Standards for quantification of EMG and neurography

Deriving pediatric nerve conduction normal values in the very young (<3 years)

OBJECTIVE

This work describes our efforts to obtain nerve conduction studies normal values in a pediatric cohort between birth and 3 years of age using the extrapolated norms or e-norms method. Interpretation of these studies poses major challenges when no reliable normal values can be found in the literature.

METHODS

The e-norms method was used to derive a reference range of upper and lower extremity sensory and motor nerve conductions normal values from a pediatric cohort referred to an EMG Laboratory for nerve conduction studies.

RESULTS

E-norms were calculated for Median, Ulnar, Superficial Peroneal, Sural, and Medial Plantar sensory studies, and for Median, Ulnar, Peroneal, and Tibial motor studies.

CONCLUSIONS

Pediatric electrodiagnostic testing is a very challenging undertaking. The ability to obtain and use normal values from the neurophysiologist's own referral pool adds great value to their diagnostic work-up.

SIGNIFICANCE

EMG and nerve conduction studies can yield invaluable information in the diagnostic work-up of young infants. Using the e-norms method improves on the analysis and interpretation of electrophysiological studies in this age group.

Evidence-based recommendations for examination and diagnostic strategies of polyneuropathy electrodiagnosis

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The best approach for electrodiagnosis of polyneuropathy (PNP) were tested in 313 patients.

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Electrodiagnostic screening for distal symmetric PNP (DSP) should start with tibial and sural NCS.

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Examination of lower limbs at one side is sufficient for electrodiagnostic screening of DSP.

The purpose of this report is to recommend evidence-based strategies for polyneuropathy (PNP) electrodiagnosis based on a large cohort of patients examined prospectively. Nerve conduction studies (NCS) of bilateral tibial, peroneal and sural nerves, the latter with both near-nerve-technique (NNT) and surface recordings, were done in 313 patients with clinically suspected PNP. Bilateral dorsal sural and medial plantar nerves, and unilateral median and ulnar nerves were further examined in a subgroup of patients. The final clinical diagnosis retrieved from the patientś medical records 1–6 years after the neurophysiological investigation served as diagnostic reference standard. The clinical follow-up diagnosis confirmed PNP in 219 patients. The tibial nerve was the most sensitive nerve (75%), with prolonged tibial F-wave as the most sensitive parameter (72%). Sural NNT recordings were more sensitive (66%) than surface recordings (49%) (p < 0.05), however, dorsal sural (68%) and medial planter (70%) nerves had similar sensitivities as NNT. There was no side difference in the incidence of abnormality for any nerve.

Based on these results, we recommend a strategy starting with tibial and sural NCS on one side for electrophysiological screening for distal symmetric PNP. If one of these is abnormal, we recommend examining the other lower and upper extremity nerves, including distal sensory nerves, particularly if NNT is not applicable. While one abnormal parameter is sufficient to interpret a nerve as abnormal, we recommend at least two abnormal nerves for PNP diagnosis, preferentially one being the sural nerve.

We believe that the strategies recommended in this study may improve PNP electrodiagnosis.

Standards of instrumentation of EMG

Standardization of Electromyography (EMG) instrumentation is of particular importance to ensure high quality recordings. This consensus report on "Standards of Instrumentation of EMG" is an update and extension of the earlier IFCN Guidelines published in 1999. First, a panel of experts in different fields from different geographical distributions was invited to submit a section on their particular interest and expertise. Then, the merged document was circulated for comments and edits until a consensus emerged. The first sections in this document cover technical aspects such as instrumentation, EMG hardware and software including amplifiers and filters, digital signal analysis and instrumentation settings. Other sections cover the topics such as temporary storage, trigger and delay line, averaging, electrode types, stimulation techniques for optimal and standardised EMG examinations, and the artefacts electromyographers may face and safety rules they should follow. Finally, storage of data and databases, report generators and external communication are summarized.