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1、Department of Neurology, Affiliated Hospital of Hainan Medical CollegeQifu Li, MDMyasthenia gravisMuscular Disorders Disorders of the neuromuscular junction Disorders of muscle fibersIntroductionMyasthenia Gravis means “grave muscle weakness” which is Greek (Myasthenia) & Latin (Gravis) in originFir

2、st described in 1672 by Oxford physician Sir Thomas WillisDefinitionMyasthenia gravis (MG) is an acquired autoimmune disorder characterized clinically by weakness of skeletal muscles and fatigability on exertionLocalization：neuromuscular junction of skeletal musclesQualitative：autoimmune disorderPat

3、hophysiologyAuto-immuneProgressive diseaseRemission & exacerbationFlaw in transmission of impulses from the nerve to the muscleNeuro-muscular junctionMost often affects the muscles regulated by the cranial nervesAch Binds AChR PathophysiologySpecifically attacks receptors for acetylcholine Prevents

4、muscle contraction Progressive weakness & fatiguePrevalence: 5/100,000Men womenAge: Average age of onset is 20, with a preference for young females below the age of 40, but the disease are more common in males over age 40, especially with thymomaClinical manifestationsThe weakness varies in the cour

5、se of a single day, sometimes within minutes, and it varies from day to day or over longer periods. The weakness worsens towards the end of the day（晨輕暮重）The factors known to increase weakness include exertion, hot temperatures, infections, emotional upsets, certain drugs (for example, aminoglycoside

6、s, phenytoin, local anaesthetics), surgery, menses, and pregnancy.Clinical manifestations Fluctuating myasthenia symptomsClinical manifestationshaving an ocular and generalized formOnsetGradualEarlyPtosisDiplopiaProgressiveMay be fast or slowWith or without remissionDysphoniaDifficulty chewing & swa

7、llowingExtreme muscle weaknessOcular muscles(levator palpebrae and extraocular muscles) are affected first in about 40% of patients and are ultimately involved in about 85%-ptosis and diplopiaFacial or oropharyngeal muscles are affected-dysarthria, dysphagia, and limitation of facial movements Limb

8、and neck weakness is also common, but in conjunction with cranial weakness. Almost never are the limbs affected alone. Clinical manifestationsMyasthenic CrisisMyasthenic crisis is an exacerbation of myasthenia leading to paralysis of respiratory muscles that requires an urgent respiratory support. T

9、his is usually caused by infections, initial high dose steroid therapy, or an inadequate treatment. Patients managed in an intensive care unit. Respiratory support, plasmapheresis or intravenous immunoglobulin treatment may be required for prompt control of the disease.Clinical manifestationsClinica

10、l manifestationsResp. paralysis (Bulbar paralysis) Vital capacity iResp. failure Myasthenia crisisweakness is improved by anticholinesterase drugsMyasthenia gravis is purely a motor disorder with no effect on sensation or coordinationClinical manifestationsOssermans Classification of MGAdult classif

11、icationI Ocular myasthenia, where disease is confined to ocular muscles.(15%-20%)II Generalized myasthenia gravis of mild (a) (30%)or moderate (b)(25%) intensity.III Acute severe generalized (15%)IV Late severe generalized (10%)V Myasthenia with muscle atrophy (rare)Diagnosis History and physical ex

12、aminationDocument weakness occurring with continuous effort and recovering with rest Important negative findings: Normal sensory examination, normal bowel andbladder function Fatigue test (Jolly test)Increasing left ptosis developing upon sustained upward gaze in patient with myasthenia gravis (A th

13、rough F). Note limited elevation of left eye, denoting superior rectus palsy (A). A initially, C after around 20 seconds, F after 1 minute.Diagnostic examsPositive response to Tensilon or NeostigmineIV Tensilon/ IM NeostigminePrevents Acetylcholine from being broken downMuscle function improves with

14、in 60 sec. & lasts 30 mins. Tensilon, a short-acting anticholinesterase given intravenously (80% of patients with generalized MG and in 50% of patients with ocular MGOther antibodiesAnti-MuSK（肌肉特異性蛋白激酶） antibodies:Anti-skeletal muscle antibody titerAcetylcholine receptor antibody titerThymomaRadiogr

15、aphs of chest: CT of thymusTherapy for MG Anticholinesterase (AchE) inhibitorsImmunomodulating agentsIntravenous immune globulin (IVIg)PlasmapheresisThymectomyTreatmentNo cureAnticholinesterase agentsNeostigmine, Mestinon, Prostigmin, MytelasePrevents the destruction of Acetylcholine, thereby increa

16、sing the muscle to nerve response and muscle strengthS/E: Sweating, weakness, bradycardia, hypotensionPyridostigmine (吡啶斯地明) 60mg-120mg tid-qidCorticosteroid（皮質(zhì)激素） initial high dose steroid therapy may worsen the myasthenia, even cause myasthenic crisis the long term use steroids is associated with

17、a significant risk of potentially serious side effects impulse therapy: methylprednidolone (MPL) 1000mg IV qd for 3-5d; then decrease the dose and oral prednisoneTreatmentImmunosuppressants（免疫抑制劑）azathioprine（硫唑嘌呤）cyclophosphamide（長春新堿）Intravenous immunoglobulin （靜脈滴注大劑量丙種球蛋白） 0.4g/kg.d for 3-5 days

18、 ExpensiveMyasthenia crisisTreatmentPlasmapheresis 血漿置換 to remove Ach-R antibodies of serumtransient improvement in patients with severe involvement;Once to twice a week for 2-4 weeksTreatmentRemove thymoma. Removed early in generalized MG may increases frequency of remissions; best results in young

19、 females with hyperplastic gland and high antibody titers. Thymectomy （胸腺切除術） TreatmentTreatmentCorticosteroidsThymusradiationPlasmapheresisPlasma exchangeNursing interventionsPlanned activitiesAvoid stressAvoid infectionDo not administer barbiturates, tranquilizers, muscle relaxants, morphine etc.Eye careMyasthenic crisisCaused byNot enough med.StressS&SRapid onset of weakness Resp. distressTreatmentMedicationIV or IMResp. supportIntu