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Thoracic epidural sympathetic anatomy — FRCA Primary MCQ

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HardAnatomyThoracic epidural sympathetic anatomyFRCA Primary

A 59-year-old patient has a thoracic epidural sited for laparotomy. After a test dose, he develops hypotension and reduced sensation from T4 to L1. Which anatomical pathway carries most sympathetic outflow affected by this block?

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Correct answer: C — Craniosacral autonomic outflow

Preganglionic sympathetic fibres arise from the thoracolumbar cord and pass through the sympathetic chain, so a thoracic epidural can block sympathetic outflow. The craniosacral outflow is parasympathetic and does not explain the sympathetic block pattern. Dorsal column and spinocerebellar tracts carry sensory/proprioceptive information. The pearl is that sympathetic block often extends beyond the perceived sensory block.

Reference: RCoA Primary FRCA Syllabus 2026; Anatomy for Anaesthetists