Reporting the Results of Nerve Conduction Studies and Needle EMG
Nerve conduction studies (NCSs) and needle electromyography (EMG) performed by a physician (MD or DO) with the appropriate education, training, and experience are used to evaluate patients with neuromuscular (NM) diseases and diagnose the presence, distribution, and severity of nerve, NM junction, and muscle pathology. 1 After NCSs and needle EMG are completed, it is necessary to prepare a written report of the test results. This report serves as a communication tool to the referring physician and documents the results and conclusions of the electrodiagnostic (EDX) evaluation.
This educational document created by the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) addresses the following two key clinical questions.
The AANEM’s goal in publishing this report is to provide practicing EDX physicians with recommendations for presenting data in their reports. It is not intended to require that all of these recommendations must be included in a report.
The EDX examination of a patient is structured to answer specific clinical questions. 2 The physician performing the examination (1) determines the initial tests to perform based on his or her education, training, and experience, and the patient’s history and physical examination, and then (2) modifies the tests as data (visual and auditory) is obtained and analyzed in real time. When finished, the physician composes a report summarizing the data and providing the diagnostic conclusions which are determined by integrating the analysis of the tests results with the findings on the history and physical examination.3 This integration process must occur concurrent to the performance of the studies and be performed by the interpreting physician at the time of testing, guiding both nerve and muscle selection.4 Due to these requirements, the interpretation of the studies cannot be performed by a physician who is offsite.
This document addresses the presentation of the data in the EMG/NCS report. It does not address the correct analysis of the EMG/NCS data necessary to provide an accurate diagnosis. Therefore, a physician who follows all of these recommendations may still document an inaccurate diagnosis. Furthermore, a physician may establish an accurate diagnosis without following all of these recommendations.
The presentation of the data is an essential part of the EDX examination. A model report should include a description of the patient’s clinical problem, the EDX tests performed, all relevant data derived from these tests, and the diagnostic interpretation of the data. The report permits (1) a review of the results by other physicians evaluating and treating the patient, and (2) comparison of these results to past and future test results. If, upon completion of testing, the physician provides only a conclusion without supporting data, it is difficult for other physicians treating the patient to determine (1) whether the test data support the conclusions, and (2) whether the identified NM disorder is stable, improving, or worsening based upon a comparison with previous and/or subsequent test results.
It is important to perform and document accurately the findings of the NCS and needle EMG examination to realize the full potential of the tests and to reduce the possible need for the patient to undergo repeated testing. These two goals are desirable because a needle EMG study is an invasive test and because both the needle EMG and NCS examination may be uncomfortable.
Providing complete NCS measurements is important. The name of each nerve tested, right or left side designation, site of stimulation, site of pickup, and distance over which the NCS was performed should be included in the data for NCSs. A quality report presents NCS data with amplitude and latency measurements. These response parameters must occur in a real-time fashion to facilitate interpretation. Amplitude measurements are important for the identification of nerve conduction block, axonal nerve pathology, and muscle pathology, and for prognostication. Latency measurements are important for determining the speed of nerve conduction in the area tested. Clearly identifying the segment over which the conduction velocity is calculated is essential for the localization of focal nerve pathology, when present. In addition to the aforementioned numerical data, including NCS waveforms within the report provides reviewing physicians the ability to ensure the quality of the study. Raw measurement data obtained and transmitted trans-telephonically, over the Internet or by other electronic means with delayed interpretation do not meet the “real time” requirement and so do not comprise quality studies.
The determination of normality is best made by the physician performing the test, taking into consideration all of the relevant clinical information. Inclusion of this information in the report is important to assist others in the proper interpretation of the data. Options include providing normal (reference) values for NCSs and criteria for abnormalities in the report, or citing appropriate reference material upon which normal values are based, which allow the reader of the report to verify why specific test data were designated as normal or abnormal. However, this designation of abnormalities depends upon several patient variables including: age, height, weight, and limb temperature during testing which are not always included in reference values. Clinical variables including, but not limited to, underlying medical conditions and prior surgeries also have an impact on whether a finding is considered normal or abnormal. The definition of normal can also vary between laboratories. The diagnostic interpretation of the needle EMG and NCS data is an integral part of the EDX examination. The diagnostic determination that the needle EMG findings are normal or abnormal occurs during the test in real time. Due to technical limitations, there is generally no complete, permanent record of the EMG waveforms analyzed during the test. Documenting in the report both the spontaneous and voluntary activity in each muscle examined with the needle EMG electrode is therefore extremely important.
Presenting the needle EMG examination findings in a way that incorporates the following data (preferably in a tabular format) makes the report easier to understand. The report should include (1) the name and side (left or right) of each muscle examined, (2) a description of insertional activity, (3) the presence or absence of abnormal spontaneous activity, and (4) assessment of the potentials generated with voluntary activity. For voluntary activity, both the morphology and the recruitment of the motor units should be described. Spontaneous and voluntary activity observed during the needle EMG examination should be reported as normal or abnormal and, if the activity is identified as abnormal, the specific abnormalities should be described in detail.
Descriptions of the findings on the needle EMG examination such as “needle EMG studies of the right upper limb muscles were normal” are not helpful. It is essential to list the specific muscles examined. Without a list of the exact muscles tested, it is impossible to determine whether the examination was adequate to evaluate the clinical problem. Tables of the findings on needle EMG examination, in contrast to narrative reports, make it easier to identify the distribution and relative severity of needle EMG abnormalities in the muscles examined. Physicians therefore may find it beneficial to list findings in a tabular format with an additional narrative description of abnormalities.
The EDX report should include the name of the individuals who performed and interpreted the study. The needle EMG examination must be performed by a physician specially trained in EDX medicine, as these tests are simultaneously performed and interpreted. When the entire examination is performed by one physician, the physician’s name should be clearly identified on the report with an appropriate signature. Some laboratories have appropriately trained NCS technologists who perform NCSs under the direction of the EDX physician. In these cases, the physician must be on-site, evaluate the patient, determine the testing to be performed, and oversee and add NCSs as deemed necessary to provide a quality test. The name of the technologist and the physician should both be included on the report, along with the signature of the physician. In cases involving a resident or fellow, the name of the trainee should also be included.
AANEM EDX Laboratory Accreditation has been introduced to provide a voluntary peer review process to ensure quality EDX testing for patients. Accreditation acknowledges EDX laboratories for achieving and meeting a level of quality, performance, and integrity based on professional standards. Accreditation provides laboratories specializing in EDX medicine with a structured mechanism to assess, evaluate, and improve the quality of care provided to their patients. Laboratories that have attained accreditation or accreditation with exemplary status should include this status on their EDX reports.
EDX testing requires the use of instruments designed to meet minimum requirements in order to provide the amplitude, latency, and configuration of the waveform data needed to make a diagnosis. 5 Some devices do not meet these requirements. Including the make and model of the EDX instrument utilized demonstrates that an appropriate device was used.
Below are specific recommendations and options for information to include in an EMG and NCS report. These recommendations do not preclude other reasonable methods of presenting EDX data. AANEM has developed a Model report that follows the recommendations and options in this document.
SPECIFIC RECOMMENDATIONS FOR REPORTING NCS AND NEEDLE EMG RESULTS
A. Description of Patient Data and the Clinical Problem Section
B. Nerve Conduction Studies Section
Specific details of the NCS procedures, including the techniques utilized, distances, laboratory reference values, and temperature monitoring may be best included in the report or referenced in a standard operating procedure manual maintained by the laboratory.
C. Needle Electromyography Section
D. Summary Section
E. Diagnostic Interpretation Section
G. AANEM Laboratory Accreditation
H. EDX Instruments
- AANEM. Recommended policy for electrodiagnostic studies.
- Dumitru D, Zwarts MJ. The electrodiagnostic medicine consultation: approach and report generation. In: Dumitru D, Amato AA, Zwarts MJ, editors. Electrodiagnostic medicine, 2nd ed. Philadelphia: Hanley & Belfus; 2002. p 515–540.
- AANEM. Proper Performance and Interpretation of Electrodiagnostic Studies.
- AANEM. Definition of Real Time Onsite
- AANEM. Electrodiagnostic Study Instrument Design Requirements.
(Links to AANEM position statements above are to the most recent version of the document.)
Creation of New Guidelines, Consensus Statements, or Position PapersAANEM members are encouraged to submit ideas for papers that can improve the understanding of the field. The AANEM will review nominated topics on the basis of the following criteria:
- Members’ needs
- Prevalence of condition
- Health impact of condition for the individual and others
- Socioeconomic impact
- Extent of practice variation
- Quality of available evidence
- External constraints on practice
- Urgency for evaluation of new practice technology