Needle-electromyography (EMG) is the most commonly used Neurodiagnostic procedure.  The most scientific term for the procedure is “needle-electroneuromyography”3  Please understand that this is decisive in your understanding of the subject.  The term “needle-electroneuromyography is derived by the structures it tests.  Thus, needle-electroneuromyography tests the nerve-muscle junction, the lower motor neuron that innervates the muscle, as well as specific muscle fibers.  Keep in mind that when the EMG is applied, it records the muscle fibers while at rest or upon active motion.  Common findings from the test include myopathies, actual nerve irritation, and nerve root irritation or problems at the nerve muscle junction.2,4 

     EMG is has found its most common utility when physicians find atrophy, muscle wasting, weakness or sensory deficit.  Further, whether you are involved with the performance of the testing, are referring out for the testing or are investigating the testing, you must understand how to comprehend the EMG report.21

     You are examining your first EMG report and note bizarre spontaneous high frequency discharges.  Think of any of the myopathies, or a lower motor neuron lesion proceeding distally.  Some that read this study will ask, “how do neuroscientists determine this criteria?”  The lesion or disease process is occurring distal to the anterior horn.  Remember that is the site of the nucleus (pleural) or beginning of the lower motor neuron.  The irritation could be occurring at the muscle spindles (detect muscle length-micro-biological detection organs) or at efferent or afferent muscle receptors.  The irritation may be in the actual muscle fibers or muscle components, or the disorder may be lower motor neuron disease occurring distally to the CNS.  In other words, the irritation is not in the CNS.  Thus, bizarre high frequency discharges occur in myopathies or a lower motor neuron irritation or disease.2,4  

     Other common findings in an EMG report are “coupled discharges” such as doublets, triplets or multiplets.  Coupled discharges generally refer to a hyperventilation syndrome, latent tetany due to hypocalcemia, ischemia or a combination of ischemia and hyperventilation syndrome.21 

     Thus, if the report you are auditing notes coupled discharges in the form of doublets, with minimal fasciculation potentials, then there is some kind of transient ischemic condition of the tissues.  Conversely, if there are coupled discharges in the form of triplets with moderate fasciculation potentials, a chronic spasticity of some disorder, disease or injury has caused the response.  Muscular spasticity of an acute or chronic nature and the whether the injury was substantial or not can be determined.  Further if you see that there was chronic spasticity with ischemic manifestations, immediately you understand why this patient is in pain.  For example, when a muscle is in spasm, it occludes the flow of blood, allowing toxic metabolites to remain in the tissue spaces.  Lactic acid, bradykinin, potassium ions, hydrogen ions and a relative soft tissue acidosis cause somatic tissue pain.  Further, ischemic conditions inhibit myoglobins’ ability to receive oxygen.  Finally, toxic metabolites that remain in the interstitial fluid can irritate nerve endings causing pain.5  Your understanding of coupled discharges, what they refer to and what they may indicate will reveal medically necessary and crucial information relative to the condition of your patient.1,2,4,21  

    Another important finding from EMG studies and often noted on the EMG report are fasciculation potentials.  The following case occurring within the confines of Industrial Medicine.  A 45-year-old female Asian American presented for a previously diagnosed industrial condition of cervical sprain.  Her chief complaints were severe neck pain, right triceps muscle pain, and a fasciculating right triceps.  Upon circumferential measurement it was discovered that her right triceps had slightly atrophied.  The patient demonstrated no sensory changes with the Wartenberg pinwheel or two-point discrimination testing.  The patient had bilaterally equivalent jammar testing and no other muscle weakness.  However, the patient’s right triceps muscle was fasciculating right before the doctor’s eyes.  Orthopedic examination and testing, such as cervical compression cervical distraction, soto hall and all tests performed were all negative for increased pain to the cervical spine and neighboring soft tissue.  The paramount question was, are the fasciculation’s and other complaints due to discogenic disease, a missed diagnosis, spinal stenosis, cord tumor, or is the patient twitching her muscle as fast as she can to simulate a visible fasciculation?  This brings up the possibility that some patients can twitch their muscles so fast that they can simulate a visible fasciculation to mislead one into believing that they have discogenic disease.  This exemplifies the situation many times in the industrial medicine arena or personal injury cases as small populations of patients have a pain-predilection or litigation-predilection personality.  Thus, in some cases when a lawyer, award or settlement are involved, these litigation predilection patients suddenly develop incredibly severe subjective complaints.  The situation further becomes complicated, as the carriers will not allow monies for MRI at this time.  This situation profoundly demonstrates the utility of referral or testing with EMG to determine whether the visible fasciculation is pathophysiologically induced or consciously induced.  Diagnostic specificity greatly assists the forensic examiner in assessing consistencies between patients’ subjective complaints, objective findings, special testing procedure, the history and review of records.  In the case discussed above, a referral to a neuroscientist for a consultation would be the prudent choice of options.

     Validating your opinions ensures that you remain the case-controlling physician and panel choice for a carrier.  For example if you’re EG report denotes fasciculation potentials, and a diagnosis of discogenic disease, you will have validating evidence that your care statistically eliminated the pain, suffering and functional impairment associated with slight to moderate cervical discogenic disease.21

     In summary when you review an EMG report and you note fasciculation potentials, you would think of discogenic disease, cord tumor, spinal stenosis, lower motor neuron disease, root sleeve tears, irritative root or peripheral nerve conditions, myopathies, a pancreatic adenoma with hyperinsulinism and ischemic necrosis of the articular facets or normal patients after exercise.2,3,4   As a general rule, fasciculation potentials indicate some disease that is occurring at the level of the nerve root, or in approximation with the vertebral motor unit.21

     In the event of a patient falling great distances especially when they land on their backs, or serious falls, if there are no broken bones yet the patient cannot move they may be suffering from spinal shock.  Any additional immediate shock to the central nervous system could hasten the impending onset of paraplegia.  In this case needle-electroneuromyographic testing in indicated.2

     Again these are serious situations and you must follow the American Medical Association tried and true historic guidelines for emergency incidents or situations, should serious impending complications be a consideration.21  Realize that fibrillation potentials may not appear for up to 10-21 days after an injury and may then persist until the muscle fibers become either reinnervated or replaced by developing fibroadipose tissue.4   Consequently, neuroscientific studies are indicated whenever the history suggests possibilities of spinal shock.  Fibrillation potentials, which are found in a neurologist’s report, can indicate crucial information necessary in correlating the correct diagnosis as well as expedient appropriate care.

     In Medical Neurodiagnostic Procedures Part 3 you will find a discussion on Motor conduction velocity studies and sensory nerve action potential studies as well as Somatosensory evoked responses. . 

By Scott D. Neff, DC DABCO ABDA DABFE CFE FFABS FFAAJTS