神经肌接头病-重症肌无力Lambert-Eaton 综合征.ppt
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1、神经肌接头病 (Disorders of neuromuscular transmission) 重症肌无力 Lambert-Eaton 综合征,Dep. of Neurology The 2nd Hospital Harbin Medical University,Neuromuscular Disorders Definition,The diseases of neuromuscular junction (NMJ) describes a sets of disease caused by circulating factors such as neurotoxins or autoa
2、ntibodies which bind with high affinity to specific proteins at the NMJ and disturb the neuromuscular transmission.,Neuromusuclar Junction (NMJ) Physiology,the nerve AP reaches the nerve terminal which inflated and without myelin and leads to the opening of calcium channel and release of ACh into th
3、e synaptic cleft by exocytosis.,Neuromusuclar Junction (NMJ) Physiology,1/3 of the ACh diffuses rapidly to the postsynaptic membrane and binds to the AChRs, leading to opening of the AChR-associated cation channel and depolarization called the end-plate potential (EPP). If the EPP exceeds certain th
4、reshold, voltage gated sodium channel at the postsynaptic membrane are opened. This generates the muscle action potential (CMAP) that propagates along the muscle fiber and activates contraction.,Neuromusuclar Junction (NMJ) Physiology,Another 1/3 of the ACh is hydrolyzed by cholinesterase (ChE). The
5、 remaining 1/3 of the ACh is recaptured by the presynaptic membrane.,重症肌无力 (Myasthenia Gravis, MG),概念 病因及发病机制 病理 临床表现 诊断及鉴别诊断 治疗,Myasthenia gravis (MG) Definition,MG was originated from Latin, meaning very severe weakness. acquired MG is an antibody and complement-mediated, T cell-dependent autoimmu
6、ne disease leading to a defect in neuromuscular transmission.,Myasthenia gravis ( MG) Epidemiology,It is the prototypic neuromuscular disorders with an incidence of 80-200 per million and prevalence about 500 per million. In China, it is estimated that 0.6 million people were diagnosed as MG and mos
7、t of them lives in the South of China. It had been a life-threatening disease before 1970s, though nowadays the incidence of death has been greatly reduced to about 0.2%.,Myasthenia Gravis (MG) Etiology,The autoimmune origin of MG is proposed long before it was established in 1973 by the direct evid
8、ence provided by Patrick and Lindstrom, who have immunized rabbit with affinity-purified Torpedo AChR with CFA and reproduced the animal models representing human MG (EAMG). The AChR is the autoantigen.,Myasthenia Gravis (MG) Etiology,The presence of anti-AChR Abs can be demonstrated in 80%-90% of M
9、G patients. There is a 3:1 female-male ratio for patients who develop MG in early adult life. Overall, the above makes MG fulfills the criteria for autoimmune diseases.,Myasthenia Gravis (MG) Etiology,Most of the patients with MG have abnormalities in the thymus, e.g. thymic hyperplastic or thymoma.
10、 Although the primary antiself event being unclear, thymus appears to be the place where it initiates. The general opinion is that virus infection or other nonspecific factors invades the thymus in genetically predisposed individuals leading to the development of MG.,Myasthenia Gravis (MG) Pathology
11、,Lymphoid folliculus can be seen in thymus. About 10% of MG patients has thymoma of epithelia type. Lymphorage, defined by aggregated lymphoid cells around the blood vessels, is sometimes seen in otherwise normal musculature in MG patients.,Myasthenia Gravis (MG) Pathology,At the NMJ, grossly simpli
12、fied postsynaptic folds with deposition of immune-complex and the anti-AChR Abs is demonstrated by immunochemical studies. There is also considerable debris within the widened synaptic cleft. Normal NMJ、NMJ in MG patients (示意图) (电镜),Myasthenia Gravis (MG) Clinical Manifestations,MG can arise at any
13、age, although young females and old males are more vulnerable to it. Precipitating factors: concurrent infection, stress, weariness, menses, pregnancy or parturition. The disease initiates insidious and follows a slowly progressive course.,Myasthenia Gravis (MG) Clinical Manifestations,Clinically, M
14、G features with fluctuated muscular weakness in intensity during the day and easy fatigability. Typically, the weakness varies in distribution and severity from day to day. Characterized by abnormal weakness, which being worse at the end of the day or after exertion and tends to improve after rest o
15、r AChE treatment.,Myasthenia Gravis (MG) Clinical Manifestations,The weakness often begins with the lateral or bilateral extra-ocular muscles, leading to asymmetric ocular palsies (e.g. diplopia, strabismic) and ptosis. Pupillary responses are not affected.,Myasthenia Gravis (MG) Clinical Manifestat
16、ions,The patients may present with less wrinkles, amimia, difficulty in closing the eyes or disclosing tooth; difficulty in chewing or swallowing, nasal speech; weakness of the neck or the proximal upper limbs.,Myasthenia Gravis (MG) Crisisdefinition,Crisis describes a rapidly developed weakness in
17、the bulbar muscles and respiratory insufficiency that necessitates assisted ventilation. It is the leading cause of death in patients with MG.,Myasthenia Gravis (MG) Crisisclassification,Myasthenic crisis: able to react to AChE drugs and being hypersensitive to the curare. Cholinergic crisis: 1. ove
18、rmedication can lead to increased weakness, which, unlike myasthenic weakness, is unaffected or enhanced by intravenous edrophonium. 2. It may be accompanied by pallor, sweating, nausea, vomiting, salivation, colic, and diarrhea (muscarinic syndrome). Brittie crisis: unresponsive to AChE.,Myasthenia
19、 Gravis (MG) Osserman Classification,Five subgroups can be defined among patients with myasthenia. I. Ocular IIa. Mild generalized IIb. Moderate generalized III. Progressively severe IV. late severe,Myasthenia Gravis (MG) Other classification,MG can also be subdivided into adolescent and adult type,
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