Arterial blood supply to the parathyroid glands: Implications for thyroid surgery

Avoiding Complications of Thyroidectomy: Preservation of Parathyroid Glands

Preservation of functional parathyroid glands during thyroidectomy and central neck surgery is crucial to avoid the common but serious complication of hypoparathyroidism. The first requirement is a solid foundational knowledge of anatomy and embryology which then enables the surgeon to use meticulous anticipatory dissection with identification and preservation of blood supply to the parathyroids. When preservation of blood supply is not possible, autotransplantation should be performed. New technologies harnessing the natural phenomenon of parathyroid autofluorescence to detect parathyroid tissue and indocyanine green to perform angiography may lead to improved outcomes with low risk to patients.

A Rare Case of Thyroidea Ima Arising From the Internal Thoracic Artery and Reaching Up to the Parathyroid Gland

The thyroidea ima artery (TIA), also known as the Neubauer artery, is a variable artery that takes part in the blood supply of the thyroid gland. The overall prevalence rate of the thyroidea ima artery is 3.3%. Though it most commonly branches off the brachiocephalic trunk or the arch of the aorta, the artery has a highly variable origin point. Herein, we present a rare case of a thyroidea ima originating from the left internal thoracic artery, found during routine dissection of a Caucasian, 76-year-old, male, formalin-fixed cadaver. The artery is a normal finding during embryological development as a part of a more extensive network of vessels supplying the thyroid gland. The latter undergoes significant remodeling, and only four superior and inferior thyroid arteries remain. Thus, the presence of the thyroidea ima is considered to be due to changes in the said remodeling process. Due to its course, anteriorly to the trachea, the thyroidea ima artery might pose problems during different surgical procedures regarding the inner anterior region of the neck, such as tracheotomy, thyroidectomy, laryngeal transplantation, and selective embolization of the thyroid arteries (SETA). Furthermore, complications during the operative treatment of parathyroid conditions and mediastinal bleeding are to be expected. The variable presence and origin of the thyroidea ima have clear and significant clinical and surgical implications. They must be considered when procedures in the neck's anterior region occur.

The anatomical basis for preserving the blood supply to the parathyroids during thyroid surgery, and a review of current technologic advances

BACKGROUND

Devascularization of the parathyroid glands is generally accepted as the most common mechanism for iatrogenic hypocalcemia, a frequently seen complication of both total and completion thyroidectomy procedures. Much has been written about iatrogenic hypoparathyroidism, but few papers have precisely delineated the arterial supply of the parathyroid glands and the common anatomical variations that may impact parathyroid preservation during thyroid surgery.

METHODS

We offer an illustrated review and discussion of the only two anatomic studies published in the medical literature focusing on parathyroid vasculature. In addition, we examine current techniques of parathyroid identification, preservation, and classification.

FINDINGS

A surgical technique that preserves the parathyroid arteries is vital to preserving the viability of the parathyroid gland(s) during thyroid surgery. In 1907, Halsted and Evans described a technique of ligating the distal branches of the thyroid arteries beyond the origin of the parathyroid arteries, a technique termed ultra-ligation. In 1982, Flament et al.. reported three distinct anatomical variations of the parathyroid arteries which place the parathyroid blood supply at risk for devascularization during thyroid surgery. Our review also highlights novel techniques that aid surgeons in identification and assessment of the parathyroid glands.

CONCLUSIONS

Recognition of the variations of parathyroid anatomy and their potential to lead to devascularization aids thyroid surgeons in their pursuit of parathyroid preservation. An awareness of the variety of novel parathyroid identification and preservation techniques can assist surgeons to achieve this goal.

In Situ Preservation of Parathyroid Gland With Vasculature for Papillary Thyroid Carcinoma Is Associated With Higher PTH Levels After Total Thyroidectomy

PURPOSE

To evaluate the impact of parathyroid gland vasculature preservation in-situ technique (PGVPIST) on postoperative parathyroid hormone (PTH) and calcium plasma levels in thyroid patients undergoing total thyroidectomy for papillary thyroid carcinoma (PTC).

STUDY DESIGN

Retrospective cohort study.

METHODS

Patients with PTC who underwent total thyroidectomy by either the conventional technique (group 1, January 2019 to January 2020) or PGVPIST (group 2, January 2020 to January 2021) were compared. Postoperative blood calcium levels and PTH levels were assessed in these groups.

RESULTS

Totally 149 patients with consecutive PTC underwent total thyroidectomy, including 60 patients in group 1 and 89 patients in group 2. Postoperative serum calcium levels in group 1 were insignificantly lower than in group 2 at day 1 (2.18 ± 0.02 vs 2.15 ± 0.01 mmol/L) and day 30 (2.27 ± 0.02 vs 2.38 ± 0.11) after surgery. But postoperative serum PTH levels in group 1 were significantly lower than that in group 2 at day 1 (23.68 ± 2.54 vs 31.46 ± 2.11 pg/mL) and day 30 (45.63 ± 3.21 vs 55.65 ± 2.89 pg/mL) after surgery.

CONCLUSION

Parathyroid gland vasculature preservation in-situ technique for PTC is associated with higher PTH level after total thyroidectomy. The parathyroid gland vasculature mostly strongly adheres with adjacent thyroid parenchyma. Therefore, deferred processing of tiny thyroid parenchyma of parathyroid gland vessels is essential to prevent devascularization.

Surgical Skills and Technological Advancements to Avoid Complications in Lateral Neck Dissection for Differentiated Thyroid Cancer

Neck dissection is a surgical procedure reserved for thyroid cancer cases with clinically evident lymphatic invasion. Although neck dissection is a reliable and safe procedure, it can determine a significant morbidity involving a variety of structures of nervous, vascular and endocrine typology. A careful pre-operative study is therefore essential to better plan surgery. Surgical experience, combined with accurate surgical preparation and merged with adequate and specific techniques, can certainly help reduce the percentage of complications. In recent years, however, technology has also proved to be useful. Its crucial role was already recognized in the safeguard of the integrity of the laryngeal nerve through neuro-monitoring, but new technologies are emerging to help the preservation also of the parathyroid glands and other structures, such as the thoracic duct. These surgical skills combined with the latest technological advancements, that allow us to reduce the incidence of complications after neck dissection for thyroid cancer, will be reported in the present article. This topic is of significant interest for the endocrine and metabolic surgeons' community.

Complications after medullary thyroid carcinoma surgery: multicentre study of the SQRTPA and EUROCRINE® databases

BACKGROUND

Surgery is the curative therapy for patients with medullary thyroid carcinoma (MTC). In determining the extent of surgery, the risk of complications should be considered. The aim of this study was to assess procedure-specific outcomes and risk factors for complications after surgery for MTC.

METHODS

Patients who underwent thyroid surgery for MTC were identified in two European prospective quality databases. Hypoparathyroidism was defined by treatment with calcium/active vitamin D. Recurrent laryngeal nerve (RLN) palsy was diagnosed on laryngoscopy. Complications were considered at least transient if present at last follow-up. Risk factors for at-least transient hypoparathyroidism and RLN palsy were identified by logistic regression analysis.

RESULTS

A total of 650 patients underwent surgery in 69 centres at a median age of 56 years. Hypoparathyroidism, RLN palsy and bleeding requiring reoperation occurred in 170 (26·2 per cent), 62 (13·7 per cent) and 17 (2·6 per cent) respectively. Factors associated with hypoparathyroidism were central lymph node dissection (CLND) (odds ratio (OR) 2·20, 95 per cent c.i. 1·04 to 4·67), CLND plus unilateral lateral lymph node dissection (LLND) (OR 2·78, 1·20 to 6·43), CLND plus bilateral LLND (OR 2·83, 1·13 to 7·05) and four or more parathyroid glands observed (OR 4·18, 1·46 to 12·00). RLN palsy was associated with CLND plus LLND (OR 4·04, 1·12 to 14·58) and T4 tumours (OR 12·16, 4·46 to 33·18). After compartment-oriented lymph node dissection, N0 status was achieved in 248 of 537 patients (46·2 per cent).

CONCLUSION

Complications after surgery for MTC are procedure-specific and may relate to the unavoidable consequences of radical dissection needed in some patients.

A rare arterial branch distributing to the thymus, ectopic intrathymic parathyroid, and thyroid glands which passed ventral to the right common carotid artery: a case report

The intrathymic parathyroid has been reported that this variation might be related with the hyperthyroidism. In this study, the arterial pattern supplying the intrathymic parathyroid was examined in detail in the human cadaver (67-year-old, female, right side). The ectopic parathyroid was only detected on the right side, but not on the left side. This ectopic intrathymic parathyroid was supplied by the supernumerary arterial branch that originated from the inferior thyroid artery and passed ventral to the common carotid artery. This supernumerary branch further divided into two thin branches: (1) the one distributing the intrathymic parathyroid and the right lobe of the thyroid gland and (2) the other descending toward the thoracic cavity to supply the mediastinum organs. Other arteries supplying the thyroid gland and thymus of both sides were normal. In the surgical resection of the ectopic intrathymic parathyroid, physicians should pay attention to arteries ventral to the common carotid artery. This supernumerary branch distributing to the intrathymic parathyroid may be caused by incomplete division into the primordium for the inferior parathyroid and the primordium for the thymus on the developmental process.

The Essentials of Parathyroid Hormone Venous Sampling

Hyperparathyroidism is an excess of parathyroid hormone in the blood due to over-activity of one or more parathyroid gland. Localization of abnormal glands with noninvasive imaging modalities, such as technetium sestamibi scan and cross-sectional imaging, has a high success rate. Parathyroid venous sampling is performed for patients with persistent or recurrent disease after previous parathyroid surgery, when repeat noninvasive imaging studies are negative or discordant. The success of invasive localization studies and results interpretation is dependent on the interventional radiologist's understanding of the normal and ectopic anatomic locations of parathyroid glands, as well as their blood supply and venous drainage. Anatomic and technical considerations for selective parathyroid venous sampling are reviewed.

Bilateral Truncal Ligation of the Inferior Thyroid Artery during Bilateral Subtotal Thyroidectomy Causes a Decrease in Parathormone without Clinically Manifest Hypoparathyroidism: A Randomized Clinical Trial

BACKGROUND

Bilateral truncal ligation (BTL) of the inferior thyroid artery (ITA) is frequently used during subtotal thyroidectomy to reduce the risk of post-operative bleeding as well as to reduce the blood loss intra-operatively. However, its effect on parathyroid function has not been evaluated in relation to age, residual and resected thyroid volume.

METHODS

A total of 83 patients were randomized to receive non-BTL or BTL. After bilateral resection, the residual thyroid tissue on each side was measured by intra-operative ultrasonography. Laboratory and clinical examinations were performed the day before operation, intra-operatively and on post-operative days 2 and 5. The primary outcome measure was the difference in intact parathormone (PTHi) on post-operative day 5. Secondary outcomes were laboratory-diagnosed hypocalcaemia or hypoparathyroidism and clinically manifest hypoparathyroidism, respectively.

RESULTS

PTHi on post-operative day 5 was significantly lower in the BTL group (29.4 vs. 34.7 ng/l in the non-BTL group, p = 0.033), especially in 61- to 80-year-old patients (0 vs. -7.91 ng/l, p = 0.029). The biggest decline in PTHi was found in the BTL group (-14.067 ng/l PTH, p = 0.018) with a residual thyroid volume of 0.5-1.9 ml. There were two cases of asymptomatic hypoparathyroidism in each group (5.1 vs. 4.8%, respectively, p = 1.000). The only case of clinically manifest hypoparathyroidism was in a BTL group patient aged 64 years (2.4%, p = 1.000).

CONCLUSION

BTL of the ITA during subtotal thyroidectomy causes a larger decrease in PTH but does not lead to a significantly higher rate of clinically manifest hypoparathyroidism. BTL of the ITA, age >61 years, and a very small thyroid remnant (<2 ml) may be risk factors for post-operative hypoparathyroidism.

The Impact of Single Parathyroid Gland Autotransplantation During Thyroid Surgery on Postoperative Hypoparathyroidism: A Multicenter Study

BACKGROUND

We compared the surgical outcomes in patients undergoing bilateral thyroid surgery with or without parathyroid gland autotransplantation (PTAT).

METHODS

One thousand three hundred nine patients underwent surgery for treatment of various thyroid diseases at three Academic Departments of General Surgery and one Endocrine-Surgical Unit throughout Italy. A nonviable gland or difficulties in dissection of the parathyroid glands were encountered in 160 (13.7%) patients. The subjects were divided into two groups: (1) patients undergoing PTAT during thyroidectomy (n = 79) versus (2) control group (n = 81), patients not undergoing PTAT.

RESULTS

Clinical manifestations occurred in 5.0% of PTAT patients and in 13.6% of control patients (P = NS). Total postoperative hypocalcemia was less among PTAT than control patients (17.7% and 48.1%, respectively; P = .0001). There was no significant difference between the two groups in terms of definitive hypocalcemia (0% vs 2.5% in PTAT and control, respectively). Transient postoperative hypocalcemia was less among PTAT than controls (17.7% vs 45.7%; P = .0002). PTAT was associated with decreased occurrence of hypocalcemia in the two subgroups of patients operated for benign euthyroid disease (P < .0001), as compared with the control group.

CONCLUSIONS

PTAT is an effective procedure to reduce the incidence of permanent hypoparathyroidism. Transient hypoparathyroidism appears to not be influenced by PTAT. Moreover, we observed that damage to one parathyroid gland has more side effects (ie, transient hypocalcemia) among patients who were preoperatively at low rather than at high risk of postoperative hypocalcemia.

The impact of surgical technique on postoperative hypoparathyroidism in bilateral thyroid surgery: a multivariate analysis of 5846 consecutive patients

BACKGROUND

Limited information exists about risk factors for postoperative hypoparathyroidism after bilateral thyroid surgery.

METHODS

Between January 1 and December 31, 1998, bilateral thyroid surgery was performed on 5846 patients for benign and malignant thyroid disease. Data were prospectively collected by questionnaires from 45 hospitals. A logistic regression model was used to determine independent risk factors.

RESULTS

The overall incidence of transient and permanent hypoparathyroidism was 7.3% and 1.5%, respectively. On logistic regression analysis, total thyroidectomy (odds ratio [OR], 4.7), female gender (OR, 1.9), Graves' disease (OR, 1.9), recurrent goiter (OR, 1.7), and bilateral central ligation of the inferior thyroid artery (OR, 1.7) constituted independent risk factors for transient hypoparathyroidism. When the multivariate analysis was confined to permanent hypoparathyroidism, total thyroidectomy (OR, 11.4), bilateral central (OR, 5.0) and peripheral (OR, 2.0) ligation of the inferior thyroid artery, identification and preservation of no or only a single parathyroid gland (OR, 4.1), and Graves' disease (OR, 2.4) emerged as independent risk factors.

CONCLUSIONS

Extent of resection and surgical technique had a greater impact on the rates of permanent postoperative hypoparathyroidism than thyroid pathologic condition. In bilateral thyroid surgery, peripheral ligation of the inferior thyroid artery at the thyroid capsule should be favored over central ligation, and at least 2 parathyroid glands should be identified and preserved. High-risk procedures, such as total thyroidectomy and Graves' disease, require special surgical training and expertise.

A rare variant of thyroid gland vascularization

Usually the thyroid gland obtains its blood via two paired arteries. One pair, the right and left superior thyroid aa., most commonly arises from the external carotid aa. and the second pair, the right and left inferior thyroid aa. commonly arises from the thyrocervical trunk of the subclavian a. In this particular case the right inferior thyroid a. was replaced by an artery branching off the right internal thoracic a.; the left inferior thyroid a. was replaced by an artery branching off the vertebral a. between the transverse process of the second and third cervical vertebrae. This finding might be explained by the suggestion that in the fetus there exists an anastomotic arterial chain ventral to the spinal column consisting of the thyrocervical trunk and the ascending cervical a. which itself is connected to the vertebral a.

Parathyroid function following ligation of the inferior thyroid arteries during bilateral subtotal thyroidectomy

A randomized controlled trial was performed to compare two techniques of bilateral subtotal thyroidectomy for non-toxic nodular goitre with regard to postoperative parathyroid function. The 50 patients in group 1 underwent ligation of the trunks of the inferior thyroid arteries. In group 2 (50 patients) the branches of these arteries were suture-ligated at the thyroid capsule. Total calcium, ionized calcium and parathyroid hormone levels were determined before operation, and 6, 24 and 72 h after surgery. Ninety-one patients were seen at follow-up 5-10 months after operation. Ten patients in group 1 and 12 in group 2 required calcium and/or vitamin D supplementation for symptomatic hypocalcaemia in the immediate postoperative period. At follow-up only one patient in each group had mild hypoparathyroidism. No statistically significant differences were found between groups regarding total calcium, ionized calcium and parathyroid hormone levels. Truncal ligation of the inferior thyroid arteries during bilateral subtotal thyroidectomy does not cause hypoparathyroidism or hypocalcaemia.

Complications in management of thyroid cancer

There are a number of complications related to the management of thyroid carcinoma, some due to the natural history of the disease regardless of its cell type and all too many which are iatrogenic. Three of these complications will be discussed: 1) airway problems, 2) related photation aspects, and 3) hypoparathyroidism.