Surgery
of salivary gland disease
The most common indication for removal of the sublingual salivary gland
is in the management of a ranula, which is a mucous extravasation/retention cyst
of the gland. Neoplasms of the sublingual gland occur only rarely but nearly all
tumours at this site will be malignant. In this situation surgery is the same
as that for any other malignancy in the floor of the mouth — resection with a
clear margin often involving the mandible and when necessary en bloc with
a neck dissection. Before an incision is made it is helpful to infiltrate the
floor of the mouth with a local anaesthetic containing a vasoconstrictor. For
simple excision of the sublingual gland, a linear incision is made in the floor
of the mouth parallel to and just lateral to the submandibular duct, with care
taken not to extend the incision more posteriorly than the first molar tooth so
as to avoid damage to the lingual nerve (Fig. 42.16). The incision should open
the cavity of the ranula and allow the mucinous contents to he aspirated. The
submandibular duct is now carefully identified and retracted medially. Stay
sutures passed through the margins of the mucosa are helpful to aid retraction.
Using blunt dissection with scissors the lingual nerve is identified. The
sublingual gland which lies adjacent to the inner cortex of the mandible is then
mobilised and its multiple ducts which drain into the submandibular duct are
divided carefully in order nor to damage the duct itself. The anterolateral part
of the sublingual gland may be attached to the periosteum of the mandible by
fibrous tissue and this must be divided carefully. Following removal of the
gland, the mucosa of the floor of the mouth is loosely closed with two or three
plain gut sutures. When sublingual gland excision is necessary for a tumour, it
should be removed with a wide margin including a rim resection of the mandible (Fig.
42.17).
Complications
Damage to the lingual nerve posteriorly or the submandibular duct
medially is avoided by careful surgical technique. Meticulous haemostasis is
required to avoid a postoperative haematoma in the floor of the mouth.
Submandibular
gland excision
The patient is positioned supine on the operating table with moderate
neck extension and the chin rotated to the opposite side. It is helpful to have
head-up tilt on the operating table as this reduces venous engorgement.
Following routine skin preparation and draping the incision is mapped out. The
line should run within a skin crease in the neck at least 3 cm below the lower
border of the mandible in order to avoid risk of damaging the mandibular branch
of the facial nerve as it loops down below the lower border of the mandible. The
incision should be approximately 7 cm long. The incision line is then
infiltrated with conventional dental local anaesthetic solution containing 2 per
cent lignocaine and 1:80 000 adrenaline. This results in some vasoconstriction
which limits capillary ooze and helps to define tissue planes.
The
incision is made with either a number 15 blade or a fine cutting diathermy
whilst the assistant puts tension across the incision line. The incision is made
directly down to platysma. The subcutaneous fat is stripped with firm pressure
and a swab from the underlying muscle for approximately 1 cm on each side of the
incision as this facilitates a layered closure later. The underlying platysma is
then incised to the full extent of the skin incision again with either a blade
or cutting diathermy. The assistant can now retract the wound margins using
‘cat paws’ or Allis forceps applied to the cur edge of the platysma muscle
(never the skin edges!).
The
underlying investing layer of the deep cervical fascia is next divided,
preferably with scissors, after the fascia is first tented outwards with toothed
forceps. Often the fascia consists of a series of separate laminae like an onion skin but
occasionally it is composed of a single thicker sheet. Again the fascia should
be divided along the full length of the incision to avoid the operative field
becoming ever smaller.
Posteriorly,
the fascial incision approaches the angular tract where the deep cervical fascia
splits to form the investing layer that has just been incised and the deeper
layer that forms the floor of the submandibular triangle containing the
submandibular gland.
The
mandibular branch of the facial nerve normally runs on the deep aspect of the
investing layer of fascia although occasionally it lies between the platysma and
the fascia. Great care must be taken to protect the mandibular branch.
The
anterior facial vein which lies in the connective tissue overlying the
submandibular gland -is clamped, divided and tied. The loose connective tissue
is separated with scissors to expose the submandibular gland. The dissection
from now on continues on the capsular surface of the gland. For chronically
infected glands there is frequently extensive fibrosis, and care and patience
are required to maintain this plane. For all tumours contained within the
submandibular gland capsule, this plane is safe as it forms an effective
barrier. For malignant tumours that have infiltrated beyond the capsule, a full
submandibular clearance, usually as part of a neck dissection, and often
including the periosteum of the lower and inner aspect of the mandible, is
needed.
The
anterior pole of the superficial lobe of the submandibular gland is first
mobilised and retracted upwards with Allis forceps (Fig.
42.18). This reveals
the posterior belly of the digastric muscle which is then gently retracted
downwards with a small Langenbeck retractor. This exposes the facial artery
which emerges from behind the stylohyoid muscle and passes upwards and forwards
to enter the deep surface of the
submandibular gland. The artery is then clamped, divided and tied. Great
care must be taken to secure the proximal ligature. As the vessel is divided it
retracts out of sight and, if the ligature slips, the bleeding end of the vessel
can be very difficult to identify.
The
course of the facial artery is variable. Often it deeply penetrates the
substance of the gland to emerge again at its upper border. Sometimes the artery
lies in a groove in the deep aspect of the gland. The dissection in the plane of
the submandibular gland capsule continues to mobilise the anterior pole of the
superficial lobe of the gland, which is then gently retracted posteriorly.
During this dissection a number of small arteries and veins will be identified
entering the gland. These should be carefully clamped, divided and tied or
diathermised according to their size. As the dissection continues posteriorly
along the lower border of the mandible, the facial artery and anterior facial
vein are encountered as they hook around the mandible. The vessels are again
clamped, divided and ligated at this point.
At
this stage in the operation, the anterior pole of the superficial lobe of the
gland can be retracted posteriorly to reveal the groove between the superficial
and deep lobes of the submandibular gland. The posterior border of the mylohyoid
muscle lies within this groove. It is gently freed with scissors and then
retracted forwards with a Langenbeck retractor. The deep lobe of the
submandibular gland can now be mobilised either with a finger or by opening the
blades of the scissors applied to the surface of the gland. On the deep aspect
of the deep lobe, one or two small veins may be encountered running from the
gland through the underlying hyoglossus into the lingual veins. If these veins
are not tied or adequately diathermised, troublesome bleeding may be
encountered.
The
submandibular salivary gland can now be pulled downwards revealing the V-shaped
lingual nerve. The apex of the V is the point at which parasympathetic secreto
motor fibres tether the lingual nerve to the salivary gland. It is very
The
wound is inspected for any bleeding points, a vacuum drain inserted and the
wound closed in layers using a subcuticular suture to close the skin. The
wound edges are reinforced with skin closure tapes.
Complications
Three cranial nerves are at risk during removal of the submandibular
salivary gland the mandibular branch of the facial nerve, the lingual nerve
(a branch of the third division of the trigeminal nerve) and the hypoglossal
nerve.
When
chronic infection and subsequent fibrosis have occurred, it is sometimes
difficult to identify the lingual nerve and the deep aspect of the deep lobe may
be attached to the hypoglossal nerve. At these stages of the operation, the
surgeon must be convinced that these structures have been identified before
using any sharp dissection.
Meticulous
haemostasis is required throughout the operation as many of the vessels
entering and leaving the submandibular gland are only apparent when the gland
is under traction and as soon as they are divided the vessels retract into the
adjacent muscle planes.
Parotidectomy
Treatment of parotid tumours is by superficial parotidectomy for all
benign tumours in the superficial lobe and total parotidectomy for all benign
deep lobe and dumb-bell tumours. Such tumours including deep lobe tumours should never be approached from the pharyngeal aspect. The facial nerve is
preserved in all cases.
The
prognosis for malignant parotid tumours is poor. There is little evidence that
radical parotidectomy, which includes sacrificing the entire facial nerve, adds
significantly
Similarly,
‘supraradical’ surgery for adenoid cystic carcinomas is nor advocated.
This tumour, although probably always fatal in the long term, is compatible with
a useful 10-year survival rate. It is difficult, therefore, to justify extensive
mutilating surgery without offering a cure. Adenoid cystic carcinomas whose
macroscopic margins remain within the parotid are treated by total parotidectomy
followed by radical radiotherapy. For more extensive tumours, radical dissection
with as wide a margin as is anatomically appropriate whilst being compatible
with reasonable rehabilitation followed by radical radiotherapy will ensure
excellent local control of tumour. The radiotherapy field should include the
skull base in order to control the perineural tumour extensions.
For
any malignant parotid tumours with skin involvement, facial nerve weakness,
mandibular invasion, extension into the infratemporal fossa or lymph node
metastasis, radical resection often in continuity with radical neck dissection
must be undertaken with reconstruction with the use of appropriate flaps and
followed by radical postoperative radiotherapy.
Surgical
technique
Whenever the facility is available and the patient fir, hypotensive
anaesthesia is used, as this considerably reduces oozing and thus makes it
easier to trace the facial nerve fibres. The incision line is infiltrated with
lignocaine hydrochloride and 1:80 000 adrenaline and the incision made with a
knife or fine cutting diathermy. Following a preauricular incision extending
downwards to continue in a suitable skin crease in the neck, the skin flap is
raised in the plane of the pre parotid fascia and then held forward by suturing
the margins for the flap to the adjacent towels. The blood-free plane anterior
to the external auditory meatus is opened up by blunt dissection and this leads
the surgeon down to the base of skull just superficial to the styloid process
and the stylomastoid foramen. This plane is then gently opened up in an
inferior direction by blunt dissection until the trunk of the facial nerve is
seen. With large posterior tumours this plane may be difficult to open up. In
this situation it is helpful to identify the posterior belly of the digastric
muscle in the cervical extension of the incision. The anterior border of the
sternocleidomastoid muscle is mobilised and retracted inferiorly to display
the digastric muscle beneath it (Fig. 42.20). This manoeuvre necessitates
sectioning the great auricular nerve. The posterior belly of the digastric is
traced upwards and backwards to its insertion on to the mastoid, which lies
immediately below the stylomastoid foramen, thus leading the operator to the
facial nerve from below.
There
are four anatomical landmarks leading to the identification of the trunk of the
facial nerve as it leaves the stylomastoid foramen (Fig.
42.21).
1. The cartilaginous external
auditory meatus forms a pointer’ at its anterior, inferior border indicating
the direction of the nerve trunk.
2. Just deep to the cartilaginous
pointer is a reliable bony landmark formed by the curve of the bony external
meatus
and its abutment with the mastoid process. This forms a palpable groove leading
directly to the stylomastoid foramen. Unfortunately this groove is filled with
fibrofatty lobules that often mimic the trunk of the facial nerve which can lie
as much as 1 cm deep to this landmark.
3. The anterior, superior aspect of
the posterior belly of the digastric muscle is inserted just behind the
stylomastoid foramen.
4. The styloid process itself can be
palpated superficial to the stylomastoid foramen and just superior to it. The
nerve is always lateral to this plane and passes obliquely across the styloid
process. A branch of the postauricular artery is usually encountered just
lateral to the nerve.
Once
the facial nerve trunk has been identified the superficial lobe of the parotid
can he exteriorised by opening up
During
the lower part of the dissection, branches of the posterior facial vein will be
encountered immediately deep to the marginal mandibular branch. Great care must
be taken when vascular clamps are applied to these branches to avoid damaging
the facial nerve.
If
the superficial partotidectomy is being performed for chronic infection, the duct
should be tied off as far forward as possible to prevent recurrent ascending
infection from the oral cavity.
If
the tumour lies in the deep lobe of the gland a conventional superficial
parotidectomy is performed as described. Next, the branches of the facial nerve
are mobilised and lifted on nylon tapes to enable the deep lobe to be freed
around its margins and removed when the mass is dropped downwards (Fig.
42.23).
As this space is wedge shaped with its apex superior, it is almost invariably
possible to do this. The deep lobe is covered by a capsule (the deep layer of
the deep cervical fascia which splits to envelope the parotid) and is surrounded
by the parapharyngeal fat. Thus, it is relatively easy to mobilise the deep lobe
by blunt dissection with either scissors or a finger. Only very rarely is it
necessary to perform a mandibulotomy to gain access to the deep lobe.
Very
rarely most often after recurrent infection with fibrosis or previous
radiotherapy — the trunk of the facial nerve cannot be confidently identified.
In this situation the peripheral branches of the nerve are identified at the
anterior border of the parotid and traced centrally towards the stylomastoid
foramen.
Following
removal of the parotid gland the blood pressure
Complications
Permanent facial nerve paralysis following superficial or total
parotidectomy is rare except when branches of the facial nerve have been
deliberately sacrificed. When the facial nerve or its branches are sacrificed as
a result of macroscopic tumour involvement, an immediate nerve graft may be
undertaken using conventional microneural techniques.
Temporary
weakness due to neuropraxia occurs in approximately 30 per cent of operations
but recovers rapidly, usually within 6 weeks. Anaesthesia of the skin flap
slowly resolves as the sensory nerves regenerate from the periphery.
Anaesthesia of the ear lobe due to sectioning of the great auricular
nerve can be troublesome, -particularly in females who find it difficult to wear
earrings. Recovery can rake up to 18 months and sometimes is never complete.
Gustatory
swearing (Frey’s syndrome) is a regular sequel to parotidectomy occurring in
up to 54 per cent of cases. Surgical manoeuvres to treat it once established are
not successful and most patients either learn to live with it or alternatively
use an antiperspirant containing aluminium chloride.
Spillage
of a benign pleomorphic adenoma should not occur if a formal superficial
parotidectomy is undertaken. However, there are four circumstances where even
with meticulous surgical technique this can happen:
• extremely large pleomorphic adenomas occupying the entire
superficial lobe making mobilisation of the gland difficult;
• tumours that are intimately associated with branches of the
facial nerve requiring very delicate dissection along the capsule of the tumour
to release the nerve;
• tumours with lobular extensions extending beneath the mastoid,
zygomaric arch or mandible;
• some tumours that are abnormally friable with even routine
retraction of the superficial lobe resulting in rupture.
Other
tare complications such as sialocele or salivary fistuIa occasionally follow
parotidectomy. Both complications are managed conservatively and resolve
spontaneously after days or weeks. Very rarely a parotid fistula persists
despite attempts at surgical closure. In this situation postoperative
radiotherapy will destroy the residual functioning acinar tissue and allow the
flstula to close.
Radiotherapy
Parotid tumours are often considered to be ‘radioresistant’.
This is not true: regression after radiotherapy is usually slow, but this
reflects the slow cell turnover time of the majority of these tumours, rather
than the inability of radiation to effect a cure. There are many reports of
long-term local control of large inoperable tumours by radiotherapy.
Nevertheless, the chance of successful radiotherapy does seem lower than in the
case of squamous cell carcinoma, and therefore the primary treatment should be
surgical wherever possible.
Radiotherapy
is of value for the inoperable tumour, and also should be used postoperatively
whenever there is a risk of incomplete excision such as rupture of a pleomorphic
adenoma. It should also be used prophylactically to radical dosage following
excision of any malignant parotid tumour. In cases where reoperation is required
for recurrence or where there is gross residual tumour, radiation in high doses
increases survival significantly.
Adenoid
cystic carcinoma has been reported to be the most, consistently radio responsive
tumour type. In view of the propensity of this tumour for later recurrence, it is doubtful whether high local control rates at 3 or 5
years really indicate radio curability.
A
wide volume around the tumour should be irradiated, especially in the case of
adenoid cystic carcinoma. A dose close to the limits of normal tissue tolerance
is necessary.