L5 Radiculopathy — SCE Rheumatology MCQ

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EasySoft Tissue RheumatologyL5 RadiculopathySCE Rheumatology

A 50-year-old man develops acute lower-back pain radiating down the lateral aspect of his left leg to the dorsum of the foot. Examination shows reduced pinprick sensation over the dorsum of the foot and weakness of ankle dorsiflexion and great-toe extension. Straight-leg raising reproduces his leg pain at 30 degrees. Which nerve root is most likely affected?

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Correct answer: C — L5

The affected root is L5. The most discriminating findings are weakness of great-toe extension, reflecting extensor hallucis longus involvement, and sensory loss over the dorsum of the foot. Ankle dorsiflexion weakness is also typical, although tibialis anterior has overlapping L4/L5 supply. Radicular leg pain reproduced by straight-leg raising supports lumbosacral nerve-root irritation but does not by itself determine the level. L4 radiculopathy more typically causes medial-leg sensory loss with weakness of knee extension or ankle inversion. S1 radiculopathy causes posterior-leg or lateral/plantar-foot sensory symptoms, plantarflexion weakness and a reduced ankle reflex. L3 and S2 do not fit this distal motor and sensory pattern.

Reference: Journal of Neurology, Neurosurgery & Psychiatry. Recent advances in neuroanatomy: the myotome update. 2023;94:643–652. https://jnnp.bmj.com/content/jnnp/94/8/643.full.pdf