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Background and Aims Horner’s syndrome (HS) is a known complication of interscalene brachial plexus block (IBPB), occurring when the local anesthetic spreads to the sympathetic chain near the brachial plexus (specifically the stellate ganglion). Patients may typically exhibit the classic HS triad (ptosis, miosis, and facial anhidrosis) shortly after surgery, often followed by spontaneous recovery. We present a case of a 68-year-old woman, ASA-III, with a traumatic left rotator cuff tear scheduled for ambulatory arthroscopic repair surgery.

Methods An ultrasound-guided IBPB was performed using 20mL of 0.375% ropivacaine, followed by general anesthesia. The procedure was performed in a beach-chair position, lasted 111 minutes, and was uneventful. In the postanesthesia care unit, the patient was hemodynamically stable, pain-free and without HS symptoms and was transferred to the ambulatory ward for further vigilance.

Results About five hours after surgery, the patient reported blurred vision and ptosis in the left eye, with no other neurological signs, clearly suggesting HS. Twenty-nine hours after surgery, Horner’s symptoms slightly improved, no residual motor block of the arm was registered and the patient was discharged with a follow-up scheduled for two weeks later. Persistent blurred vision and left eyelid ptosis were noted and an ophthalmological consultation documented slight anisocoria and left palpebral ptosis. A cerebral CT scan showed no abnormalities. Two months after surgery, HS spontaneously resolved.

Conclusions This case aims to illustrate a prolonged HS after an ultrasound-guided IBBP. Anesthesiologists should remain vigilant, reassure patients, and conduct additional evaluations until full recovery.