Electroneuronography

Electroneuronography (ENoG) is a neurological non-invasive test that was first described by Esslen and Fisch in 1979 and is used to examine the integrity and conductivity of a peripheral nerve. It consists of a brief electrical stimulation of the nerve in one point underneath the skin, and at the same time recording the electrical activity (compound action potentials) at another point of the nerve's trajectory in the body. The response is displayed in a cathode ray tube (CRT) or through the video monitor of a computer. The stimulation as well as the recording are carried out by disc electrodes taped to the skin, and the technician may use electrically conducting gel or paste to bolster the signals being input and output. Alternatively, the recording electrodes may also be used to pick up the electrical activity of a muscle innervated by that nerve. In such instances electroneuronography is closely related to electromyography.

Usually, nerves in the limbs (arms and legs) are tested in this way, but one of the most common applications of electroneuronography is the test of the facial nerve, such as in cases of muscle weakness in one side of the face (Bell's palsy). It is performed by an audiologist, who carries out tests to compare the two sides of the face. The stimulation electrode is located at the stylomastoid foramen and the recording electrode is located near the nasolabial fold. The ENoG test is the only objective measure of facial nerve integrity.