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Suspected cauda equina syndrome with spinal cord stimulator of unverified MR safety status — MSRA MCQ

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HardMRISuspected cauda equina syndrome with spinal cord stimulator of unverified MR safety statusMSRA

A 61-year-old man contacts his GP with a 2-day history of severe low back pain radiating into both legs. Since this morning he has been unable to pass urine, has numbness around the perineum and reports worsening weakness in both feet. He has a spinal cord stimulator implanted in 2017 after lumbar surgery. He has no implant card, and the device manufacturer and model are not documented in his record. Examination shows reduced perianal sensation, bilateral ankle plantarflexion weakness (4/5) and reduced ankle reflexes. He is haemodynamically stable. The local emergency pathway uses urgent lumbar MRI for suspected cauda equina syndrome, but the MR safety status of the stimulator cannot currently be verified. What is the most appropriate management plan?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Refer immediately through the emergency cauda equina pathway, alerting the receiving team to the unverified stimulator and arranging urgent implant identification and MRI safety risk assessment if its MR conditions cannot be confirmed.

Explanation lettering: D = shown as C · C = shown as D

This presentation requires immediate assessment for cauda equina syndrome: severe bilateral radicular back pain is accompanied by new urinary retention, perineal sensory loss and bilateral motor deficit. NICE advises immediate referral via local pathways when severe low back pain radiating into a leg is associated with new bladder, bowel or sexual dysfunction, or new perineal numbness. The stimulator must be communicated to the receiving service, but uncertainty about its MR status must not delay emergency referral. MRI safety is device- and condition-specific: the relevant system includes the pulse generator, leads, configuration and the manufacturer’s scanning conditions. An unverified implant is therefore not a reason to perform a standard MRI without checks. MHRA guidance permits consideration of scanning where implant compatibility is unknown if the expected benefit outweighs risk, but requires documented multidisciplinary risk assessment, appropriate precautions, specialist input and consideration of alternative imaging. B fails because clinical urgency does not remove implant-safety responsibilities. C is plausible because CT myelography may be used if MRI proves unsuitable, but a stimulator does not automatically preclude MRI and specialist assessment should first determine feasibility. D introduces an unnecessary and dangerous delay; explantation is not a prerequisite for every MRI. E wrongly makes recovery of patient-held documentation a condition for emergency assessment.

Reference: Suspected neurological conditions: recognition and referral — Recommendations for adults aged over 16, recommendation 1.7.3 (2019) — https://www.nice.org.uk/guidance/ng127/chapter/Recommendations-for-adults-aged-over-16 MHRA Safety Guidelines for Magnetic Resonance Imaging Equipment in Clinical Use — section 4.11.4 (February 2021) — https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/958486/MRI_guidance_2021-4-03c.pdf