EMG Primer: A Guide to Practical Electromyography and Electroneurography

71 Pages·1974·1.606 MB·English

by  Frieder Láhoda M.D., Arno Ross M.D., Walter Issel M.D. (auth.)

F. Lahoda A. Ross W. IsseI
EMG Primer
A Guide to
Practical Electromyography
and Electroneurography
With a Preface by A. Schrader
English Version: J. Payan
With 30 Figures
Springer-Verlag
Berlin Heidelberg New York 1974
Original title of the German edition: "EMG-Fibel", 1973.
Published by Johann Ambrosius Barth, Frankfurt/Main.
ISBN -13: 978-3-540-06992-8
Frieder Lahoda, M. D.
Specialist in Internal Medicine, Senior Physician in the Neurological Clinic of
the University of Munich, Reader in Neurology at the University of Munich
Neurologische Klinik, D-8 Miinchen 70, Marchioninistr. 15
Arno Ross, M.D.
Specialist in Neurology and Psychiatry, Senior Physician in the Neurological
Clinic of the University of Munich
Neurologische Klinik, D-8 Miinchen 70, Marchioninistr. 15
Walter IsseI, M.D.
Specialist in Neurology and Psychiatry, Research Assistant in the Medical
Clinic of the University of Erlangen-Niirnberg
Medizinische Klinik und Poliklinik, D-852 Erlangen, Krankenhausstr. 12
The authors wish to extend their thanks to Fred Berninger, engineer in Munich,
for preparation of the technical chapter, and to Dr. J. Payan of The National
Hospital for Nervous Diseases, Queen's Square, London, for reviewing the
English translation.
ISBN -13: 978-3-540-06992-8 e-ISBN -13: 978-3-642-65989-8
001: 10.1007/978-3-642-65989-8
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is
concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, repro
duction by photocopying machine or similar means, and storage in data banks.
Under § 54 of the German Copyright Law where copies are made for other than private use, a fee is
payable to the publisher, the amount of the fee to be determined by agreement with the publisher.
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence
of a specific statement, that such names are exempt from the relevant protective laws and regulations
and therefore free for general use.
library of Congress Cataloging in Publication Data
Lahoda,F.
EMGprimer.
Translation of EMG-FibeJ.
Bibliography: p.
1. Electromyography. 2. Neuromuscular diseases-Diagnosis. I. Ross, Arno, 1934- joint
author. II. Issei, W., 1940-- joint author. III. Title.
RC77.5.L3313 616.07'54 74-19171
© by Springer-VerIagBerlin . Heidelberg 1974.
Composition and Bookbinding by: Appl, Wemding
Preface to the German Edition
In the last twenty years electromyography and electro
neurography have earned a secure position amongst
methods of electrophysiological investigation; indeed, it is
no longer possible to think of neurological diagnosis with
out them. In particular, it is in the early recognition of peri
pheral neuromuscular disorders that these techniques are
so dependable and objective. The present text may be
thought of as an introduction to method and to diagnostic
application, and it should be of value to the physician both
in hospital and in his practice. The authors have thought
it best to omit discussion of basic scientific problems, which
may be found in the neurophysiological literature.
Munich, Spring 1974 A. Schrader
v
Contents
1.1 Anatomical Foundations ........................ . 1
1.1.1. The Motor Unit. . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2. Structure of the Peripheral Nerve ...... . 1
1.1.3. The Neuromuscular Junction .............. . 1
1.2 Electrophysiological Foundations . . . . . . . . . . . . . . . . . . 2
1.2.1. Origin of Muscle Action Potentials. . . . . . . . . . . . 2
1.2.2. Conduction in the Peripheral Nerve. . . . . . . . . . . . 3
1.2.2.1. Stimulation: Basic Considerations. . . . . . . . . . . . . 3
1.2.2.2. Form, Duration and Amplitude of Action Potentials. . . 4
a) Evoked Muscle Action Potentials . . . . . . . . . . . 4
b) Nerve and Sensory Action Potentials. . . . . . . . . 4
c) Reflex Potentials . . . . . . . . . . . . . . . . . . . . 5
2.1. Technical Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1. Structure and Function of the Machine. . . . . . . . . . 6
2.1.1.1. The Structure of an Electromyograph. . . . . . . . . . 6
2.1.1.2. The EMG Amplifier. . . . . . . . . . . . . . . . . . . . 7
2.1.1.3. Supplementary Measuring Methods in Electromyo-
graphy . . . . . . . . . . . . . . ... . . . . . . . . . . . . 7
a) The Stimulator and the Latency Measuring Device. . 8
b) The Delay Line . . . . . . . . . . . . . . . . . . . . . 9
c) The A verager . . . . . . . . . . . . . . . . . . . . 9
d) The Digital A verager . . . . . . . . . . . . . . . . . . 9
2.2. Electrodes ................................... . 9
2.2.1. Main Groups . . . . . . . , . . . . . . . . . . . . . . . . 10
a) Electrodes for Action Potential Recording ..... . 10
b) Electrodes for Stimulation . . . . . . . . . . 10
c) Earth Electrodes . . . . . . . . . . . . . . . 10
2.2.2. Areas of Use . . . . . . . . . . . . . . . . . . . 10
2.2.3. Treatment and Care of Electrodes . . . . . . . 12
3.1. General Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1.1. The Normal Electromyogram. . . . . . . . . . . . . .. 13
3.1.1.1. Methods of Recording. . . . . . . . . . . . . . . . . .. 13
a) With Surface Electrodes. . . . . . . . . . . . . . .. 13
b) With Needle Electrodes. . . . . . . . . . . . . . . .. 13
3.1.1.2. Procedure in the Electromyographical Examination. .. 13
3.1.1.3. Elements of the Needle Myogram. . . . . . . . . . . .. 15
VI
a) Spontaneous Activity . . . . . . . . . . . . . . 15
b) Activity During Voluntary Innervation. 15
3.1.1.4. Methods of Registration. 16
a) Optical . . . . . . . . . . . . . 16
b) Acoustical . . . . . . . . . . . 16
3.1.2. The Normal Electroneurogram . 17
3.1.2.1. The Motor Electroneurogram. . 17
Stimulation and Recording. . . . . . . 17
The Normal Examination Procedure. 18
Registration and Evaluation. . . . . . 19
3.1.2.2. The Sensory Electroneurogram . . . . 20
The Normal Examination Procedure . 20
Registration and Evaluation. . 21
The Examination in Children . . . . 22
Repetitive Stimulation . . . . . . . . 23
3.1.3. The Pathological Electromyogram. 23
3.1.3.1. Lesions of the Lower Motor Neurone. 23
a) Fasciculation Potentials. . . . . . . 23
b) Fibrillation Potentials and Positive Sharp Waves. 24
Pathological Changes in the Pattern on Voluntary Effort 25
a) Reduction of the Interference Pattern. . . . . . 25
b) Changes in Motor Unit Action Potential Form. 25
c) Discharge Frequency . . . . . . 25
3.1.3.2. EMG in Primary Muscle Disease. . . . . . . . . . 26
Spontaneous Activity. . . . . . . . . . . . . . . . . 26
Pathological Changes in the Pattern on Voluntary Effort 26
a) Changes in Motor Unit Action Potential Form. 26
b) Discharge Frequency . . . . . . . . . . . . . . . . .. 27
3.1.3.3. The EMG in Metabolic Electrolyte Disturbances. . .. 27
3.1.3.4. The EMG in Centrally-Determined Movement Distur-
bances . . . . . . . . . . . . . . . . . . . . . 27
3.1.4. The Pathological Electroneurogram. . . . . . 27
3.1.4.1. The Pathological Motor Electroneurogram. . 27
3.1.4.2. The Pathological Sensory Electroneurogram . 28
3.1.5. Disorders of the Neuromuscular Junction. 28
3.2. Special Section (Diagnosis) . . . 29
3.2.1. Peripheral Neurogenic Diseases. 30
3.2.1.1. General Aspects . . . . . . . . . 30
3.2.1.2. Anterior Horn Cell Diseases. . . 30
a) Generalised Anterior Horn Cell Diseases. 31
b) Local Disorders of Anterior Horn Cells: Poliomyelitis 32
VII
Syringomyelia . . . . . . . . . . . . . . . . . . . . .. 33
3.2.1.3. Root Lesions . . . . . . . . . . . . . . . . . . . . . . " 33
a) The Intervertebral Disc. . . . . . . . . . . . . . . .. 33
b) Cervical 'Whiplash' Injury . . . . . . . . . . . . . .. 33
c) Polyradiculitis (Gui1lain-Barre) . . . . . . . . . . .. 34
d) Other Varieties of Root Lesion. . . . . . . . . . . .. 34
3.2.1.4. Plexus Lesions . . . . . . . . . . . . . . . . . . . . . .. 34
3.2.1.5. Local Lesions of the Peripheral Nerve. . . . . . . . . .. 35
a) Neuronotmesis ..................... 35
b) Axonotmesis . . . . . . . . . . . . . . . . . . . . . .. 35
c) Neurapraxia . . . . . . . . . . . . . . . . . . . . . .. 36
d) Reinnervation . . . . . . . . . . . . . . . . . . . . .. 36
Compressive Neuropathy. . . . . . . . . . . . . . . .. 37
a) Carpal Tunnel Syndrome. . . . . . . . . . . . . . .. 37
b) Cubital Sulcus Syndrome . . . . . . . . . . . . . . .. 37
c) Chronic Compressive Neuropathies of the Lower 38
d) Radial Nerve ("Saturday Night Palsy") ....... .
Limb. . . . . . . . . . . . . . . . . . . . . . . . . .. 38
Idiopathic Facial Nerve Palsy (Bell's) . . . . . . 38
Trigeminal Neuropathy. . . . . . . . . . . . . . . 39
Polyneuropathies . . . . . . . . . . . . . . . . . . 39
Peroneal Muscular Atrophy. . . . . . . . . . . . 41
3.2.2. Primary Muscle Disease. . . . . . . . . . . . . . . . .. 41
3.2.2.1. Progressive Muscular Dystrophy (Duchenne) .... " 42
3.2.2.2. Inflammatory Muscle Disease (Myositis and Polymyositis) 42
3.2.2.3. Late-Onset Myopathies ................ " 43
3.2.2.4. Hereditary Distal Myopathy (Welander) . . . . . . . .. 43
3.2.2.5. Myotonia . . . . . . . . . . . . . . . . . . . . . . . . .. 43
3.2.3. Secondary Myopathies. . . . . . . . . . . . . . . . . .. 44
3.2.4. Myasthenic Syndromes. . . . . . . . . . . . . . . . . .. 44
3.2.4.1. Myasthenia Gravis . . . . . . . . . . . . . . . . . . . .. 44
3.2.4.2. Symptomatic Myasthenia. . . . . . . . . . . . . . . . .. 45
3.2.5. Electrolyte Disturbances. . . . . . . . . . . . . . . . .. 45
3.2.6. Myxoedema......................... 46
3.2.7. Tetanus . . . . . . . . . . . . . . . . . . . . . . . . . .. 46
3.2.8. Centrally-Determined Disturbances of Movement. . .. 47
3.2.8.1. Spasticity ..... . . . . . . . . . . . . . . . . . . . .. 47
3.2.8.2. Rigidity .......................... , 47
3.2.8.3. Tremor ........................... 47
a) Rest Tremor in Extrapyramidal Disease. . . . . . .. 47
b) Intention Tremor . . . . . . . . . . . .. 47
3.2.8.4. Torticollis . . . . . . . . . . . . . . . . . . . . . . . . .. 48
VIII
3.2.9. EMG, ENG and the "Floppy Infant" Syndrome. . 48
3.2.9.1. Peripheral Neurogenic Lesions. . . . . . . . . . . 49
3.2.9.2. Myogenic Pareses. . . . . . . . . . . . . . . . . . . 49
3.2.9.3. Centrally-Determined Disturbances of Movement. . .. 49
4.0. EMG of the Extraocular Muscles. . . . . . . . . . . . . . . . . . 49
4.1. Myopathies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
a) Oligo-Symptomatic Form of Ocular Myositis. . . " 50
b) Acute Exophthalmic Myositis . . . . . . . . . . . .. 50
c) Ocular Muscle Dystrophy . . . . . . . . . . . . . " 50
d) Endocrine Ocular Myopathy. . . . . . . . . . . .. 51
e) Ocular Myotonia . . . . . . . . . . . . . . . . . . " 51
f) Ocular Myasthenia . . . . . . . . . . . . . . . . . " 51
4.2. Peripheral Neurogenic Paresis. . . . . . . . . . . . . . . . . . . . 51
4.3. Centrally-Determined Disturbances of Movement. . . . . 51
5.0. Possibilities of Error in the EMG. . . . . . . . . . . . . . . . . . 52
5.1. POSSibilities of Error in the ENG. . . . . . . . . . . . . . . . . . 52
a) Motor Electroneurogram. . . . . . . . . . . . . . .. 52
b) Sensory Electroneurogram . . . . . . . . . . . . . .. 52
6.0. Short Introduction to an EMG Examinatiou. . . . . . . . . . 53
7.0. Index of Important Terms in Clinical EMG . . . . . . . . . . 54
8.0. Index of Important Technical Terms and Abbreviations. 56
9.0. Selected Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
10.0. Subject Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
IX
Introduction
The recording of action potentials from muscle, electromyography
(hereafter EMG), has become an essential aid in several branches of
medicine since the early experiments of the '20s and '30s. It is valuable
in diagnosis not only in neurology but in neurosurgery, accident surgery,
orthopaedics, internal medicine, paediatrics and ophthalmology. It can
be used to distinguish between neurogenic and myogenic pareses, to
clarify acute and chronic denervation processes, and to study primary
myopathies of degenerative and inflammatory origin, as well as myas
thenic syndromes. It is also valuable in the recognition of the disturbance
of nerve and muscle function associated with metabolic disease, and
in the analysis of centrally-determined movement disorders. Elec
troneurography is a further refinement, as the function of peripheral
nerves may be assessed by means of motor and sensory fibre conduction
studies. An important aspect of these techniques is the means they afford
of detecting subclinical or latent affection of muscle or nerve, an early
appreciation of which is essential in toxic and metabolic disorders. In
the same way, regeneration of peripheral nerve is sometimes detectable
before clinical recovery.
Until recently the high cost of the complicated apparatus necessary re
stricted EMG to the larger clinics, but the evolution of equipment has
led to widespread and everyday use in keeping with its importance as
a diagnostic tool.
Effective use of such equipment demands, as always, familiarity with
basic theory, practical experience and an understanding of the diagnostic
possibilities. The latter requirement emphasises that EMG differs from
EEG and EKG in that it must be performed not by a technician, but
by a doctor who has examined the patient clinically.
x
1.1. Anatomical Foundations
A knowledge of certain neuroanatomical facts, briefly indicated below,
is indispensable to the practice of EMG and ENG.
1.1.1. The Motor Unit
This term is of great importance in EMG, and was coined by Sherrington
to describe an anterior horn cell, its axon and all the muscle fibres sup
plied by it. The number of muscle fibres innervated by a single anterior
horn cell varies greatly, the "innervation ratio" in the eye muscles, for
example, being 1: 5 to 1: 10, while in long extremity muscles it may
be as much as 1: 1500.
1.1.2. Structure of the Peripheral Nerve
The gross structure of the nerve is of less importance in the present
context than its histology. There are three essential parts: a) the axon
cylinder in the centre of the fibre is the extension of the protoplasm
of the ganglion cell; b) the myelin sheath which wraps the axon cylinder,
and has a varying thickness, is a complicated structure of concentric
and radial lipoid and protein lamellae ; c) the Schwann cell, lying between
each internode, is, with the axon, essential in the formation of the myelin
sheath. The peripheral nerve comprises motor, sensory and autonomic
fibres.
1.1.3. The Neuromuscular Junction
The nerve impulse is not transferred directly to the muscle fibre: a
neuromuscular "endplate" is interposed as a chemical synapse, and the
junction consists, therefore, of the presynaptic termination of the axon,
a synaptic fissure of a few hundred Angstrom units, and the sub-synaptic
membrane of the muscle fibre. As a rule the endplate zone is in the
middle of the muscle fibre, only very long fibres having more than one
such zone.
1