In all the above mentioned reflexes are caused by a relay from the brain. A disturbance in the reflex procedure may help diagnosis damage to certain, specific areas of the brain stem.
Blinking occurs automatically, when skin close to the eye is touched. When there is damage to the sensory nerves of the face or in certain areas of the brain stem, blinking may occur too late or not at all. At the beginning of the procedure, small metal plates are taped to the upper and lower eye lid as well as on the forehead. They record the reflex through short, very weak electric stimulus. A pair of small metal nodes are placed on the face in order to help capture exact data.