Electrical activity or response tests
Nerve Conduction Studies
NCSs test how well signals travel along a nerve and can help find the cause of abnormal nerve function. Signals are made to travel along the nerve by applying small electric pulses to the nerve at one site and recording the response at a different place along the nerve. The small electric pulses cause a short, mild tingling feeling. The nerve’s response is picked up by a recording instrument and then is measured by the physician or technologist performing the test. Several nerves may need to be tested depending on the type of problem.
Needle Examination (EMG or electromyogram)
During the needle EMG portion of the examination, the physician inserts a small needle into a muscle to record the electrical activity of the muscle. The electrical activity of the muscle is fed into the recording instrument and the physician then analyzes it by looking at a signal on the scope and listening to the sounds the activity makes through the speaker. This test can help determine if there are abnormalities in the muscle or the nerve going to it.
There may be mild discomfort when the need is inserted into the muscle. The needles are discarded after use to prevent the transmition of infections.
- Special Precautions
You should inform the physician prior to the examination if you are on blood thinners or have hemophilia. The physician should also be informed if you have a cardiac pacemaker or use a transcutaneous electrical nerve stimulator(TENS) unit. Avoid using skin lotions the day of the test. If you have myasthenia gravis you should ask your physician whether or not to take medications, such as Mestinon, before the examination.
EEG measures the electrical activity of the brain. It is primarily used in the evaluation of seizures and other transient alterations of awareness and consciousness. Activity of the brain is passively recorded, no electrical stimulation is given. The test typically takes 20-30minutes. You may be asked to take deep breaths and may be exposed to flashing lights during the EEG. Once the technician completes the recording, a physician will review the test and send a report to your doctor.