Myasthenia gravis: Difference between revisions

Revision as of 03:27, 31 January 2015

Autoantibody degradation, dysfunction, and blockade of acetylcholine receptor at the NMJCite error: Closing </ref> missing for <ref> tag
Steroids
Anticonvulsants (phenytoin, barbiturates, lithium)
Psychotropics (haloperidol)
Beta-blockers / calcium-channel blockers
Local anesthetics
Narcotics
Anticholinergics (diphenhydramine)
NMJ blocking agents (roc, sux)

Neuromuscular weakness
- Upper motor neuron:
  - CVA
  - Hemorrhagic stroke
  - Multiple sclerosis
  - Amyotrophic Lateral Sclerosis (ALS) (upper and lower motor neuron)
- Lower motor neuron:
  - Spinal and bulbar muscular atrophy (Kennedy's syndrome)
- Spinal cord disease:
  - Infection (Epidural abscess)
  - Infarction/ischemia
  - Trauma (Spinal Cord Syndromes)
  - Inflammation (Transverse Myelitis)
    - Acute flaccid myelitis
  - Degenerative (Spinal muscular atrophy)
  - Tumor
- Peripheral nerve disease:
  - Guillain-Barre syndrome
  - Toxins (Ciguatera)
  - Tick paralysis
  - Diabetic peripheral neuropathy
- Neuromuscular junction disease:
- Muscle disease:
  - Rhabdomyolysis
  - Dermatomyositis
  - Polymyositis
  - Alcoholic myopathy
Non-neuromuscular weakness
- Can't miss diagnoses:
  - ACS
  - Arrhythmia/Syncope
  - Severe infection/Sepsis
  - Hypoglycemia
  - Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
    - Hypokalemic periodic paralysis
    - Thyrotoxic periodic paralysis
  - Respiratory failure
- Emergent Diagnoses:
  - Symptomatic Anemia
  - Severe dehydration
  - Hypothyroidism
  - Polypharmacy
  - Malignancy
  - Aortic disease - occlusion, stenosis, dissection
- Other causes of weakness and paralysis
  - Acute intermittent porphyria (ascending weakness)

Always evaluate tidal volume, FEV, negative inspiratory force, ability to handle secretions

Meds
1. Pyridostigmine
  1. If pt's usual dose has been missed the next dose is usually doubled
  2. PO route: 60-90mg q4hr
  3. IV route: 1/30th of the PO dose (2-3mg) by slow IV infusion
2. Neostigmine
  1. 0.5mg IV
Intubation
1. If possible avoid depolarizing AND non-depolarizing agents
  1. If pt requires paralysis use non-depolarizing agent at smaller dose
  2. If must use depolarizing agents, will need higher doses
Plasmapherisis
IVIG

Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e (2010), Chapter 167. Chronic Neurologic Disorders

Authors:

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 ==Background==
-*Autoantibody degradation, dysfunction, and blockade of acetylcholine receptor at the NMJ
+*Autoantibody degradation, dysfunction, and blockade of acetylcholine receptor at the NMJ<ref>Medications and Myasthenia Gravis (A Reference for Health Care Professionals) [http://www.myasthenia.org/LinkClick.aspx?fileticket=JuFvZPPq2vg%3d PDF]<?ref>
 *Thymus is abnormal in 75% of pts
 **Thymectomy resolves or improves symptoms in most pts, especially those with a thymoma