Electrodiagnostic testing is used to detect disorders of the peripheral nervous system. The main parts of the peripheral nervous system are nerves and muscles, but neuromuscular junctions (nerve-muscle connections) and motor nerve cells in the spinal cord are also included. We perform two types of electrodiagnostic testing, namely electromyography and autonomic testing.
Electromyography (EMG)
Electromyography consists of two parts, nerve conductions and the actual electromyogram or needle examination.
What are nerve conductions?
A technician or physician electrically stimulates a nerve from the skin surface causing it to fire resulting in either a muscle contraction or sensory impulse that is recorded by electrodes. Nerve conductions measure the speed and efficiency of nerve transmission. The stimulation is mildly painful but well-tolerated by the vast majority of patients.
What is the electromyogram or needle examination?
For this part, a physician inserts a thin needle electrode into muscles and records their activity at rest and with contraction. The patterns seen can identify the presence of muscle disease or the results of nerve dysfunction. The needle examination is a little painful at times, but again, most patients tolerate it easily. The needle portion lasts 10-30 minutes depending on the problem, and nerve conductions take 20-40 minutes to perform.
Most Common Conditions Diagnosed by EMG
- Carpal tunnel syndrome
- Radiculopathies (“pinched nerves”)
- Ulnar neuropathy
- Peripheral Neuropathy
- Muscle diseases
- Motor neuron disease
- Myasthenia gravis
Scheduling An EMG
You need a prescription from your physician prior to scheduling.
- Orders are placed electronically or faxed to (412) 647-5162
- Call (412) 647-5424
Preparing for an EMG
- Eat and drink normally
- Do not apply any lotions or body creams as they can interfere with testing
- You may want to wear shorts and a short sleeve shirt, or you will need to change into a gown
- Notify the technician and physician if you are taking any blood thinners. If you are taking pyridostigmine (Mestinon), it should be held for 12 hours prior to testing with the consent of your physician
- Studies take 40 mins to 1 ½ hours depending on the complexity
Following testing, you will be able to participate in normal, daily activities.
EMG with Needle Muscle Biopsy
If your physician thinks you have a myopathy (muscle disease), an EMG with possible muscle biopsy can be ordered with Dr. Lacomis. Suspected autoimmune myopathy/myositis is most appropriate for this combination testing. After the EMG study and sometimes with ultrasound guidance, Dr. Lacomis selects an appropriate muscle for biopsy using a spring-loaded needle biopsy device that removes small cores of muscle that are examined microscopically. The biopsy is performed at the bedside without making an incision, and it takes about 15 minutes. Patients cannot be on blood thinners. EMG with needle biopsy is only performed during morning appointments.