Interpretation of the electromyogram.

IN RENEWING electromyographic investigations of human muscles after an interval, I find that considerable differences of opinion have accumulated in regard to the interpretation of several electromyographic changes encountered in neurologic disorders. Since electromyography is in common use in some clinics and can provide useful diagnostic information, it may be of general interest to discuss critically some of the fundamental principles involved in the method. Early work on the action potentials of muscle has been reviewed by others,1and Pennybacker and I2previously discussed at length the relation of action potentials of single muscle fibers to those series of much larger rhythmic variations which are associated with the natural discharge of a single motor nerve cell. Physiologically, the "motor unit" is defined as a motor cell, its axon process and the group of muscle fibers which this one cell innervates. The rhythmic pattern of electrical changes (action potentials)

[1]  D. Lindsley.  ELECTROMYOGRAPHIC STUDIES OF NEUROMUSCULAR DISORDERS , 1936 .

[2]  S. Cobb.  Review of neuropsychiatry for 1945. , 1946, Archives of internal medicine.

[3]  Olive C. Smith,et al.  ACTION POTENTIALS FROM SINGLE MOTOR UNITS IN VOLUNTARY CONTRACTION , 1934 .

[4]  D. Denny-Brown,et al.  FIBRILLATION AND FASCICULATION IN VOLUNTARY MUSCLE , 1938 .

[5]  K. Wachholder,et al.  Willkürliche Haltung und Bewegung , 1928 .

[6]  R. Swank,et al.  FASCICULAR MUSCLE TWITCHINGS IN AMYOTROPHIC LATERAL SCLEROSIS: THEIR ORIGIN , 1943 .

[7]  M. Brazier,et al.  CONCEPTS OF MUSCLE DYSFUNCTION IN POLIOMYELITIS: BASED ON ELECTROMYOGRAPHIC STUDIES , 1943 .

[8]  E. Adrian,et al.  The discharge of impulses in motor nerve fibres , 1929, The Journal of physiology.

[9]  B. Ingebrigtsen.  PRACTICAL APPLICATION OF ELECTROMYOGRAPHY IN DIAGNOSIS OF TREMOR1) , 1938 .

[10]  D. Denny-Brown.  On Inhibition as a Reflex Accompaniment of the Tendon Jerk and of other Forms of Active Muscular Response , 1928 .

[11]  Fritz Buchthal,et al.  ON THE DIFFERENTIATION OF MUSCLE ATROPHY BY ELECTROMYOGRAPHY , 1941 .

[12]  R. Creed,et al.  Reflex Activity of the Spinal Cord , 1933 .

[13]  R. P. Schwartz,et al.  THE SIGNIFICANCE OF MUSCLE SPASM: IN THE ACUTE STAGE OF INFANTILE PARALYSIS BASED ON ACTION CURRENT RECORDS , 1944 .

[14]  E. Liddell,et al.  Observations on Ipsilateral Contraction and "Inhibitory" Rhythm , 1925 .

[15]  D. Denny-Brown,et al.  On the Nature of Postural Reflexes , 1929 .

[16]  D. Lindsley.  MYOGRAPHIC AND ELECTROMYOGRAPHIC STUDIES OF MYASTHENIA GRAVIS , 1935 .

[17]  D. Lindsley,et al.  ELECTRICAL ACTIVITY OF HUMAN MOTOR UNITS DURING VOLUNTARY CONTRACTION , 1935 .

[18]  P. F. Hoefer.  INNERVATION AND TONUS OF STRIATED MUSCLE IN MAN , 1941 .

[19]  S. Cobb.  ELECTROMYOGRAPHIC STUDIES OF PARALYSIS AGITANS , 1922 .

[20]  Stanley Cobb,et al.  SIMULTANEOUS ELECTROMYOGRAMS AND ELECTROENCEPHALOGRAMS IN PARALYSIS AGITANS , 1939 .

[21]  G. Weddell,et al.  THE ELECTRICAL ACTIVITY OF VOLUNTARY MUSCLE IN MAN UNDER NORMAL AND PATHOLOGICAL CONDITIONS , 1944 .

[22]  C. Sherrington.  QUANTITATIVE MANAGEMENT OF CONTRACTION IN LOWEST LEVEL CO-ORDINATIONHUGHLINGS JACKSON LECTURE , 1931 .

[23]  C. Sherrington,et al.  REFLEX INHIBITION AS A FACTOR IN THE CO‐ORDINATION OF MOVEMENTS AND POSTURES , 1913 .

[24]  T. J. Putnam,et al.  ACTION POTENTIALS OF MUSCLES IN NORMAL SUBJECTS , 1939 .

[25]  D. Denny-Brown,et al.  Responses to stimulation of the motor area of the cerebral cortex , 1927 .

[26]  T. J. Putnam,et al.  ACTION POTENTIALS OF MUSCLES IN RIGIDITY AND TREMOR , 1940 .

[27]  D. Denny-Brown,et al.  PARALYSIS OF NERVE INDUCED BY DIRECT PRESSURE AND BY TOURNIQUET , 1944 .

[28]  T. J. Putnam,et al.  ACTION POTENTIALS OF MUSCLES IN SPASTIC CONDITIONS , 1940 .

[29]  R. P. Schwartz,et al.  MUSCLE SPASM IN THE ACUTE STAGE OF INFANTILE PARALYSIS: AS INDICATED BY RECORDED ACTION CURRENT POTENTIALS , 1942 .

[30]  E. Adrian.  The spread of activity in the tenuissimus muscle of the cat and in other complex muscles , 1925, The Journal of physiology.