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Medical Video: 25. Interpreting neurophysiology (EMG & NCS)
Definition
What is electronagmography?
Electronistagmography (ENG) is a method used by doctors to examine eye movements and nystagmus, rhythmic movements without control of the eye due to small tremors that are fast and uncontrolled. This procedure will also examine the muscles of eye movement. ENG will test how well the condition of the eyes, inner ear and brain helps coordinate your balance (such as when you stand up after lying down).
ENG is done to help check for possible injuries or problems in the inner ear, brain, or nerves that connect the two. This disorder can cause complaints of dizziness, vertigo, or loss of balance.
Nystagmus usually occurs when the head is moved. However, if nystagmus occurs all the time and does not disappear, it may be caused by a number of conditions that affect the inner ear, brain, or nerve that connect the two.
During the ENG procedure, a number of electrodes will be placed in the area around the eye to record eye movements. This movement will be reflected on graph paper. Maybe some tests will be done.
When do I have to undergo electronagmography?
ENG is done if you report a complaint of a period of unexplained dizziness, vertigo, or hearing loss. Other conditions that allow this procedure to be performed are acoustic neuroma, labyrinthitis, Usher's syndrome, and Menier's disease. If a lesion wound is detected, ENG can identify its initial location.
There may be other reasons for your doctor to recommend ENG.
Prevention & warning
What do I need to know before undergoing electronistagmography?
In some clinics, you cannot do ENG if you use a pacemaker, because electronystagmography tools will affect the performance of the pacemaker. ENG cannot detect some problems in the inner ear, normal test results do not mean there is no interference with the inner ear. To check the cause of hearing loss or tinnitus, other tests such as the audiometry test or auditory brain stem response (ABR) can be done. If there is a suspected tumor or stroke in a particular part of your brain, a CT scan or MRI can be done to confirm the diagnosis.
Process
What do I need to do before I undergo electronistagmography?
Inform all the medicines you are taking, including blood thinning drugs such as warfariin, clopidigrel, and aspirin. You may be advised to fast a few hours before the procedure and caffeine or alcohol for 24 - 48 hours before the ENG procedure. Your doctor may also recommend that you stop using sedatives, anesthesia, or anti-vertigo temporarily before the procedure. In the morning before the procedure, clean the ears from excess dirt. If you use a hearing aid or glasses, take it to the test room with you.
You may be required to sign an agreement before undergoing the procedure.
What is the electron process of electagmography?
Five electrodes will be attached to the area around the eyes using special glue. You will be examined in a dark room during the procedure. ENG consists of 6 parts:
- To set the test equipment in the right settings, you will be required to look at the moving laser point. Don't move your head while going through this section.
- The reading will be done with your eyes closed. You will be given assignments to do, such as mental arithmetic, during this section. Readings will be taken when you look straight ahead and both sides.
- The reading will be done when your eyes follow the pendulum's back and forth movements
- The reading will take place when your eyes follow the movements of some objects that move out of your view. Every time an object crosses, you will need to immediately focus on the movement of the next object.
- The reading will take place when you move your head from side to side, and raise your head up and down. You will be asked to move your body (along with your head) in several positions.
- Towards the end of the procedure, eye movements will be recorded while cold water and warm water are placed in your ears. In certain cases, cold and warm air will be blown into your ear. This part of the test is called a caloric test, and can be done without electrodes attached to your face. Caloric tests will not be done if you have a perforated eardrum, because the water used can enter the middle ear and is at risk of infection. Caloric tests can be done with water or air, but if the eardrum is hollow, the doctor will not do this test at all.
The length of this examination ranges from 60 - 90 minutes.
What should I do after undergoing electronagmography?
When the test is complete, the electrode will be removed and the remaining glue on your face will be cleaned. Do not rub your eyes to avoid spreading electrode glue. You will be examined for signs of pain, dizziness, and nausea, and may need to lie down or sit for a while to wait for recovery. Your doctor will explain to you about when you will be allowed to continue other treatments that were stopped before undergoing the procedure. The doctor will give special instructions or additions after the procedure, depending on your condition.
Explanation of Test Results
What do the test results mean?
Normal results
Abnormal eye movements were not found during the procedure. Keep in mind that some nystagmus are normal when you move your head.
Caloric test results are said to be normal if uncontrolled eye movements have normal direction and intensity.
Abnormal results
Detected wild nystagmus that occurs at any time and does not disappear. Caloric test results are said to be abnormal if there is little to no eye movement during the procedure.
Abnormal results can:
- find damage to nerves or structures near the teleats or brain that affect balance coordination
- detect possible signs of Ménière’s disease, multiple sclerosis, or labyrinthitis, or diseases of the brain or history of stroke
What can affect the test?
The reason you cannot follow the ENG procedure or the test results are said to be not credible, including:
- taking several drugs, such as stimulants (including caffeine), depressants, sedatives, and medicines for vertigo
- too much head movement or other eye movements, like blinking
- unable to complete instructions during the test. Health conditions that can affect focus, blurred vision, or that cause drowsiness
- find damage to nerves or structures near the ear or brain that affect balance coordination
- detect possible signs of Ménière’s disease, multiple sclerosis, or labyrinthitis, or diseases of the brain or history of stroke
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