Upper vs Lower Motor Neuron Lesions

Muscle Tone

• flexion/extension, pronation/supination of joint through its ROM

Hypotonia

• • LMN lesions, spinal shock, cerebellar lesions-flaccidity

Hypertonia

• Spasticity - UMN lesion. Pyramidal tract involved
• limb moves, then catches, and then goes past catch (clasp-knife)
  • test by rapidly supinating forearm
• Rigidity
  • UMN lesions, extrapyrimidal tract lesion
  • increased tone throughout ROM (cog-wheeling, lead-pipe)
  • circumducting the wrist

Power

• UMN
  • flexors > extensors in upper limbs
  • extensors > flexors in lower limbs
• LMN
  • reduced power in specific motor neuron distribution
    • deltoids - arm abduction - C5 C6 (axillary)
    • biceps - elbow flexion - C5 C6 (musculocutaneous)
    • triceps - elbow extension - C6 C7 C8 (radial)
    • thumb flexion - C6 C7 (median)
    • wrist extensors - C7 C8 (radial)
    • interossei of hand - finger abduction/adduction - C8 T1 (ulnar)
    • hip flexion - L1 L2 L3 (femoral)
    • hip adduction - L2 L3 L4 (obturator)
    • hip abduction - L4 L5 S1 (superior gluteal)
    • knee extension - L2 L3 L4 (femoral)
    • knee flexion - L5 S1 S2 (sciatic)
    • ankle dorsiflexion - L4 L5 (deep peroneal)
    • ankle plantar flexion - S1 S2 (tibial)
    • foot inversion - L4 L5 (posterior tibial)
    • foot eversion - L5 S1 (superficial peroneal)
• compare between L and R

• GRADE
  • 0 nil
  • 1 flicker of movement
  • 2 movement cannot overcome gravity
  • 3 movement cannot overcome any resistance
  • 4 movement is weaker than normal
  • 5 normal

Special Tests

Pronator Drift

• have the patient stand with eyes closed and arms held straight out and hands supinated
• + → patient cannot maintain this position
  • muscle weakness (pronation and outward drift)
  • UMN lesion (pronation and downward drift)
    • standing problems

Fine Finger Movements

• ask patient to touch each finger to crease of thumb (show patient how) and speed it up
• look for right and left differences, slow if UMN lesion

Clonus

• Ankle or Patellar clonus in UMN Lesion

Other OSCE Modules