Facial Electroneuronography (ENOG)
Facial electroneuronography (ENOG) can provide useful information about the function of the facial nerve. The facial nerve allows movement of the muscles of facial expression. When you smile, close your eyes and raise your eyebrows the facial nerve is at work. Inability to move the muscles of the face occurs when electrical impulses cannot travel along the facial nerve to reach the muscles that need to move. Lack of facial motion can be secondary to a conduction block along the nerve or can indicate more significant damage to the nerve fibers themselves.
Facial paralysis or weakness can occur secondary to trauma or a virus as well as other causes. In most cases, facial paralysis occurs on one side of the face only. If absolutely no movement of the muscles of one side of the face is noted facial ENOG testing may be performed. In order to perform facial ENOG testing, small cup electrodes are placed on the face. One electrode is placed on each side of the nose with one additional electrode placed on the forehead. The skin in the area of electrode placement is prepared in the same manner described for ABR and ECochG testing.
In order to test the facial nerve an electrical stimulator is used. The stimulator is placed along the side of the face just in front of the ear and varying levels of electrical current are applied. The test can be uncomfortable but is performed as quickly as possible to minimize patient discomfort. Electrical recordings are obtained using a computer. Results obtained can indicate how well the facial nerve is working and can provide information regarding the likelihood that the nerve will recover.