Optimal electrode placement in facial nerve conduction study.

This study was designed to determine the optimal sites for the active electrode in a nerve conduction study of each branch of the facial nerve. Twenty healthy male and female volunteers between 20 and 40 years old were investigated. Our criteria for the optimal site of the active electrode were initial negative deflection and maximal amplitude of the response and the most synchronized response. Optimal sites were found to be as follows: 1. Frontalis (temporal branch): a point midway between the hairline and the eyebrow along a line passing vertically through the pupil. 2. Orbicularis oculi (zygomatic branch): the medial quarter between the medial and lateral canthus. 3. Nasalis (buccal branch): muscle belly. 4. Triangularis (mandibular branch): 15 mm lateral and 25 mm below the corner of the mouth. 5. Orbicularis oris (zygomatic, mandibular and buccal branches): 2 mm below the lower lip midway between the midline and the corner of the mouth.