Jaw Jerk
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 mandibleForamen
Foramen ovaleV3
Mandibular branchTrigeminal GanglionMesencephalic nucleus
Midbrain, ponsTrigeminal Motor Nucleus
Upper ponsV3
Mandibular branchForamen
Foramen ovaleMuscle
Masseter
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