What is the most likely cause of paresthesias, hand spasms, hyperactive deep tendon reflexes, and carpopedal spasm in a patient 7 days post-thyroidectomy (thyroid removal surgery)?

Hypocalcemia (Answer: C)

The most likely cause of this patient's perioral paresthesias, hand spasms, hyperactive reflexes, and carpopedal spasm (Trousseau sign) seven days post-thyroidectomy is hypocalcemia secondary to iatrogenic hypoparathyroidism.

Clinical Presentation

The patient exhibits classic signs of hypocalcemia:

• Perioral numbness and peripheral tingling are pathognomonic for hypocalcemia, presenting with muscle cramps and carpopedal spasm 1
• The carpopedal spasm triggered by blood pressure cuff inflation represents a positive Trousseau sign, a hallmark of neuromuscular irritability from hypocalcemia 1
• Hyperactive deep tendon reflexes indicate increased neuromuscular excitability, consistent with low ionized calcium levels 1

Mechanism of Post-Thyroidectomy Hypocalcemia

• Temporary hypoparathyroidism affects 5.4-12% of patients after thyroidectomy, while permanent hypoparathyroidism occurs in 1.1-2.6% 1
• The mechanism involves iatrogenic injury to parathyroid glands through direct surgical trauma, devascularization, or inadvertent removal during thyroid excision 2, 3
• Symptoms typically manifest within hours to days postoperatively, with the 7-day timeframe in this case being consistent with transient hypoparathyroidism 4

Why Not the Other Options

• Hypercalcemia (Option A) would cause lethargy, confusion, and constipation—not neuromuscular irritability or tetany 5
• Hyperphosphatemia (Option B) alone does not cause these acute neuromuscular symptoms; it occurs secondary to hypoparathyroidism but is not the primary cause 3
• Hypomagnesemia (Option D) can occur after thyroidectomy (72% incidence) and may contribute to hypocalcemia, but the classic presentation described is primarily hypocalcemia-driven 6. Hypomagnesemia causes functional hypoparathyroidism and makes hypocalcemia refractory to treatment, but the primary diagnosis remains hypocalcemia 6

Diagnostic Confirmation

• Immediate serum calcium measurement confirms the diagnosis, with monitoring every 6-8 hours until stable 1
• Intact parathyroid hormone (iPTH) levels less than 15 pg/ml the morning after surgery predict hypocalcemia with 71% sensitivity and 99% specificity 7
• Serum phosphorus levels greater than 4 mg/dl under oral calcium therapy indicate high risk for permanent hypoparathyroidism 3

Clinical Pitfalls

• Do not confuse this presentation with recurrent laryngeal nerve injury, which causes voice changes, hoarseness, and dysphonia—not perioral numbness or limb symptoms 8, 1
• Both calcium AND magnesium should be monitored and corrected, as attempting to correct hypocalcemia alone when hypomagnesemia coexists may prolong symptoms 6
• A decrease in serum calcium of ≥1.1 mg/dl from pre-operative to immediate post-operative levels predicts symptomatic hypocalcemia with high sensitivity 2

Immediate Management

• Administer intravenous calcium gluconate for symptomatic hypocalcemia with neuromuscular irritability 5
• Dosing should be individualized based on symptom severity, with careful cardiac monitoring during administration to avoid arrhythmias 5
• Oral calcium supplementation plus vitamin D should be initiated for patients at high risk based on early post-operative calcium drops 2