Nerve Conduction Velocity (NCV) Electromyography (EMG)
What is an NCV/EMG test?
Nerve conduction velocity (NCV) is a test that is performed to evaluate nerve function.
Electromyography (EMG) is a test that assesses the health of the muscles and the nerves controlling the muscles.
How is the test performed?
The NCV test uses surface electrodes, which are small, patch-like electrodes placed on the skin over the nerve at various locations. A very small electrical stimulus is applied in some body areas along the course of the nerve while the surface electrodes record.
The resulting electrical activity is recorded on a computer. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the nerve function.
For an EMG, a small acupuncture-like needle is inserted through the skin into the muscle. The electrical activity detected by this needle is displayed on a computer, and is heard through a speaker.
After placement of the needle, you may be asked to contract the muscle (for example, by bending your arm). The presence, size, and shape of the wave form produced on the computer provide information about the function of the muscle and the nerve being recorded.
An NCV/EMG test will take approximately 45 minutes to an hour.
An NCV test is usually performed in conjunction with an EMG, but not in all cases.
How do I prepare for the test?
” You should wear loose and comfortable clothing
” You must not wear any type of body lotion, ointments or oils
” You can eat and take meds before the test but sedatives should be avoided
” Inform Triad Diagnostic Solutions if you have a Pacemaker
” Inform Triad Diagnostic Solutions if you take blood thinners such as Coumadin
How will this test feel?
The stimulations from the NCV may feel like a very small, mild electric shock. Depending on how strong the stimulus is, you will feel it to varying degrees, although the impulse is more surprising than painful. You should feel no pain once the test is finished.
With an EMG you may feel slight discomfort when the small needle is inserted and you may feel slight muscle soreness at the site afterwards as well, but most people are able to complete the test without significant difficulty.
Why is this test performed and what are the indications for an NCV/EMG Test
This test is used to diagnose nerve damage or dysfunction. If your doctor suspects you may be suffering from nerve damage, you may be evaluated with an NCV /EMG test.
EMG is most often used when people have symptoms of weakness and an examination shows impaired muscle strength. It can help to differentiate primary muscle conditions from muscle weakness caused by nerve disorders.
If you have any of the following symptoms or suffer from the following medical conditions, an NCV/EMG is the most effective diagnostic tool to show nerve damage:
- Feelings of pins & needles, numbness, tingling, and burning sensations in feet or hands
- Muscle weakness in the arms or the legs, loss of sensation
- Pain in arms, legs, back or neck
- Thyroid disorders or other metabolic conditions
- Carpal tunnel syndrome, tarsal tunnel syndrome
- Herniated disc
- Trauma to nerve or any suspected neuropathy (nerve damage)
Video – Nystagmography (VNG)
Video-nystagmography (VNG) is a series of tests used to determine the causes of a patient’s dizziness, balance disorder or migraine which may be vestibular in nature. Various causes are due to ear or sinus infections, allergies or often by a whiplash type of injury which alters the balance of the calcium carbonate “crystals” within the inner ear canal.
Most common symptoms:
- Sinus pain
How does VNG work?
VNG is a complete diagnostic system for recording, analyzing and reporting involuntary eye movements, (Nystagmus), using video imaging technology. Hi-tech video goggles with infrared cameras are worn while you look or lie in different positions.
There are four main parts to the VNG. The saccade test evaluates rapid eye movements. The tracking test evaluates movement of the eyes as they follow a visual target. The positional test measures dizziness associated with positions of the head. The caloric test measures responses to warm and cold air circulated through a small, soft tube in the ear canal. The cameras record the eye movements and display then on a video/computer screen. This allows the examiner to see how the eyes move which is very helpful in assessing balance system health.
In Benign Paroxysmal Positional Vertigo (BPPV) dizziness is generally thought to be due to debris which has collected within a part of the inner ear. While the saccule also contains otoconia, they are not able to migrate into the canal system. The utricle may have been damaged by head injury, infection, or other disorder of the inner ear, or may have degenerated because of advanced age.
BPPV is a common cause of dizziness. About 20% of all dizziness is due to BPPV. While BPPV can occur in children, the older you are, the more likely it is that your dizziness is due to BPPV. About 50% of all dizziness in older people is due to BPPV. In a recent study, 9% of a group of urban dwelling elders were found to have undiagnosed BPPV.
The symptoms of BPPV include dizziness or vertigo, lightheadedness, imbalance, and nausea. Activities which bring on symptoms will vary among persons, but symptoms are almost always precipitated by a change of position of the head with respect to gravity. Getting out of bed or rolling over in bed are common “problem” motions. Because people with BPPV often feel dizzy and unsteady when they tip their heads back to look up, sometimes BPPV is called “top shelf vertigo.” Women with BPPV may find that the use of shampoo bowls in beauty parlors brings on symptoms. An intermittent pattern is common. BPPV may be present for a few weeks, then stop, and then come back again.
How to prepare:
The test will take approximately 40 minutes.
Please dress comfortably and wear clothes that will not be affected by possible contact with water.
Do not wear eye make-up. This interferes with the infra-red cameras in the goggles as they try and track your eye movement.
Please continue to take heart, high blood pressure, thyroid, diabetes, antiseizure, and anticonvulsant medications.
Most common symptoms:
The following medications must not be taken for 48 hours prior the test.
Anti-nausea (Dramamine, Compazine, Bonine, Marezine, Phenergan, Thorazine, etc.)
Anti-vertigo medication (Antivert, Meclizine, etc.)
Tranquilizers (Valium, Librium, Atarax, Vistaril, Equanil, Miltown, Triavil, Serax, Etrafon, etc.)
Sedatives (Nembutal, Seconal, Dalmane, Doriden, Placidyl, Qualude, Butisol or any sleep pills)
Do not eat 3 hours before the test.
Brain cells talk to each other by producing very small electrical signals, called impulses.
An EEG helps measure this activity. The test is done by an EEG specialist in a doctor’s office or at a hospital or laboratory.
Patient will be asked to lie on his/her back on a bed or in a reclining chair.
Flat metal disks called electrodes are placed all over the scalp. The disks are held in place with a paste. The electrodes are connected by wires to a speaker and recording machine.
The recording machine changes the electrical signals into patterns that can be seen and interpreted on a computer.
The patient needs to lie still during the test with their eyes closed because movement can change the results. We ask the patient to do certain things during the test, such as breathe fast and deeply for several minutes or look at a bright flashing light.
How the Test Will Feel
The electrodes may feel sticky and strange on their scalp but should not cause any other discomfort. Patient should not feel any discomfort during the test.
Why the Test is Performed?
EEG is used to look at the brain activity. It may also be used to diagnose or monitor the following health conditions:
- Abnormal changes in body chemistry that affect the brain
- Brain diseases such as Alzheimer’s disease (Dementia)
- Epilepsy (Seizures)
- Head injuries
- Brain tumors
- Abnormal brain bleeding
- Cerebral infarction
EEG is also used to:
- Evaluate sleep disorders
- Attention problems
- Investigate periods of unconsciousness
Medical Necessity for Ordering an EEG
Alzheimer’s Disease 331
Sleep Disorder 780.5
How to Prepare for the Test:
Patients need to wash their hair the night before the test. We recommend they not use any oils, sprays, or conditioner before this test. Patients should bring a hat to wear or shower immediately after the test because there will be EEG paste in the hair.
We may recommend to stop taking certain medications before the test, the patient will not change or stop taking medications without first talking to their health care provider. Patients have to avoid all food and drinks containing caffeine for 8 hours before the test.
Sometimes the patient may need to sleep during the test, so they may be asked to reduce their sleep time the night before. If asked to sleep as little as possible before the test, we recommend the patient do not eat or drink any caffeine, energy drinks, or other products that help you stay awake.