Electromyography (EMG) and Nerve Conduction Study (NCS): An Important Diagnostic Tool

Electromyography (EMG) and Nerve Conduction Study (NCS) is an important diagnostic tool to assess and analyze nerve and muscle function and pinpoint the underlying causes of symptoms, such as pain, weakness and numbness.

Good Shepherd Rehabilitation’s Andrew Reish, MD, is a physiatrist with Good Shepherd Physician Group specializing in interventional pain management, musculoskeletal medicine and EMG/NCS. We asked Dr. Reish to explain EMG/NCS testing and how it helps in the development of patient treatment plans.

What is an EMG/NCS?

Dr. Reish: Electrodiagnostic testing evaluates the electrical activity produced by nerves and muscles and is a powerful tool for diagnosing various neuromuscular conditions. An EMG/NCS test evaluates the peripheral nervous system to determine what type of neuropathy or myopathy (pain, numbness, tingling, weakness) is present.

NCS testing is a diagnostic test that measures the flow of electrical current through sensory nerves and motor nerves using a brief electrical stimulation to measure the strength and speed of electrical activity to detect the presence and extent of peripheral nerve damage.

EMG needle testing measures the electrical activity of the muscle during rest, slight contraction and forceful contraction. During the test, one or more small sterile needles (also called electrodes) are inserted through the skin into the muscle. The electrical activity picked up by the electrodes and EMG needle and can be amplified and displayed on a monitor in the form of waveforms that can be quantitatively interpreted to assist a clinical diagnosis.

How do EMG/NCS evaluations impact treatment plans?

Dr. Reish: EMG/NCS results provide essential information for correctly diagnosing diseases of the peripheral nervous system and muscles. As a rapid intervention, EMG/NCS helps streamline diagnoses because about 50% of the time the initial diagnosis changes after an EMG/NCS evaluation is performed. Plus, EMG/NCS results change the nature of managing and treating a patient’s condition about 63% of the time.

If someone is experiencing an ankle/foot drop, for example, an EMG/NCS evaluation can determine if the weakness is caused by a pinched nerve at the lumbar spine, by nerve entrapment at the side of the knee (fibula) or by a systemic polyneuropathy affecting multiple nerves. This diagnostic evaluation helps guide the examiner and other specialist physicians to recommend the best treatment plan (surgery versus orthotics versus further evaluation of vascular blood flow by imaging or serum blood evaluation for neuropathy depending on the EMG/NCS findings, when coupled with physical exam and clinical history).

Another example is when a patient is having burning-numbness foot pain; an EMG/NCS may find the cause is the patient’s poorly controlled diabetes instead of the known spine arthritis noted on imaging, which is typically managed with medication rather than surgery.

It’s important that primary care physicians and other clinicians utilize EMG/NCS as a tool in diagnosing suspected peripheral nervous system disorders or injuries. Patients are often referred for an EMG/NCS to clarify a diagnosis only after they fail physical therapy or a physician cannot pinpoint the cause of pain, weakness, numbness and tingling. However, the EMG/NCS study, if performed early, can help expedite a definitive diagnosis and speed up recovery.

What type of conditions are evaluated with EMG/NCS?

Dr. Reish: At Good Shepherd, we use EMG/NCS to evaluate clinical conditions that include symptoms of:

• Neck pain and hand/arm weakness or pain such as in cervical radiculopathy, carpal tunnel syndrome and cubital tunnel syndrome
• Back pain and foot/leg weakness such as in lumbosacral radiculopathy or tarsal tunnel syndrome
• Fibromyalgia, which is a diagnosis of exclusion (a disorder that causes pain and tenderness throughout the body, as well as fatigue and trouble sleeping)
• Multiple etiologies of polyneuropathy (damage or disease affecting peripheral nerves in roughly the same areas on both sides of the body) featuring weakness, numbness and burning pain) that can be inherited or acquired later in life either rapidly over hours to days or extremely slowly over years
• Myopathy, such as muscular dystrophy, polymyositis and inclusion body myositis
• Motor neuron diseases, such as primary lateral sclerosis, spinal and bulbar muscular atrophy or amyotrophic lateral sclerosis (ALS).
• Neuromuscular junction disorders, such as Myasthenia Gravis or Lambert-Eaton syndrome.

EMG/NCS support the prompt evaluation and diagnosis of complex neuromuscular symptoms.

Are there side effects from am EMG/NCS needle study?

Dr. Reish: There are few serious complications from an EMG/NCS study. The most common side effect is a bit of site tenderness or localized bleeding from EMG needle evaluation, but being a board-certified electromyographer allows me to perform the test with a minimal amount of discomfort and risk for my patients. There are a few very rare case reports in the literature (probably less than 1 in 10,000) of medically significant hematomas, the majority in patients with known bleeding disorders, either medically induced or acquired. EMG is a temperature-sensitive study, so I encourage patients to dress extremely warmly to make the testing go as smoothly as possible. Patients can also be nervous/anxious about needles and therefore we use Teflon-coated, small 27-gauge needles (smaller than IV needle placement and smaller than most vaccination needles) to minimize pain and discomfort. 

How did you become specialized in conducting EMG/NCS evaluations (Electrodiagnostics)?

Dr. Reish: During my Physical Medicine and Rehabilitation residency training at the Hospital of the University of Pennsylvania (Penn Medicine), I worked for four years and performed more than 200 EMGs as part of the criteria to graduate. I subsequently did a Spine Medicine fellowship at the University of Michigan for one year before practicing on my own. I have since done significant further training and received a separate board certification in electrodiagnostics (EMG/NCS). I have been performing EMG/NCS at Good Shepherd for over a decade and have performed several thousand EMG/NCS evaluations since completion of my fellowship.

Where do you perform EMGs at Good Shepherd Rehabilitation?

Dr. Reish: I perform EMGs on an outpatient basis at Hyland Center for Health & Technology on Good Shepherd’s South Allentown campus (850 S. 5th St., Allentown).

To learn more about EMG/NCS or Dr. Reish’s practice, call 1.888.447.3422 (44-REHAB).