Nerve conduction study

Overview

A nerve conduction study (NCS), also known as a nerve conduction velocity (NCV) test, is a diagnostic procedure used to assess the functionality of peripheral nerves in the body. These peripheral nerves are the ones located outside the central nervous system, which includes the brain and spinal cord. 

During the NCS, a nerve is stimulated by attaching electrode patches to the skin. Two electrodes are strategically placed over the nerve of interest. One electrode delivers a mild electrical impulse to stimulate the nerve, while the other records the resulting electrical activity. This process is repeated for each nerve under examination. 

The test calculates nerve conduction speed by measuring the distance between the electrodes and the time it takes for electrical impulses to travel between them. More specifically, the NCS assesses the flow of electrical current through two types of nerves: 

• Motor nerves: These nerves control muscle function and movement. 
• Sensory nerves: These nerves transmit signals to the brain related to touch, taste, smell, and vision. 

An NCS may be recommended by your healthcare provider if you experience symptoms such as tingling or numbness in various parts of your body, including the arms, legs, hands, feet, and face. Depending on your specific situation, you may undergo this study in an outpatient setting or as part of your hospital stay. Typically, NCS is performed in conjunction with an Electromyography (EMG) test for a comprehensive evaluation of nerve and muscle function.

Reasons for undergoing the procedure 

Nerve conduction studies diagnose peripheral nerve issues, like neuropathy and nerve compression. They determine the cause, severity, and prognosis of these conditions.  

• Peripheral neuropathy: Peripheral neuropathy arises from nerve damage, often due to: 

• • Diabetes. 
  • Alcohol–related condition  
  • Thyroid disorders. 
  • Nerve trauma or surgery. 
  • Vitamin deficiencies. 
  • Infections (e.g., HIV, Lyme disease). 
  • Medications (e.g., chemotherapy). 
  • Autoimmune diseases (e.g., lupus, rheumatoid arthritis). 

• Nerve compression syndromes: Nerve compression syndromes, leading to neuropathy, include: 

• • Sciatica. 
  • Radial tunnel syndrome. 
  • Thoracic outlet syndrome. 
  • Carpal tunnel syndrome. 
  • Meralgia paresthetica. 

Risk  

The electrical pulses used in NCV tests are typically very low in voltage, but the potential risks associated with the procedure can vary based on your individual medical condition. It is crucial to address any concerns with your healthcare provider beforehand. Several factors, such as spinal cord damage, severe pre–test pain, and body temperature, may affect the accuracy of NCV results. Additionally, it’s important to inform your healthcare provider if you have a cardiac defibrillator or pacemaker, as special precautions may be necessary.

Procedure  

Nerves function like cables, transmitting electrical signals from the brain to the body’s organs, allowing muscle movement and sensations. In a nerve conduction study, electrodes are placed on the skin along the nerve’s path, and a mild electrical shock stimulates the nerve. This test measures the strength and speed of the electrical impulses. Motor nerve responses are measured in the controlled muscles, while sensory nerve responses are recorded elsewhere along the nerve. 

Healthy nerves conduct electrical signals at speeds up to 120 miles per hour. Damage to the nerve results in weaker and slower signals. By stimulating the nerve at multiple points, healthcare providers can pinpoint the location of the damage. 

Electromyography (EMG) is a similar test that measures muscle electrical activity and is often performed alongside nerve conduction studies. These tests help identify the presence, location, and severity of muscle and nerve disorders. 

Before the procedure  

Before undergoing a nerve conduction study, it is important to: 

• Complete a consent form that grants permission for the procedure. It is essential to carefully review the form and ask any questions if you find any unclear points. 
• Note that, in most cases, fasting or sedation before the procedure is not required. 
• Ensure that you maintain a normal body temperature before and during the procedure, as a low body temperature can slow down nerve conduction. 
• Inform your healthcare provider about all the medications (both prescription and over–the–counter) and herbal supplements you are currently taking. 
• Wear clothing that allows easy access to the area to be tested or can be easily removed. 
• Refrain from using lotions or oils on your skin for several days before the procedure. 
• Be aware that, depending on your specific medical condition, your healthcare provider may recommend additional preparation steps. 
• If you have a pacemaker or any other electrical medical device, please inform the healthcare provider performing the study. 

During the procedure  

The procedure for a nerve conduction study can vary based on the specific purpose of the test and which nerves are being evaluated. However, generally, you can anticipate the following steps during a nerve conduction study: 

• Preparation: You will be either seated or lying down for the examination. 
• Electrode placement: A healthcare professional will affix electrodes to the surface of your skin over the nerves under investigation. 
• Muscle or skin electrodes: Different types of electrodes will be attached to the muscles or skin areas controlled by these nerves. 
• Nerve stimulation: The healthcare provider will then administer a small electrical impulse to your nerves to trigger a signal to the associated muscle. You might experience a mild tingling sensation during this process. 
• Response recording: The time it takes for your muscle or skin to respond to the nerve signal will be recorded. 
• Sequential assessment: This procedure will be repeated for each nerve being studied until sufficient data is collected. 
• EMG test: Typically, an electromyography (EMG) test is performed after the nerve conduction study to further assess muscle function and detect any potential abnormalities.

After the procedure  

Following the completion of the test, the adhesive paste securing the electrodes to your skin will be removed. Typically, you can resume your usual activities unless your healthcare provider recommends otherwise, which may include avoiding strenuous activities for the remainder of the day. Furthermore, additional post–procedure instructions may be provided by your healthcare provider based on your specific circumstances.

Outcome  

Nerve conduction studies, while valuable for diagnosis, may not be standalone diagnostic tools. Healthcare providers typically assess the results in conjunction with additional tests, the patient’s medical history, and their symptoms to arrive at a diagnosis. When a patient displays signs of nerve injury or damage, a nerve conduction study can offer supplemental insights to the healthcare provider, aiding in both diagnosis and treatment planning.