Rationale: Horner syndrome (HS) is a rare but underrecognized complication of thyroidectomy, typically resulting from intraoperative injury to the cervical sympathetic chain. Its clinical manifestations include ptosis, miosis, enophthalmos, anhidrosis, and vasodilation. However, data on causative factors, progression of ocular signs, and clinical recovery timing remain limited. This study aimed to clarify these aspects to establish reference intervals for patient management. Patient concerns: A 29-year-old female developed postoperative miosis and ptosis following endoscopic thyroidectomy. Her primary concern was persistent ocular symptoms affecting daily life. Diagnoses: HS was confirmed through comprehensive evaluation, including ptosis measurement, scotopic pupillometry, and positive response to 0.2% brimonidine testing. Interventions: She received intravenous methylprednisolone (80 mg/day for 10 days) and oral methylcobalamin (0.5 mg 3 times daily for 30 days). Outcomes: At 16-month follow-up, partial persistence of miosis and ptosis was observed; however, facial sweating normalized, and other ocular symptoms resolved completely. Lessons: HS should be considered a potential complication of thyroidectomy, even when rare. Simple clinical and pharmacologic tests (e.g., brimonidine test) suffice for confirmation. Notably, complete recovery from iatrogenic HS secondary to endoscopic thyroidectomy may exceed 12 months, highlighting the need for long-term follow-up and patient counseling.
Li et al. (2026) studied this question.