(Myotonia   Congenita — Congenital  Muscular  Spasm. ^

In  this  disease,  a  tendency  of  the  muscles  to  tonic  spasm  during
attempts  at  voluntary  movement  is  the  characteristic  feature.
By  such  spasms,  the  execution  of  intended  movements  of  the  limbs
is  always  more  or  less  delayed,  and  sometimes  entirely  prevented.
This  disease  is  also  known  as  "  Myotonia  Congenita,"  because  it  is
seldom,  if  ever,  observed  except  in  patients  who  are  not  predisposed  to
it  by  heredity.  Dr.  Thomsen,  who  first  described  this  aflfeetion,  noted
its  occurrence  in  five  generations  of  his  own  family.  He  suffered  from
it  himself,  as  did  also  one  of  his  sons.  A  very  complete  monograph  on
this  subject  has  been  published  by  Erb,  who  has  collected  and  analyzed
all  cases  reported  to  that  date.  Jacoby  and  Dana  have  lately  added  to
the  literature  of  this  affection.
Etiology. — As  has  already  been  stated,  heredity  plays  a  very  im-
portant part  in  this  disease.  In  one  reported  case,  fright  seems  to  have
acted  as  an  exciting  cause.  It  is  questionable,  howcA^er,  if  this  disease
ever  occurs  without  some  congenital  defect  either  in  the  spinal  cord  or
in  the  muscles  themselves.  A  late  monograph  upon  this  subject  by
Dr.  G.  W.  Jacoby  seems  to  show  conclusiveh'  that  muscular  anomalies
w^ere  present  in  the  case  reported  by  him.
Morbid  Anatomy. — Although  this  disease  has  been  classed  by  me  as
a  functional  disease  of  the  spinal  cord  (because  no  spinal  changes  have
ever  been  shown  to  exist  in  connection  with  it),  it  must  be  said  that  the
muscles  appear  to  show  characteristic  conditions  which  are  probably
congenital.     The   individual  muscular  fibres  are  greatly  augmented   in


thomsen's  disease.  441

point  of  size,  and  the  number  of  their  nuclei  is  in  excess  of  that  observed
in  healthy  muscle.
