Risk of Hypoparathyroidism Seen After Lymph Node Removal
Condition also develops after thyroid gland removal for cancer, study finds
Central lymph node dissection, or the removal of lymph nodes in the neck, increases the risk of both temporary and permanent post-surgical hypoparathyroidism in people with thyroid cancer who undergo surgery to remove the thyroid gland, a 10-year French study reports
Also, lateral lymph node dissection along with total thyroidectomy (full thyroid gland removal) was linked to a higher risk of recurrent laryngeal nerve palsy, a condition characterized by problems in the voice cords and, in some patients, in swallowing.
“Surgeons should balance the oncologic benefit of lymph node dissection with the risk of surgical complications. Among these, hypoparathyroidism remains the most common complication after thyroid surgery,” the researchers wrote.
The study, “Impact of Lymph Node Dissection on Postoperative Complications of Total Thyroidectomy in Patients with Thyroid Carcinoma,” was published in the journal Cancers.
Total thyroidectomy is considered the most effective treatment for thyroid cancer. In patients where the cancer has spread, or metastasized, to the neck’s lymph nodes — oval-shaped organs that contain immune cells — it is recommended that patients undergo lymph node dissection.
However, whether patients without evidence of cancer spread to lymph nodes benefit from their preventive (prophylactic) surgical removal remains debatable. While this procedure could lower the chances of the cancer coming back, lymph node dissection does not seem to affect the long-term survival of these patients.
Moreover, lymph node dissection with total thyroidectomy has been linked to a high incidence of temporary or permanent hypoparathyroidism. The surgery also may cause injuries to the inferior recurrent laryngeal nerve, leading to temporary or permanent vocal cord palsy.
The study and its results
In this study, a team led by researchers in France conducted a retrospective analysis to assess complications following lymph node dissection, especially in the central neck compartment, and identify its potential risk factors.
They analyzed the outcomes of 1,547 thyroid cancer patients (77.1% women, with a mean age of 49.1 years) who underwent total thyroidectomy at the University Hospital of Lille, France, between January 2000 and December 2009.
From these, 535 (34.6%, mean age 45.8 years) underwent lymph node dissection, while the remaining 1,012 (65.4%, mean age 50.9 years) did not.
From the patients who underwent central lymph node dissection (CLND), 147 (9.5%) had ipsilateral CLND to remove lymph nodes on the same side of the thyroid cancer, and 194 (12.5%) had bilateral CLND to remove all lymph nodes around the thyroid.
Lymph node dissection of the lateral neck’s compartment included 64 (4.1%) cases of ipsilateral lateral lymph nodes sampling (LLNS), 124 (8%) bilateral LLNS, 137 (8.9%) ipsilateral LLND, and 57 (3.7%) bilateral LLND.
Temporary hypoparathyroidism was seen in 209 (13.5%) patients and permanent hypoparathyroidism in 26 (1.7%).
Patients who underwent total thyroidectomy along with lymph node dissection had significantly higher rates of temporary hypoparathyroidism compared with those who did not undergo lymph node dissection. Also, those with temporary post-surgical hypoparathyroidism were more frequently submitted to ipsilateral or bilateral CLND and ipsilateral LLND.
Risk factors of post-surgical hypoparathyroidism
Researchers then conducted statistical analyses to assess the potential risks factors associated with temporary post-surgical hypoparathyroidism. This analysis revealed that being female, as well as undergoing ipsilateral CLND and bilateral CLND, were independent risk factors.
Additional risk factors included the surgical removal of the parathyroid glands — small glands in the neck — along with the thyroid gland. Another risk factor was parathyroid autotransplantation, a procedure in which parathyroid tissue is placed into the muscle of either the neck or forearm.
Bilateral CLND and the presence of parathyroid gland tissue on the resected thyroid “were the two major independent predictive factors of permanent postoperative hypoparathyroidism,” the researchers wrote.
Taking into account all patients studied, 137 (8.9%) and 44 (2.8%) experienced temporary or permanent damage to the recurrent laryngeal nerve, respectively. In 18 patients (1.1%), both sides of the nerve were damaged.
Higher rates of temporary (15.3% vs. 5.4%), permanent (6.5% vs. 0.9%), or bilateral (2.6% vs. 0.4%) recurrent laryngeal nerve injuries were seen in patients who underwent total thyroidectomy along with lymph node dissection, compared with those who only had thyroid surgery.
Statistical analysis showed that both ipsilateral and bilateral CLND increased the risk of temporary and permanent nerve injuries. Bilateral LLNS also increased the risk of temporary recurrent laryngeal nerve injuries.
Additional analyses demonstrated that bilateral LLND was the main independent predictor of temporary, permanent, or bilateral damage to the recurrent laryngeal nerve.
Researchers also assessed the frequency of other post-surgical complications. This analysis showed that a compressive hematoma — an accumulation of blood that can cause airway obstruction — was found in 10 patients (0.6%). The majority occurred in those who underwent thyroid surgery alone (nine patients). All patients with compressive hematoma underwent a follow-up surgery, and the origin of the bleeding was successfully located in eight of them.
Thirteen patients (2.2%) experienced chyle leakage, a condition in which lymph vessels become damaged, causing chyle, a fluid, to leak into nearby tissues, triggering swelling.
Nerve palsy — impairment in nerves other than the laryngeal nerve — was seen in 10 patients, all of whom had thyroid surgery along with lymph node dissection.
“In our study, we demonstrated that central lymph node dissection, and more particularly bilateral CLND, drastically increases the risk of transient and permanent postoperative hypoparathyroidism, while lateral lymph node dissection exposes a higher risk of recurrent laryngeal nerve palsy,” the researchers wrote.
“A wider knowledge of lymph-node-dissection-related complications associated with thyroid surgery could help surgeons to carefully evaluate the surgical and medical therapeutic options and to be able to give the patient adequate information about the benefits and the risks of surgery,” they wrote.