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Disorders of the Neuromuscular JunctionDisorders of the Neuromuscular Junction
Myasthenia gravisMyasthenia gravis
Radim Mazanec, MD, PhDRadim Mazanec, MD, PhD
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DefinitionDefinition
An autoimmune disease due to an antibody An autoimmune disease due to an antibody mediated attack directed against nicotinic mediated attack directed against nicotinic AchR at neuromuscular junctionAchR at neuromuscular junction
10% have thymoma10% have thymoma 70% have thymic hyperplasia70% have thymic hyperplasia
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5
Synaptic aSynaptic antigenntigenss
nerve
muscle
VGCC
AChRMuSK
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EpidemiologyEpidemiology
Incidence 1 : 20 000 in USAIncidence 1 : 20 000 in USA
Women slightly higher incidence 3 : 2Women slightly higher incidence 3 : 2 Majority of the MG are young women in Majority of the MG are young women in
the third decade and middle aged men in the third decade and middle aged men in 5th and 6th decade5th and 6th decade
Children account for 11% of all patients Children account for 11% of all patients with MGwith MG
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Clinical FeaturesClinical Features
Fluctuated muscle weakness and excessive Fluctuated muscle weakness and excessive fatiguabilityfatiguability
Diplopia and ptosisDiplopia and ptosis Bulbar weakness – swalloving, dysarthriaBulbar weakness – swalloving, dysarthria Generalized weakness of the trunk and Generalized weakness of the trunk and
extremitiesextremities
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Diagnostic algorhitmDiagnostic algorhitm
ElectromyographyElectromyography
AChR antibodiesAChR antibodies
MR of mediastinum – thymomas, hyperplasiaMR of mediastinum – thymomas, hyperplasia
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Low frequency stimulation - Low frequency stimulation - decrementdecrement
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TreatmentTreatment
ThymectomyThymectomy
Plasma exchange in myasthenic crisis (TPE)Plasma exchange in myasthenic crisis (TPE)
Human immune globuline (IvIg)Human immune globuline (IvIg)
Corticosteroids + cytostaticsCorticosteroids + cytostatics
AChE inhibitors (pyridostigmine, distigmine)AChE inhibitors (pyridostigmine, distigmine)
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Myasthenic crisisMyasthenic crisis
Respiratory insuficiency – paralysis of Respiratory insuficiency – paralysis of respiratory musclesrespiratory muscles
Assisted ventilation requiredAssisted ventilation required
Affect 15-20% myasthenic patientsAffect 15-20% myasthenic patients Females : males = 2 : 1Females : males = 2 : 1 Average age : 55 yearsAverage age : 55 years
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Clinical featuresClinical features
Respiratory tract infection, pneumonia ( 38%)Respiratory tract infection, pneumonia ( 38%)
Respiratory failure 99%Respiratory failure 99%
Oropharyngeal or ocular weakness 86%Oropharyngeal or ocular weakness 86%
Arms and legs weakness 76%Arms and legs weakness 76%
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Complication of crisisComplication of crisis
Ateletactic pneumonia (40%)Ateletactic pneumonia (40%)
HypotensionHypotension
Cardio-respiratory arrestCardio-respiratory arrest
Pneumothorax Pneumothorax
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Treatment Treatment
ICU is required for assisted ventilationICU is required for assisted ventilation Cardiopulmonary monitoringCardiopulmonary monitoring
Plasmapheresis ( 5 sessions) or IvIg 2g/kg Plasmapheresis ( 5 sessions) or IvIg 2g/kg in five consecutive daysin five consecutive days
Antithrombotic treatmentAntithrombotic treatment Antibiotics Antibiotics Respiratory rehabilitationRespiratory rehabilitation
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OutcomeOutcome
Duration of intubation : 13 daysDuration of intubation : 13 days Duration of hospitalization : 35 daysDuration of hospitalization : 35 days
Tracheostomy cca 40%Tracheostomy cca 40% Mortality cca 4% Mortality cca 4%