramen. Cervicofacial branch divides into cervical (for platysma) and marginal mandibular branch which runs below the horizontal ramus of the mandible within the platysma muscle to supply lower lip. is branch does not have any communicating branch unlike other branches of facial nerve. is branch is more often super cial to posterior facial vein. Buccal and zygomatic branches have numerous communications which supply periorbital and upper lip muscles. Temporal branch supplies frontalis muscle but does not have cross communications and has got weak regenerative power and so often paralysis of frontalis stands permanent in facial nerve palsy. Buccal branch is situated close to parotid duct and so if duct is identi ed it is easier to look for buccal branch. Dissection from distal to proximal is more di cult than dissection from proximal to distal.

Separation of Gland o the Facial Nerve

Branches

It requires patience and ne dissection. ere are two methods to dissect the facial nerve. (1) Forward/antegrade technique – Dissection from main trunk of facial nerve; (2) Retrograde technique – Dissection from branches towards main trunk (it is followed in many centres in China).

Dissection using ne haemostat and ne scissor is ideal with tip of the instrument facing forward. Tiny oozing points need ligation using ne vicryl. Bipolar cautery can be used carefully away from the nerve branches. All parotid tissue is cut only with visualisation of nerve branches. One of the division and its branches are separated and dissected completely rst; later other division and branches. Monopolar cautery should not be used. Dissection is rst started

along the upper divisions of the facial nerve. Dissection is carried out up to the anterior margin along the faciovenous plane of Patey to remove the entire super cial lobe. Deep lobe (20% of total gland) is nicely visualised. Haemostasis is achieved. If deep lobe needs to be removed after partial dissection of super cial gland from facial nerve branches, branches are gently retracted to dissect beside the isthmus of the parotid gland to reach deep lobe which can be removed. Often this is technically di cult and somany advocate removal of super cial lobe rst followed by identi cation of deep lobe; facial nerve branches are retracted and deep lobe is dissected and removed. Parotid duct is located in relation to deep lobe. Upper buccal branch is above the duct which is larger than lower buccal branch. Ideally all the branches should be identi ed and dissected. In malignant parotid, branches which are invaded are sacri ced. Main trunk if divided then nerve graft is done using great auricular nerve or sural nerve. Operating microscope is needed for nerve suturing. Even though nerve is not injured post operative neuropraxia is common which recovers completely at a later period. Many use short term steroid therapy to prevent this. In removal of deep lobe retromandibular vein should be ligated. e parotidectomy should be done with the tumour ‘en bloc’ (Fig. 17-21)

Removal of the Deep Lobe in Total

Conservative Parotidectomy

Branches of facial nerve which are dissected are gently retracted away using nerve hook or smooth loops to visualize the deep lobe. Parotid duct is transected at its anterior part and ligated. One should not injure upper buccal branch of facial nerve. Duct may be dissected up to the mucosa through buccinator if needed before ligation. Deep lobe is separated from nerve branchesfrom its deeper plane. Often it is required to ligate the retromandibular vein to facilitate easy dissection and reduce bleeding. Deeper part of the deep lobe is dissected of the stylopharyngeus and stylohyoid muscles by blunt dissection while retracting the deep lobe. Super cial temporal vessels, maxillary artery deep to ramus of mandible, the occipital artery, posterior auricular artery and pterygoid venous plexus are deep to deep lobe. Deep lobe can be extirpated superior/inferior/in between nerve branches. Haemostasis should be achieved using bipolar cautery.

Main trunk of the facial nerve is stimulated with 0.5 mA to con rm the anatomical and physiological integrity of the branches of the facial nerve.

Points to be remembered are -

Dissection of the facial nerve should be done just super cial to the nerve to expose it clearly. Dissection deep to the nerve is inadvisable. e sheath of the facial nerve should not be opened to avoid damage

to the nerve bers.

Using wet gauze is better than dry gauze for haemostasis. Clearing of blood from the operative eld should be done by mild pressure absorption of the blood rather than scrubbing. e dissected nerve should be covered by wet gauze to avoid dryness following exposure to air.

Bleeding from capillary vessels should be stopped by the pressure of wet gauze, as some blood vessels are distributed along with the nerve. e facial nerve is readily damaged if artery forceps are used for haemostasis. e dissection is continued in the other areas of the gland while attaining this haemostasis.

e bifurcation of the nerve is close to the retromandibular vein, and its ne branches should be ligated. Suction is used to achieve a

clear surgical eld. Any bleeding vessel should be carefully clipped or ligated.

e branching ducts of the gland must be distinguished from the facial nerve. e nerveiswhite and shiny, while the duct isgrey and dull.

The parotid duct if ligated like done by many, in traditional superficial parotidectomy, then remaining deep lobe of parotid atrophies spontaneously. But it is possible to preserve the duct so that the saliva secreted from the parotid remnant will be made to extrude into mouth. So that partial function of the retained gland is achieved. It is important to ligate the interlobular ducts identi ed during the dissection carefully to prevent the formation of salivary stula.

After parotidectomy, even though not practiced widely, parotid remnant is often sutured by absorbable sutures to achieve proper haemostasis and to prevent formation of salivary stula. If the duct and function of the parotid remnant are to be preserved, deep sutures should be avoided in order to prevent ductal ligation.

The wound is irrigated with hypertonic saline/distilled water probably to destroy spilled tumour cells. e integrity of the facial nerve is checked by nger pinch or nerve stimulator. If the nerve has been disrupted, an end to end anastomosis of the nerve is carried out or with suitable graft immediately.

Closed suction drainage is used with suction tube placed away from the dissected facial nerve to prevent damage to the nerve. Compression bandage is kept often for 3 days.

Deep lobe mass may appear as lateral oropharyngeal masses. Tail of the parotid mass mimics cervical lymph node. Common site of the parotid tumour is tail of the parotid.

Only FNAC and imaging (CT scan) are the investigations done for parotid tumour. Open biopsy is not done in parotid tumour.

Enucleation of the parotid tumour should not be done. This increases the risk of facial nerve injury, risk of tumour recurrence.

Loupe or microscope is useful in dissecting the branches especially in reoperation.

Nerve stimulator should be used judiciously otherwise it itself can cause neuropraxia.

Closure

Proper haemostasis is achieved using ne vicryl ligatures or bipolar cautery. Often it is of practice to pour distilled water in the parotid bed and keep it for few minutes to kill spilled tumour cells from the capsule. Digastric ap is often used to cover the area of facial nerve. Posterior belly of digastric is detached from its hyoid/pulley attachment and rotated upwards over the facial nerve and attached to zygoma. An acellular dermal matrix graft can be placed into the wound prior to skin closure to cover the facial nerve trunk and auriculotemporal nerve area to prevent scar adhesion into the facial nerve trunk and formation of Frey’s gustatory sweating. Suction drain is placed before closure which is removed in 3 days. Drainshould not come into contact with the facial nerve main trunk. Skin is closed with interrupted polypropylene or polyethylene 4 zero or 3 zero sutures. Slight pressure dressing is often used (Fig. 17-22).

Postoperative Care

Drain is removed in 48 hours. Facial expressions are observed for features of facial palsy. Temporary facial nerve paralysis is common in the postoperative period for which the surgeon should not worry. If closure of eyes is inadequate due to neuropraxia, repeated saline drops to eye and eye cover is needed to prevent exposure keratitis. Neuropraxia recovers in 4 weeks.

COMPLICATIONS OF PAROTIDECTOMY

Haemorrhage

It is rare, usually of venous origin and ooze from the bed. Major arterial injury is rare. When haematoma once develops, patient presents with swelling, pain, distress with blood in the drain. It is usually due to bleed from retromandibular vein or its tributaries. If haematoma is progressive then wound is reopened under general anaesthesia. Retromandibular vein is ligated both proximally and distally. Ligation of this vein causes ipsilateral facial oedema which gradually subsides in few weeks.

Facial Nerve Injury

It is the most important, common and worried complication. It may be due to simple neuropraxia due to handling during dissection or nerve

injury at various levels either of the main trunk in case of neoplastic conditions or few of branches. Incidence of temporary facial nerve palsy due to neuropraxia is 40%; whereas permanent palsy is 4%. Features are – inability to close the eyelid, di culty in blowing and clenching; drooping of angle of the mouth; obliteration of nasolabial fold; loss of forehead wrinkles; wide palpebral ssure and epiphora. E ects of temporary facial nerve injury/neuropraxia will recover in few days to few weeks (12 weeks). Oral or intravenous steroids with vitamin B1 and B12 injection are often tried. Permanentfacial nerve injury needs specialised methods to correct the deformity. Nerve grafting is done using greater auricular, sural, lateral cutaneous or hypoglossal nerves. It needs operating microscope and is done using 6 zero polypropylene sutures. Angle of mouth can be suspended to zygomatic bone using temporal facial sling. Corneal ulceration is prevented using lateral tarsorrhaphy. Epiphora is controlled by reconstruction of medial canthus. Dynamic surgery like neurovascular muscle graft can also be used (Fig. 17-23).

may help. Total conservative parotidectomy is done in failed cases.

Loss of Sensation of Ear Lobule

It is due to cutting of the great auricular nerve. Numbness of ear lobule causes di culty in wearing ear ring. It slowly subsides and ear lobule gains its sensation in 1½ to 2 years. It can be prevented by preserving greater auricular nerve or its posterior branch.

Flap Necrosis

It is not uncommon. It usually heals on its own.

Frey’s Syndrome

It is also called as auriculotemporal syndrome or gustatory sweating (Lucie Frey – Polish surgeon 1032). It is probably due to injury to auriculotemporal nerve wherein postganglionic parasympathetic bres from the otic ganglion become united to sympathetic nerves from the superior cervical ganglion creating pseudosynapsis. Auriculotemporal nerve has got two branches. Auricular branch supplies external acoustic meatus, tympanic membrane surface, skin of auricle above external acoustic meatus. Temporal branch supplies hairy skin of the temple. Sweating and hyperaesthesia occurs in this area of skin. Whenever salivation is stimulated or during mastication, ushing, sweating, pain and hyperaesthesia occur in this area of skin. Involved skin is painted with iodine and dried. Dry starch applied over this area will turn blue in Frey’s syndrome due to more sweat (Minor’s Starch iodine test). It is usually treated with conservative treatment with reassurance, drugs like antiperspirants like aluminium chloride, injection of botulinum toxin to skin, topical scopolamine. 10% of such patients later need surgical intervention. Tympanic branch of glossopharyngeal nerve below the round window of middle ear is cut

– intratympanic parasympathetic neurectomy (Jacobsen). Condition can be prevented by raising skin ap deep to platysma or deep to parotid fascia or by placing sternocleidomastoid/posterior belly of digastric or temporal fascia or arti cial membranes over parotid bed.

DRAINAGE OF PAROTID ABSCESS

It is drained under general anaesthesia (intubation may be di cult if there is trismus) with a small vertical skin incision in front of the tragus with a transverse incision/split on the parotid fascia to allow pus to drain. Sinus forceps is used to break the loculi; pus should be sent for culture. Facial nerve should not be injured. Irrigation of the cavity with normal saline and packing is needed. Facial nerve palsy and salivary stula are the complications (Fig. 17-25).

SUBMANDIBULAR SALIVARY GLAND

It is J shaped salivary gland situated in the anterior part of the digastric triangle which is indented by posterior border of the mylohyoid with larger part is located super cial to it and smaller part is deep to it.

Submandibular region extends 1.5 cm above the base of the mandible and below to the greater cornu of the hyoid bone. Gland is marked outside as an oval area posterior half of the base of the mandible and posterior border of the ramus.

Superficial lobe fills the digastric triangle extending above to mylohyoid line deep to mandible. Super cial lobe is covered by super cial and deep lamina of deep fascia of neck; deep lamina is

Parotid abscess being within the tense parotid fascia will not show uctuation and uctuations should not be awaited. Brawny induration

with tenderness over the parotid is diagnostic; often with trismus.

Fig. 17-25: Incision for parotid abscess. Vertical skin incision and horizontal parotid sheath incision.

attached to mylohyoid line; super cial lamina is attached to base of the mandible. Inferior surface is covered with skin, platysma, cervical branch of facial nerve, deep fascia, facial vein and submandibular lymph glands. Medial surface is related to mylohyoid muscle, vessels and nerve anteriorly; hyoglossus, styloglossus, lingual nerve, submandibular ganglion and hypoglossal nerve in the middle; styloglossus, stylohyoid ligament, 9th (glossopharyngeal) nerve and wall of pharynx.

Smaller deep lobe lies deep to mylohyoid and superficial to hyoglossus and styloglossus, continuing posteriorly with super cial part after winding round the posterior border of mylohyoid muscle. Anterior end of deep lobe is close to sublingual gland.

Wharton’s submandibular salivary gland duct is 5 cm long with thin wall begins at the anterior end of deep part of the gland running over hyoglossus muscle between lingual and hypoglossal nerves. Duct is crossed by lingual nerve at the anterior border of the hyoglossus muscle; duct later opens on the oor of the mouth on the side of tongue frenum on the summit of the sublingual papilla.

Secretomotor bres of submandibular salivary gland: Preganglionic bres from superior salivary nucleus → facial nerve → chorda tympani nerve → lingual nerve → Langley’s submandibular ganglion → post ganglionic bres → submandibular and sublingual salivary glands

(Figs 17-26 to 17-28).

Suprahyoid muscles are –

Digastric muscle has got anterior belly which arises from the digastric fossa of the mandible running downwards and backwards towards intermediated tendon on the fibrous pulley of the hyoid bone; posterior belly arises from mastoid notch of temporal bone runs forward and downwards towards intermediate tendon. Anterior belly is supplied by nerve to mylohyoid; posterior belly is supplied by facial nerve.

Stylohyoid muscle arises from posterior surface of the styloid process to insert into the greater cornu of hyoid bone at its junction to the body. Its tendon is perforated by the tendon of the posterior belly of digastric muscle. It is supplied by facial nerve.

Mylohyoid is triangular muscle arising from mylohyoid line of mandible runs medially downwards to get inserted to body of hyoid bone and median raphe in the midline connecting to opposite mylohyoid muscle forming oor of the moth. It is supplied by nerve to mylohyoid.

Geniohyoid muscle arises from genial tubercles/inferior mental spine runs backwards and downwards to insert on the anterior surface of the body of the hyoid bone. It is supplied by C1 nerve through hypoglossal nerve.

Hyoglossus arises from entire length of greater cornua and lateral part of the hyoid bone running upwards and forwards to attach to side of tongue between styloglossus and inferior longitudinal muscle of the tongue. It is supplied by hypoglossal nerve.

Facial Artery

It was earlier called as external maxillary artery arises from external carotid artery just above the tip of greater cornu of hyoid bone (just above the origin of the lingual artery) in the carotid triangle. It shows tortuous course running beneath the digastric and stylohyoid muscles, grooving posterior surface of the groove of the submandibular salivary gland in front of hypoglossal nerve. It curves over the body of the mandible at anteroinferior angle of the masseter muscle, running across the cheek to the angle of the mouth, side of the nose, medial

Fig. 17-26: Surgical anatomy of submandibular salivary gland.