Electromyoneurography (EMNG) is the combined use of

electromyography Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyog ...

and electroneurography This technique allows for the measurement of a peripheral nerve’s conduction velocity upon stimulation (electroneurography) alongside electrical recording of muscular activity (electromyography). Their combined use proves to be clinically relevant by allowing for both the source and location of a particular neuromuscular disease to be known, and for more accurate diagnoses.

Characteristics

Electromyoneurography is a technique that uses surface electrical probes to obtain electrophysiological readings from

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

and muscle cells. The nerve activity is generally recorded using surface electrodes, stimulating the nerve at one site and recording from another with a minimum distance between the two. The time difference of the

potential Potential generally refers to a currently unrealized ability. The term is used in a wide variety of fields, from physics to the social sciences to indicate things that are in a state where they are able to change in ways ranging from the simple re ...

is a measure of the time taken for the

to travel the distance across the two sites and is a measure of the conduction velocity along the nerve. The amplitude of the

, measured baseline to peak, or peak to peak, is a measure of the number of fibers conducting the response. Abnormality in data obtained from nerve measurements, such as absent or low amplitude, indicates potential nerve damage. This technique is used in many medical fields today. One example of its use is to detect neuropathy due to diseases like

diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

. It can also be used to detect muscle weakness or paralysis due to

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

or multi-organ failure in

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

tose patients. This method remains a largely used medical technique due to its efficiency and relative simplicity. It is especially attractive due to the lack of special precautions or preparation involved with this procedure. There is minimal pain and no significant risks except those associated with needle use."Electroneuromyography." MedInstitute Y&C Institute of medical rehabilitation. MedInstitute, n.d. Web. 26 Apr 2013. .

History

The technique of electromyoneurography was first practiced in the late 1970s by the American Academy of General Practice. The use of this technique enhances diagnostic capability by defining and localizing the target site. In 1978, Milton B. Spiegel, research physician with The Rehabilitation Institute of South Florida, wrote one of the first major academic papers surrounding the uses and benefits of electromyoneurography. It was in this paper that Dr. Spiegel suggested that pre-examination of the patients'

range of motion Range of motion (or ROM), is the linear or angular distance that a moving object may normally travel while properly attached to another. It is also called range of travel (or ROT), particularly when talking about mechanical devices and in mechanic ...

and reflexes would eliminate time and exploration of nerve entrapments during the electromyoneurographic procedure. In the early 1980s, the practice of utilizing electromyoneurography became more widely accepted in the medical community, specifically aiding in the diagnoses of

neuropathy Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or o ...

radiculopathy Radiculopathy, also commonly referred to as pinched nerve, refers to a set of conditions in which one or more nerves are affected and do not work properly (a neuropathy). Radiculopathy can result in pain (radicular pain), weakness, altered sens ...

, and

axonopathy Polyneuropathy ( poly- + neuro- + -pathy) is damage or disease affecting peripheral nerves (peripheral neuropathy) in roughly the same areas on both sides of the body, featuring weakness, numbness, and burning pain. It usually begins in the hand ...

. As to more recent use, electromyoneurography has been employed throughout the 21st century, aiding in the diagnosis of carpal tunnel syndrome, abnormal glucose levels, and many other myopathies. This procedure now analyzes the nerve conduction and muscle potentials through the use of

H-Reflex The H-reflex (or Hoffmann's reflex) is a reflectory reaction of muscles after electrical stimulation of sensory fibers (Ia afferents stemming from muscle spindles) in their innervating nerves (for example, those located behind the knee). The H-re ...

and F-Wave studies. Combined with a pre-examination, electromyoneurography is utilized to detect neuromuscular abnormalities.

Modern Application

Electromyoneurography has a variety of modern applications. The high level of sensitivity that electromyoneurography employs makes it ideal for detecting peripheral nerve damage as well as a variety of myopathies in their early stages. This electrophysiological data obtaining technique has been able to heighten diagnostic capabilities when looking at peripheral neuropathy disorders like

, and axonopathy in addition to myopathies such as

muscular dystrophy Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare neuromuscular diseases that cause progressive weakness and breakdown of skeletal muscles over time. The disorders differ as to which muscles are primarily affe ...

myotonia Myotonia is a symptom of a small handful of certain neuromuscular disorders characterized by delayed relaxation (prolonged contraction) of the skeletal muscles after voluntary contraction or electrical stimulation. Myotonia is the defining sympt ...

, and

myasthenia gravis Myasthenia gravis (MG) is a long-term neuromuscular junction disease that leads to varying degrees of skeletal muscle weakness. The most commonly affected muscles are those of the eyes, face, and swallowing. It can result in double vision, dro ...

. Electromyoneurography was the main technique used in a study to detect diabetic polyneuropathy, a serious condition that is progressive in nature. Electromyoneurography can also be used to measure patient recovery from surgical procedures, such as nerve repair. A study conducted on patients with proximal radial nerve injuries used the procedure to indicate the degree of both pre- and postoperative nerve damage. In this particular study, electromyoneurography was the preferred method of measuring recovery, chosen over magnetic resonance imaging (

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

) and computed tomography ( CT) scans. When looking at the sample data table, one can see that postoperative patients generally see an increase in mean radial nerve amplitude, a decrease in mean radial nerve latency and increases in nerve motor conduction velocity. These results are all general trends that would be expected when operating on damaged nerves in effort to increase their performance. Electromyoneurography's unique combination of recording in muscle and nerve simultaneously typically results in a higher level of diagnostic ability in the field of medicine. This heightened utility often results in a lesser demand for more invase techniques for acquiring electrophysiological data, such as myelography, a procedure where complications are not uncommon and the amount of attention required for post-operative care is more involved.

Conditions Diagnosed with Electromyoneurography

Electromyoneurography has been found to be particularly useful in diagnosing the following neuromuscular conditions, though it is not an exhaustive list:

Procedure Outline

In an electromyoneurography procedure, recording of the muscle is done by insertion of a needle. The recordings are taken when the muscle is at rest and when the muscle is contracting; the muscle will contract based on the directions of the one performing the test (instructing the patient to move certain body parts in certain directions forming muscle contractions). Various regions of muscle on the body are examined in an electromyoneurography test and the procedure lasts anywhere between 30–60 minutes (2–5 minutes per muscle). In addition to examining the muscles, the

conduction velocity In neuroscience, nerve conduction velocity (CV) is an important aspect of nerve conduction studies. It is the speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factor ...

of nerve signals are measured. The nerve's ability to transmit signals is tested by inserting recording electrodes to capture the data and signal electrodes to initiate signals down a nerve by applying a small shock. Self-generated potentials also occur naturally for recording, in addition to the artificial "shock". Evaluating a nerve's conduction velocity, together with testing potentials, allows for a beneficial diagnosis that can detect pain and sensory problems at the neuromuscular level.

Expected Test Results

The needle is normally attached to a recording device known as an electromyography machine. The results show the appearance of

action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...

graded potential Graded potentials are changes in membrane potential that vary in size, as opposed to being all-or-none. They include diverse potentials such as receptor potentials, electrotonic potentials, subthreshold membrane potential oscillations, slow-wave ...

spikes. While interpretation of the results requires background knowledge, irregular data can be used to diagnose many diseases. If the activity of the nerves at rest is abnormal, this may indicate nerve lesion,

, or lower motor nerve degeneration. The amplitude or duration of the potential spike may also be used to gather information. A decreased amplitude or duration may indicate nerve damage due to a muscle diseases, whereas an increase in these demonstrates reinervation, or repair by new nerve connections to the muscles, has occurred. {{clear

References

Electrodiagnosis Electrophysiology Neurophysiology Neurotechnology Neurology procedures