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Our office is by referral only, it is up to your referring physician to decide if the test is appropriate for your condition. Your PCP may determine you need a diagnostic test or may send you to a specialist who may make the determination to send you to our office. The list below may provide some insight into what diagnoses the test is typically associated with.
Diagnoses in which NCV/EMG tests are MOST useful:
Carpal Tunnel Syndrome
Carpal tunnel refers to the area within the wrist and adjacent palm, through which tendons that connect forearm muscles to the fingers pass through. There are 9 tendons (1 for thumb and 2 for each finger) which keep on sliding through the tunnel as we move our fingers during all kinds of activities. There is also a single nerve (median nerve), which passes through the tunnel. It carries sensations (feelings) from the thumb, index finger, middle finger and adjacent part of ring finger. It also makes the muscles that are responsible for moving the thumb.
Carpal tunnel syndrome refers to a group of symptoms resulting from pressure on the median nerve within the carpal tunnel. Initial symptoms are related to malfunction of nerve components that carry sensations from the fingers and the thumb; the result may be tingling, numbness, burning sensations or the feeling that the “fingers are asleep” often forcing the person to move or shake the hand repeatedly. The symptoms may be worse at night causing sleep interruption. Worsening may also occur with activities like driving, holding the telephone to the ear or doing your hair. At the next stage, loss of feelings in the hand may be severe enough to cause accidentally dropping objects like cups or plates carried in the hand. With further worsening, the muscles at the base of the thumb starts to atrophy (Figure 1, 2) leading to weakness of the hand. For More Information: Carpal tunnel syndrome
Cubital Tunnel Syndrome
Cubital tunnel refers to a tunnel at the elbow through which the ulnar nerve (funny bone nerve) travels. It carries sensations from the small finger and adjacent part of ring finger as well as the back of the hand to the brain. It also carries signals that cause contraction of several muscles in the hand.
Cubital tunnel syndrome refers to a group of symptoms resulting from pressure on the ulnar nerve at the elbow: numbness and tingling of small finger and ulnar side of ring finger; symptoms get worse on bending the elbow. As the condition progresses muscle of the hand become weak and later atrophy and the small and ring fingers start clawing (see Fig 3, 4). For More Information: Cubital tunnel syndrome
Wrist drop results when muscles that extend the hand at the wrist become weak. If the wrist can be extended, but not the fingers, the term finger drop is used (Figure 5). These conditions result from loss of function of the radial nerve. One of the most well-known causes is compression of the nerve against the upper arm bone (humerus), often called Saturday night palsy. Fracture of humerus is another cause. For More Information: Wrist drop
Cervical Radiculopathy / Brachial Plexopathy
Nerves in the upper extremities are connected to the spinal cord via five nerve roots: C5, C6, C7, C8 and T1 (C stands for cervical and T for thoracic); the roots mingle together into a complex network called brachial plexus from which all the nerves in the upper extremity arise. Nerve roots, components of brachial plexus and the nerves in the upper extremity all have 2 major functions: 1. Form part of the “information highways” letting our brain know what is in the hand (Example, making it instantly possible to sense if you hold a ball vs rock vs pear vs apple). 2. Carry bioelectric signals to the different muscles of the upper extremity to perform all kinds of activities (Example, to bring the coffee cup to the mouth, throw a stone, punch someone or caress the kid). Nerve conduction and EMG studies are crucial in determining where the problem is (nerve root/plexus/nerve/muscle) and how bad it is. For More Information:
Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig’s disease)
ALS results from progressive loss of nerve cells (motor neurons) that control muscles that involved in voluntary movements. It may start in the motor neurons that control the upper extremity or lower extremity muscles and eventually all muscles (Figure 7). Sometimes muscles of speaking and swallowing (bulbar muscles) may also be involved. The affected muscles show loss of bulk and may twitch. Sometimes muscles may be stiff or go into cramps. EMG studies are crucial in making diagnosis of ALS. For More Information: ALS
When many nerves show loss of function simultaneously the term polyneuropathy is used. When the distal portions of nerves are symmetrically affected, it is called peripheral polyneuropathy which is most often a complication of diabetes mellitus (diabetic neuropathy). However, there are many causes for polyneuropathy and extensive workup may be necessary to determine the cause. For More Information: Polyneuropathies
Foot drop results when muscles that move the foot up at the ankle joint are weak. These muscles are supplied by Lumbar 5 (L5) nerve root through the sciatic and its branch, the common peroneal nerve. It is a common cause for trip & fall injuries. Most often foot drop results from pressure on the common peroneal nerve against the fibula bone. However, precise localization needs NCV/EMG studies. For More Information: Foot drop
Diagnoses in which NCV/EMG tests are LEAST useful:
Pain as the only symptom
Primary disorders of joints