EMG, used in conjunction with a neurological examination, helps
establish a diagnosis and the extent of a problem by measuring the
electrical activity of a muscle in response to stimulation.
An EMG is done by inserting electrodes in fine needles into the muscles being tested, and by placing electrodes on the skin over peripheral nerves.
An EMG may be used to evaluate a variety of problems, including the following:
In many instances, an EMG can provide critical diagnostic information
that can not be obtained in any other way.
Although there is some discomfort associated with the procedure, an EMG is usually done on an outpatient basis.
No special preparation is usually necessary.
nerve conduction study (NCS) is a test commonly used to evaluate
the function, especially the ability of electrical conduction, of
the motor and sensory nerves of the human body.
Nerve conduction studies are mainly used for the evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs. It can be used to diagnose disorders of the peripheral nerves and muscles.
Preparation:Normal body temperature must be maintained (low body temperature slows nerve conduction).
Procedure:The nerve is stimulated, usually with surface electrodes, which are patch-like electrodes (similar to those used for ECG) placed on the skin over the nerve at various locations.One electrode stimulates the nerve with a very mild electrical impulse. The resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to calculate the nerve conduction velocity. Electromyography is the second part of this test and is often done within one week of the NCS.
How It Feels:The test is not invasive, but can be a little painful due to the electrical shocks. However, the shocks are associated with such a low amount of electrical current that they are not dangerous to anyone.
How It Feels:This procedure is painless
Cerebrospinal fluid (CSF) collection is a test to look at the fluid that surrounds the brain and spinal cord. Cerebrospinal fluid acts as a cushion, protecting the brain and spine from injury. The fluid is normally clear. The test is also used to measure pressure in the spinal fluid.
How the Test is Performed
There are different ways to get a sample of CSF. Lumbar puncture, commonly called a spinal tap, is the most common method. The test is usually done like this:
Occasionally, special x-rays are used to help guide the needle
into the proper position. This is called fluoroscopy.
Lumbar puncture with fluid collection may also be part of other procedures, particularly a myelogram (x-ray or CT scan after dye has been inserted into the CSF).
Alternative methods of CSF collection are rarely used, but may be necessary if the person has a back deformity or an infection.
Cisternal puncture uses a needle placed below the occipital bone (back of the skull). It can be dangerous because it is so close to the brain stem. It is always done with fluoroscopy.
Ventricular puncture is even more rare, but may be recommended in people with possible brain herniation. This test is usually done in the operating room. A hole is drilled in the skull, and a needle is inserted directly into one of brain's ventricles.
CSF may also be collected from a tube that's already placed in the fluid, such as a shunt or a venitricular drain. These sorts of tubes are usually placed in the intensive care unit.
How to Prepare for the Test
The patient (or guardian) must give the health care team
permission to do the test.
Afterward, you should plan to rest for several hours, even if you feel fine. You won't be required to lie flat on your back the entire time, but rest is advised to prevent additional leakage of CSF around the site of the puncture.
How the Test Will Feel
The test is usually done with you curled up on your side
with knees pulled up and chin to chest. Sometimes, CSF is collected
with the person seated and bent forward over a table or chair.
Holding the position may be uncomfortable, but it is extremely
important to stay in this bent position to avoid moving the
needle and possibly injuring the spinal cord. The person doing
the test may ask you to straighten out slightly after the needle
is in place, in order to accurately measure the CSF pressure,
called the "opening pressure."
The anesthetic will sting or burn when first injected. There will be a hard pressure sensation when the needle is inserted, and there is usually some brief pain when the needle goes through the tissue surrounding the spinal cord. This pain should stop in a few seconds.
Overall, discomfort is minimal to moderate. The entire procedure usually takes about 30 minutes, but it may take longer. The actual pressure measurements and CSF collection only take a few minutes.
Why the Test is Performed
This test is done to measure pressures within the cerebrospinal fluid and to collect a sample of the fluid for further testing. CSF analysis can be used to diagnose certain neurologic disorders, particularly infections (such as meningitis) and brain or spinal cord damage.
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