Electroneuronography or electroneurography (ENoG) is a neurological non-invasive test used to study the facial nerve in cases of muscle weakness in one side of the face (Bell's palsy).
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.
[citation needed] Facial nerve paralysis can impact several aspects of a person's life, ranging from emotional or psychological effects to the actual physical limitations themselves.
[citation needed] Facial nerve disorders may stem from a myriad of contributing factors: Bell's palsy, injury resulting from surgical error, trauma to the temporal bone, otitis media, multiple sclerosis, mumps, chicken pox, and other conditions.
Typically, the system calculates the difference between compound muscle action potentials generated near the nose (nasolabial fold) in response to supramaximal electrical stimulation near the ear (stylomastoid foramen).
Increasing sensitivity and specificity of the recordings has been a constant goal, and it is believed that variability arises from the location and pressure of the electrodes, the stimulating current, and skin resistance.
With regard to the supramaximal threshold, the nasal alae demonstrated a superior biphasic waveform while requiring less input stimulation to yield adequate results.
[citation needed] It is common for a general feeling of discomfort to accompany the electrical stimulation of the nerve, but nearly all patients prefer to undergo the procedure in order to effect a treatment for their condition.
A ground electrode is placed in the center of the patient's forehead, sufficiently far from the facial nerve as to not give an output reading.
Massive amounts of clinical experience may be required to accurately interpret the data received from testing, and misreading the results may put the patient at serious risk of developing further damage or creating a problem with otherwise healthy facial nerves.
Among those who develop the disorder, unilateral paralysis of the facial muscles occurs in a day or two, but it is common for the patient to recover on their own over the span of a few weeks.
Even if the condition is resolved, the patient still stands a 20% chance of having lifelong weakness in their facial muscles, and 5% of these people will have permanent damage equivalent to a level of 4 or higher on the House-Brackmann scale.
Because of the slow-acting nature of this pathology, a patient may present healthy electroneuronography results despite a lack of volitional control of the facial muscles immediately following the onset of Bell's palsy.
Therefore, it is standard procedure to wait at least three days after symptoms present themselves to perform an electroneuronography test, in order to prevent false negatives.
Lastly, axonotmesis consists of damage to the inner nerve fibers while the outer covering remains whole, and also yields a flat line in response to stimulation.