Interscalene Block Complications — FRCA Final MCQ
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Correct answer: A — Horner syndrome
The correct answer is **Horner syndrome**. Ipsilateral ptosis, miosis and apparent enophthalmos are characteristic of interruption of the ocular sympathetic pathway. After an interscalene block, this results from local-anaesthetic spread to the cervical sympathetic chain and is usually transient. Phrenic nerve palsy causes ipsilateral hemidiaphragmatic weakness, potentially with dyspnoea or reduced pulmonary function. Recurrent laryngeal nerve palsy typically presents with hoarseness or vocal-cord dysfunction. Local anaesthetic systemic toxicity causes neurological or cardiovascular features such as circumoral paraesthesia, tinnitus, seizures or arrhythmias rather than an isolated ocular sympathetic syndrome. A Pancoast tumour can cause Horner syndrome but would not explain its acute onset immediately after the block.
Reference: Electronic Medicines Compendium. Levobupivacaine 5 mg/ml solution for injection/infusion, Summary of Product Characteristics, section 4.8, updated 2025. https://www.medicines.org.uk/emc/product/13644/smpc