Myasthenia gravis Walid Reda Ashour


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Walid M. Reda Ashour
M.D Neurology, Lecturer of Neurology, Faculty of Medicine, Zagazig University, Egypt

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Myasthenia gravis Walid Reda Ashour

  1. 1. .By Dr Walid Reda Ashour
  2. 2. Myasthenia Gravis • Definition: • It is a chronic disorder in NMJ characterized by easy muscle fatiguability on repetition of movement & relieved by rest.
  3. 3. Etiology : • It is due to impairment of conduction at the neuromuscular junction. Pathogenesis : Unknown. theories: 1- Acetyl choline deficiency. 2- Choline esterase in excess. 3- Curare- like substance at the N.M.J. increasing the threshold of motor end plate to Acetyl Choline . the thymus gland is blamed for secretion of such substance. • 4- Recently the disease is considered as an auto-immune disorder, antibodies against receptors in NMJ.
  4. 4. • • • • • Age: 20-40 . Sex : female > male. Gradual onset. Progressive course. Skeletal muscles only.
  5. 5. C/P * Most characteristic feature is Easy Fatiguability on repetition of movement. • Characteristic descending march course: A) Ocular: ptosis is the earliest symptom. Later ophthalmoplegia & diplopia. pupillary reaction are normal. B) Facial: expressionless (mask face). On smiling (myasthenic snarl). C) Jaw muscles: mouth hanging open. D) Bulbar: dysarthria, dysphagia, nasal regurgitation & nasal tone of voice. E) Other muscles: neck muscles (head lolling), upper limbs more than lower limbs (prox. > distal), respiratory muscles leading to dyspnea.
  6. 6. * Diurnal variation: After night rest the patient wakes up in the morning nearly normal but as the day goes on with its activity the muscle gradually become weaker. * Tendon reflexes: normal but after repeated tapping  lost . * Muscles atrophy: may occur in long standing cases. * Some cases may be associated with thyrotoxicosis or enlarged thymus gland .
  8. 8. Diagnosis : 1- Clinically: a ) The descending march character and the diurnal variation. b) Induction of fatigue by repetition of movements. c) Walker's test: sphygmomanometer is applied to the arm. The pressure is raised above the systolic. The patient is asked to do rapid repetitive movements with his hand till exhaustion occurs. The cuff is then released. In case of myasthenia  ptosis will occur within a few seconds .
  9. 9. 2- Pharmacological tests: a) Prostigmine test : I.M injections of 2.5 mg prostigmine + one ampoule atropine ( to counteract the action of prostigmine on the smooth muscles of intestine), improvement occurs within 1/2 h in myasthenia. b) Tensilon test: 8 mg I.V improvement occurs within 1 min. 3- EMG: Reduction in amplitude of the motor action potentials on successive motor activity (decrementing response).
  10. 10. Tensilon test Before After
  11. 11. 4) CT & Plain X-ray chest may show thymic enlargement. 5) Serological tests: Anti-AchR Ab in serum of 85-90% pt. N.B. seronegative myasthenia gravis refers to disease without detectable (anti-AChR) Ab. In these patients, IgG antibodies against the musclespecific kinase (MuSK) have been described. 6) Muscle biopsy: increased lymphocytes.
  12. 12. • Treatment
  13. 13. 1 ) Rest: avoid excessive exercise and exhaustion. 2 ) Medical: I) Anticholinesterase drugs: * Prostigmine. * Pyridostigmine. II) Steroids: Prednisolone in pt. not responding to I) may give remission up to 5 years. III) Other immunosuppressant drugs: e.g. Azathioprine in pt. not responding to steroids.
  14. 14. 3) Plasmapharesis: Pt.’s plasma exchanged for albumin to reduce AchR ab level. Repeated every 2-3 weeks 4) Surgical: a) Thymectomy: May be needed in severe cases especially in young patient with duration less than 3 years . the prognosis is better if no thymoma. In pt. with thymoma irradiation should be tried before operation . b) Thyroidectomy: If there is associated thyrotoxicosis.
  15. 15. Secondary Myasthenia Easy fatiguability secondary to known diseases: 1) Bronchogenic carcinoma. 2) Polymyositis. 3) Lupus erythematosis. • In this condition there: - No descending march. - Not responding to prostigmine but to guanidine Hcl. - E.M.G after repetitive movement  increase amplitude of motor action potential (incrementing response). Eaton- Lambert phenomenon.
  16. 16. Neonatal Myasthenia Myasthenic women's infants show myasthenic manifestations at birth. • Due to transplacental passage of AchR Ab. • Poor crying, suckling & floppy infant. • They recover spontaneously within 2 – 6 weeks. • We may use Anticholinesterase drugs.
  17. 17. Congenital Myasthenia * Very rare. * Starts in infancy. * Structural abnormality in the AchR at NMJ. * persists for life. * No treatment.
  18. 18. • Crisis in myasthenia : It is of two types : 1 ) Myasthenic crisis : due to increase of the severity of myasthenia with sudden deterioration in pt.'s condition. 2) Cholinergic crisis : due to over dosage in ttt (choline esterase intoxication ). • C/P. I) weakness of the muscles which simulate myasthenic crisis . II) Fasciculations , pallor , sweating , small pupils and excessive salivation.
  19. 19. THANK YOU