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2625 pages added, reviewed or updated during the last month (last updated: 15/4/2021)


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The cardinal feature of myotonic dystrophy is myotonia although this often lessens and may disappear as the disease progresses.

In the face:

  • frontal baldness
  • myopathic face with ptosis, hanging jaw, wasting of muscles of mastication, hollowing of temporal fossae and cheeks - sometimes described as a fish face
  • wasting of sternocleidomastoid - weak neck flexion, normal neck extension, swan neck appearance
  • cataracts in 80% of cases

In the limbs:

  • characteristic is the inability of the patient to let go of the examiner's hand when they shake hands
  • percussion myotonia - via tapping over the thenar eminence - may result in contraction and slow relaxation of opponens pollicis
  • wasting and weakness distally

Others features include:

  • testicular atrophy in males
  • mental impairment in 30% of cases

Note that non-neurological manifestations - frontal baldness, cataracts especially in the posterior part of lens, infertility - may predate muscle weakness and myotonia.

Last reviewed 01/2018

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