Potential complications (consent)
• Facial nerve weakness- temporary (20-30%), permanent (1%)
• Greater auricular nerve numbness
• Freys syndrome
• Salivary fistula
• Treatment of parotid tumours is classically by superficial lobectomy for all tumours within the superficial lobe and total parotidectomy for all tumours within the deep lobe.
• Such deep lobe tumours should never be approached from the pharyngeal aspect even when they present as lateral pharyngeal masses.
• The facial nerve, if not macroscopically invaded by malignant tumour, is preserved in all cases.
• The parotid gland is described as having deep and superficial ‘lobes’ united by an isthmus. However the gland is not embryologically a bilobed structure, but its developmental relationship to the facial nerve results in the two surgical ‘lobes’.
• The facial nerve, except when invaded by tumour, does not enter the substance of the gland.
• Posterior belly of digastric inserts into the mastoid process, directly below the stylomastoid foramen.
• The stylomandibular artery, which lies just superficial to the nerve as it enters the gland, may provoke troublesome bleeding if not ligated and divided
• Gland covered by parotid fascia (which is in fact the investing layer of deep cervical fascia)- on top of parotid fascia is SMAS.
• Inferiorly to gland is platysma, which lies superficial to the investing layer of deep cervical fascia.
• Therefore you raise a subplatysmal flap in the neck which takes you sub SMAS as you go superiorly.
• On the undersurface of platysma and SMAS are the terminal branches of the nerve.
• The platysma muscle and the SMAS in the parotid region can be raised as a continuous sheet and can be easily separated from the parotid fascia.
• SMAS is continuous with the temperoparietal fascia and galea superiorly.
• Nerve comes out of stylomastoid foramen.
• Splits after approximately 1cm into upper and lower trunks.
Landmarks to identify the trunk of the facial nerve
The following are antegrade methods to identify it as it leaves the stylomastoid foramen. Alternatively a retrograde approach finds more peripheral branches and chases them back.
• Tragal pointer: the cartilaginous external auditory meatus forms a ‘tragal point’ at its anterior inferior border indicating the direction of the nerve trunk.
• Tympanomastoid fissure: found just deep to the cartilaginous pointer. Formed by curve of the bony external meatus and its abutment with the mastoid process. This palpable groove leads directly to the stylomastoid foramen. Groove filled with fibrofatty lobules that often mimic the nerve trunk. The facial nerve trunk lies 3-9 mm (mean 4 mm) distal to the end point of this fissure.
• Posterior belly of the digastric muscle: the nerve lies approximately 1.0 cm deep to the attachment of the muscle into the mastoid bone.
• Styloid process: superficial and just superior to the stylomastoid foramen. Generally not recommended as a landmark since believed to increase risk of damaging the nerve
Preparation prior to scrubbing
• Sandbag under back in midline and turn neck away from operation side
• Attach nerve stimulator leads- red (double) to upper lip, blue (double prong) to just above upper eyebrow, other two leads (both single prongs, usually white and green, over sternum)
• Mark up landmarks- angle mandible, lower border mandible, midline
• Mark up incisions- preauricular modified Blair incision and extension into neck crease- may need temporal extension if mass superior in the gland
• Infiltrate with local anaesthetic to hydro dissects the plane above the tightly adherent parotid capsule
Preparation once scrubbed
• Drape to leave forehead one side of mouth and ear exposed
• Clear plastic film just over corner of mouth to seal off but leaving lips visible for twitches
• Jelonet in the ear
• Rubber eyeshield on side of operation only
• Incision with number 15 blade
• Raise the neck portion first as makes raising the pre auricular bit easier
• Incision down to platysma and raise a sub platysmal flap
• Dissect superiorly to raise a pre auricular (sub SMAS) flap
• Push scissors in and open them up
• This should create plane on top of parotid capsule
• Dissect forwards up to anterior border of masseter
• Retract the flaps with elasticated cords and gauze
• Dissect your cervical part down to sternocleidomastoid
• Use SCM to find post belly of digastric
• Follow that to its insertion into the mastoid
• The stylomastoid foramen should be just above the mastoid
• Pre auricular dissection with scissors- use macindoes as less sharp than Jameson's
• Spread in direction of nerve
• Dissect down to cartilagenous tragal point
• Once identified the nerve them dissect along the nerve roots
• Spread with a curved clip and cut with number 11 blade parallel to nerve
• Careful bipolar diathermy
• Dissect out the lump
• Insert size 10 vacuum drain- through the posterior margin below the ear
• 3/0 vicryl deep closure
• 5/0 ethilon to close ear and behind ear
• Staples or 5/0 ethilon to close the neck component of the incision
• 2 x post op IV antibiotics and dexamethasone (Hanu)
• Drain out next day if less than 30ml in it
• Home next day
• Sutures and staples out in a week
Author: Johno Breeze
Last updated: 16/02/15