II. Indications

  1. Muscle disease
  2. Neuromuscular Junction disease
  3. Nerve or nerve root disease with denervation

III. Background

  1. Electrical test to measure Muscle physiology

IV. Myopathy Findings

  1. Nonspecific for Myopathy type
  2. Motor unit potential abnormalities
    1. Low amplitude
    2. Short duration
    3. Complex, polyphasic
  3. Increased Insertional activity
    1. Ectopic high frequency discharges
  4. Fibrillation potentials present in some myopathies
    1. Polymyositis
    2. Muscular Dystrophy

V. Myotonia findings

  1. Waxing and waning hyperexcitability
  2. Repetitive discharges
    1. Electromyogram machine creates "dive bomber" sound

VI. Neuromuscular Junction disorder findings

  1. General
    1. Increased variation in Muscle response time (latency)
  2. Presynaptic disorders
    1. Examples
      1. Botulism
      2. Eaton -Lambert Syndrome
    2. Findings
      1. Enhanced response to repetitive nerve stimulation
      2. Normal amplitude miniature end-plate potentials
  3. Postsynaptic disorders
    1. Examples
      1. Myasthenia Gravis
    2. Findings
      1. Decreased response to repetitive nerve stimulation
      2. Subnormal amplitude miniature end-plate potentials

VII. Denervation Findings

  1. Increased polyphasic Action Potentials
  2. Ectopic high frequency discharges
  3. Fibrillations
    1. Onset 3 to 4 weeks after nerve injury
  4. Fasciculations
  5. Positive sharp waves
  6. F Response prolonged (proximal Motor Nerve reflex arc)
    1. Guillain-Barre Syndrome
  7. Hoffman Reflex (Stretch reflex arc - sensory and motor)
    1. Sensory Nerve root lesion
    2. Motor Nerve root lesion

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Related Studies

Ontology: Electromyography (C0013839)

Definition (NCI) An assessment of skeletal muscle function and nerve control, obtained by recording and studying the intrinsic electrical properties of the muscles.
Definition (CSP) measurement and interpretation of the electrical manifestations of muscle activity.
Definition (MSH) Recording of the changes in electric potential of muscle by means of surface or needle electrodes.
Concepts Diagnostic Procedure (T060)
MSH D004576
ICD9 93.08
ICD10 11012-00
SnomedCT 72330000, 141997004, 42803009
CPT 1013340
LNC LP6246-5
English Electromyographies, EMG, ELECTROMYOGR, EMG (electromyography), electromyography, electromyogram, electromyography (procedure), Electromyography [EMG], electromyography emg, Electromyogram (procedure), Electromyography Procedures, EM-Electromyography, EMG - Electromyography, Electromyogram, Electromyography, NOS, Electromyogram, NOS, EMG (Electrophysiology), Electromyography, Electromyography (procedure), Electromyography (regime/therapy)
Portuguese EMG, Electromiografia, Eletromiografia
Spanish EMG, electromiografía (régimen/tratamiento), electromiograma (concepto no activo), electromiografía, Electromiograma, electromiografía (procedimiento), electromiograma, Electromiografía
Japanese EMG, 筋電図, キンデンズ, EMG
Swedish Elektromyografi
Czech elektromyografie, EMG, Elektromyogram
Finnish Elektromyografia
French EMG, Electromyogramme, Électromyographie
Polish Elektromiografia
Hungarian Elektromiogram, EMG
Norwegian Elektromyografi
Dutch elektromyogram, EMG, Elektromyografie
German Elektromyogramm, EMG, Elektromyographie
Italian Elettromiografia