Parathyroidectomy

Types

• Minimal invasive
  • Single gland
• Unilateral neck
  • Localised to one side
    • Should find a adenoma and a normal gland
    • IF find two normal glands then need to stop or continue to bilateral
• Bilateral neck
  • Indications
    • No localisation
    • 4 gland
  • Two options
    • Subtotal
      • Leave 1/2 a node (inferior as easier access)
    • Total
      • With re implant
        • SCN or BC
      • Without re implant
        • Not good practice although done

Guidline statements (ANZES)

• The majority of PHPT patients have single gland disease and a focussed approach is appropriate following discussion with the patient regarding the possibility of persistent disease.
• BNE should be preferentially considered in any patient with negative/discordant localisation imaging, known bilateral/ multi‐gland disease, known genetic/familial risk factors for multi‐gland disease or those on provocative medications (e.g., lithium).
• Lithium was previously considered to be routinely associated with multi‐gland disease. However, recent data shows some contrary evidence and where a single adenoma is localised on imaging, a focussed approach may be entertained.

Conventional Bilateral Neck Exploration

• Basic Principles
  • Gold standard
  • Success rate 95-98%
    • Low morbidity, mortality close to 0, cosmesis excellent
  • Success based on anatomical knowledge and understanding of embryological evolution
  • Exploration should aim to expose all parathyroid tissue (at least 4 glands) in all cases
  • Frozen section only contributes to tell you if it is parathyroid tissue or not
    • Cannot reliably tell difference between adenoma/hyperplasia/normal
  • Tell if gland is pathological by its macroscopic appearance
    • Need to visualise all 4 glands to be able to compare them
      • But beware the risk of devascularisation with over dissection
  • Average weight 40g, must be > 75g to be considered abnormal
  • Biopsy of suspected carcinoma is strictly contraindicated
    • May cause local spread (parathyromatosis)

Setup and Entry

• Usually GA, can be regional
• IV Abx
• Supine position with 30 degrees of Trendelenburg to reduce vascular engorgement.
• Extend neck with the use of a head ring.
• Kocher incision midway between cricoid cartilage and jugular notch within a skin crease.
• Through skin and platysma layers
• Subplatysmal flaps
• Midline separation of strap muscles

Search for Superior Parathyroid (P IV)

1. Displace thyroid lobe anterior medially
   • Need to retract jugulocarotid bundle laterally
   • Middle thyroid vein and superior thyroid artery usually can be persevered
2. Inferior thyroid artery should be preserved
3. RLN should be identified

• In 85% of cases the above steps allow identification of Superior Parathyroid in its normal site
  • Typical location - posteromedial surface of the superior pole
    1. At the level of the cricoid cartilage
    2. Posterior RLN
    3. 1cm superior to the junction of Inferior Thyroid Artery and Recurrent Laryngeal Nerve
• If abnormal/enlarged, P IV tends to migrate posteriorly and downwards
  • Look beside/behind oesophagus
  • May go very low (lower than Inferior Thyroid Artery)
    • Lower it goes, the more posterior it becomes
    • Can follow its vascular pedicle (originates middle/upper 1/3 of thyroid lobe)
    • Can emerge with simple traction on the pedicle
  • NB: Closely related to RLN, can be attached to their capsule
  • Ectopic locations
    • Tracheoesophageal groove
      • Most common
    • Retropharyngeal
    • Retroesophageal
    • Posterior mediastinal
    • Intra- thyroidal

Search for Inferior Parathyroid (P III)

• Higher variability (further to travel)
  • Typical location - posteriorlateral surface of the inferior pole of the thyroid lobe
    1. Anterior to the RLN
    2. Along the posterolateral aspect of the inferior pole to the thyroid gland
    3. Approximately 1 cm caudal to the junction to the RLN and inferior thyroid artery
  • Search from
    • Inferior Thyroid Artery to Inferior Thyroid pole then down to thymus
    • PIII’s are rarely posterior
      • Become more anterior the lower they are
    • Ectopic locations
      • Thyro-thymic ligament and Thymus
        • 25%
      • Anterosuperior mediastinum
      • Undescended in a submandibular location
      • Within the thyroid gland
      • Within the carotid sheath

If you can’t find the superior parathyroid

• Look in the retropharyngeal, tracheoesophageal groove, retro-oesophageal, and carotid sheath, and posterior superior mediastinum.
• This generally means you are dissecting posteriorly to its usual location.

If you can’t find the inferior parathyroid.

• Look in the thyro-thymic/ligament tract – runs from the inferior lobe of the thyroid down to the thymus.
• You should perform a Cervical thymectomy and examine its substance - this involves identifying the thymus at the lower border of the thyroid -  gentle traction on the thymus superiorly out of the chest, and ligating the inferior thymic vein once visible.
• A hemithyroidectomy should also be considered as the gland can be within the substance of the thyroid.
• Other sites include within the anterior mediastinum, in the carotid sheath.
• You should also explore high - up near the submandibular gland.

Evaluation after Initial Bilateral Exploration

• Abandon/finish dissection if:
  • All 4 glands discovered, and one or more abnormal
    • Unless familial hyperparathyroidism
  • One abnormal gland, other gland(s) normal, but fewer than four located
• Continue/peruse dissection if:
  • No gland discovered
  • Fewer than 4 glands discovered, but none are pathological
  • Probable adenoma remains
  • Fewer than 4 glands found, and ≥ 2 glands enlarged
  • Multi-gland disease, must find remaining gland
  • All 4 glands identified but none are pathological
  • Likely ectopic supernumerary adenoma

Continuation of Exploration

• Congenital ectopias (neck or mediastinum) caused by abnormal embryological migration are related to P III’s (Inferior Parathyroids)
• Acquired ectopias in posterior mediastinum caused by migration associated with gravity, are related to P IV’s (Superior Parathyroids)

Minimally Invasive Options

• Limited incisions, target 1 specific gland
  • Based on the fact most cases are single adenomas
• Contraindications
  • Pre-op suspected multi-gland disease
  • Familial hyperparathyroidism
  • Suspected carcinoma
  • Relative – previous surgery or large goiters

Open Minimally Invasive Parathyroidectomy

• Two approachs
  • Lateral or medial approach (in relation to the strap muscles)
• Pre-op localisation prerequisite
  • ioPTH also heavily used
• 2-4cm unilateral incision
• Can be day case, shorter op time
• Fewer overall complications
• Cure rates compatible with bilateral neck exploration
• Can also do minimally invasive radio-guided approach

Endoscopic Parathyroidectomy

• Can do like traditional endoscopic approach
• Use low pressure insufflation
• Can do MIVAP
  • Minimally invasive video assisted parathyroidectomy

Reoperations

• Initial procedure have cure rates of > 95% and complication rates of < 2%
• Indications
  • Persistent disease
    • Failure of normalised Ca2+ post-op within 6 months of surgery
  • Recurrent disease
    • Over 6 month normocalcaemic interval prior to reappearance of hypercalcaemia
      • Can be after several years
    • Most seen in familial disease or multi-gland disease
• Re-operative surgery can be technically challenging and associated with increased morbidity
  • Threshold for surgical intervention should be higher
• Influenced by symptoms and signs as well as the ability to localize the diseased gland pre-op
  • Attempt to localise using non-invasive methods
  • May be more of a role for selective venous sampling if can’t otherwise locate
• Pre-operative imaging localisation mandatory

Total/Subtotal Parathyroidectomy

• Indications
  • 4 Gland Hyperplasia
  • 2° Hyperparathyroidism
  • 3° Hyperparathyroidism
• Need to complete bilateral neck exploration initially

Subtotal Parathyroidectomy

• Remove nearly all of abnormal glands, leaving a well vascularised remnant of 1 gland in its anatomical location
  • Low rate of post-op hypocalcaemia, but recurrence 5-30%
• First create remnant
  • Means you can assess vascularity later in the case
  • Aim to leave 50-100mg tissue (50-75% of gland)
• Try to leave an inferior gland
  • Most readily accessible if need to re-operate, anterior to RLN
  • Also leave titanium clip in the vicinity
• Remember blood supply from medial
  • Take lateral portion

Total Parathyroidectomy with Reimplantation

• Removes all glands and implants morcellate pieces of tissue in non-anatomical sites
  • Most common in non-dominant Brachioradialis or SCM, (can also be subcutaneous chest)
    • Multiple small pockets created
• Recurrences easier to treat than for subtotal
  • Don’t need further neck exploration
• Risk of profound hypocalcaemia if graft fails
• Not recommended for first time operations in 2° or 3° hyperparathyroidism due to risk of severe hypocalcaemia

Total Parathyroidectomy without Reimplantation

• Most effective surgical treatment for severe refractory 2° Hyperparathyroidism
• May need Ca2+ supplementation lifelong

Surgical Adjuncts

IoPTH

• Utilises short plasma circulating half-life of PTH - 4.5 mins
• “Miami” criteria
  • Takes 4 measurements
    • Pre-skin excision
    • Pre-gland excision (Take higher of these two as ‘baseline’)
    • 5 mins post-gland excision
    • 10 mins post-gland excision
  • 50% decrease in PTH levels from baseline
    • 10 minutes after resection
    • Indicates successful surgery in 97% cases
  • If doesn’t drop by 50%
    • Remeasure at 20 mins
  • If still not, continue exploring
• Dual Criteria
  • Take 2 measurements
    • Pre-gland excision
    • 10 mins post-gland excision
• If drops by > 50%, and returns to normal range, then dual criteria met
  • Has led to decreased operative failure rates

Gamma Probe Localisation

• Pre-op injection of 99mTc sestamibi
• Intra-op localization with a hand-held quantitative gamma counter
• Excised gland should be > 20% background
• Not done by most centers

RLN Monitoring

• A meta-analysis comparing
  • RLN monitoring versus RLN visual identification
  • Effect on true vocal cord palsy rates after thyroid surgery
  • Found no statistically significant difference in RLN injury rates between the two groups

Complications

• Failure to cure
  • Cure = Biochemical normalisation of calcium lasting > 6 months post-op
  • Cure rates 99% for MIP, 97% for BNE in high vol centres
    • ? Not as high in low volume centres
• RNL or ELN injury
• Post-op Hypocalcaemia
  • Atrophy of remaining glands
  • Damage to remaining glands in surgery
• Transient hypocalcaemia common
• Bleeding/Haematoma
  • < 0.5% of patients
  • Can be surgical emergency
• Hungry bone syndrome
  • This can occur after surgery for secondary or tertiary hyperparathyroidism
  • Occurs because after surgery, there is a sudden drop in PTH, which means bone Ca release stops, leading to severe hypocalcaemia, hypophosphatasemia and hypomagnesaemia.
  • Managed with high dose IV calcium replacement