Origin:  Brainstem nuclei, facial nerves, trigeminal nerves

Recording Site:  Orbicularis Oculi

Reference Site:  Lateral orbit or side of nose

Ground:  Forehead

Stimulation Site:  Supraorbital notch

Procedure:  The recording electrode is placed over the orbicularis oculi.  To pick up the contralateral R2, a second recording electrode is placed over the opposite orbicularis oculi.  The reference electrode is placed on the lateral aspect of the orbit or on the side of the nose; a second reference electrode will be required for contralateral recording.  Stimulation occurs at the supraorbital notch, with the cathode placed below the orbital ridge.  The anode is above the orbital ridge.  Stimulation should occur at a slow rate and the patient should be relaxed.  The early response (R1) is obtained ipsilateral to the stimulus and a delayed bilateral response (R2) is obtained.  Since the R2 response varies, several responses should be superimposed for accurate latency measurement.