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Primary Lateral Sclerosis — SCE Neurology MCQ

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HardPeripheral Neuropathy & NeuromuscularPrimary Lateral SclerosisSCE Neurology

A 70-year-old man presents with a 1-year history of progressive asymmetric weakness in the right leg with upper motor neurone signs (spastic gait, brisk reflexes, extensor plantar). There are no lower motor neurone signs (no wasting, no fasciculations). EMG shows no denervation in any region. He has no sensory or bladder symptoms. MRI brain and spine are normal. What diagnosis should be considered?

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Correct answer: A — Primary lateral sclerosis

Primary lateral sclerosis (PLS) is a rare motor neurone disease variant characterised by progressive upper motor neurone dysfunction without lower motor neurone signs. Diagnosis requires UMN signs for at least 4 years without development of LMN features (to distinguish from the UMN-predominant onset of ALS). EMG must show no denervation. PLS has a much better prognosis than ALS (median survival >10 years). A: ALS requires combined UMN and LMN signs. C: MS would show brain/spinal lesions. D: HSP is hereditary and bilateral. E: Myelopathy is excluded by normal MRI.

Reference: NICE NG42 MND (2016); EAN PLS Consensus (2019)