Myasthenia Gravis Flashcards
What is the clinical name for a droopy eyelid
Ptosis
What is the clinical term for double vision
Diplopia
What is the cause of diplopia in MG?
One eye doesn’t move properly
Face and throat muscles are affected in what % of people?
15%
What are the initial signs and symptoms of MG?
Ptosis
Diplopia
Altered speech (may be soft or nasally)
Limited facial expression
Problems chewing and swallowing
What are some symptoms of MG which affect the limbs?
-Difficulty holding head up
-Climbing stairs
-Activities involving holding arm up for some time
-Waddling gait
What is a very serious symptom of MG?
Diaphragm muscle is affected and you can’t breathe properly - artificial ventilation is needed
What is the basic PATHOPHYSIOLOGY of MG?
Antibodies bind to nicotinic receptors in the NMJ so ACh can’t bind - EPP can’t be generated and muscle can’t contract
MG is an autoimmune disease t/f
True
List some tests used to diagnose MG
-test for muscle weakness with repeated action
-anticholinesterase test
-neurophysiological testing
-test for anticholinergic receptor antibodies
How do you test for muscle weakness which worsens with repeated action?
Ask patient to look at ceiling/hold arms at side for an extended time
Eventually head/arms will droop
What is another name for the anticholinesterase test?
Tensilon Challenge Test
How do you Carry out an anticholinesterase test
Give the patient anticholinesterase
Muscle strength will improve immediately
What drugs are used in Tensilon Challenge test ?
Neostigmine/edrophonium
How do you carry out neurophysiological testing?
Repeatedly stimulate the nerve
A fall in compound muscle actions will occur
Anticholinergic receptor antibodies are present in what % of patients?
80%
Why does MG get worse with repeated action?
-when action is initiated lots of ACh is released
- only a limited store on ACh in the presynapticc terminal so less ACh released with each AP
- less ACh released + less nicotinic receptors available means weakness is more pronounced.
What is the incidence rate of MG
15/100,000
Many autoimmune diseases get progressively worse t/f?
False. Many have relapses and remissions
Women of what age are most likely to get MG?
3rd decade/20’s
Men of what age are most likely to get MG?
In 6th/7th decade
50’s and 60’s
List ways to treat MG
-Anticholinesterases
- Thymectomy
- immunosupression
-plasmaphoresis
-intravenous immunoglobulin
What do anticholinesterases do?
Prevent breakdown of ACh
List some anticholinesterases
Neostigmine
Pyridostigmine Bromide
Edrophonium
Name an Anticholinesterase which works immediately
Edrophonium
What is a thymectomy
Removal of thymus gland
How many patients benefit from a thymectomy
85% of patients under 55 benefit
How many patients who have a thymectomy no longer require drug treatment?
35%
What drug can be used to dampen the immune system when using imunosupression as a treatment?
Azathioprine
What class of drugs are used when treating a patient with immunosupression and what do they do?
Steroids
They dampen the immune system
What is plasmaphoresis
Wash out the antibodies from the plasms
What happens to the patient when you administer intravenous immunoglobulin?
It dampens the production of antibodies in the patients body.
