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Neuromuscular disorders. Myasthenia gravis Eaton Lambert syndrome Botulism. MYASTHENIA GRAVIS. AUTOIMMUNE DISORDER ANTIBODIES DIRECTED TOWRDS THE ACETYLCHOLINE RECPTORS AT POST SYNAPTIC MEMBRANE AFFECTS ANY AGE BUT MAINLY AGE 20-30 YEARS 2 FEMALE >1 MALE ROLE OF THYMUS.

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Neuromuscular disorders


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    1. Neuromuscular disorders Myasthenia gravis Eaton Lambert syndrome Botulism

    2. MYASTHENIA GRAVIS • AUTOIMMUNE DISORDER • ANTIBODIES DIRECTED TOWRDS THE ACETYLCHOLINE RECPTORS AT POST SYNAPTIC MEMBRANE • AFFECTS ANY AGE • BUT MAINLY AGE 20-30 YEARS • 2 FEMALE >1 MALE • ROLE OF THYMUS

    3. Role of the thymus • Abnormalities of the thymus in 80 % • Production of T-cell lymphocytes which participate in the immune responses

    4. Pathophysiology • Neuromuscular junction is composed of • I-Presynaptic nerve ending which contains the synaptic vesicles(Ach) • II.Synaptic cleft • III-postsynpatic membrane:Ach receptors • Reuptake of the Ach by choline-estetrase

    5. Clinical features I • Fatigability

    6. DEFINITION • FAILURE TO SUSTAIN A MAINTAINED OR REPEATED CONTRACTION OF STRIATED MUSCLES

    7. Clinical features II • Onset usually insidious • Fluctuating weakness • Weakness at the end of the day • Extraocular muscles (ptosis) • Bulbar muscles • Limbs • generalized

    8. Clinical features III • Onset can be fulminant • With involvement of respiratory muscles • Weakness may be provoked by : • Infection, hypo k., hypocalcemia • Drugs : • Quinine.betablockers,phenytoin • Sedatives (diazepam) • Antibiotics • Surgery,pregnancy

    9. Clinical exam I • Look for fatigability • Examine motor power :first movement is normal • Repeat movements; weakness will appear • All muscles should be examined • Induce fatigue (no change of power in normal individual)

    10. Clinical exam II • Every thing else is normal • Reflexes unaffected • No wasting • No deformity • Tone is normal • No sensory change

    11. Clinical exam III • May be associated with diseases • Malignancy • Autoimmune disorders. • Then look for associated features

    12. Test to be used in the clinic :Tensilon test • Technique: • Inject edrophonium (10 mg in 1cc) • First 2 mg (0.2 cc) • If no hypotension or hypersensitivity • Inject the rest (8mg) • Result: • Weakness improves within 1-2 minutes

    13. CRISiS • I- Myasthenic crisis • II-Cholinergic crisis

    14. I.Myasthenic Crisis • Precipitating factors • Infections • Changes of drugs • Pregnancy • Surgery

    15. II-cholinergic crisis • Excessive use of anticholinergic medication • Myosis,diarrhea, • increased salivation • Abdominal cramps • bradycardia

    16. Investigations I • Logical (immune disorder) • Look for antibodies in serum EMG • Repetetive stimulation test • Technique : • Exert repetetive stimulation o nerve (ulnar) at 3,10,30-50 (tetanization) and look for response -> decremential response • Single fiber EMG :increased jitter.=delayed NMJ transmision

    17. Investigations II • Biopsy of the neuromuscular joint • And electron microscope study • Severe Loss of receptors • Look for the thymus by CXR,CT,MRI

    18. Neonatal MG • 12-16 % of infant born to myasthenic mother have myasthenic features (ptosis,weakness,poor cry and suck) • Last up to 6 weeks • Due to transplacental transfer of maternal circulating anti-Ach receptor antibodies • Temporary administration of anti choline esterase agents may be needed

    19. Treatment I • 1-Anticholine esterase agents • A-Short acting :neostigmine (Prostigmine) • B-Long acting : pyridostigmine (Mestinon) • 20.60 and 180 mg • 2-4 times a day • SE : increased bronchial secretions bronchspasm,miosis,diarrhea,abdominal cramps,bradycardia

    20. Treatment II • Reduce circulating antibodies • Plasmpheresis

    21. Treatment III :immunemodulation • Steroids • Immunosupressants • IVIG

    22. Treatment VI Thymus • Thymectomy • Thymic hyperplasia ? More common :70%

    23. EATON LAMBERT SYNDROME I • Male > female • Later onset • Associated with oat cell carcinoma of the lung in 70% • Affects mainly lower extremities • Clinically initial fatigability-weakness which improves on continuing the effort • Due to impairment of the Ach release in the presynaptic part

    24. E-L syndrome II • Neurophysilogy:incremental response • Treat the underlying cause

    25. Botulism • Bacterial :clostridium botilinum an anaerobic spore forming bacteria -> very strong toxin • May be present in improperly canned food • In raw meat • Toxin impairs pre-synaptic Ach release • Leads to severe weakness and autonomic features

    26. Botulism • Supportive treatment • Tracheostomy • Death in about 15 % • Botulinum toxin (Botox) is used in dystonia, spasticity and for cosmetic purposes