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Cauda Equina vs Conus Medullaris — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularCauda Equina vs Conus MedullarisSCE Neurology

A 55-year-old man presents with bilateral lower limb weakness, saddle anaesthesia, urinary retention, and areflexia in the legs. He has severe lower back pain. MRI lumbar spine shows a large central disc prolapse at L4/L5 compressing the cauda equina. How do cauda equina lesions differ from conus medullaris lesions?

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Correct answer: E — Cauda equina lesions cause LMN signs (flaccid paralysis, areflexia, wasting), asymmetric deficits, radicular pain, and bladder atonia. Conus lesions cause mixed UMN/LMN signs, symmetric deficits, less pain, and early bladder dysfunction with an automatic bladder

Cauda equina (nerve roots below L2): LMN pattern — flaccid paralysis, areflexia, atrophy, asymmetric, severe radicular pain, saddle anaesthesia, urinary retention (atonic bladder). Conus medullaris (tip of spinal cord at L1–L2): mixed UMN/LMN, symmetric, early bladder involvement (may be automatic/reflex bladder), less prominent pain, perianal sensory loss, impotence. A: Different patterns. C: Cauda equina is LMN. D: Conus has mixed signs. E: The distinction is clinically important.

Reference: Clinical Neuroanatomy; NICE NG62