Horner's Syndrome and Mediastinal Schwannoma.

A 13-year-old boy developed right-sided Horner's syndrome following resection of a benign mediastinal schwannoma extending from T1 to T3. Postoperatively, he exhibited ptosis, miosis, and anhidrosis, confirmed by starch iodine testing. The tumor likely involved the upper thoracic sympathetic ganglia-a rare site for schwannomas. This image highlights a rare iatrogenic cause of preganglionic Horner's syndrome. While Horner's is classically associated with apical lung or cervical lesions, this case emphasizes the importance of recognizing postoperative Horner's syndrome as a clinical clue to cervicothoracic sympathetic injury. It highlights the value of anatomical-clinical correlation in localizing lesions along the sympathetic pathway.