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Here are some answers to some common questions about EMG and NCV studies:
What can be Learned From an EMG? The electromyogram studies the electrical characteristics of nerves and muscles. This information can show injury or disease of the nerves and muscles. For example, if you have back pain because a slipped disc is pinching a nerve, the EMG can tell which nerve it is, how bad it is, and sometimes even how long it has been pinched. This helps your physician in managing your problem either medically or surgically.
How is an EMG Done? The EMG is done with tiny needle electrodes. These are inserted into selected muscles, depending on your particular problem. The pins (electrodes) are so tiny that they are not very uncomfortable. Some patients can't even feel them, but the amount of discomfort associated with them is different in each patient. (Everyone has a different level of pain feeling and tolerance). Any discomfort you may experience during the EMG is temporary, and the EMG will not make your pain problem worse.
What are Nerve Conduction Velocity Studies? Nerve conduction is done by giving a very small amount of electrical current to a nerve, and it measures how fast the current travels in the nerve. If the nerve is sick or injured the current travels slowly and this helps figure out which nerves are affected. This test is not painful.
What Side Effects Can I Expect? One of the reasons why physicians so frequently order an EMG is that it gives a lot of helpful information with a very small risk of side effects. The most common side effect is a bruise, which can occur if the physician happens to bump a vein in the skin with the pin. Infections due to bacteria or viruses being carried by the pin into the body are possible, but exceedingly rare. The EMG will not make you drowsy or cause reactions since nothing is injected through the pin.
Can I Have This Done if I am Pregnant? Yes.
Do Drugs Interfere with the EMG? Almost never, but please tell the doctor what drugs you are on at the time of the examination.
Can I drive After an EMG? It does not affect your ability to drive.
Does the EMG Have a Therapeutic Value? Some patients do report that their pain is less afterwards, but EMG is not a treatment and should not be confused with acupuncture.
Can I go back to Work After an EMG? The EMG does not affect your work status.
A chemodenervation procedure is done to decrease muscle spasms and twitching, including facial twitching. A small amount of medicine (Botox or Myobloc) is injected, usually under EMG control, into specific muscles. The effect of the procedure lasts for about three to four months. The procedure is usually very well-tolerated and has minimal side effects.
A Tensilon Test is used to diagnose Myasthenia Gravis. A small amount of Tensilon (Edrophonium) is injected intravenously under a controlled environment, and improvement in the muscle strength is noted. A repetitive nerve stimulation test can also be used to diagnose Myasthenia Gravis. In this test, a nerve is stimulated at specified intervals and a decrement response is measured.
This study is used to determine the cause of facial weakness and pain. It can also be used to find out the prognosis in Bells Palsy, and for the evaluation of more generalized nerve disorders.
VEPs evaluate the visual nervous system from the eyes to the occipital (visual) cortex of the brain. Electrodes are applied to the scalp, and the patient is usually asked to stare at a pattern on a video screen while remaining fully alert. Each eye is tested separately. It is most commonly done to diagnose Optic Neuritis and Multiple Sclerosis.
SSEPs assess pathways from nerves in the arms or legs, through the spinal cord to the brainstem or cerebral cortex. Electrodes are placed on the scalp and along the spinal cord, and a small electrical current is then applied to the skin overlying nerves on the arms or legs. The current creates a tingling sensation but is not painful. Each leg or arm is tested separately. It is most commonly done to study spinal cord function.
The BAEP assists in evaluating the auditory nerve pathways from the ears through the brainstem. Electrodes are attached to the scalp and earlobes, and earphones are placed over the ears. The phones deliver a series of clicks or tones to each ear separately. It is most commonly done to study hearing, brainstem tumors and dizziness.
An EEG records the electrical activity of the brain. Highly sensitive monitoring equipment records the activity through electrodes that are placed at measured intervals on a patient's scalp. The test is not painful. The head is measured and the electrodes are placed on the scalp with a paste-like substance. The test itself usually takes about 60 to 90 minutes, and the principal role of the patient is simply to remain still, relaxed and comfortable.
During the test, the patient may be asked to take repeated deep breaths (hyperventilate) and may be shown a strobe light that flashes at different speeds. Both activities can help reveal different brain patterns that are useful for diagnosis. Sometimes, physicians also want to observe brain patterns that occur during sleep. For sleep-deprived EEGs, the patient may be asked to stay awake most of the night prior to the EEG appointment. EEGs assist physicians in the diagnosis of a variety of neurological problems, from common headaches and dizziness to seizure disorders, strokes, and degenerative brain disease. The EEG is also used to look for organic causes of psychiatric symptoms and disabilities in children, and can assist physicians in determining irreversible brain death.
An ambulatory EEG is done to study seizure activity, which is sometimes difficult to record during normal EEG time. The electrodes are placed on head and secured with a special procedure. A portable unit records EEG activity continuously for 24 hours.
NICS is an ultrasound that provides a method by which anatomy can be imaged and blood flow detected and measured for diagnostic purposes. This is accomplished by sending ultrasound into the tissues and receiving the echoes returning from the tissues, a two-dimensional cross-sectional image and blood flow displays. It is most commonly done to study blood flow to brain for strokes.
TCD is an ultrasound that provides a method by which intracranial flow velocities and flow direction measurements can be sampled. It is most commonly done to study blood supply to the brain and brainstem, through the circle of Willis for strokes and dizziness.