LECTURE
Interpreting Electrodiagnostic Studies for the Management of Nerve Injuries

Authors: Mackinnon SE1, Yee A1
Published: September 22, 2021

Author Information
1Division of Plastic and Reconstructive Surgery, Washington University, St. Louis, Missouri

Standard Edition (201012.201012)
Extended Edition (201012.201012)

ABSTRACT
The accurate interpretation of electrodiagnostic studies (EDX) for nerve injuries is critical for determining appropriate management and achieving optimal outcomes. In this lecture, we build the foundations for understanding nerve classification of nerve injuries and review nerve conduction studies and electromyography. Furthermore, the concept of timerelated changes to electrodiagnostic findings from the degree and timing of nerve injuries is presented with case studies.

KEYWORDS
Nerve classification, nerve injuries, electrodiagnostic studies, nerve conduction studies, electromyography

TABLE OF CONTENTS
00:00 Introduction
00:23 Classification of Nerve Injuries
03:38 Rate of Recovery from Ischemic, Demyelination, Axonal, and Mixed Injuries
06:04 Referring EDX Reports
07:11 Electrodiagnostic Studies
07:30 Nerve Conduction Studies
07:40 Conduction Velocity
08:01 Amplitude
08:27 Conduction Block
10:25 Electromyography (EMG)
10:45 Spontaneous Activity
11:18 Fibrillations and Positive Sharp Waves
14:03 Insertional Activity
14:46 Motor Unit Action Potentials (MUPs)
16:50 Normal MUPs
17:01 Acute MUPs (Collateral Sprouting vs. Nascent Axonal Regeneration)
19:21 Chronic MUPs
19:43 EMG Findings for Complete and Mixed Fascicular Injuries
21:04 Percent Denervation for Functional Loss
22:25 Concept of Supercharge Nerve Transfers for Mixed Injuries
23:22 Surgical Management for Classification of Nerve Injuries
24:40 Management Review of Neurapraxia, Axonotmesis, and Neurotmesis Injuries
25:54 EDX Case Studies of Compression Neuropathy
26:00 Types of Conduction Blocks
27:36 Cubital Tunnel Syndrome with Conduction Slowing and Block
31:28 Compression of Radial Nerve at Spiral Groove with Conduction Block
31:46 Severe Carpal Tunnel Syndrome with Conduction Block
32:23 Clinical Correlations and TimeRelated Electrodiagnostic Changes
33:26 CMAP Amplitude
33:53 Immediate Considerations of CMAP and SNAP Amplitudes
34:34 Fibrillations and Positive Sharp Waves
35:20 Collateral Sprouting MUPs
35:58 Nascent MUPs
36:16 Chronic MUPs
36:52 Case Study of Collateral Sprouting MUPs and Axonotmetic Injury
38:21 Case Study of Nascent Maturing to Chronic MUPs
41:00 Case Study of Neurotmetic Injury
41:31 Reference of EMG and Neuromuscular Disorders
41:40 Credits