Objective: Horner’s syndrome (HS) occurs due to damage to the cervical sympathetic nerve pathway and is considered a rare complication following thyroid surgery with an incidence of approximately 0.2%. This paper reports a case of HS that developed after thyroid surgery and provides a literature review of this rare complication.

Case report: A 29-year-old female patient diagnosed with suspected right thyroid cancer cT3bN0M0 underwent total thyroidectomy and central neck dissection. On the second postoperative day, the patient developed right-sided ptosis and miosis (right pupil 2mm compared to left pupil 4mm). The patient was diagnosed with HS secondary to thyroid surgery. After 3 months of follow-up, the symptoms showed no improvement.

Conclusion: HS following thyroid surgery is a rare complication that may result from various mechanisms such as direct injury to the cervical sympathetic chain, hematoma compression, ischemia, or traction of the cervical sympathetic chain. Standardized surgical procedures and refined surgical techniques are necessary to prevent this complication. Patients should be counseled about the possibility of permanent injury and long-term aesthetic impact.

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