Myasthenia gravis is a disease of the neuromuscular

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Myasthenia gravis is a disease of the neuromuscular junction in which antibodies are formed against the nicotinic Ach receptors . The thymus is an important site for immune function and myasthenia gravis probably originates in the thymus gland. Myasthenia gravis patients have high incidence of thymic abnormalities. 377
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Myasthenia gravis is associated with - (PGI-DEC 01) a) Decreased acetylcholine at nerve endings b) Decreased myosin c) Absent troponin C d) Decreased myoneural junction transmission 378
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The characteristic pathological feature of myasthenia gravis is presence of antibodies against acetyl choline receptors. These autoantibodies against the acetylcholine receptors lead to loss of functional acetylcholine receptors at the neuro muscular junction. 379
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So the greatly reduced number of acetylcholine receptors and the competitive activity of acetylcholine receptors antibodies, produce end plate potentials of insufficient amplitude to generate action potentials in some nerve fibres. Because of the blocked transmission at many end plates there results a reduction in the contractile power of the muscle. This deficiency is reflected first in the ocular and cranial muscles , the ones that are both, most continuously active and have the fewest acetylcholine receptors per motor unit. 380
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Myasthenia gravis is associated with - (PGI-DEC 01) a) Decreased acetylcholine at nerve endings b) Decreased myosin c) Absent troponin C d) Decreased myoneural junction transmission D 381
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All are clinical features of myasthenia gravis, except - (AIIMS Fed 97) a) Spontaneous remission b) Absent deep tendon reflexes c) Proximal muscle involvement d) Worsen by exertion 382
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It is a fluctuating weakness of certain voluntary muscles. The special feature about weakness is that repeated or persistent activity of a muscle group exhausts its contractile power, leading to progressive weakness. Therefore there is tendency to increase in weakness of muscle as the day progresses due to the repeated use. The strength of the muscle is restored with rest. The special vulnerability of certain muscles to be affected in a case of myasthenia gravis is a characteristic stamp. 383
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The muscles which are mainly affected are those innervated by motor nuclei of brainstem. - Occular - Masticatory, - Facial, - Deglutition and - Lingual muscles. 384
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Involvement of occular muscles in myasthenia. The weakness of levator palpebrae or extraoccular muscle is the initial manifestation of disease in about half the case and these muscle are involved eventually in more than 90%. Occular palsy and ptosis are usually accompanied by weakness of eye closure.
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  • Winter '16
  • jean grey

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