Putting Brains in Muscles

Towards an Accessible Web-Based Health Education Platform on Neuromuscular Diseases

Nerve Conduction Test / Electromyography Exam

What is the Nerve Conduction Test ?

Nerve conduction test stimulate the nerve with an electric current and then record through an electrode piece attached to the skin. By applying a very low amount of current to the motor and sensory nerves, it generally an electric shock. The amount of electrical current is very small and does not cause harm to the human body.

The purposes of doing NCT are as follows:

  • To localize the lesion as either nerve, the neuromuscular junction or the muscle.
  • To determine the nature of the lesion.
  • To assess the severity of the lesion and its recovery prospects.

What is EMG study ?

EMG study use a needle to penetrate different parts of muscles, it records the electrical activity of the muscles in the resting state, mild contraction and strong contraction respectively. The results of different parts of study are combined to determine the type, location, extent and severity of nerve and muscle lesions. EMG study is commonly used to diagnose neuronal, peripheral, neuromuscular junction and muscle lesions.

Why do we need a EMG study ?

By combining with a nerve conduction tests, it helps detect the integrity and pathology of the entire pathway of the motor nervous system, including motor neurons, nerve roots, motor nerves, neuromuscular junctions and muscle.

How is the EMG examination performed ?

EMG study must be performed by a qualified neurologist or rehabilitation specialist. Doctor will select different muscle group to study needles according to patient’s clinical condition. The needles used for EMG study are all disposable stainless needles. After local disinfection of the skin, the needles are inserted. Doctor will ask the subject to relax the muscles to observe the resting potential of the muscles. The subject are then asked to undergo mild contraction and strong contraction. Throughout this contraction, the electrical activity of the muscles are being studied. The number of needles per study will varies depending on the condition. Only a small pinhole will be left afterwards.

Will EMG study be painful ?

Electromyography study will create a bit of sour, numbness or other uncomfortable feelings, particular when patient undergone contraction while the needle is in place. There will be repeated insertion and removal of the needles in the same muscle as doctor need to sample different parts of the same muscle to detect the electrical activity. In general, EMG study is a test that can be painful but most people can tolerate.

Any side effect of EMG study ?

The EMG study is performed by a trained neurologist or rehabilitation specialist and is generally a safe procedure. Rare side effects include local infections, hematomas. 

Is there a contraindication for EMG study?

EMG study will not be performed if there is active skin infection, coagulopathy condition or marked edema of the limbs.