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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