Expansion
Each reflex pairs a sensory nerve with a motor nerve
Expansion
| Reflex | Afferent | Efferent | Level |
|---|---|---|---|
| Pupillary light | II | III | Midbrain |
| Corneal | V1 | VII | Pons |
| Gag | IX | X | Medulla |
| Cough | X | X | Medulla |
| Jaw jerk | V3 | V3 | Pons |
| Oculocephalic | VIII | III, IV, VI | Pons and midbrain |
| Oculovestibular (caloric) | VIII | III, IV, VI | Pons and midbrain |
| Lacrimation | V1 | VII | Pons |
These form the basis of brainstem death testing, which examines pupillary, corneal, oculovestibular, gag and cough reflexes plus the motor response to pain, followed by an apnoea test, and tests the brainstem from midbrain to medulla.
Two clinical points: the consensual pupillary response demonstrates the crossing at the Edinger-Westphal nuclei, so an afferent lesion abolishes both direct and consensual responses to light in that eye while the consensual response from the other eye is preserved; and the jaw jerk is the only monosynaptic cranial reflex, being brisk in upper motor neurone lesions above the pons.