EMG
Electromyography is a neuroelectrophysiological test that evaluates the health and integrity of the facial nerve. It is usually employed greater than 6 months following the onset of facial nerve paralysis. Small needles are inserted into select facial muscles and patients are asked to contract those muscles. Nerve signals are thereby recorded which yield information about the health of the nerve and muscle. Muscles which are undergoing reinnervation demonstrate the presence of action potentials and spike and wave activity. Muscles which are not experiencing reinnervation demonstrate fibrillation potentials or baseline, random electrical noise. This means that the muscles are still alive and awaiting a signal from a nerve, but that a nerve has not yet demonstrated evidence of the onset of recovery. Electrical silence is associated with a chronically denervated muscle, which can no longer be successfully reinnervated.
ENoG
Electroneuronography is a test usually performed by audiologists to assess the integrity of the facial nerve. Two electrodes are taped to one side of the face. The first is taped over the stylomastoid foramen behind and under the ear and the second is taped near the nasolabial fold. The electrode behind the ear emits an electrical pulse and the electrode at the nasolabial fold picks up the any signal that is transmitted by the facial nerve fibers. Comparing the size, speed and strength of the transmitted signal allows for the measurement of the integrity of the facial nerve. Comparison between tests performed on the different sides of the same face permit an estimation of the degree of difference between the normal and the disordered nerve. ENoG’s performed on different days permits assessment of the worsening or potential improvement in nerve health.