,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,*,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,*,Myasthenia Gravis,重症肌无力,Myasthenia Gravis重症肌无力,What is Myasthenia Gravis?,Myasthenia gravis(MG)is a,chronic autoimmune,disorder of,neuromuscular,transmission,which characterized by,fluctuating,weakness,and,fatigability,of,striated skeletal muscles,.,What is Myasthenia Gravis?Myas,Etiology and Pathogenesis,Etiology and Pathogenesis,神经病学英文ppt课件：03-Myasthenia-Gravis,Neuromuscular Junction(NMJ)in MG,Neuromuscular Junction(NMJ)i,Thymus Gland and MG,In patients with MG,the thymus gland is abnormal,.,10-15%developed thymoma,60-70%with thymic hyperplasia,It is believed that the thymus gland may give incorrect instructions about the production of,AChR-Ab,.,Thymus Gland and MGIn patients,Clinical Manifestations,Prevalence:,10-20/100,000,Annual incidence:,1.5/100,000,MG can occur at,any age,.,50%,Extraocular muscle weakness or ptosis is present initially in 50%of patients and occurs during the course of illness in 90%.,Bulbar muscles-,15%,Proximal limb muscles-,80-90%,AChR-Ab(+),in,generalized,MG,about 40-55%,AChR-Ab(+),in,ocular,MG,110%against,MuSK,(muscle-specific tyrosine kinase),and very few against,LRP4,(low density lipoprotein receptor-related protein 4),This is in general a,highly specific,test,(,up to 100%,),.,Laboratory TestsSerum antibodi,Electrophysiological Testing,Repetitive nerve stimulation(RNS),6-10 times repetitive electrical stimulation of motor peripheral nerve at 2-3 Hz could evokes a progressive decline(10%)in the amplitude of compound muscle action potentials(CMAP)-,decremental response(+),75%,in,generalized,MG,50%,in,ocular,MG.,Electrophysiological Testing,Decremental Response,in RNS,Decremental Response in RNS,Single-fiber electromyography(SFEMG),(+),92-99%,of,generalized,MG,(+),85-95%,of,ocular,MG,Chest CT scan,thymus enlargement or thymoma,Single-fiber electromyography,CT scan of thymoma,CT scan of thymoma,Diagnosis,Clinical presentation,symptoms and signs are consistent with MG and not another disorder.,Physical examination,Bedside fatigue Test,The ptosis may increase with sustained upward gaze,Limb strength may decrease with repetitive lifting or squatting,DiagnosisClinical presentation,Pharmacologic tests,Neostigmine methylsulfate,0.5-1.0 mg,i.m.,improvement occurs in,10-15 min,reaches its peak at,20 min,and last,2-3 hours,Atropine sulfate,0.3-0.5 mg,should been given to counteract muscarinic effects,The sensitivity is 80-90%.,Laboratory Tests,AChR-Ab,RNS and SFEMG,Pharmacologic tests,Differential Diagnosis,Lambert-Eaton myasthenic syndrome(LEMS),95%,patients with,antibodies to,presynaptic voltage-gated calcium channel(VGCC)(P/Q-type),which causes a deficient quantal release of ACh.,Approximately half of patients have cancer,usually,small cell lung cancer,.,Differential DiagnosisLambert-,NMJ in Lambert-Eaton syndrome,NMJ in Lambert-Eaton syndrome,Differentiate from MG,muscles of the,trunk and limbs,rather than ocular muscles are involved frequently,a temporary increase,in muscle power with a brief exercise and,a decrease,following continuing contraction,RNS at 20-50Hz evokes a marked increase(200%)in the amplitude of CMAP-,incremental response(+),poor response,to AChE inhibitors,Differentiate from MG,Incremental Response,in RNS,Incremental Response in RNS,Botulism,Intoxication usually is caused by ingestion of food containing,Clostridium botulinum,and infection via wounds is very uncommon.,Botulism toxin is a metalloendopeptidase,which cleaves specific proteins required for neuroexocytosis and therefore blocked the release of ACh.,Botulism,Typical clinical presentation is,a descending flaccid paralysis,.,cranial muscle paralysis-diplopia,ptosis,dilated pupils,difficulty in swallowing and speaking,and facial paralysis,paralysis of the limbs and respiratory muscles become apparent as the disease progresses,dysfunctions of the autonomic nervous system-reduced salivation and lacrimation,nausea,vomiting and abdominal pain,Typical clinical presentation,Polymyositis,Progressive muscle weakness mainly in proximal limb and ocular muscles are not involved in general,No,fluctuation,in weakness,RNS,-,no,decrementing response,Increasing CK level in serum,Polymyositis,Oculopharyngeal dystrophy,A progressive weakness in muscles of ocular and pharyngeal,No,fluctuation,in weakness,Chronic progressive external ophthalmoplegia(CPEO),Thyroid ophthalmopathy,Brainstem and motor cranial nerve pathology,Oculopharyngeal dystrophy,Treatment,Target of treatment:,completely clinical remission,-all symptoms disappear,4 basic therapies for MG,Symptomatic treatments-,anticholinesterase(AChE)agents,Chronic immunomodulating treatments-,corticosteroids,and,other immunosuppressive drugs,Rapid immunomodulating treatments-,plasma exchange,and,intravenous immun,o,globulin,Surgical treatment-,thymectomy,TreatmentTarget of treatment:,The factors may trigger or worsen exacerbations,Bright sunlight,Surgery,Immunization,Emotional stress,Menstru