Electromyography (EMG), electroneurography (ENG) and single fiber electromyography (SFEMG) are neurophysiological methods that are used to study the peripheral nervous system (PNS) from a functional point of view. It represents a reliable method that can give information about the functionality of peripheral nerves and skeletal muscles. It is also a diagnostic tool that allows to frame neurological diseases of the peripheral nervous system regarding pathologies affecting nerve roots, nerve plexuses, peripheral nerves, neuromuscular plate and muscles. If the neurological examination shows a deficit in the peripheral nervous system, electromyography is an indispensable tool to further the diagnosis, especially when the site, extent and type of lesion are unclear.
Electromyography is used in the diagnosis of muscular and neuromuscular pathologies, which are classically associated with symptoms such as tingling, numbness, muscle weakness, cramps, spasms or paralysis of a particular anatomical district.
From the instrumental point of view, the electromyography involves the use of some electrodes and needle electrodes, and a particular computerized equipment (the electromyograph), able to record and translate into a graph the muscle activity and nerve signals passing along the nerves responsible for muscle control. The electromyograph and typically includes two moments: the study of nerve conduction, obtained by means of surface electrodes, and the evaluation of electrical activity, established by means of special needle electrodes.
Low-risk procedure; electromyography does not present any absolute contraindication; however, its use requires specific precautions in patients with pacemakers or implantable cardioverter devices, in subjects undergoing anticoagulant therapy or individuals affected by some coagulation disease.
Typically, a neurologist is responsible for interpreting the data provided by electromyography.
In more detail, electromyography allows is useful in the diagnosis or differential diagnosis of:
- Muscle diseases. This category essentially includes inflammatory conditions (myositis and polymyositis) and degenerative diseases (muscular dystrophies).
- Peripheral Nerve Diseases. Peripheral nerves are responsible for connecting the various elements of the central nervous system (encephalon and spinal cord) and for transmitting information from the central nervous system to the periphery and vice versa.
- Classic examples of peripheral nerve diseases are compression neuropathies (carpal tunnel syndrome, cubital tunnel syndrome, tarsal tunnel syndrome, piriformis syndrome) and peripheral neuropathies and polyneuritis due to causes such as diabetes, alcoholism, nutritional deficiencies and renal failure.
- Diseases of motor neurons located in the brain and spinal cord. In such circumstances, the aforementioned motor neurons undergo, at first, a deterioration and, subsequently, go to death.
- Examples of such serious diseases are amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and poliomyelitis.
- Radiculopathies. These are the diseases characterized by pinching or compression of the roots of a spinal nerve; of a spinal nerve, the roots are the two emergences that sprout from the spinal cord and come together to form the nerve itself.
- Radiculopathies are classically associated with herniated discs, cervical arthrosis, and spondylolisthesis.
In addition, electromyography plays a key role in identifying conditions such as spasmophilia, traumatic peripheral nerve injury, and myotonia.