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Cranial Nerves

Myaesthenia Gravis

February 15th, 2021


Patients with myaesthenic syndromes exhibit muscle fatigability, or the inability to maintain contraction of muscles over time.
  • Signs of Myaesthenia Gravis

  • Skeletal Muscle Fatiguability

  • Simpson's test - ptosis on sustained upward gaze
  • Peek sign - inability to maintain sustained eye closure
  • Bulbar fatiguability - development of nasal speech with reading
  • Proximal muscle fatigability - inability to maintain arms above the head
  • Signs of Management

  • Thymectomy scar

Simpson's Test

  • How to Perform

  • Ask the patient to sustain upward gaze over an extended period of time, and look for drooping of the upper eyelids.
  • Significance

  • Patients with fatiguability secondary to myaesthenia will develop ptosis on sustained upward gaze.

Peek Sign

  • How to Perform

  • Ask the patient to keep their eyelids closed for an extended period of time, and look for appearance of the sclera.
  • Significance

  • In patients with myaesthenia, the sclera will become visible with prolonged eye closure due to fatigability.

Bulbar Fatigability

  • How to Perform

  • Ask the patient to read a paragraph aloud.
  • Significance

  • The progressive development of nasal speech while reading is suggestive of fatigability, a sign of myaesthenia.
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