Weak legs four days after a stomach upset, a 48-year-old: a case to work up

Why rapidly progressive leg weakness matters

Weakness that climbs over days can reach the breathing muscles without much warning. Tell a nerve problem from a spinal cord problem, and measure breathing early and repeatedly rather than waiting for the oxygen to fall.

What to ask in the history

• How it started and how it has spread: feet first, upwards, arms, face, swallowing
• Numbness, tingling, pain
• Bladder and bowel
• Back pain
• Recent infection: gut or chest, and vaccinations
• Breathlessness, weak cough
• Palpitations, dizziness on standing
• Diet, alcohol, medicines

Red flags

• Breathlessness or a weak cough
• Trouble swallowing or pooling saliva
• Swinging blood pressure or heart rate
• Rapid worsening
• A sensory level, or bladder and bowel loss

What to examine

• Tone, power and reflexes in legs and arms
• Sensation, and a sensory level on the trunk
• Cranial nerves: face, eye movements, swallowing
• Breathing: rate, use of neck muscles, counting in one breath
• Blood pressure and heart rate

First investigations

• Vital capacity, measured repeatedly
• Electrolytes including potassium, creatine kinase, glucose
• Nerve conduction studies
• Lumbar puncture
• MRI of the spine if the cord is a possibility
• ECG and monitoring

Differential diagnosis of rapidly progressive leg weakness

Grouped, not ranked. Which one fits this patient is for you to work out in the case.

Common mistakes

• Relying on oxygen saturation to judge breathing: it falls late.
• Missing a cord problem because the sensory level was not looked for.
• Forgetting that blood pressure and heart rate can become unstable.