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Case 1 Myasthenia Gravis ( 重症肌无力 ) 指导老师 : 韩晓华

Case 1 Myasthenia Gravis ( 重症肌无力 ) 指导老师 : 韩晓华. Wendy Chu is a 23-year-old photographer

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Case 1 Myasthenia Gravis ( 重症肌无力 ) 指导老师 : 韩晓华

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  1. Case 1 Myasthenia Gravis (重症肌无力)指导老师: 韩晓华

  2. Wendy Chu is a 23-year-old photographer for a busy local newspaper. Over the last 8 months, she experienced strange symptoms. She had severe eyestrain when she read for longer than 15 min. She became tired when she chewed her food, brushed her teeth, or dried her hair, and she had extreme fatigue on the job.

  3. Despite her strong work ethic, Wendy had to excuse herself from several shoots because she simply could not carry the heavy equipment. Wendy is not a complainer, but she began to worry out these vague symptoms. • She was evaluated by her physician, who suspected myasthenia gravis (MG).

  4. While awaiting the results of a serum antibody test, the physician initiated a trial of pyridostigmine, an acetylcholinesteraseinhibitor. Wendy immediately felt better while taking the drug; her strength returned to almost normal. Meanwhile, the results of the antibody test were positive, confirming the diagnosis of myasthenia gravis.

  5. Questions: • What steps are involved in neuromuscular transmission? • What antibody was measured in Wendy’s serum? • Explain why severe muscle weakness occurs in MG. • Why does pridostigmine (吡啶斯的明) improve muscle strength in MG?

  6. The following drugs act at various steps in neuromuscular transmission. What is the action of each drug, and which drugs are contraindicated in MG? • Botulinus toxin (肉毒毒素)：抑制Ach 释放 • Curare (箭毒)： Ach 竞争性抑制剂 • Neostigmine (新斯的明) • Hemicholinium (宓胆碱)：减少胆碱重摄取

  7. Ca2+ Na+ K+ N2-AChR

  8. Case 2 Pheochromocytoma (嗜铬细胞瘤）: Effects of catecholamines

  9. Helen is a 51-year-old homemaker who experienced what she thought was severe menopausal symptoms. These awful attacks were becoming more frequent. Her heart raced and pounded; she had a throbbing headache and visual disturbances; she felt hot, but her hands and feet were cold; and she was nauseated, sometimes to the point of vomiting.

  10. Helen called her physician, who agreed that the symptoms were probably menopausal and prescribed hormones, but they did not relieve her symptoms. The attacks were occurring almost daily. She made an appointment with her physician.

  11. In the physician’s office, Helen’s blood pressure was severely elevated at 200/110 mmHg, and her heart rate was increased at 110 beats/min. To rule out a pheochromocytoma ( a rare tumor of the adrenal medulla), the physician ordered a 24-hour urine measurement of VMA (vanillylmandelic acid, 香草扁桃酸).

  12. To his surprise, the results of the 24-hour urinary VMA test were positive, a finding that provided nearly conclusive evidence of a pheochromocytoma. A computerized tomographic scan confirmed • that Helen had a 3-cm mass on her right • adrenal gland. While awaiting surgery to • remove the tumor, she was given • phenoxybenzamine (酚妥拉明) , • anα1-adrenergic antagonist.

  13. After an appropriate dosage of Phenoxybenzamine was established, she was also given a low dose of propranolol (心得安), a β-adrenergic antagonist. She was cleared for surgery when the medications had decreased her blood pressure to 140/90 mmHg.

  14. Questions: • What is the relationship of the adrenal medulla to the automomic nervous system? • What hormones are secreted by a pheochromocytoma? • Why does an elevated urinary level of VMA suggest the presence of a pheochromocytoma? Why is it necessary to do a 24-hour measurement of VMA, rather that a spot-urine test?

  15. In view of the pathophysiology of pheochromocytoma, explain Helen’s symptoms, especially her increased heart rate, pounding heart, cold hands and feet, visual disturbances, and nausea and vomiting. What receptors are involved in each of these symptoms? • Why are two values reported for arterial pressure, and what is the significance of each value? Why both the systolic and the diastolic blood pressures elevated?

  16. Is there a plausible explanation for the fact that Helen felt hot even though her hands and feet were cold? • How did phenoxybenzamine lower Helen’s blood pressure? • After the dosage of phenoxybenzamine was established, what was achieved by adding a low dose of propranolol? • What might have happened if Helen had been given propronolol alone?

  17. 交感神经 副交感神经 起源（节前　脊髓胸腰段灰质侧角的 脑神经核、脊髓骶部灰质 神经元）　　中间外侧柱 　 相当于侧角的部位 神经纤维　　节前短、节后长 节前长、节后短 1：10以上 1：2 分布 　　广泛、几乎是所有脏器 局限、部分脏器不受支配

  18. 图16-5

  19. 儿茶酚-O-甲基转移酶： catecholo-methytransferase, COMT 单胺氧化酶：momo-amine oxidase, MAO • 香草扁桃酸： vanillyl mandelic acid， VMA

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