Nerve Conduction Studies (NCS) Test Information

A nerve conduction study is performed to assess primarily the peripheral sensory and neuromuscular system; it’s often done in conjunction with an electromyography (EMG). The nerve conduction study component comprises of percutaneous stimulation of the nerve fibers and recording the potential generated. In other words, it’s a small shock to the nerve fibers, the stimulation travels from the stimulated site, along the nerve, much like water through a hose, and eventually reaches the recording devices, where the ‘output’ is measured.

Motor nerve stimulation causes very brief muscle contraction of the selected nerve & muscle. Sensory nerve stimulation is generally ‘lighter’ and doesn’t cause muscle contraction as such. The stimulation is uncomfortable, and is likened to TENS machines used by various Allied Health specialists to stimulate muscles. Most people tolerate the stimulation, as it is more uncomfortable than painful.

The most common nerve condition studied at Cairns Neurophysiology is Carpal Tunnel Syndrome (CTS), which is a compressed median nerve at the wrist. The median nerve innervates the first three fingers (and half of the fourth). The median nerve is stimulated at the wrist with recording devices over the thumb. If the nerve is compressed, it is like having a kink in a garden hose, and the response at the recording device end of the nerve is subsequently delayed or reduced analogous to a trickle of water coming out of the kinked hose.

Preparation: there is no significant preparation for the investigation. It is recommended to wear clothes that allow access to the top of the arm, and knee access in the leg.

Frequently asked NCS questions

How long does the test take?

It depends how many nerves are being tested and how well you tolerate the test. It can take from half an hour to one hour. Time is taken to explain all aspects of the test to you.

Is there any preparation for the test? (see above information)

No preparation is required, just wearing clothes that allow access to upper arm and leg. No fasting required.

Do I still take my medications?

YES continue all regular medications.

Will I be able to drive after the test?

Yes, you will be able to drive after the test.

Are there any after affects of the test?

No, there are no after affects or complications of the test.

I have a pacemaker can I still have the test done?

You can still have the test done, however, it will need to be arranged through Cairns Hospital for safety reasons.

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