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    E-Note for Adult Medicine
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Neurology

Myasthenia Gravis (MG)                      SX  |  LAB |  DX |  Diff-Dx  | RX                                                

It is a relatively rare autoimmune disorder in which

Symptoms & Signs of Myasthenia Gravis

Severe exacerbations of MG present dramatically.

Respiratory Distress:

Cholinergic Crisis:

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Lab Studies:

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DX of Myasthenia Gravis

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Differential diagnosis of Myasthenia Gravis

MG must be differentiated from other diseases or agent-induced disorders that present similar clinical pictures, such as botulism, organophosphate poisoning, d-penicillamine toxic reaction, mitochondrial myopathy, compressive lesion affecting cranial nerves, LEMS, and congenital myasthenic syndromes.

RX of Myasthenia Gravis
Patients with myasthenic crisis can develop apnea very suddenly and must be closely observed.

Consultations: Emergent consultation with a neurologist is indicated. Patients with severe exacerbations requiring intubation and mechanical ventilation are managed in an intensive care setting with appropriate consultation.

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Exacerbation of MG Sx:

The activity of the disease fluctuates and adjustments in medication dosage must be made accordingly.
Non-compliance with medications may result in a fulminant exacerbation of the disease.

Many other factors influence cholinergic transmission, including drugs, temperature and emotional state.

Exacerbations may be provoked by adverse effects of many medications. Thus, a careful medication history is important. Some of the medications reported to cause exacerbations of MG include:


In case of endotracheal Intubation:

Rapid sequence intubation should be modified in that depolarizing paralytic agents, such as succinylcholine, have less predictable results in patients with myasthenia. The relative lack of ACh receptors makes these patients relatively resistant to succinylcholine; higher doses must be used to induce paralysis. Once paralysis is achieved, it may be prolonged.   A rapid onset nondepolarizing agent (i.e., rocuronium or vecuronium), is the preferred paralytic agent in this circumstance.   Although the onset is delayed compared with succinylcholine, these medications will not result in unwanted prolonged paralysis.

Infection:

REF:
SAM 8-1999
E-Medicine 8-1999 Edward Newton, M.D., Department of Emergency Medicine, LAC-USC Medical Center
Manual of Neurologic Therapeutics - Martin A. Samuels

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