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Myotonic Dystrophy

Physical Examination

  • Myotonia:

    • Grip Myotonia: Difficulty in releasing the hand after a firm grip.

    • Perioral Myotonia: Prolonged contraction and slow relaxation of muscles around the mouth.

    • Percussion Myotonia: Sustained muscle contraction induced by tapping on a muscle belly, such as the thenar eminence.

  • Muscle Weakness:

    • Preferentially affects distal more than proximal muscles.

    • Notable in hands, feet, neck flexors, and facial muscles.

    • Muscle Wasting:

    • Visible in the temporalis, sternocleidomastoid, and distal limb muscles, often presenting a thin, wasted appearance.

  • Facial Muscle Involvement:

    • Bilateral ptosis.

    • Facial muscle weakness leading to a "hatchet face" appearance and diminished facial expressions (mask-like facies).

  • Gait Abnormalities:

    • A waddling gait may be evident due to hip muscle weakness.

    • Foot Drop: Weakness of the dorsiflexors of the foot, leading to challenges in foot clearance during walking.

  • Absence of Deep Tendon Reflexes:

    • Reflexes such as the bicep, tricep, and ankle jerk may be reduced or absent.

  • No Sensory Deficits:

    • Sensation generally remains intact, as myotonic dystrophy primarily affects the muscular system.

Additional Examination



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