Lower Motor Neuron Lesion


Lower Motor Neuron Lesion, Lower Motor Neuron Deficit, Lower Motor Neuron

  • Physiology
  1. Corticospinal tract (motor, lateral cord) transmits motor signals from the cerebral cortex
    1. Fibers cross the midline at the Brain Stem and course to the contralateral Muscles
  2. Motor fibers Synapse in the anterior horn (grey matter of the spinal cord)
    1. Upper Motor Neurons (UMN) are from the cerebral cortex to the Synapse
      1. Affect the cerebral cortex, Brainstem and Corticospinal tracts
    2. Lower Motor Neurons (LMN) are from the Synapse to the Muscle
      1. Affect the anterior horn (spinal cord), nerve roots, and Peripheral Nerves
  • Signs
  • Lower Motor Neuron Lesion findings
  1. Flaccid Paralysis
  2. Muscular atrophy
  3. Muscle fasciculations and fibrillations
  4. Hyporeflexia
  5. Absent Babinski Reflex