EMG Precision: Advanced Nerve and Muscle Evaluation Techniques
Introduction to EMG
An electrodiagnostic study, commonly known as EMG (short for electromyography), measures electrical activity in muscles and nerves, and can be an important test in the diagnosis of certain conditions that affect the nerves. An EMG is often very helpful in finding what nerve(s) are causing numbness, tingling, pain and/or weakness, as well as assisting in determining the severity of the injury. It can also help identify areas where the nerve may be compressed (“pinched”), which is critical in determining treatment, especially if surgery is needed.
Explaining EMG: What It Is and How it Works
Nerve Conductions Studies (NCS)
The nervous system acts similarly to an electrical circuit. To move a muscle, the brain creates an electrical signal that travels through the spinal cord and eventually out specific nerves connected to make it move. These are referred to as “motor nerves.”
When we touch something, an electrical signal is sent to the brain where it is felt (examples are pain, light, touch). These are referred to as “sensory nerves.” We can give a safe electrical current to different nerves in the body and record their responses. These tests are Nerve Conduction Studies (NCS) and are performed prior to an EMG.
The responses are recorded from “electrodes” which are placed on the skin. The current is given to the nerve through the skin with a “simulator.” We know how fast these nerves should be activated, travel through the body, and how large the response should be from years of collecting information from patients. We can use this information to tell if a patient has certain problems with the nerve or nerves.
Needle Electromyography (EMG)
Typically, after the NCS, a needle EMG is performed. The needle is another type of electrode that can help the physician “look and listen” to the electrical activity when the muscle is resting and when it is contracted. What muscles we check is based on what your doctors believe the possibilities of your problem are. For a problem in a single limb, usually five to six muscles are studied. If there are abnormalities found from the Needle EMG, the nerve or nerves affected can be identified.
Applications of EMG in Physical Medicine & Rehabilitation
EMGs help support the diagnosis in common conditions such as carpal tunnel syndrome, cubital tunnel syndrome, radiculopathies (“pinched nerves”) in the neck or low back, and many diseases of the nerves (“neuropathy”). The EMG can also help identify if there is nerve damage, the severity of the damage, as well as look for nerve regeneration.
How EMG Enhances Precision in Care
EMGs can aid in the precise diagnosis of various nerve problems by identifying which nerve or nerves are affected. Because it can also tell the severity of the injury, it may also allow the physician and patient to establish how quickly surgery should be considered, as well as assist in knowing the chances of significant improvement following the operation. This knowledge also allows the team to plan rehabilitation strategies depending on severity. For example, with significant nerve damage from a herniated disc in the lower back and a foot drop, an aggressive physical therapy program is likely needed to help regain strength.
Integrating EMG into Rehabilitation
As EMG findings often help identify the specific nerve problem and how severely it is affected, it can help guide the physician in a specific rehabilitation plan. When someone has nerve damage that causes weakness to specific muscles, they can be targeted for strengthening. With significant injuries, EMGs are useful to monitor nerve recovery. Comparing a previous EMG to one after a certain period (often 2-3 months) can show if the nerve is healing. This information is useful when considering surgery or helping to know if injuries can be permanent.
Future Implications of EMG in Orthopedic Medicine
The technology is constantly improving in EMGs. As a computer is used in obtaining information, better processors and filters allow for a more accurate and faster test. Advancements from using older to the current machines already have made the test less uncomfortable and faster than prior to the 1990’s. With better equipment, the diagnosis can be more accurate.
Conclusion
EMGs play a critical role in the diagnosis and prognosis of many disorders of the nerves in the peripheral nervous system. They are a very well-established test to assess nerve function and are important for identifying specific nerve injuries and nerve diseases. In many cases, EMGs help your team know not only which nerves are affected, but how badly they are injured, and assist in helping know the chances of recovery. The EMG test is uncomfortable, but not unbearable. It is tolerated well by most patients. To learn more or to schedule an EMG, visit our Appointments page today.
