ice pack test in myasthenia gravis

8 Aug

Myasthenia gravis

Autoimmune disease

Acetylcholine receptor antibodies are antagonists at the neuromuscular junction.

 

presenting symptoms

  • weakness and fatigue after repetitive use of voluntary muscles.
  • Ptosis and diplopia are the most common
  • limb weakness or oropharyngeal symptoms
  • Life threatening myasthenia crisis respiratory failure can be seen before diagnosis or due to inadequate drug therapy or tolerance.

 

TESTING:

ACH-R antibody testing is the most specific test, although 15% can have false negatives.

quick test: placing an ice pack over the effected eye and see if symptoms improve.

Improvement of symptoms in 2 minutes is positive for myasthenia gravis.

 

HOW DOES THIS WORK?

by cooling the tissues, and more specifically the skeletal muscle fibers, the activity of the acetylcholinesterases are inhibited and there is enough acetocholine to fire the muscle fibers and contract.

 

Submitted by C. Stokes.

 

References: Kearsey C, et al. The use of the ice pack test in myasthenia gravis. Journal of the Royal Society of Medicine Short Reports. 2010 June; 1(1): 14.; picture

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