What is jaw jerk reflex?

The jaw jerk reflex, also known as the masseter reflex, is a stretch reflex that is elicited by tapping the chin with a reflex hammer while the mouth is slightly open. This causes a contraction of the masseter muscle, which is one of the muscles responsible for chewing.

The presence or absence of the jaw jerk reflex can be used as an indicator of certain neurological conditions, such as lesions in the brainstem or disorders affecting the trigeminal nerve (cranial nerve V). A hyperactive jaw jerk reflex may indicate an upper motor neuron lesion, while a absent or diminished reflex may suggest lower motor neuron involvement.

The jaw jerk reflex is typically tested as part of a neurological examination to assess the function of the trigeminal nerve and associated neural pathways. It is important to note that the jaw jerk reflex is just one component of a comprehensive neurological assessment and should be interpreted in the context of other neurological findings.