Comprehensive Electromyography: With Clinical Correlations and Case Studies

Description

Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by nerves and muscles. Interpreting EMG is a mandatory skill for neurologists and rehabilitation specialists. This textbook provides the reader with a detailed discussion of the concepts and principles underlying electrodiagnostic medicine. It is written for an audience without pre-existing knowledge in this discipline, including beginner technicians and physicians in training. It is an ideal review for seasoned practitioners and those preparing for board examinations. It begins with a review of the foundational sciences and works through the field in twenty chapters, including a large number of case studies demonstrating correct application and interpretation. Appendices of information frequently required in the EMG laboratory, such as Nerve Conduction Study techniques and their age-related normal values, anatomic regions assessed by each NCS and needle EMG studies, safety issues, and other important topics, are also included. Cover......Page 1 Half-title......Page 3 Title page......Page 5 Copyright information......Page 6 Dedication......Page 7 Table of contents......Page 9 Preface......Page 11 Acknowledgments......Page 14 Section 1 Introductory Chapters......Page 15 Introduction......Page 17 Charge......Page 18 Current......Page 22 Voltage......Page 24 Resistance......Page 25 Ohm’s Law......Page 26 Types of Circuits and Current......Page 27 Series DC Circuits......Page 28 Parallel DC Circuits......Page 32 Capacitors......Page 34 Alternating Current......Page 37 The Quantification of AC Signal......Page 38 Household Electricity......Page 40 Transformers......Page 44 Electromagnetic Radiation......Page 45 Recommended Reading......Page 46 Capacitance......Page 47 Filters......Page 48 Filter Arrangements......Page 54 Analog-to-Digital Converters and Digital-to-Analog Converters......Page 55 Stimulators......Page 57 Monopolar Amplifiers......Page 58 Differential Amplifiers......Page 59 The Common Mode Rejection Ratio......Page 61 Suggested Reading......Page 62 The Cell Membrane......Page 63 Motor Neurons......Page 64 Sensory Neurons......Page 65 Nerve Fiber Classification......Page 66 Ion Channels......Page 67 Transmembrane Potentials, Nernst Equilibrium Potentials, and Selective Permeability......Page 69 Depolarization and Repolarization......Page 71 The Absolute Refractory Period and the Relative Refractory Period......Page 72 Local Responses......Page 73 The Advantage of Myelin......Page 75 Action Potential Propagation Speed......Page 76 Connective Tissue Elements of Nerve Trunks......Page 79 References......Page 80 Introduction......Page 82 Synaptic Space......Page 83 Postsynaptic Region......Page 84 Postsynaptic Membrane Depolarizations......Page 85 References......Page 86 Structural Organization of Muscle......Page 87 The Sarcomere......Page 88 The CNS Influence......Page 90 Muscle Shortening......Page 91 Motor Unit and Muscle Fiber Physiology, Biochemistry, and Metabolism......Page 92 Motor Unit Size and Distribution......Page 93 References......Page 94 Section 2 Nerve Conduction Studies......Page 97 Introduction......Page 99 History......Page 100 Proper Placement of the Recording Electrodes......Page 101 The Basic Technique......Page 102 Volume Conduction......Page 104 Orthodromic versus Antidromic......Page 106 The Stimulating Electrodes and Their Proper Placement......Page 107 References......Page 108 Biphasic Morphology......Page 109 The E2 Electrode Is Not Inactive......Page 110 Positive Dip......Page 111 Nerve Stimulation......Page 112 Physiologic Temporal Dispersion......Page 113 What We Measure and What It Means......Page 115 Amplitude......Page 116 Negative AUC......Page 118 Distal Latency......Page 119 The Contributors to the Distal Latency Time......Page 120 Conduction Velocity......Page 121 References......Page 123 Technique......Page 125 Measurements......Page 126 Amplitude......Page 127 Orthodromic versus Antidromic Techniques......Page 128 Fixed Landmarks versus Fixed Distances......Page 130 Peak Latencies versus Onset Latencies......Page 131 Conduction Velocity......Page 132 Effects of Filtering......Page 133 Ideal Interelectrode Distance......Page 134 Mixed Nerve Conduction Studies......Page 135 References......Page 136 Effects of Focal Demyelination on Action Potentials......Page 137 Introduction......Page 138 The Pathology of Focal Demyelination......Page 139 Uniform Demyelinating Conduction Slowing......Page 140 Nonuniform Demyelinating Conduction Slowing......Page 141 Focal Demyelinating Conduction Block......Page 142 Conduction Failure......Page 145 The Major Advantages and Disadvantages of the Motor NCS......Page 146 The Sensory NCS Manifestations of Pathology and Pathophysiology......Page 147 The Timing of NCS Manifestations......Page 149 References......Page 150 The Effect of Focal Demyelination and Axon Disruption on the NCS......Page 151 Motor NCS......Page 152 References......Page 154 Introduction......Page 155 Technique......Page 156 Technical Errors......Page 157 Amplitude and Latency Measurements......Page 158 Utility of H Wave Testing......Page 159 Physiology and Technique......Page 160 Utility......Page 161 A Waves......Page 162 Blink Reflexes......Page 163 References......Page 164 Introduction......Page 166 Introduction......Page 167 Technique......Page 168 Postexercise Facilitation and Postexercise Exhaustion......Page 169 Technical Errors......Page 170 High-Frequency RNSS Technique......Page 171 References......Page 172 Section 3 The Needle EMG Examination......Page 173 Introduction......Page 175 Motor Unit Anatomy and Physiology......Page 176 Duration......Page 177 Motor Unit Recruitment (Force Generation)......Page 178 The Measurements We Make and Their Meanings......Page 183 Insertional Phase......Page 184 Miniature Endplate Potentials......Page 185 Endplate Spikes......Page 186 MUAP Amplitude (Peak-to-Peak)......Page 187 MUAP Duration......Page 189 The Number of Phases and Turns Composing the MUAP......Page 191 Needle Recording Electrode Types......Page 192 Concentric Needle Electrodes......Page 193 Monopolar Needle Electrodes......Page 194 References......Page 195 Chapter Organization......Page 197 Resting Phase......Page 198 Morphology and Duration......Page 199 The Auditory Characteristics and Firing Frequency of Fibrillation Potentials......Page 200 Specificity and Utility......Page 201 Fasciculation Potentials and Cramp Potentials......Page 202 Electrodiagnostic Features......Page 203 Myotonic Potentials......Page 204 Neuromyotonia......Page 205 Grouped Repetitive Discharges (GRDs) and Myokymia......Page 206 Activation Phase......Page 207 MUAP Duration......Page 208 Reinnervation via Collateral Sprouting......Page 209 MUAP Recruitment......Page 210 Grading Neurogenic Recruitment......Page 211 Decreased Spatial And Temporal Recruitment......Page 212 Non-Myopathic Motor Unit Disintegration Disorders......Page 213 MUAP Stability......Page 214 Motor Axon Loss Following Reinnervation via Collateral Sprouting......Page 215 References......Page 216 Single-Fiber Needle Electrodes......Page 218 Technique and Measurements Made......Page 219 Jitter Using a Concentric Needle Electrode......Page 220 Macro EMG Needle Electrodes......Page 221 References......Page 222 Section 4 Other Pertinent EDX Information......Page 225 The Importance of Proper Initial Management......Page 227 Correlations between Lesion Acuteness and the Underlying Pathophysiology......Page 228 Electrodiagnostic Grading......Page 229 Timing of the Study......Page 230 The Value of Motor Responses in the Assessment of Lesion Severity......Page 231 Collateral Sprouting......Page 232 Proximodistal Axon Regeneration......Page 233 Determining the Potential for Reinnervation......Page 234 Neurapraxia......Page 235 Sunderland Grade 2......Page 236 Sunderland Grade 5......Page 237 Surgical Intervention......Page 238 Approach to Axon Loss (Grades 2–5)......Page 239 Major Surgical Interventions......Page 240 Types of Nerve Injuries......Page 241 Compression Injuries......Page 242 Acute Compression......Page 243 Chronic Compression......Page 244 Ischemic Injury......Page 245 References......Page 246 Upper Motor Neuron Disorders......Page 249 Anterior Horn Cell Disorders......Page 250 Post-Poliomyelitis Syndrome......Page 251 Spinal Muscular Atrophy, Type 3......Page 252 Radiculopathies......Page 253 Plexopathies......Page 255 The Brachial Plexus......Page 256 The Lumbosacral Plexus......Page 259 Focal Neuropathies (Mononeuropathies)......Page 260 Acquired Axon Loss Polyneuropathies......Page 261 Acquired Demyelinating Polyneuropathies......Page 262 Chronic Inflammatory Demyelinating Polyradiculoneuropathy......Page 263 Hereditary Polyneuropathies......Page 264 Neuromuscular Junction Disorders......Page 265 Repetitive Nerve Stimulation Studies......Page 266 Needle EMG Study......Page 267 Myopathic Disorders......Page 268 References......Page 269 Studying Cool Limbs......Page 271 Nerve Conduction Studies......Page 272 Repetitive Nerve Stimulation Studies......Page 273 Nerve Conduction Studies......Page 274 Body Habitus–Related issues......Page 275 Introductory Comments......Page 276 MGA to the Hypothenar Eminence......Page 277 MGA to the Adductor Pollicis Muscle......Page 278 MGA with Concomitant Carpal Tunnel Syndrome......Page 279 MGA with a Concomitant Ulnar Neuropathy......Page 280 Atypically Proximal MGA......Page 281 Identifying an RCA......Page 282 Identifying an Accessory Deep Peroneal Nerve......Page 283 The Presence of a Positive Dip......Page 284 Stimulus (Shock) Artifact......Page 285 Stimulus Artifact Reduction......Page 286 Rotation of the Anode about the Cathode......Page 287 Submaximal Stimulation......Page 288 Excessive Stimulation......Page 289 60 Hz Power Artifact......Page 290 Measurement Errors......Page 291 Filtering Issues......Page 293 Needle EMG......Page 295 Changing the Sensitivity to Better Identify the Onset Latency......Page 296 Sweep Speed and Sensitivity......Page 297 Identifying Demyelination Based on the Latency of a Very Low Amplitude Response......Page 298 Measurement Errors......Page 299 References......Page 300 Electrical Injury......Page 304 Indwelling Medical Devices......Page 307 Bleeding......Page 309 Transmission of Infection......Page 310 Prevention......Page 312 References......Page 313 EDX Testing as an ‘‘Extension of the Neurological Examination’’......Page 316 The Timing of the EDX Examination......Page 317 The Limitations of Electrodiagnostic Testing......Page 318 The EDX Study Components Performed and Their Order of Performance......Page 319 Supervision......Page 320 Reviewing the Consult......Page 321 Explaining the EDX Study to the Patient (Verbal Informed Consent)......Page 322 Brief Discussion......Page 323 Tips to Lessen the Discomfort Associated with the Needle EMG Study......Page 324 Format of Report......Page 326 References......Page 327 Section 5 Case Studies in Electrodiagnostic Medicine......Page 329 Lesion Localization......Page 331 Identifying Nonorganic Lesions......Page 332 Initial Studies......Page 333 Abbreviations......Page 334 Needle EMG......Page 335 The Electrodiagnostic Exercises......Page 336 References......Page 493 Section 6 Appendices......Page 495 The Lumbosacral Plexus......Page 497 The Median Nerve......Page 498 The Ulnar Nerve......Page 499 The Radial Nerve......Page 500 The Obturator Nerve......Page 501 The Femoral Nerve......Page 502 The Sciatic Nerve Proper......Page 503 The Tibial Nerve......Page 504 The Peroneal Nerve......Page 505 Appendix 3: Myotome Tables for the Upper and Lower Extremities......Page 506 Appendix 4: The SNAP, CMAP, and Needle EMG Domains of the Brachial Plexus Elements^......Page 507 Reference......Page 509 The Median Sensory NCS, Recording Second Digit......Page 510 The Ulnar Sensory NCS, Recording Fifth Digit......Page 511 Superficial Radial Sensory NCS......Page 512 Median Motor NCS, Recording Abductor Pollicis Brevis (Thenar Eminence)......Page 513 Ulnar Motor NCS, Recording Abductor Digiti Minimi (Hypothenar Eminence)......Page 514 Radial Motor NCS, Recording Extensor Digitorum Communis......Page 515 Musculocutaneous Motor NCS, Recording Biceps......Page 516 Suprascapular Motor NCS, Recording Infraspinatus......Page 517 Superficial Peroneal Sensory NCS......Page 518 Peroneal Motor NCS, Recording Extensor Digitorum Brevis......Page 519 Tibial Motor NCS, Recording Abductor Hallucis......Page 520 Femoral Motor NCS, Recording Rectus Femoris......Page 521 Appendix 6: The Age-Related, Normal Control Values Used in Our EMG Laboratories......Page 523 Lower Extremity......Page 524 Needle EMG......Page 525 Myopathy......Page 526 Index......Page 527