Motor Neuron Lesion Signs

Snapshot

  • A 62-year-old man is in the stroke unit after experiencing a severe right-sided middle cerebral artery stroke. On physical exam there is left-sided upper extremity muscle weakness. The affected arm has increased muscle tone, and the bicep and tricep tendon reflex is 3+. There is also a left-sided Hoffman’s sign.

Introduction

  • Upper motor neurons
    • are neurons from the cerebral cortex to the anterior horn
  • Lower motor neurons
    • are neurons from the anterior horn to the peripheral muscle
Motor Neuron Signs
TypeClinical Features
Upper motor neuron signsWeaknessIncreased muscle toneHyperreflexia Babinski’s signHoffmann’s signPosturing
Lower motor neuron signsWeaknessAtrophyFasciculationsDecreased toneHyporeflexia