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LANDMARKS IN THE HISTORY OF MYOTONIA. International Conference on the Nondystrophic Myotonias, June 3-4, 2007 Robert Layzer University of California, San Francisco. CLINICAL DESCRIPTIONS. Myotonia congenita Dr. JuliusThomsen, 1876

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landmarks in the history of myotonia

LANDMARKS IN THE HISTORY OF MYOTONIA

International Conference on the Nondystrophic Myotonias, June 3-4, 2007

Robert Layzer

University of California, San Francisco

clinical descriptions
CLINICAL DESCRIPTIONS
  • Myotonia congenita
    • Dr. JuliusThomsen, 1876
    • Monograph described disease in himself and 20 members of his family in 4 generations
    • Symptoms static and benign
    • Work extended by Erb, 1886
clinical descriptions4
CLINICAL DESCRIPTIONS
  • Recessive myotonia congenita: Becker, 1961
    • Myotonia more severe, muscles larger (“Infant Hercules”) with distal thinning
    • Transient weakness during initial contraction after rest
    • Declining electrical response of muscle to nerve stimulation
clinical descriptions5
CLINICAL DESCRIPTIONS
  • Paramyotonia congenita
    • Episodes of myotonia and weakness induced by exposure to cold: Eulenberg 1888; Rich 1894
    • Myotonia typically paradoxical: Magee 1963
clinical descriptions6
CLINICAL DESCRIPTIONS
  • Hyperkalemic periodic paralysiswithout myotonia: Helweg-Larsen et al 1955, Gamstorp 1956
  • Paramyotonia with attacks of generalized weakness induced by oral potassium: French & Kilpatrick, 1957
clinical descriptions7
CLINICAL DESCRIPTIONS
  • Hyperkalemic periodic paralysis with myotonia: Drager et al 1958; Van der Meulen et al 1961; Van’t Hoff 1962; McArdle 1962; Layzer et al 1967
  • Myotonia aggravated by cold and potassium (without weakness): Heine et al 1993
treatment of myotonia
TREATMENT OF MYOTONIA
  • “Quinine: An Effective Form of Treatment for Myotonia.” Arch Neurol Psychiat 1936;36:382-3.

“I shall give a brief report of the effectiveness of quinine in the treatment of myotonia, a condition hitherto almost entirely uninfluenced by any mode of therapy.”--A. Wolf, M.D. Cornell 1932 (Bellevue, Foster Kennedy)

treatment of myotonia9
TREATMENT OF MYOTONIA
  • Procaine amide: Geschwind & Simpson, 1955
  • Diphenylhydantoin: Munsat, 1967
myotonia in goats
MYOTONIA IN GOATS
  • Descended from a small flock imported [from Syria?] into Marshall County, Tennessee
  • 1904: White & Plaskett: Nervous, stiff-legged or fainting goats
  • 1932: Clark et al: “A form of congenital myotonia in goats”
  • 1938: L.C. Kolb (b. 1911): clinical and electrical features typical of myotonia; relieved by quinine
clinical physiology
CLINICAL PHYSIOLOGY
  • EMG: Myotonia is associated with profuse electrical activity (Lindsley & Curnen 1936), interpreted as neurogenic!
  • After-discharge attributed to spinal reflex from “hyperexcitable sensory end-organs in the muscle.”
clinical physiology12
CLINICAL PHYSIOLOGY
  • Mechanically-induced myotonia persists
    • after spinal anesthesia (Grund 1919; Kennedy & Wolf 1938)
    • after nerve block (Denny-Brown & Nevin 1941; Buchthal & Clemmensen 1941)
clinical physiology13
CLINICAL PHYSIOLOGY
  • Mechanical myotonia persists
    • after curare blockade
      • in goats (Brown & Harvey 1939)
      • in man (Lanari 1946; Landau 1952)
    • after nerve section and degeneration of motor nerve endingsingoats (Brown & Harvey 1939)
clinical physiology14
CLINICAL PHYSIOLOGY

“It appears, then, that the myotonia is due to an abnormality of some part of the muscle fibre itself. . .The essential abnormality appears to be a tendency of the muscle fibres to respond repetitively to any form of stimulation.”

Brown & Harvey, 1939

membrane physiology
MEMBRANE PHYSIOLOGY
  • Rm 3-4 times normal in goat (Bryant et al 1962-69) and man (Lipicky et al 1971)
  • Chloride conductance markedly reduced in goat, accounting for increased Rm: Bryant & Morales-Aguilera 1971
membrane physiology16
MEMBRANE PHYSIOLOGY
  • Accumulation of potassium in T-tubules is responsible for repetitive activity: Adrian & Bryant 1974
  • Computer modeling of membrane excitability with low chloride conductance explains why sodium channel blocking drugs control myotonia: Barchi 1975
molecular pathology
MOLECULAR PATHOLOGY
  • Chloride channel gene mutations in myotonia congenita (George et al 1993):
    • one abnormal copy: autosomal dominant
    • two abnormal copies: autosomal recessive
molecular pathology18
MOLECULAR PATHOLOGY
  • Sodium channel mutations: Ptacek et al 1971
    • Hyperkalemic periodic paralysis
    • Paramyotonia congenita
    • Potassium-aggravated myotonia