The American Association of Electrodiagnostic Medicine (AAEM) is committed to the development of sound and clinically relevant guidelines through review of literature, expert opinion and consensus. In 1979, with the assistance of its Professional Practice Committee and association leaders, the association published its initial guidelines, Guidelines in Electrodiagnostic Medicine, covering the practice of electrodiagnostic medicine. The committee is charged with ongoing revision of the document, as needed, and the current version includes standards of practice in clinical electromyography, risks in electrodiagnostic medicine, basic equipment requirements, and the role of paramedical support. In 1988, Educational Guidelines for Electrodiagnostic Training Programs (Appendix A) was prepared by the AAEM Training Program Committee and added to aid training program directors in establishing new training programs or in reviewing the current status of the educational aspects of existing programs. In 1986, the AAEM charged its Quality Assurance Committee with the responsibility for the development of guidelines pertinent to electrodiagnostic medical consultations. The impetus for the charge was the requests received from members of the AAEM and other interested parties for educational material on indications for and conduct of electrodiagnostic medical consultations. As a result of the committee’s efforts, Suggested Guidelines for Electrodiagnostic Medical Consultations (Appendix D), was published in 1989 and additional sections added subsequently. The current document includes (1) general indications for an electrodiagnostic medical consultation for patients with suspected myopathies, neuromuscular junction disorders, polyneuropathies, mononeuropathies, plexopathies, radiculopathies, neuronopathies and central nervous system disorders, (2) specific indications for patients with suspected lumbosacral or cervical radiculopathies, (3) general principles of electrodiagnostic studies, including techniques and diagnostic categories, and (4) an overview of electrodiagnostic studies for patients with suspected carpal tunnel syndrome, idiopathic polyneuritis, amyotrophic lateral sclerosis and myasthenia gravis. MUSCLE 81 NERVE 15:229-253 1992

GUIDELINES IN ELECTRODIAGNOSTIC MEDICINE AMERICAN ASSOCIATION OF ELECTRODIAGNOSTIC MEDICINE

PREFACE

The American Association of Electrodiagnostic Medicine (AAEM), originally the American Association of Electromyography and Electrodiagnosis, was founded in 1953 with the purpose expressed in its constitution “. . .to increase and extend as widely as possible the knowledge of electromyography and electrodiagnosis and to promote the professional association of those physicians most interested in electromyography and electrodiagnosis.”

Address reprint requests to American Association of Electrodiagnostic Medicine (formerly the American Association of Electromyography and Electrodiagnosis), 21 Second Street S . W , Suite 306, Rochester, MN 55902 O1992 American Association of Electrodiagnostic Medicine. Published by John Wiley 8. Sons, lnc

AAEM Guidelines in Electrodiagnostic Medicine

AAEM is now an association of over 2900 members pursuing these educational goals in three broad areas. The niajor effort is to increase members’ knowledge of the anatomy, neurophysiology, pathophysiology , instrumentation and procedures necessary to maximize the usefulness of clinical electromyographic and related neurophysiologic techniques in understanding neuromuscular disorders. This is accomplished through a wide range of AAEM publications and annual didactic programs, symposia, courses, and workshops. AAEM also seeks to inform its members of both basic and clinical research activities in electrodiagnosis of neuromuscular diseases through its annual meeting sessions, journal and other publications, videotapes, and journal abstracting service. In so doing, AAEM fosters the conduct and enhances the quality of this research.

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In addition, an annual examination is given by the American Board of Electrodiagnostic Medicine through which candidates and training program directors are able to assess their level of competence. This annual examination may be one means by which a candidate may qualify for a specific category of membership in AAEM; however, the AAEM is not itself a certifying organization. Finally, the AAEM is committed to the development of sound and clinically relevant guidelines through literature review, expert opinion and consensus of AAEM association leaders and committee members, as well as input from the general membership. Publication of these guidelines in Muscle L9 Nerve was then designed to facilitate review by AAEM members and other interested parties. Comments should be forwarded to the AAEM office. The association emphasizes that these guidelines are not to be understood or utilized as absolute requirements for training in electrodiagnostic medicine or for professional practice in electrodiagnostic medical laboratories. Training and practice among physicians are subject to a broad variety of private and governmental criteria including those with respect to medical education and residency, state licensing, medical association ethical standards, institutional practice boards, certification and accreditation systems, etc. These AAEM guidelines are informative suggested norms that are intended to complement and enhance the existing mechanisms for advancing the quality of medical training and practice. They embrace minimum criteria for appropriate educational training and for safe and effective medical practice; in many instances educators or practitioners may exceed the criteria. Medical training and practice are the responsibilities, first and foremost, of those providing the training or those engaging in the practice, respectively. The promulgation of these guidelines does not remove or replace that responsibility.

STANDARDS OF PRACTICE IN CLINICAL ELECTROMYOGRAPHY

The electrodiagnostic consultation consists of a clinical and electrophysiologic evaluation of the function of nerve roots, peripheral nerves, neuromuscular junctions, muscles, spinal reflexes, and evoked potentials arising from the spinal cord and brain. The term electromyography (EMG), strictly speaking, refers only to the needle or surface elec-

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trode examination of electric activity of muscles, but is often used to mean the entire spectrum of the electrodiagnosis of nerve and muscle diseases. EMG will be used here in both its broadest, as well as more specific, sense since it is unlikely that this terminology will be dropped from common usage; however, it should be noted that the needle or surface electrode electromyographic examination per se is only one component of a clinical electromyographic (electrodiagnostic) evaluation or consultation. Clinical EMG is an extension of the neurologic portion of the physical examination and requires detailed knowledge of the patient and his or her disease. Unlike many laboratory tests, EMG is not done in the same fashion every time but must be specifically designed for each individual patient. In addition, it is often necessary to modify or add to the procedure during the examination depending on the findings as they unfold. Only in this way can appropriate data be collected and the proper conclusions drawn. The depth of knowledge in clinical medicine necessary for this requires that the electromyographer be a physician with specialized training in electrodiagnostic medicine, so that the clinical EMG may be used to arrive at an accurate diagnosis preliminary to development of the best treatment plan. Improper performance or interpretation of the EMG may be dangerous to the patient and misleading to the referring physician. For example, the exact site and type of surgical operation performed on a patient may be determined in part by EMG findings of disease discovered during the course of an EMG examination. T h e physician’s knowledge of diseases and their manifestations is needed to properly interpret such results. In addition, EMG carries a small but real risk of transmitting possibly lethal diseases, such as hepatitis, Jakob-Creutzfeldt disease, or acquired immune deficiency syndrome, that can only be reliably identified by a physician. Further, some patients have additional risk-factors that require testing by a physician knowledgeable in the recognition and management of those problems. Such patients include those who require examination near major blood vessels or the abdomen or lung, are on anticoagulants, or have pacemakers, bleeding disorders, indwelling central venous or arterial lines, or undergone recent cardiac surgery for valve replacement. For these reasons EMG should be performed only by physicians fully trained in electrodiagnostic medicine. This position is endorsed by the American

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Medical Association, the American Hospital Association, the American Academy of Neurology, the American Neurological Association, the American Academy of Physical Medicine and Kehabilitation, and the Veterans Administration, as well as many state medical examining boards. It is hoped that these Guidelines i n Electrodingnostic Medicine will assist in the improvement of clinical EMG practice. If the standards set forth here cannot be met, it would be well to consider NOT operating an EMG laboratory.

Scope of Electromyography and Electrodiagnosis

'The electrodiagnostic medical consultation usually begins with the referral of a patient by a physician. The physician performing the consultation reviews the available referral information and medical record, takes a history, and performs a physical examination, paying particular attention to the neuromuscular system. S/he then formulates a diagnostic impression of the nature and extent of the problem and decides which electrodiagnostic tests are necessary. The testing procedure is dynamic rather than a rigidly performed ritual, and the electrodiagnostic tests may be changed if necessary during the course df the examination based on the abnormalities noted. This obviously requires broad knowledge of anatomy and pathology as well as familiarity with electrodiagnostic equipment. At the end of the study, the electrodiagnostic medical consultant must interpret the data and prepare a report for the referring physician which should include an anatomical diagnosis and a differential diagnosis. As can be seen, this constitutes a medical consultation in the traditional sense and clearly belongs to the standard practice of physicians. Specifically, the electrodiagnostic medical consultation consists of a diagnostic electrophysiologic evaluation of the function of the peripheral nervous system, as well as spinal reflexes and evoked potentials arising from the spinal cord and brain. The range of tests employed are many and include motor and sensory nerve conduction latency and velocity studies, invasive needle or surface electrode EMG, repetitive stimulation studies, reflex latency measurements, and measurements utilizing electronic averaging of evoked potentials. Other tests that may be performed in electrodiagnostic laboratories include twitch tension measurements, exercise tests, and evaluation of autonomic nervous system functions.

AAEM Guidelines in Electrodiagnostic Medicine

Qualifications Electrodfagnostic Medical ConSUltant

Clinical EMG is a medical consultation in the specialized area of neuromuscular diseases using electrophysiologic techniques. The electrodiagnostic medical consultant, therefore, must be a physician who has special training in the diagnosis and treatment of neuromuscular diseases and is also an expert in the application of particular neurophysiologic techniques to the study of these tlisorders. Training should include the basic sciences pertinent to the understanding of these diseases, as well as additional special knowledge of electrophysiologic techniques. T h c recommended educational requirements for the electrodiagnostic medical consultant are as follows: 1. Completion of an approved (AMA, American Board of Medical Specialties) postgraduate medical specialty training program in neurology, physical medicine and rehabilitation, or their equivalent, that has included accredited academic training in: a. Anatomy of peripheral and trunk niusculature and of the peripheral and central nervous systems. b. Physiology of muscle and the peripheral and central nervous systems. c. Pathology of peripheral nerve and muscle. d . Clinical aspects of neurologic, neuromuscular, and musculoskeletal disorders, including their diagnosis and treatment. e. Electrophysiology, including knowledge o f I . Applied electronics. 2. Instrumentation. 3 . Nerve conduction studies. 4. Needle EMG, including motor unit analysis, motor unit recruitment and firing rates. 5. Neuroniuscular junction testing, including repetitive stimulation and single fiber EMG. 6. Somatosensory evoked potentials. f. Ethics of practice of electrodiagnostic medicine as related to test utilization and the economics o f practice. g. T h e epidemiology of infectious diseases as they relate to the EMG laboratory. h. Use of statistics as related to EMG including development and use of normal values. These requirements are met by completing three or more years of postdoctoral training in neurology or physical medicine and rehabilitation. I

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2. A period of preceptorship in electrodiagnostic medicine that combines clinical and didactic material and is directly supervised by an electrodiagnostic medical consultant who is committed to teaching and has the necessary knowledge, skills, and experience. This period of preceptorship should be at least six months full-time or equivalent. The first three months should be rigidly structured and supervised. During the entire training period, at least 200 patients should be examined; the studies should be documented and interpreted, and include representative neuromuscular disorders in adults and children, such as, neuropathies, myopathies, radiculopathies, neuromuscular junction, spinal cord and brain disorders. It is recommended that the laboratory be in an institution that has an approved residency training program in neurology and/or physical medicine and rehabilitation. The preceptorship may be taken during or after an approved medical specialty training program. Since a variety of clinical experiences is needed in order to become a competent electrodiagnostic medical consultant, institutions may vary in their ability to provide training in all areas. Arrangements with other institutions providing the appropriate training may be necessary, although the primary training institution (laboratory) and the chief electrodiagnostic medical consultant must assume overall responsibility for adequate training. An AAEM document, “Educational Guidelines for Electrodiagnostic Training Programs,” has been developed to assist directors in reviewing their programs, if desired (see Appendix A). 3 . Competency in electrodiagnostic medicine can only be achieved with at least one more year performing and interpreting electromyographic examinations on an additional 200 or more patients. This period of independent experience must begin after completion of the preceptorship. The year of independent experience may be part of a postresidency program when the candidate is given primary responsibility for the electrodiagnostic evaluation, interpretation of the results, and preparation of the electromyographic reports.

EMG Laboratory Directors

T o help insure standardization of procedures and normal values, diagnostic EMG and nerve conduction studies should be performed, where

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feasible, in a single electrodiagnostic laboratory in any one hospital. Although a number of electrodiagnostic medical consultants, as well as paramedical personnel may work at such a laboratory, it should be under the direction of an actively practicing electrodiagnostic medical consultant.’ T h e minimal qualifications for the director of an EMG laboratory include the qualifications for an electrodiagnostic medical consultant as outlined. Ideally, the director should have training and experience, beyond the minimal qualifications, in the evaluation of the full spectrum of neuromuscular diseases. To insure that at least minimal standards have been met, certification by an examining Board in electrodiagnostic medicine is also strongly recommended. It is expected that the directors of large EMG laboratories in university centers and large metropolitan hospitals would have even more comprehensive training and experience in light of their greater responsibility as referral centers.

Laboratory Organization

The laboratory director should have direct control over the selection of all laboratory personnel, including other staff and technicians, and control over selection of equipment, normal values, and procedures offered as clinical services. All needle EMG should be performed under the direction of a qualified electrodiagnostic medical consultant as described under Qualifications, and the reports prepared by the electrodiagnostic medical consultant as described under Reports. While it is permissible for a technician to assist an electrodiagnostic medical consultant in performing nerve conduction studies, under no circumstances should a technician, regardless of qualifications or experience, perform needle EMG examinations. Somatosensory evoked potential (SEP) testing requires supervision by, but not the direct presence of, an electrodiagnostic medical consultant trained in its use. T h e electrodiagnostic medical consultant supervising the SEP study has the responsibility for insuring appropriate technique and for planning, modifying, and interpreting the study. When SEP testing is performed during surgery, the electrodiagnostic medical consultant must be available during those critical portions of the surgical procedure that require immediate interpretation of results.

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Reports and Records Reports

A written report should be prepared promptly. The report should include: 1. Identification of the patient. 2. Statement of the problem and the indication for the study. 3. Description of the findings. 4. Statement of the normality or abnormality of these findings. 5. Clinical correlation and diagnostic conclusions. The statement of the problem should include at least a brief description of symptoms and clinical signs, as well as the clinical diagnosis and problem that was elucidated by the study. The report of the findings should contain a description of the nerve conduction studies and evoked potential tests conducted, including the limb temperature (if outside of normal range), sites of stimulation and recording, amplitudes of responses, configuration, latencies, and distances or velocities. For late responses, limb length or body height should be measured. For repetitive stimulation tests, measurements should be those described in standard texts.y”6”s The method of measuring, for example, peak-to-peak or baselineto-negative peak, should be mentioned. Technical problems, such as local swelling or deformity, should be recorded. In reporting needle electromyographic studies, the type of needle electrode should be specified, and the data should be quantified according to currently accepted standards.* Insertional activity, spontaneous activity, and parameters of motor unit action potentials, such as, amplitudes, durations, form, and recruitment pattern, should be recorded and quantified when indicated. In single fiber EMG, accepted methods of This should endescription should be able another electrodiagnostic medical consultant to interpret the tests or make a comparison with prior and subsequent tests. The statement regarding the normality or abnormality of the findings should be directed to the referring physician and be as succinct as possible. It should include a statement regarding the degree and significance of‘the abnormalities. Sometimes a list of normal values may be included. This is particularly important in nerve conduction studies of children. The diagnostic conclusion should attempt to explain how the findings of the electrical tests fit, or do not fit, the clinical picture. In many instances, EMG can be diagnostic of a definite ana-

AAEM Guidelines in Electrodiagnostic Medicine

tomic or physiologic abnormality but not of a definite clinical disease. In such cases, a differential diagnosis should be offered. When the referring diagnosis is at odds with EMG findings, possible reasons for the discrepancy should be mentioned, including clinical findings elicited by the electrodiagnostic medical consultant. The electrodiagnostic medical consultant may inform the patient of the findings of the examination. Suggestions for changes in clinical management should be made to the referring physician and should not be discussed with the patient unless the referring physician has requested that the electrodiagnostic medical consultant participate in clinical management. Records

Records should be kept and filed in an easily retrievable manner. When practical, tracings or photographic samples of data may be kept for future reference or for comparison with subsequent examinations. Referring physicians have the right, and may delegate the right, to examine any records of EMGs pertaining to their own patients. In addition, patients’ written requests that reports be sent to appropriate outside physicians and other parties, including attorneys and insurance companies, should be promptly honored if the request is in accordance with state law. Ethical Issues

The AAEM subscribes to the Principles of Medical Ethics as adopted by the American Medical Association in 1980 (Appendix B). The behavior and/or practice of its members are expected to be in conformity with such principles. The purpose of the electrodiagnostic consultation should be explained to the patient together with the nature of the procedures to be carried out. In conformity with existing standards of practice, written informed consent documents are not ordinarily necessary. If reasonable explanation fails to elicit a patient’s consent to carry out the electrodiagnostic consultation, the electrodiagnostic medical consultant should not undertake or continue the evaluation. If any procedure is to be undertaken that entails more risk than usual, it is necessary to so inform the patient and obtain his consent before undertaking that procedure. Written informed consent documents may be necessary in circumstances of experimental or investigational studies of procedures, pharmaceuticals or medical devices using human subjects if required

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by the study protocol or Institutional Review Board. Electrodiagnostic medical consultants must perform needle electromyographic examinations personally and not delegate these examinations to technicians or others who are not electrodiagnostic medical consultants. If a technician performs the nerve conduction examination, the supervising electrodiagnostic medical consultant has the ultimate responsibility for the procedure and must be involved in the pretest evaluation of the patient and the plan of study. The electrodiagnostic medical consultant must be readily available and must promptly review and evaluate the results of such testing. The electrodiagnostic consultation should address the issues involved for a reasonable differential diagnosis and be pertinent and thorough but neither excessive nor superficial. Fees should be reasonable, commensurate with the difficulty of the study, time involved, and number of procedures performed. Disclosure of fees should be made upon the request of a patient or referring physician. RISKS IN ELECTRODIAGNOSTIC MEDICINE

When electrodiagnostic tests are performed on patients with certain underlying medical conditions, untoward effects can result. For example, when doing needle EMG in patients with cardiac valvular disease, consideration may be given to prescribing antibiotic coverage similar to that prescribed for dental procedures. Guidelines follow for approaching some commonly encountered problems. Disturbances in Hemostasis

Patients who are receiving antiplatelet or anticoagulant therapy, or who suffer from thrombocytopenia or clotting factor deficiencies, may be referred for electromyographic testing. Each case should be considered individually regarding the potential benefits of the study relative to the risks of intramuscular hemorrhage or other bleeding. (There is only one report of bleeding complications secondary to electromyography. The patient was a 64-year-old man with a prothrombin time of 23112.4 and partial thromboplastin time of 68/26; platelet count was 334,000. The hematocrit dropped from 43% to 29% due to subcutaneous bleeding secondary to the electromyographic exa m i n a t i ~ n . ~The ) risk of bleeding is increased when the platelet count is less than 50,000 per cubic mm, when the prothrombin time is more than

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1V2 to 2 times the control value, and when intravenous heparin therapy is administered so that the partial thromboplastin time is greater than the 1% to 2 times control values. If the decision is made to perform a needle EMG in such a patient, it is advisable to first examine the small, superficial muscles and to watch for bleeding problems. Prolonged pressure over the needle site will usually produce hemostasis. The needle EMG examination should be avoided in patients with hemophilia and other disorders of coagulation unless clotting functions have first been appropriately corrected.'' Transmissible Diseases

Common and acceptable methods of needle sterilization to prevent contamination by most viral and bacterial agents include autoclaving under pressure, boiling, glass bead sterilization, and gas sterilization. Of these methods, only autoclaving is currently recommended for the treatment of needle electrodes used for patients diagnosed or suspected of having Jakob-Creutzfeldt disease or infectious hepatitis, since the efficacy of the other methods mentioned has not been demonstrated for these conditions. The electromyographer has the responsibility to inform hidher assistants, students, technicians, and other staff, that slhe is potentially being exposed to infectious agents (more detailed information follows). Jakob-Creutzfeldt Disease

The transmissible agent that causes JakobCreutzfeldt disease is highly infective and resistant to sterilization by conventional means. It is therefore essential that needles used for any patient who is clinically suspected of having this disease be discarded. Before being discarded, needles as well as any blood-contaminated material from such patients should be autoclaved at 121°C at 15 pounds of pressure per square inch for 60-90 minutes or incinerated l o to prevent contamination of ancillary personnel. At the time of preparation of these guidelines, no cases of Jakob-Creutzfeldt disease transmitted via an EMG needle have been reported. Hepat/t/s

Disposable needles may be used if appropriate disposal procedures are followed, or nondisposable needles may be reused after adequate sterilization. EMG needles that have been used on patients who are suspected or known to have infectious hepatitis should be sterilized at 121°C at

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15 pounds of pressure per square inch for 15 minutes.5 These procedures are important to control percutaneous spread of hepatitis. In addition, electromyographers should also follow the selfprotective procedures described in the "Universal Precautions" published by the Centers for Disease Control in the Morbidity and Mortality Weekly Report. Human Immunodeficiency Virus

Human immunodeficiency virus (HIV) may be a risk to the electrodiagnostic medical consultant during the electrodiagnostic examination and to laboratory personnel handling needles used on patients infected with the virus.6 EMG testing is not contraindicated, however, in patients who have HIV. Since this virus can be transmitted through blood or other body fluids, direct contact of the examiner with blood and body fluids, mucous membranes, or nonintact skin of all patients should be avoided. Skin fluids produced during the preparation of the skin for somatosensory evoked potential (SEP) studies could be infectious. Gloves should be worn when performing potential invasive procedures and skin preparation for SEP studies. Hands should be washed immediately if contaminated. Care must be taken to avoid accidental wounds from EMG needles contaminated with blood. Blood-contaminated materials should be placed in a prominently labeled container and reprocessed or disposed of according to hospital policy for the handling of hepatitis B virus-contaminated items and other infectious wastes. Needles may routinely be reused without risk of transmission of the HIV virus to subsequent patients, if standard disinfection protocols are followed after chemical treatment. For exaniple, viral infectivity is undetectable within 1 minute with 0.5% sodium hypochlorite, 70% alcohol, or 0.5% nonidet-P40, and within 10 minutes with 0.08% quaternary ammoniumchloride or with a 1 : 1 mixture of acet~ne-alcohol.'~~'~ A recommended reference for additional infection control guidelines is "Universal Precautions" published by the Centers for Disease Control in the Morbidity and Mortality Weekly Report. Cardiac Pacemakers

EMG and nerve conduction studies using percutaneous nerve stimulation may be performed in patients with implanted cardiac pacemakers with little risk. " Special care, however, should be given to proper grounding of the patient. In general,

AAEM Guidelines in Electrodiagnostic Medicine

the closer the stimulation site is to the pacemaker and pacing leads, the greater the chance for inducing a voltage of sufficient amplitude to inhibit the pacemaker. A stimulator, therefore, should be used only with extreme caution if it is necessary to stimulate the brachial plexus ipsilateral to the pacemaker implantation site.3o In patients with external cardiac pacemakers, the conductive lead, inserted into the heart (usually transvenously) and connected to the external cardiac pacemaker, presents a serious potential hazard of electrical injury to the heart. Nerve conduction studies are not recommended in any patient with an external conductive lead terminating in or near the heart. Electrically Sensitive Patients

T h e critically ill patient is at particular risk for electrical injury from smaller than usual currents because certain protective factors may not be operative. There are two important defenses against electrical injury which are frequently lost in these patients. First, the high skin resistance provided by dry, intact skin is often breached by intravenous and intra-arterial catheters with leakage and spills around the catheter site. With lowered resistance, current applied in these areas will be conducted more efficiently to the rest of the body, including the heart.7"22'5220 Two common sources of current which might affect the hospitalized patient are leakage current from attached electrical equipment and applied current from stimulators as part of electrodiagnostic machines. Complications from the latter can be avoided by refraining from stimulating next to areas with percutaneous catheters and especially avoiding areas where there is leakage of fluid. Leakage current is current which leaks to the instrument chassis which then can be delivered to the connected patient if improper grounding conditions exist. T h e minimum current allowed to leak from the case is 100 pA and 50 pA from patient connections."*",28 In electrically sensitive patients, lower leakage limits (20 PA) are recommended.2.".'6 It is the responsibility of the electromyographer to insure the particular machine in use meets these minimum specifications. Providing proper patient grounding is necessary to protect patients from electrical injury. The third ground wire is required on all electrical equipment for patient use because this provides a harmless route for any chassis leakage current to avoid going to the patient by flowing directly to ground. Testing of the third ground wire integrity

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and outlet grounds should be performed at regular intervals.26 When patients are connected to multiple machines, special safety considerations arise. Defects in outlet grounds or ground faults may occur in individual outlets. Thus, if a person is connected to equipment supplied from different outlets, one with a functioning ground, the other nonfunctional, leakage current may flow from the machine connected to the outlet with the nonfunctional ground, through the patient into the outlet with the functioning ground wire of lower voltage. Thus, it is recommended that the patient be disconnected from all nonessential electrical equipment. The remaining equipment should be plugged into the same outlet or, at least, outlets in the same vicinity which are likely to share a common ground. When using EMG equipment, it is recommended that the ground be placed between the stimulator and the recording electrodes, as well as keeping ground and needle electrodes in close proximity. This helps insure that any leakage current or applied current will return to ground and not spread to the rest of the body. The second important protection against electrical injury is the large volume of soft tissue which surrounds the heart (i.e., the trunk) and dilutes any electrical current applied to the body, protecting the heart from direct electrical current application. In the critically ill patient, intracardiac catheters are now commonplace. Such catheters bypass this large electrical sink and provide small, usually harmless currents, direct access to the immediate vicinity of the heart, making them potentially lethal (microshock). Most manufacturers make intracardiac devices electrically isolated so that they will not conduct electricity. T h e same attention, however, must be given to these catheters as to other percutaneous catheters; for example, stimulation in the immediate vicinity of the catheter should be avoided and should never be done in the presence of fluid spills or leakage. i f proper attention is given to equipment leakage current, grounding, and location and type of percutaneous catheters, electrodiagnostic testing of the electrically sensitive patient can be performed without risk.

Chest Wall and Abdominal Musculature EMG

At times, needle nerve stimulation or EMG of intercostal muscles or muscles in the supraclavicu-

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lar region, supraspinatus muscles, or paraspinal muscles (cervical or thoracic) may be indicated. Because of the proximity of these nerves and muscles to the pleura and lung, pneumothorax is a complication that may occur if the needle penetrates these structures. One must use clinicaljudgment to decide if the value of the data to be obtained is greater than the risk of producing a pneumothorax. 13*23 Peritonitis is a potential hazard following inadvertent penetration of the peritoneum during intercostal or abdominal muscle EMG.

Other Problems

In certain circumstances, the performance of EMG or nerve conduction studies may lead to an increased incidence of untoward effects or erroneous results. These may include a patient who is agitated and unable to cooperate, a patient with a very recent myocardial infarction, a patient with hyperesthesia, or a patient with a neuromuscular problem in an edematous limb. Clinical judgment in each individual circumstance should be used in deciding if the risk of complication is greater than the value of the information to be obtained from an electrodiagnostic evaluation. In the vast majority of cases, it makes no difference if the skin is prepared prior to needle insertion; however, alcohol is a simple, rapid, and effective antiseptic to use. The disadvantage of the stinging discomfort that may occur with alcohol preparation of the skin must be weighed against possible advantages. Most importantly, areas of the skin which are obviously dirty or contaminated must be cleaned with soap and water prior to any studies or preparation with alcohol.

EQUIPMENT

In general, an EMG instrument must fulfill two requirements: (1) that it be accurate in making required measurements, and (2) that it be safe.” T h e electrical activity recorded in a standard clinical EMG examination varies widely in several important characteristics, and the EMG instrument must be capable of accurately reproducing this activity in all circumstances. T h e clinical EMG examination typically consists of measurements of motor and sensory nerve conduction and recording of spontaneous and voluntary activity from muscles. Specialized techniques in common use include signal averaging of evoked responses generated from central struc-

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tures to peripheral stimulation and single fiber EMG. Each technique requires different stimulating and recording characteristics. T h e EMG instrument must be capable of recording and accurately reproducing electrical signals that range from submicrovolt levels to greater than 10 mV. Gain settings should be available to make recordings over this 10,000-fold range. T h e frequency spectrum of EMG signals may vary over a range from 2 Hz to 20 kHz, and specific applications may emphasize particular frequency bands. The instrument should have either adjustable lowand high-frequency cutoffs or present filter settings that are appropriate for the types of electrical activities studied. An important component of any EMG instrument should be a volumecontrolled loudspeaker for auditory monitoring of EMG activity. Since the measurement of the time of occurrence of specific electrical events is crucial for accurate EMG recording, the machine should be equipped with an accurate time-base generator and controls for a range of sweep durations from less that 10 ms to 1 second. A number of different options are available for display of the electrical signals which allow for accurate measurements of time. Among these are the following: a moveable time index, electronic storage for displays from digital memory, permanent recording on heatsensitive paper, photographic film, or any system that allows accurate reproduction of the signals on paper. An electrical nerve stimulator should be an integral component of the EMG instrument. T h e stimulator should have the capability of delivering either single or repetitive stimuli. Each electrodiagnostic medical consultant must select the instrument that provides the most appropriate pattern of repetitive stimulation for a given laboratory. Stimulators are available that deliver either constant current or constant voltage stimuli, and there is no consensus among electrodiagnostic medical consultants as to the preferred type. T h e stimulator, however, should be capable of delivering a stimulus of variable intensity and duration and should have separate controls for each. Any electrical equipment used in the examination of human subjects should fulfill minimum electrical specifications. Underwriters Laboratories has set standards for the amount of allowable leakage current for medical and dental equipment.28 Any equipment used in an EMG laboratory should conform to these standards and be regularly checked to maintain electrical safety.

AAEM Guidelines in Electrodiagnostic Medicine

The electrodiagnostic medical consultant is responsible for insuring that EMG equipment is not used in an electrically hazardous manner. Ungrounded devices should not be used in a patient area, and liquid spillage near any instrument should be promptly removed to avoid highleakage current flow.

PARAMEDICAL SUPPORT

Many clinical neurophysiology laboratories utilize technical assistants to improve the efficiency of operation. Laboratories performing more than a minimal number of evoked potential tests find such help essential. A technician must always work under the supervision and direction of an electrodiagnostic medical consultant fully trained in EMG as defined by the guidelines of the AAEM. The electrodiagnostic medical consultant will be responsible for planning and interpretation of electrodiagnostic studies, but a technician may perform a variety of functions and tests in the laboratory depending on the level of training and experience (Appendix C). A trainee should have at least a high school diploma and will require onthe-job training in the apparatus used, in human anatomy, physiology, nerve conduction responses and in the range of disorders commonly studied. There is also a place for technologists with a much more advanced educational level. A technician should be able to establish good rapport with patients and staff and be able to deal with severely ill patients. S/he should be able to instruct the patient in the tests to be conducted, prepare the patient, apply surface electrodes, make accurate measurements, keep the equipment in good condition, file, and retrieve reports. With suitable training the technician may perform a variety of nerve conduction studies, reflex studies, repetitive Stimulation tests and evoked potential tests. T h e results of such tests must be recorded adequately for review by the electrodiagnostic medical consultant. The electrodiagnostic medical consultant must be available to review any problems that develop during the nerve conduction studies. A senior technologist may have responsibility for work assignment, in-service training and instruction of junior personnel. Acquisition of knowledge and skills should be demonstrated through oral, written and practical examinations. Such examinations are provided by the American Association of Electrodiagnostic Technologists and

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the Canadian Society of Clinical Neurophysiologists. For the reasons discussed earlier in these guidelines, only the electrodiagnostic medical con-

sultant should insert needle electrodes used for recording through the skin of patients into subcutaneous tissue, muscles, the vicinity of nerves or other deep structures.

REFERENCES 1. Accreditation Council for Graduate Medical Kducation: Dirrcloiy of Graduutr Mrdical Educntion Progrg-rcim.~ Chicago, Accreditation Council for Graduate Medical Education, 1987;

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