An exaggerated jaw jerk reflex indicates an upper motor neuron lesion above the level of the pons. The afferent and efferent limbs of this reflex are carried by:

• A Afferent limb by the maxillary nerve, efferent limb by the mandibular nerve
• B Both limbs by the mandibular division of the trigeminal nerve ✓
• C Both limbs by the maxillary division of the trigeminal nerve
• D Afferent limb by the facial nerve, efferent limb by the mandibular nerve

Explanation

Tapping the chin stretches the muscle spindles of the masseter and temporalis. Proprioceptive impulses travel centrally through neurons whose cell bodies lie in the mesencephalic nucleus of the trigeminal nerve, and the efferent limb travels through the motor root in the mandibular division to the muscles of mastication. Both limbs therefore run in the mandibular nerve, and the reflex centre lies in the midbrain and pons, so supranuclear lesions exaggerate it.

Reference: Snell's Clinical Neuroanatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.