Medical imaging tests such as Bone Scans, X-Rays, MRI's, and CT scans are good at showing back injuries that involve bones, and soft tissue injuries to the joints, tendons, and spinal ligaments. These tests are good at showing much of the anatomy of the spine, as well as and conditions that are putting pressure on the spinal nerves. However, these types of tests are not precisely accurate at showing doctors how much patients are affected by back conditions that may involve the spinal nerves.
Many back cases involve back surgeries in which the supposed cause of the patient's back pain - herniated discs - were removed, though the patients would subsequently still complain of their original symptoms. Why in these cases does the patient still report back pain even after the supposed cause of the patient was corrected? In actuality, these patients often do have herniated discs that press on the spinal nerve roots, but this nerve root compression is not the cause of the patient's pain. Electrodiagnostic tests may be performed to offer medical doctors additional information about which nerves have been compressed, and how serious the nerve compression is.
A pair of nerves exits each side of the spine through openings known as the intervertebral foramina. Due bone remodeling rated to osteoarthritis, as well as other spinal conditions such as lumbar disc herniations, the size of these openings for the nerves may be reduced. The reduction of the size of these openings may result in a constriction of the nerves, also called nerve root compression. As these nerves leave the spine, they become part of the peripheral nervous system. Each of these peripheral nerves supplies a specific set of muscles or tissues in the body. Therefore, we may indirectly test the health and functioning of these nerves by testing the strength of the muscles that they supply.
Electrodiagnostic tests are done to evaluate the functioning of the peripheral nerves, which may be compressed or irritated due to back conditions such arthritis, sciatica, neuropathy, herniated discs and spinal stenosis. These tests may help us find which peripheral nerves are affected, and the extent of the damage. As a result of nerve compression, patients may experience pain at the source of compression, as well as pain that radiates away from the injury source. Nerve compression that involves paint radiating down one of the limbs is known as radiculopathy.
Nerve compression may also involve symptoms other than just pain. Nerve compression may also cause symptoms such as burning pain, numbness, muscular weakness, and the gradual loss of reflexes. Electrodiagnostic tests are done to assess the muscle and nerve functioning of the structures supplied by specific nerves. Nerve conduction velocity (NCV) studies measure the speed of the transmission of the electrical signal in a nerve. One of these tests is the Electromyogram (EMG). The EMG tests measures the electrical activity of the muscles while at rest and while at work. As a result of the NCV and EMG tests, doctors may be able to differentiate among the neurologic disorders associated with leg and back pain. These tests are usually performed when the patient's symptoms includes radiculopathy (pain that radiates down the leg).
Nerve conduction velocity (NCV): When the nerve has become compressed or damages for several weeks or longer, the strength of that nerve may be diminished, as well as the speed of the signals provided by that nerve. The NCV test measures the conduction velocity of certain peripheral nerves, which may be diminished due to long term nerve compression. For this test, surface electrodes are placed throughout the upper and lower leg, including the muscles in the foot. This test measures the speed at which the nerve signals travel from one electrode to the other.
Electromyogram (EMG): EMG tests are done to measure the strength of muscle signals when patients flex and relax their muscles. To perform this test, doctors insert needles directly into the muscles. These needles are connected to sensors, which are connected to a digital graph that records the various strengths of electrical activity that are present throughout the test. In normal muscles, these is increased electrical activity when patients activate these muscles while flexing them. When the nerves supplying these muscles have been compressed for weeks or months, the activity in these muscles decreases compared to what you would expect in normal patients. When the main branch of the nerve has become damaged, the number of nerve fibers supplying that muscle decreases, and there is atrophy to that muscle.