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Cranial Nerves
 
 

Jaw Jerk

 
 
 
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On this page:Jaw Jerk Pathway

Overview

The jaw jerk is also known as the masseter inhibitory reflex; it involves the mandibular branch of the trigeminal nerve as both its afferent and efferent arms.
  • How to Elicit

  • Place a finger horizontally over the chin with the mouth open, and then strike this finger with a tendon hammer. 
Warn the patient beforehand!
While a slight jerk may be normal, an exaggerated jerk is a sign of an upper motor neuron lesion.
  • Interpretation

  • Slight / absent jerkNormal, mandibular nerve (V3) lesion
  • Exaggerated jerk (± clonus)Upper motor neuron lesion

Jaw Jerk Pathway

Receptors
Muscle spindle within mandible
 
 
Foramen
Foramen ovale
V3
Mandibular branch
 
Trigeminal Ganglion
 
 
Mesencephalic nucleus
Midbrain, pons
 
 
Trigeminal Motor Nucleus
Upper pons
 
V3
Mandibular branch
Foramen
Foramen ovale
 
 
Muscle
Masseter
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