|Dr. Richard Lewis goes over electromyography results with patient Alani Price during one of the Neuromuscular Disorders Program's clinic days for Charcot-Marie-Tooth patients.|
Expert Performance of EMG Central to Personalized Care for Patients
For diagnosing neuromuscular disorders like amyotrophic lateral sclerosis (ALS), perhaps nothing is as important as the correct performance and interpretation of a test that relies on needles, electric impulses and a really good set of eyes – electromyography, also known as EMG.
Unlike other tests that utilize data-producing devices, EMG is reliant on the physician performing the test and interpreting the results in real time, said Robert H. Baloh, MD, PhD, director of Neuromuscular Medicine in the Department of Neurology and a member of the Brain Program at the Board of Governor's Regenerative Medicine Institute at Cedars-Sinai.
"It is completely dependent on the experience of that physician in neuromuscular medicine and electrodiagnostics," Baloh said. "Therefore the expertise of the neuromuscular physicians at Cedars-Sinai significantly improves the chances of a patient receiving an accurate diagnosis, which is the most important step in proper patient care."
The premier expert at Cedars-Sinai is neurologist Richard A. Lewis, MD, director of the EMG Laboratory, co-director of the Neuromuscular Clinic and among the best in medicine at performing and interpreting EMG.
Electromyography, quite literally, attempts to pinpoint what is affecting a patient's muscles and nerves. The test, which usually takes 30-60 minutes, requires a physician to insert electrode needles into the muscles to monitor and record their electrical activity, both at rest and while the patient is contracting the muscle.
The activity recorded from the needles is projected on a screen that requires the specialist to interpret the readings as they are being transmitted. This can then be analyzed relative to the degree of effort and strength required to produce the signal.
Another part of the EMG test is the nerve conduction study that examines both the size (amplitude) of the responses from muscles and sensory nerves and the speed (conduction velocity) that it takes for the nerves to transmit the signal. The findings on nerve conduction testing are important in diagnosing the various forms of peripheral neuropathy such as diabetic neuropathy, Guillain Barre Syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP), and inherited neuropathies which are Charcot-Marie-Tooth (CMT) disease.
"We can see and sometimes figure out where the nerves were injured and how badly they were injured, whether they are going to require surgery or not," Lewis said.
"There are two aspects of ALS. Part of the disease occurs in cells in the brain, and so there is a central nervous system component to the disease. The EMG doesn't show that part up very well, but you can tell clinically by their reflexes being brisk, and they have stiffness in their muscles and spasticity," Lewis said. "The other aspect of ALS is the lower motor neuron, which are primarily in the spinal cord. In that instance the EMG can show changes of the lower motor neuron. And to diagnose ALS, you need to show that people have lower motor neuron problems in three of four regions in the body. The regions being: the head and neck, the arms, the trunk and the legs."
While EMG is commonly used, it is important that the study be done by someone with expertise both in the performance of the test as well as in the various neuromuscular disorders.
"The power of EMG is to be able to interpret the study in context of the clinical picture," said Lewis, adding that Cedars-Sinai EMG Laboratory has a well-deserved reputation for providing this expertise.