Chvostek Sign After Graves' Disease Surgery: Hypoparathyroidism
The cause of a Chvostek sign after Graves' disease surgery is hypoparathyroidism, which occurs when parathyroid glands are inadvertently damaged or removed during thyroidectomy, leading to hypocalcemia. 1
Mechanism of Postoperative Hypoparathyroidism
The most common significant complications of thyroidectomy are hypoparathyroidism and recurrent laryngeal nerve injury, with hypoparathyroidism occurring more frequently after total thyroidectomy. 1 During thyroid surgery for Graves' disease, parathyroid glands can be damaged or inadvertently removed, resulting in transient or permanent postoperative hypoparathyroidism that manifests as hypocalcemia. 1
Postoperative parathyroid hormone (PTH) levels below 10 pg/mL are the most powerful predictor of postoperative hypocalcemia (odds ratio 23,95% CI 3.3-156), making transient hypoparathyroidism the most significant parameter determining hypocalcemia development. 2
Why Not the Other Options
Neck Hematoma
While neck hematoma is a surgical complication that can occur after thyroidectomy and may require reoperation for bleeding, it does not directly cause Chvostek sign. 3 Hematoma causes airway compromise through mechanical compression, not the neuromuscular hyperexcitability that produces Chvostek sign.
Recurrent Laryngeal Nerve Injury
Recurrent laryngeal nerve injury is indeed a common complication of thyroidectomy (occurring in approximately 3% of total thyroidectomies by experienced surgeons), but it manifests as vocal cord palsy and voice changes, not Chvostek sign. 1 The nerve injury affects phonation and airway protection, not calcium homeostasis or neuromuscular excitability.
Unique Considerations in Graves' Disease
Surgery for Graves' disease carries a higher risk of hypocalcemia compared to surgery for benign atoxic goiter for several reasons:
Secondary hyperparathyroidism: Patients with Graves' disease often have preoperative secondary hyperparathyroidism due to increased bone turnover and relative calcium/vitamin D deficiency from accelerated bone restoration during medical therapy. 4
Vitamin D deficiency: Graves' patients frequently have low 25-hydroxyvitamin D levels with elevated 1,25-dihydroxyvitamin D levels and increased renal 25OHD-1-hydroxylase activity, making them particularly susceptible to tetany when hypoparathyroid function occurs postoperatively. 4
Disease duration and bone turnover: Longer disease duration correlates with significantly lower postoperative PTH concentrations and higher bone turnover markers, increasing hypocalcemia risk. 2
Clinical Recognition
The Chvostek sign—contraction of ipsilateral facial muscles following percussion over the facial nerve—indicates neuromuscular hyperexcitability from hypocalcemia. 5 However, it's worth noting that in the general population, a positive Chvostek sign can paradoxically be associated with normal to increased calcium levels rather than hypocalcemia, so it should be confirmed with serum calcium and PTH measurements. 5
PTH should be measured 4 hours after surgery to predict postoperative hypoparathyroidism, with intensive calcium monitoring unnecessary when PTH concentration is >1.6 pmol/L (15 pg/mL) measured ≥30 minutes after surgery. 1