Neurophysiology

This term refers to a type of test performed in neurology, most commonly a Nerve Conduction Study (NCS) and an Electromyogram (EMG). Sometimes both tests are performed.

 

Other types of neurophysiology tests include Electroencephalogram (EEG), Evoked Potentials (EPs) and Vestibular Function Tests (VFTs), but these are not performed at MNG.

 

Any doctor can order neurophysiology tests, but most commonly these tests are ordered by a Neurologist.

 

Neurophysiology testing is complicated, and requires specialised training to perform. A/Professor Day is a neurologist who has undertaken detailed training in Australia and USA in neurophysiology, and is widely regarded as one of Australia’s expert neurophysiologists.

 

Nerve Conduction Studies (NCS) examine the integrity of the peripheral nerves. All peripheral nerves consist of a motor component – which makes the muscles work – and a sensory component – which provide sensation to parts of the limb.

  • A small current of electricity is applied to the nerve and its effect on the muscle is measured – this assesses the integrity of the motor aspect of the nerve.
  • A small current of electricity can be applied to a patch of skin, and its effect on the nerve can be detected – this assesses the integrity of the sensory aspect of the nerve.
  • The neurophysiologist can determine if there is a problem with the nerve, and where along the course of the nerve the problem might be.
  • Common peripheral nerve problems include carpal tunnel syndrome (compression of the median nerve at the wrist), and peripheral neuropathy, most often caused by diabetes.

NCS is generally not painful, but some people find it a little uncomfortable.

 

No special preparation is required before an NCS. You should try to keep your arms and legs warm in the half hour or so before your test, as being cold can affect the results.

 

An Electromyogram (EMG) examines the function of an individual muscle. As all muscles in the body are supplied by a nerve, studying a muscle can tell us about both the state of the muscle and the state of the nerve that supplies it. An EMG is rarely performed without first doing an NCS.

  • A fine needle is inserted into the muscle through the skin. The needle is similar in size to an acupuncture needle. It has a recording wire that connects to the EMG machine.
  • The response of the muscle to the needle, at rest and in response to contraction, is recorded on the computer.
  • The neurophysiologist can determine from these recordings whether there is muscle damage or nerve damage, and if there is nerve damage, the neurophysiologist can determine the distribution of the problem to help localise which nerve is damaged and where.
  • Common muscle problems include myopathy – due to polymyositis or inclusion body myositis – and muscle damage due to drugs such as statins and steroids.
  • Common nerve problems diagnosed by an EMG include nerve root problems, often due to a disc bulge in the neck or back, and motor neuron disease.

An EMG can be uncomfortable, but A/Professor Day is an expert and thus able to keep any pain to a minimum. You may experience bruising and mild muscle pain for a few days after the test.

 

Please inform A/Prof Day if you are taking warfarin or any anticoagulant drugs.