[The trigemino-facial reflexes: a methodological approach to the evaluation of facial nerve function (author's transl)].

Since 1952 electromyographic registration of the trigemino-facial reflexes have been repeatedly described to evaluate facial nerve function. Comparable to peripheral nerve conduction velocity studies, this method enables us to detect intratemporal lesions. In order to obtain optimal results, we modified the registration technique of the trigemino-facial reflexes as regard to the following items: 1. Because of great interindividual variability of latencies and amplitudes this method should be used only by comparing the right and the left side. For a reliable assessment of both, recovery and detoriation of the facial nerve a standardized stimulation and recording technique is necessary. Stimulus strength should be defined by the applied current rather than voltage. 2. Since, in many cases, only certain neurones of the facial nerve are affected with different degree, important information is gained by recording not only from the M. orbicularis oculi but also from M. levator labii, M. zygomaticus and M. orbicularis oris. 3. In order to detect small reflex responses in severe and advanced cases, averaging technique should be applied. Thus, minute potentials hidden in the amplifier noise can be detected and clearly defined as either a stimulus dependent reflex response or unvoluntary muscle activity.