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June 19 2014

Myasthenia Gravis

Write a short note on the clinical presentation and management of Myasthenia Gravis

Neuros
Neuros
June 19 2014 #

MG is an autoimmune condition characterised by progressive muscle fatigue.

CLINICAL PRESENTATION

  • The most common and typical complains are;
  • Blurry vision, diplopia or drooping of eyelids as the day progesses or while watching TV for a long time
  • In abillity to complete meals due to fatigue of mastication muscles
  • Loss of facial expressions, especially smile
  • Altered voice when the patient speaks for a longer time, this can also be tested by asking the patient to count from 1 to 40
  • Difficulty swallowing
  • Performing simple tasks using hands
  • Waddling gait, when the legs are involved

  • All these symptoms improve with rest*

CLINICAL SCENARIOS

  • If the patient is young, then it is mostly a female who has an underlying autoimmune pathology, which becomes worse, when she gets pregnant.
  • If the patient is old, then it is mostly a male who has an underlying thymoma as the cause of Myasthenia gravis

WORK UP

  • Tensilon test: the symptoms improve within 2-5 mins of administration of this drug. However, the improvement is not as drastic as described in text books.
  • Afternately, ice packs can be placed on the drooping eyelids for 2 mins and any improvement can be noted
  • Blood tests show presence of anti acetylcholine receptor antibodies
  • Repeated nerve stimulation will show muscle fatigue quicker than in normal individuals
  • Electromyography studies
  • Chest CT scan for thymoma

TREATMENT

  1. Symptomatic treatment with: Cholinesterase (pyridostigmine or neostigmine)
  2. Prednisone for relapses or non responsive to cholinesterase treatment
  3. Thymomectomy
  4. Ventilatory support in case of breathing muscles involvement
  5. Plasmapheresis
  6. IV immunoglobulins

FURTHER READING

AUTHOR: Dr. Waiz Wasey

REFERENCES:

  1. Conrad Fischer; Sonia Reichert. Neurology: Myasthenia Gravis. Master the Boards USMLE Step 3.  New York (USA): Kaplan; 2012: 225.
  2. Murray Longmore et al. Neurology: Myasthenia Gravis. Oxford Handbook of Clinical Medicine.  New York (USA): Oxford University Press; 2010: 516.