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,#,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,#,1,Myasthenia Gravis,重症肌无力,1Myasthenia Gravis重症肌无力,2,Outline,Background,Anatomy,Pathophysiology,Epidemiology,Clinical Presentation,Diagnosis of MG,Therapy For MG,Diagnosis of MG Crisis,Rehabilitation,2OutlineBackground,3,Background,First clinical description in 1672 by Thomas Willis,Acquired autoimmune disorder,abnormal communication between nerves and muscles.,Name from Latin and Greek word,Clinically characterized by:,Weakness of skeletal muscles,Fatigability on exertion.,3BackgroundFirst clinical desc,4,Anatomy-,Neuromuscular Junction(NMJ),Neuromuscular Junction(NMJ),Components:,Presynaptic membrane,Postsynaptic membrane,Synaptic cleft,The Acetylcholine receptor(AChR)is a sodium channel that opens when bound by ACh,There is a partial depolarization of the postsynaptic membrane and this causes an excitatory postsynaptic potential(EPSP),If enough sodium channels open and a threshold potential is reached,a muscle,action potential is generated in the postsynaptic membrane,4Anatomy-Neuromuscular Junct,5,Anatomy-thymus gland,the thymus gland may give incorrect instructions to developing immune cells,ultimately resulting in autoimmunity and the production of the acetylcholine receptor antibodies,thereby setting the stage for the attack on neuromuscular transmission.,5Anatomy-thymus glandthe thy,6,Pathology,thymus,15%of MG patients have thymoma,of the lymphoepithelial type,70%have,lymphoid,hyperplasia of the thymus,：,numerous,germinal centers,6Pathology thymus15%of MG p,7,Pathology,muscles contain lymphorrhages,thymoma with MG,loss of synaptic folds and widened clefts,7Pathology muscles contain ly,8,Pathophysiology,In MG,antibodies are directed toward the acetylcholine receptor at the neuromuscular junction of skeletal muscles,Results in:,Decreased number of nicotinic acetylcholine receptors at the motor end-plate,Reduced postsynaptic membrane folds,Widened synaptic cleft,8PathophysiologyIn MG,antibod,9,Epidemiology,Frequency,Annual incidence in US-2/1,000,000(E),Worldwide prevalence 1/10,000(D),Mortality/morbidity,Recent decrease in mortality rate due to advances in treatment,3-4%(as high as 30-40%),Risk factors,Age 40,Short history of disease,Thymoma,Sex,F-M(6:4),Mean age of onset(M-42,F-28),Incidence peaks-M-6-7,th,decade F-3,rd,decade,9EpidemiologyFrequency,10,Clinical presentation,Ocular and generalized MG,Modified osserman classification,Burnt-out stage,:after 15-20 years,untreated weakness becomes fixed,and atrophic,10Clinical presentation Ocular,11,Ocular,Ptosis,(dropping eyelid),asymmetric,fatigues with upgaze,Diplopia,(double vision),most common involved MR,(,medial rectus,),11Ocular Ptosis(dropping eyeli,12,Bulbar,Dysarthria,Dysphagia,Dysphonia,Masticatory weakness,jaw closure jaw open,Limbs,Commonly proximal,symmetric,Arms more affected than legs,Respiratory muscles,Exertional dyspnea,Tachypnea,Respiratory failure,(Myasthenic crisis),Axial muscles,Neck flexion,Neck extension,12Bulbar Dysarthria Limbs Co,13,Clinical presentation,muscle weakness is:,painless,fluctuates,and progressively worsens over course of day,worsens with prolonged use of affected muscles(i.e.,fatiguable,),variable distribution and severity,occasionally very asymmetric,distal weakness less common and leg weakness often later(rule out steroid myopathy in treated patient).,most commonly affected muscle groups:jaw closure,neck flexors,deltoids,triceps,may involve respiratory muscles,bowel and bladder function preserved,13Clinical presentation,14,Neurologic Examination,muscle weakness depending on distribution,no muscle shrinking(atrophy):muscular wasting is found in about 10%of patients,the reflexes are preserved,even in muscles that are weak,Fasciculations do not occur,sensation is normal,14 Neurologic Examination mus,15,Osserman Classification of MG,Based on the severity of the disease,1.Ocular myasthenia,where disease is confined to ocular muscles.(focal disease),2.Generalized myasthenia gravis of mild(a)or moderate(b)intensity.,3.Severe generalized disease,4.Acute severe generalized disease with respiratory failure.,5.Myasthenic crisis with respiratory failure(progression within 2 year).,15Osserman Classification of M,16,Other types of MG,1.,Neonatal MG,：12%of infants born to myasthenic mothers begin in the first 48 hours and may last several days or weeks,2.,Congenital MG,：rarely,3.,Drug Induced MG,:Penicillamine Gentamicin disappear when drug is discontinued,16Other types of MG 1.Neonata,17,Laboratory test,Repetitive nerve stimulation,Single fiber electromyography,Normal SFEMG,Increased jitter:MG patient,17Laboratory testRepetitive ne,18,Laboratory test,1.Antibodies to AChR,generalized MG:80%,iocular MG:50%,MG and thymoma:98-100%,The titer does not match the severity of symptoms,2.,Anti-muscle specific receptor tyrosine kinase(MuSK)antibodies,Used if MG suspected,patien
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