Conus medullaris syndrome — SCE Neurology MCQ

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HardSpinal CordConus medullaris syndromeSCE Neurology

A patient develops acute severe back pain, early urinary retention, saddle sensory loss and symmetrical leg weakness. Examination shows absent ankle jerks but brisk knee jerks, and MRI identifies a lesion centred at the L1 vertebral level involving the tapering cord and adjacent roots. Where is the neurological lesion?

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Correct answer: B — The conus medullaris

The best answer is “The conus medullaris”. Conus lesions combine cord and root signs, often produce symmetrical deficits, early sphincter dysfunction and saddle anaesthesia, and anatomically lie around the T12–L2 vertebral region in adults. “A unilateral common peroneal nerve” is less appropriate because a peroneal lesion cannot explain bilateral saddle and sphincter involvement “The cervical spinal cord” is less appropriate because a cervical lesion would usually affect long tracts below and may involve the arms “The neuromuscular junction” is less appropriate because junctional disease does not cause a sensory level or bladder retention “The right motor cortex” is less appropriate because a hemispheric cortical lesion would not produce saddle anaesthesia and mixed segmental signs

Reference: NICE NG127: Suspected neurological conditions — recommendations. https://www.nice.org.uk/guidance/ng127/chapter/Recommendations