Definition
Myasthenia gravis is a disease characterized by impaired transmission at N.M.J. Aetiology: Autoimmune disease due to formation of antibodies that attack the nicotinic receptors in N.M.J. Â
Clinical picture
- Marked weakness of skeletal muscles.
Diagnosis
- Edrophonium: it improves the contraction of skeletal muscles in patient with myasthenia gravis.
- Neostigmine but Atropine is given before Neostigmine
Treatment
Choline estrase inhibitors:
Neostigmine + Atropine ( If ambenonium or pyridostigmine are unavailable).
Ephedrine: Facilitates transmission at N.M.J.
Immunosuppressives, corticosteroids, ACTH or cyclosporine.
Thymectomy.
Kcl & Spironolactone
| Myasthenic crisis | Cholinergic crisis | |
|---|---|---|
| Cause | Deficient cholinergic transmission | Excessive cholinergic transmission e.g. ch. E inhibitor overdosage. |
| Nicotinic manifestations Muscarinic manifestations | Flaccid paralysis. No | Spastic paralysis. Weakness in cholinergic crisis is due to permanent depolarization of nicotinic receptors at motor end plate. ↓ H.R. – ↓ B.P. – Miosis – Colic – sweating. |
| Edrophonium test | Improves | Aggrevates. |
| Treatment | *Edrophonium or neostigmine + atropine. *Artificial respiration | 1-PAM (pralidoxime)+ Atropine 2. Artificial respiration 3. Stop causative drug |