Flashcards in Myasthenia Gravis Deck (14):
what is the prevalence of myasthenia gravis?
15 per 100,000 in the UK
what are the three different presentations of Myasthenia Gravis?
pure ocular Myasthenia Gracis
generalised Myasthenia Gravis
Crises (Myasthenic and cholinergic crisis)
what is one of the most common symptoms of ocular MG
ptosis (drooping /fatigue of eyelid)
what are some common features of Generalised Myasthenia Gravis?
usually ocular disease plus weakness of another muscle group such as :
what clinical examination is useful in myasthenia gravis?
test for muscle fatigue
what investigations are useful when diagnosing myasthenia gravis?
what is the ice test?
when ice is applied to the eye lids, the patient can open their eyes for around 40 seconds, then the eyes begin to fatigue
what antibodies can be tested for when looking for myasthenia gravis?
anti acetylcholine receptor (85%)
anti MUSK (7%)
around 7 % no antibody is found (suggest another unfound)
what is the edrophonium test and how does it work?
edrophonium is an acetly choline-esterase inhibitor
it can temporarily reverse myasthenia gravis signs
administed IV and in a double Blind fashion
what are the typical EMG features seen in myasthenia gravis?
decremental loss of the compound muscle action potential (CMAP)
and on a single fibre EMG, the phenomenon of jitter and block is seen
what is jitter and block?
jitter the phenomeneon of a delay between the firing of muscles more distal to the nerve.
block is when the more distal muscle fibres never actually fire.
what are the three treatment mechanisms for myasthenia gravis
increasing the synaptic cleft acetylcholine concentration
avoiding immune mediated end plate damage
removing antibodies and their production (plasmapherisis)
what two drugs can be used to test for Myasthenia Gravis
block the breadown of acetylcholine by acetylcholine esterase in the synapse hence increasing the amount of acetylcholine available for the receptor
not used for treatment as they have cardiac risks