Nerve Testing: Electromyography (EMG) / Nerve Conduction Velocity (NCV)

Nerve conduction studies are utilized to determine if the patient is suffering from nerve damage or inherent deficiency. This allows the doctor to either rule out or confirm a diagnosis of nervous system issues, instead of musculoskeletal problems that could cause similar symptoms. They can also help determine the source of nerve damage, such as substance abuse, nerve compression or another peripheral neuropathy, as the specific cause can be vital to effective treatment.

Nerve conduction studies are often performed in conjunction with electromyography, which helps to diagnose muscle disease and neuromuscular conditions such as myasthenia gravis and Lou Gehrig’s disease (amyotrophic lateral sclerosis).

The nerves are essentially electrical systems and are thus best observed using an oscilloscope. This device displays signal voltages and charts them along a graph according to time. Electrodes are attached to the skin to deliver mild electrical impulses and then record the body’s response.

This allows the oscilloscope to show exactly how long it takes a nerve to respond to direct stimulation, as well as the magnitude of such response. This vital information is contained within the frequency and amplitude of the resulting graph. In addition, the overall shape of the impulse graph can be also be used for diagnostic purposes.

The electric activity produced by the neural network is inherently variable in all humans due to complicating factors such as height, weight, sex, age, and body temperature. However, the diagnostic value of the nerve conduction study is still effective in determining activation velocities that are outside of the normal range. These abnormal values can help ensure a correct diagnosis.

The test itself is non-invasive and evokes no side effects whatsoever. However, there may be a varying degree of discomfort due to the multiple low-intensity electric pulses sent through the electrodes. Additionally, the paste or gel used to affix the electrodes securely onto the skin may irritate certain people with abnormally sensitive skin.



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