1.b.miyasteniagravis 02

7/27/2019 1.b.miyasteniagravis 02

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MYASTENA GRAVS(Myasthenia gravis)Anwar Wardy*

(07.30-08.20)anwar wardy.FKK-UMJNeurologist, DFM


2/21

Dokter dengan Tingkat kemampuan3b.

Mampu membuat diagnosis klinik berdasarkanpemeriksaan fisik dan penunjang lain: Lab

sederhana dan X-rays.

Mampu memutuskan diagnoses danmemutuskan terapi pendahuluan, serta

merujuk ke spesialis yang relevan kasus gawatdarurat.

anwar wardy wfkk umj


3/21

Myasthenia Gravis

Autoimmune

Incidence < 1/100,000

Prevalence 1/7500

Females 20s - 30s

Males 70s - 80s

anwar wardy.FKK-UMJNeurologist, DFM


4/21

Myasthenia Gravis

Fatigue, Weakness

Proximal Muscles

Bulbar musclesptosis, diplopia, weakness, dysphagia, dysarthria

worst as day progresses, prolonged activity (reading,chewing)



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Myasthenia Gravis - Diagnosis

Edrophonium

Antibodies

EMG



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Myasthenic Crisis

Respiratory failure due to severity of symptoms

FVC < 1L - consider intubation

Ensure the known myasthenic patient receives their regulardosing while in the ED (ie. Pyridostigmine 60mg q4h)



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Myasthenic Crisis VersusCholinergic Crisis

Myasthenic : inadequate drug delivery

Cholinergic : excessive drug delivery



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Edrophonium (Tensilon) 1-2mg IV (1/10thdose)

resolution (total/partial) suggests myastheniccrisis

give rest of dose (8mg) for full effect

follow with neostigmine IM/SC 0.5 - 2mg

doses q4h



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Exacerbation, fasiculations, respiratorydepression suggests cholinergic crisis

beware possible need for intubation at thispoint

further Tensilon contraindicated effects

wear off quickly



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Tensilon

Cholinergic (muscarinic) agent

Atropine to treat bradycardia, AV block, cardiac

arrestMuscle paralysis (nicotinic) atropine not effective

Unpleasant side effects



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Treatment of MG

Neostigmine / Physostigmine

Plasmapheresis

Steroids

Thymectomy



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Myasthenia gravisneuromuscular junction

disorder

weakness and fatigue of

skeletal muscles



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Normal and myasthenicneuromuscular junctions



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Immunopathogenesis of MGantigen: acetylcholine receptor

antibody: IgG to Ach receptor (80% of cases)

passive transfer: injection of patients IgG into mice

reproduces disease

immunization with antigen reproduces disease

good correlation between antibody levels and clinical

disability in the same patient



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Origin of the autoimmune

response in myasthenia gravis

antibodies produced by B cells

T cell clones reactive to Ach receptors in blood and

thymuses of MG patients

75% of patients have thymus hyperplasia or thymoma

thymectomy improves clinical condition

thymus gland contains muscle-like cells with surface

Ach receptors



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MuSK antibodies in MG((Myastheniagravis)

70% of patients with former seronegative MG

antibody to the muscle specific tyrosin kinase (agrinreceptor)

Agrin mediates clustering of Ach receptors during synapse

formation


MuSK


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Acquired presynapticNMJ disorders

LEMS: idiopathic or paraneoplastic antibodies to

voltage-gated calcium channels on the presynaptic

membrane

Botulism: toxin inhibits release of Ach

from presynaptic vesicles

therapeutic use for muscle

overactivity disorders



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Congenital myasthenic disorders


Paucity of synaptic vesicles

Choline acetyltransferase def

Ach-esterase deficiency

Ach receptor deficiency

Rapsyn deficiency

presynaptic

synaptic

post-synaptic

basal lamina


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MG istirahat



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EMG

Normal

anormal

anwar wardy.FKK-UMJ Neurologist, DFM


21/21

Wassalam, Wr,Wbr

Reference: Text Book of Neurology Gilroy. 2005

Thank U

anwar wardy.FKK-UMJ Neurologist, DFM

1.b.miyasteniagravis 02

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