eMedicine Specialties > Neurology > Electromyography and Nerve Conduction Studies

Assessment of Neuromuscular Transmission: Multimedia

Author: Stephen A Berman, MD, PhD, Professor, Department of Internal Medicine, Section of Neurology, Dartmouth Medical School; Chief, Neurology Service, White River Junction Veterans Medical Center
Coauthor(s): Donald B Sanders, MD, EMG Laboratory Director, Professor of Medicine (Neurology), Division of Neurology, Duke University Medical Center
Contributor Information and Disclosures

Updated: May 17, 2007

Multimedia

A typical decrementing response to repetitive ner...
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Media file 1: A typical decrementing response to repetitive nerve stimulation in myasthenia gravis. The amplitude of the initial response is normal, and the decrement is maximal in the fourth response. Thereafter, the responses increase somewhat, giving a U-shaped envelope to the train of responses.
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A typical decrementing response to repetitive ner...

A typical decrementing response to repetitive nerve stimulation in myasthenia gravis. The amplitude of the initial response is normal, and the decrement is maximal in the fourth response. Thereafter, the responses increase somewhat, giving a U-shaped envelope to the train of responses.

A diagram of pseudofacilitation in the muscle res...
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Media file 2: A diagram of pseudofacilitation in the muscle responses seen during high-frequency repetitive nerve stimulation. Amplitude of the responses increases due to shortening of the waveforms, but the area under the waveforms remains relatively constant.
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A diagram of pseudofacilitation in the muscle res...

A diagram of pseudofacilitation in the muscle responses seen during high-frequency repetitive nerve stimulation. Amplitude of the responses increases due to shortening of the waveforms, but the area under the waveforms remains relatively constant.

Typical activation cycles seen during repetitive ...
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Media file 3: Typical activation cycles seen during repetitive nerve stimulation. The vertical lines represent the amplitude of muscle responses during 3-Hz repetitive nerve stimulation before and at indicated intervals after activation of the muscle by brief maximum voluntary contraction (arrow). In myasthenia gravis (MG), a decrementing response is observed initially, which partially repairs after activation and is later exaggerated. In Lambert-Eaton myasthenic syndrome (LEMS), the responses are small. A decrementing response occurs, and activation is followed by a marked and brief increase in response amplitude.
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Typical activation cycles seen during repetitive ...

Typical activation cycles seen during repetitive nerve stimulation. The vertical lines represent the amplitude of muscle responses during 3-Hz repetitive nerve stimulation before and at indicated intervals after activation of the muscle by brief maximum voluntary contraction (arrow). In myasthenia gravis (MG), a decrementing response is observed initially, which partially repairs after activation and is later exaggerated. In Lambert-Eaton myasthenic syndrome (LEMS), the responses are small. A decrementing response occurs, and activation is followed by a marked and brief increase in response amplitude.

Electrode positions for performing repetitive ner...
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Media file 4: Electrode positions for performing repetitive nerve stimulation of the trapezius muscle. The active recording electrode (black) is placed over the belly of the muscle and the reference-recording electrode (red) distally over the shoulder. The spinal accessory nerve is stimulated as it crosses the sternocleidomastoid muscle. The green wire is the ground.
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Electrode positions for performing repetitive ner...

Electrode positions for performing repetitive nerve stimulation of the trapezius muscle. The active recording electrode (black) is placed over the belly of the muscle and the reference-recording electrode (red) distally over the shoulder. The spinal accessory nerve is stimulated as it crosses the sternocleidomastoid muscle. The green wire is the ground.

Action potentials from a single motor unit in a p...
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Media file 5: Action potentials from a single motor unit in a patient with Lambert-Eaton myasthenic syndrome. The waveforms vary from discharge to discharge, indicating abnormal neuromuscular transmission.
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Action potentials from a single motor unit in a p...

Action potentials from a single motor unit in a patient with Lambert-Eaton myasthenic syndrome. The waveforms vary from discharge to discharge, indicating abnormal neuromuscular transmission.

Repetitive nerve stimulation studies in Lambert-E...
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Media file 6: Repetitive nerve stimulation studies in Lambert-Eaton myasthenic syndrome. The initial response amplitude is low, and a decrementing response to low-frequency stimulation is noted (A). Immediately after activation, the amplitude is increased (B). During high-frequency stimulation (C), the initial decrement is followed by an increase in amplitude to more than twice the initial value.
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Repetitive nerve stimulation studies in Lambert-E...

Repetitive nerve stimulation studies in Lambert-Eaton myasthenic syndrome. The initial response amplitude is low, and a decrementing response to low-frequency stimulation is noted (A). Immediately after activation, the amplitude is increased (B). During high-frequency stimulation (C), the initial decrement is followed by an increase in amplitude to more than twice the initial value.

Muscle responses to nerve stimulation in a patien...
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Media file 7: Muscle responses to nerve stimulation in a patient with Lambert-Eaton myasthenic syndrome. The initial response (left) is very small. After brief maximum voluntary contraction, the amplitude (right) increases markedly.
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Muscle responses to nerve stimulation in a patien...

Muscle responses to nerve stimulation in a patient with Lambert-Eaton myasthenic syndrome. The initial response (left) is very small. After brief maximum voluntary contraction, the amplitude (right) increases markedly.

Muscle responses to 3-Hz nerve stimulation in a ...
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Media file 8: Muscle responses to 3-Hz nerve stimulation in a hand muscle of a patient with familial infantile myasthenia. The initial response (A) is normal, but a decrementing response occurs after prolonged 3-Hz stimulation (B).
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Muscle responses to 3-Hz nerve stimulation in a ...

Muscle responses to 3-Hz nerve stimulation in a hand muscle of a patient with familial infantile myasthenia. The initial response (A) is normal, but a decrementing response occurs after prolonged 3-Hz stimulation (B).

Responses to 3-Hz nerve stimulation in a hand mu...
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Media file 9: Responses to 3-Hz nerve stimulation in a hand muscle in a patient with slow channel syndrome. A decrementing pattern is noted, and a repetitive discharge (black) is seen following the response to the initial stimulus.
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Responses to 3-Hz nerve stimulation in a hand mu...

Responses to 3-Hz nerve stimulation in a hand muscle in a patient with slow channel syndrome. A decrementing pattern is noted, and a repetitive discharge (black) is seen following the response to the initial stimulus.

Repetitive nerve stimulation study. The baseline ...
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Media file 10: Repetitive nerve stimulation study. The baseline is unstable, causing the compound muscle action potential (CMAP) waveforms to move up and down, giving an irregular envelope to the train. Muscle movement is the most likely cause.
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Repetitive nerve stimulation study. The baseline ...

Repetitive nerve stimulation study. The baseline is unstable, causing the compound muscle action potential (CMAP) waveforms to move up and down, giving an irregular envelope to the train. Muscle movement is the most likely cause.

This figure shows a decremental response to repet...
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Media file 11: This figure shows a decremental response to repetitive nerve stimulation in the deltoid muscle of a patient with a severe cervical radiculopathy.
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This figure shows a decremental response to repet...

This figure shows a decremental response to repetitive nerve stimulation in the deltoid muscle of a patient with a severe cervical radiculopathy.

Repetitive nerve stimulation test in a hand muscl...
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Media file 12: Repetitive nerve stimulation test in a hand muscle.
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Repetitive nerve stimulation test in a hand muscl...

Repetitive nerve stimulation test in a hand muscle.

More on Assessment of Neuromuscular Transmission

References
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Further Reading

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Keywords

assessment of neuromuscular transmission, motor signals, neuromuscular transmission, NMJ, neuromuscular junction testing, repetitive nerve stimulation, Harvey-Masland test, Tensilon test, single-fiber EMG, myasthenia gravis, MG, acetylcholine, Lambert-Eaton myasthenic syndrome, LEMS, conventional needle electromyography, congenital myasthenic syndromes, slow channel syndrome, congenital acetylcholinesterase deficiency, low-affinity fast channel syndrome, botulism, botulinum toxin

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Contributor Information and Disclosures

Author

Stephen A Berman, MD, PhD, Professor, Department of Internal Medicine, Section of Neurology, Dartmouth Medical School; Chief, Neurology Service, White River Junction Veterans Medical Center
Stephen A Berman, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, and Phi Beta Kappa
Disclosure: Nothing to disclose.

Coauthor(s)

Donald B Sanders, MD, EMG Laboratory Director, Professor of Medicine (Neurology), Division of Neurology, Duke University Medical Center
Donald B Sanders, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, American Neurological Association, and New York Academy of Sciences
Disclosure: Nothing to disclose.

Medical Editor

Dianna Quan, MD, Associate Professor of Neurology, Director, Electromyography Laboratory, University of Colorado Health Sciences Center
Dianna Quan, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Phi Beta Kappa
Disclosure: e-medicine Honoraria Other

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Glenn Lopate, MD, Associate Professor, Department of Neurology, Division of Neuromuscular Diseases, Washington University School of Medicine; Chief of Neurology, St Louis ConnectCare, Consulting Staff, Barnes Jewish Hospital
Glenn Lopate, MD is a member of the following medical societies: American Academy of Neurology, American Association of Neuromuscular and Electrodiagnostic Medicine, and Phi Beta Kappa
Disclosure: Nothing to disclose.

CME Editor

Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital
Matthew J Baker, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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