Anatomy
Bloodless plane at sup pole
Ligament of Berry
Nerve variability:In 1 percent of patients, the right recurrent nerve arises from the vagus but passes medially almost directly from its origin to the larnyx without looping under the subclavian (the subclavian arises from the descending aorta and passes to the right behind the oesophagus) Even rarer is a non recurrent left nerve.
CAUSE OF VULNERABILITY %ENCOUNTERED
Lat and ant location 1.5-3
Tunnelling through thyroid 2.5-15
Fascial fixation 2-3
Arterial fixation 5-12.5
Close proximity to inf thy v.1.5-2
Can identify nerve where it enters larynx just posterior to the inferior cornu of the thyroid cartilage. If not found a non recurrent nerve should be suspected esp on right. (1% cases) Nerve may be palpated as a tight strand over the tracheal surface.
The sup laryngeal nerve passes inferiorly, medial to the carotid artery. At the level of the sup cornu of hyoid it divides into large sensory int laryngeal branch and small motor external laryngeal branch to cricothyroid. Bifurcation is usually within bifurcation of carotid artery. In 20% patients, the nerve will pass between the branches of the sup thyroid artery. In 20% it runs a high course into the constrictor and may not be seen at all. Cernea Classification for EBSLN: Type 1: well clear of thyroid, 1cm above upper pole passing directly into cricopharyngeus. Type 2a: passes in vicinity of sup thyroid vessels as they enter gland substance Type 2b: passes over anterior surface of gland
Nerve of Galen: communicating branch b/w RLN and EBSLN
Be careful removing a lymph node in papillary thyroid cancer: this could be a fused cervical ganglion (related to vertebral artery and fixed in front of tranverse process of 7th vertebra: this will cause a Horners
strap mm: sternohyoid is superficial to stenothyroid
In 90% cases the superior parathyroid (P4) is within 1cm of the junction of inferior thyroid artery and RLN
History
Dunhill procedure
Thomas Dunhill 1911 surgeon St V Melb
Lobectomy with removal 2/3 to half contralateral lobe
Evolution of technique
1970’s
lateral approach: identify nerve along its whole length and removing tissue medial to it: this actually caused a higher nerve injury rate and more disruption to PT glands
PROCEDURE
Head ring/shoulder roll/Tilt table to 15 deg to empty veins
Head light
LA infiltration preop
A high, long incision is often cosmetically better than a short low one
Collar incision 2 fingers above sternoclavicular joint
Mark incision with vicryl tie
Subplatysmal flaps with 11 (?22) blade well up to thyroid cartilage and down to sternal notch
Johl retractor
Unipolar pickup diathermy
diathermy deep fascia longitudinally and divide strap mm to get into spidery plane
If need to divide staps transversely do it in upper third to avoid injuring nerve supply (ansa)
Ligasure vessels, divide and tie middle thyroid vein with 3-0 vicryl and fine right angle (Mixter)
Mobilise sup pole esp in bloodless plane or Reeves. Can use an artery on sup pole to retract downwards. Watch for ESLN. This may be identified on the inferior constrictor before entering the cricothyroid muscle. Key to identifying is to develop avascular plane b/w cricothyroid and medial border of upper pole of thyroid, facilitated by lateral retraction of upper pole
Start dissection high on thyroid taking peripheral branches of ITA. RLN is thus encountered usually near the ligament of Berry.
SILAB: beware mistaking for non recurrent nerve
Use large pack or artery to retract lobe medially to expose RLN.
Often you can palpate it as a cord in the tracheo-oesophageal groove before you can see it. Can then dissect carefully onto to with a small artery clip taking each fascial layer. Nerve often has a small blood vessel running on its surface. It is more vulnerable on the right due to obliquity of the course in the lower third of the wound. Nerve usually lies deep to inferior thyroid artery (but may trap you by sitting on top of the artery and pulsating. Identify nerve in the lower third before ligating veins.
The inferior cornu of the thyroid cartilage is the most reliable indentification marker for entry of the RLN into the larynx
do not ligate main trunk of inferior thyroid artery to avoid cutting blood supply to inferior parathyroid (P3) If P3 cannot be found check thyrothymic ligament and thymus
Ligasure across isthmus or change sides to dissect other side
If a central LN dissection needs to be done then clear the tissues from the carotid artery to the trachea, up to the thyroid cartilage and down to the great vessels (including the thymus). Evidence suggests this is justified only for medullary cancer. No clear evidence for its benefit in papillary tumours.
10 Fr Redivac drain
Valsalva
3-0 vicryl interrupted to deep fascia
4-0 monocryl skin
Comfeel
(1)For mega-thyroids, can divide strap muscles with GIA55 linear cutter stapler.
Dissection for visualisation of all parathyroid glands may do more harm than good
if reimplanting in hyperparathyroidism, mince into 1-2mm cubes and put into pocket of brachioradialis muscle. Clip site
PROBLEMS
Cancer operations
Parathyroids: preserve superior, Tx inferior
Tracheal invasion: shave and post op ablation
Segmental resection, primary repair or flap closure, tracheostomy
RLN involvement: preserve nerve and post op ablation vs en bloc resection
Oesophageal invasion: local resection and repair
COMPLETENESS OF RESECTION
Thyrothymic thyroid rests (50% of patients)
Tubercle of Zuckerkandl:
lateral thyroid component arising from 4th branchial cleft and ultimobranchial body fuses with medial component (this fusion is the source of thyroid C cells
Found in 2/3 patients
Usually enlarges lateral to RLN, with nerve appearing to bass in cleft medial to it
SupPT (P4) also from 4th cleft is often found close and usually cephalad to it
Thyroglossal tract and pyramidal remnants
