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ALS – Diagnostic Investigation — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularALS – Diagnostic InvestigationSCE Neurology

A 60-year-old man presents with progressive bilateral hand weakness over 8 months. He has prominent wasting of the first dorsal interosseous muscles bilaterally and fasciculations in the forearms and tongue. Deep tendon reflexes are pathologically brisk in all four limbs with bilateral extensor plantar responses. Sensation is intact. He has no cognitive symptoms. Which investigation is most important to confirm the suspected diagnosis?

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Correct answer: B — EMG and nerve conduction studies

The clinical picture of combined upper motor neurone (brisk reflexes, extensor plantars) and lower motor neurone (wasting, fasciculations) signs in multiple segments with intact sensation is classic for ALS/MND. EMG/NCS is the most important investigation to confirm widespread lower motor neurone involvement (active and chronic denervation in ≥3 body regions) and exclude mimics (e.g., CIDP, MMN). MRI spine is important to exclude structural causes but does not confirm MND. A: MRI cervical spine should be done to exclude cervical myelopathy but does not confirm MND. C: LP is not routinely needed. D: CK may be mildly elevated but is non-specific. E: CT chest is not the primary investigation.

Reference: NICE NG42 MND (2016); Revised El Escorial Criteria; Awaji-Shima Criteria