Sciatic Nerve Roots — FRCA Primary MCQ

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ModerateAnatomySciatic Nerve RootsFRCA Primary

Which set of spinal nerve ventral rami contributes to the formation of the sciatic nerve?

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Correct answer: E — L4, L5, S1, S2 and S3

Explanation lettering: C = shown as A · D = shown as B · A = shown as C · E = shown as D · B = shown as E

The correct answer is B. The sciatic nerve arises from the ventral rami of L4–S3 within the sacral plexus. It contains two components enclosed in a common connective-tissue sheath: the tibial component, derived from anterior divisions of L4–S3, and the common fibular component, derived from posterior divisions of L4–S2. L2–L4, as in option E, principally supplies major lumbar plexus nerves such as the femoral and obturator nerves. Options C and A incorrectly restrict or extend the contribution into predominantly lumbar levels, while option D omits the essential L4 and L5 contributions and incorrectly includes S4. The usual root value is therefore L4–S3.

Reference: Muniz Neto FJ et al. Demystifying MR Neurography of the Lumbosacral Plexus: From Protocols to Pathologies. BioMed Research International. 2018;2018:9608947. https://pubmed.ncbi.nlm.nih.gov/29662907/