Myasthenia Gravis Flashcards
What is myasthenia Gravis?
Autoimmune disease characterised by weakness of skeletal muscle. Where antibodies are made against Nicotinic acetylcholine receptors in skeletal muscle. (Decreases transmission through NMJ)
What are the signs and symptoms of Myasthenia Gravis?
Present with ocular problems:
- Drooping eyelids (Ptosis)
- Double vison (Diplopia)
- Restricted eye movement
Also:
- Lack of facial expressions
- Difficulty chewing
- Dysphagia
- Weakness in arms, legs, neck
- SOB (Myasthenic Crisis - severe)
What is the ICE test?
Where you apply ice to the muscle and you see improvement of symptoms.
What is a neurophysiology test?
Electromyogram measures muscle compound AP in response to stimulus.
Edrophoium test
Short acting cholinesterase –|
Injectino causes an increase in muscle strength.
Not used often due to side effects
What are the most affected muscles?
Muscles that are always in use.
What treatments are there for MG?
Acetylcholineesterase –| Which prevent the breakdown of acetylcholine thus improving muscle contraction.
What are the 3 mains groups of Cholinesterase –|?
Short acting - Edrophonium
Medium duration - Neostigmine, pyridostigmine, Donepezill.
Irriversible - Mathalion, Dyflos, Sarin, VX
What does AchE –| do?
Work at the NMJ, inhibit AChE which allow for the build up of ACh and then allow for muscle contraction.
What are some of the triggers of MG?
Infection, Stress/Trauma, Thyroid dysfunction, Withdrawal from AChE –|, Anaemia.
What are some medicines that interfere with Neuromucular transmission?
Phenytoin, Carbamezapine.
Aminoglycosides, macrolides, clindamycin, Fluroquinolone.
Antimuscarinic Agents.
Lidocaine
Lithium.
What are some medicines that cause muscle weakness?
Magnesium -> hypermagnesaemia
Benzos
Beta-blockers
Diuretics
Verapamil
Statins.
What is the systemic treatment MG?
Oral AChE –| Pyridostigmine.
What is the starting dose of pyridostigmine?
15mg QDS with food.
Assess cholinergic affect.
What is the maintenance dose?
60mg 4-6 x a day
