Neurology Book

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Myasthenia Gravis

Aka: Myasthenia Gravis
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  1. Pathophysiology
    1. Neuromuscular autoimmune disease
    2. Antibodies form to nicotinic acetylcholine receptors
    3. Results in progressive weakness and fatigability
  2. Symptoms: Muscle Weakness provoked by exertion
    1. Proximal, Asymmetric Limb Muscle Weakness (85%)
    2. Cranial Muscle Weakness
      1. Lid lag
      2. Diplopia
      3. Facial Muscle Weakness
      4. Slurred speech
      5. Dysphagia
  3. Signs
    1. Muscle Weakness as above
    2. Deep Tendon Reflexes normal
  4. Labs
    1. Anticholinesterase (edrophonium) Test
      1. Results in improved Muscle Strength
    2. Electromyogram (EMG)
      1. Decremental response to repetitive nerve stimulation
    3. CT neck or MRI neck
      1. Thymoma evaluation
    4. Thyroid Function Test
      1. Hyperthyroidism (3-8%)
    5. Rheumatoid Factor (RF)
    6. Antinuclear Antibody (ANA)
  5. Differential Diagnosis
    1. Lambert-Eaton Syndrome
    2. Botulism
    3. Drug-induced Myasthenia
      1. Penicillamine
      2. Polymyxin
      3. Tetracycline
      4. Aminoglycosides
      5. Procainamide
      6. Propranolol
      7. Phenothiazine
      8. Lithium
    4. Neurasthenia
    5. Hyperthyroidism
    6. Intracranial mass lesion with extraocular affect
  6. Complications
    1. Respiratory compromise
    2. Aspiration Pneumonia
    3. Cholinergic crisis
  7. Management: Medication
    1. Anticholinesterase (Cholinergic)
      1. Mestinon (Neostigmine and Pyridostigmine)
    2. Immunosuppressive therapy
      1. Prednisone
        1. Start at 20 mg qd
        2. Increase gradually by 5 mg every 3 days to 60mg
        3. Continue for 3 months OR
          1. Until clinical improvement stops or declines
        4. Taper gradually to every other day
      2. Azathioprine (Imuran)
        1. Dosing
          1. 2 mg/kg/day
        2. Efficacy
          1. Effective when given with Prednisone
          2. Effect not seen for 6 months or more
        3. Monitoring
          1. Complete Blood Count (CBC)
          2. Liver Function Tests (LFT)
    3. Plasmapheresis (Plasma Exchange) and IVIg
      1. Indicated for emergent worsening/crisis
      2. Response rate: 70%
  8. Management: Thymectomy
    1. Indications
      1. Age <60 years
      2. Inadequately controlled on Mestinon
      3. Thymoma discovered
    2. Effect
      1. Clinical improvement after thymectomy in 80%
      2. Benefits may not be seen for 6 months
      3. Transcervical thymectomy may be preferred
    3. References
      1. Calhoun (1999) Ann Surg 230:555-61

Myasthenia Gravis (C0026896)

Definition (MEDLINEPLUS)

Myasthenia gravis interferes with messages your nerves send to your muscles. Myasthenia gravis often affects muscles in your head. Common symptoms are trouble with eye and eyelid movement, facial expression and swallowing. If you have myasthenia gravis, it is important to follow your treatment plan. If you do, you can expect your life to be normal or close to it.

Myasthenia gravis is caused by a problem in the transmission of nerve signals to your muscles. Normally, nerve endings release a substance that attaches to receptors on your muscles. That tells your muscles to contract. If you have myasthenia gravis, your body's own immune system makes antibodies to block that signal.

Medicine can help improve nerve-to-muscle messages and make muscles stronger. Other medicines can keep your body from making so many abnormal antibodies. Sometimes surgery to take out the thymus gland helps.
Definition (NCI) A chronic autoimmune neuromuscular disorder characterized by skeletal muscle weakness. It is caused by the blockage of the acetylcholine receptors at the neuromuscular junction.
Definition (NCI) A disease in which antibodies made by a person's immune system prevent certain nerve-muscle interactions. It causes weakness in the arms and legs, vision problems, and drooping eyelids or head. It may also cause paralysis and problems with swallowing, talking, climbing stairs, lifting things, and getting up from a sitting position. The muscle weakness gets worse during activity, and improves after periods of rest.
Definition (MSH) A disorder of neuromuscular transmission characterized by weakness of cranial and skeletal muscles. Autoantibodies directed against acetylcholine receptors damage the motor endplate portion of the NEUROMUSCULAR JUNCTION, impairing the transmission of impulses to skeletal muscles. Clinical manifestations may include diplopia, ptosis, and weakness of facial, bulbar, respiratory, and proximal limb muscles. The disease may remain limited to the ocular muscles. THYMOMA is commonly associated with this condition. (Adams et al., Principles of Neurology, 6th ed, p1459)
Definition (CSP) disease characterized by progressive weakness and exhaustibility of voluntary muscles without atrophy or sensory disturbance and caused by an autoimmune attack on acetylcholine receptors at the neuromuscular junction.
Concepts Disease or Syndrome (T047)
MSH D009157
ICD9 358.0
ICD10 G70.0, G70.00
SnomedCT 155092009, 193208002, 91637004
English Erb-Goldflam syndrome, Myasthenia gravis, NOS, Myasthenia gravis NOS, Myasthenia Gravis, MYASTHENIA GRAVIS, MG, myasthenia gravis (diagnosis), myasthenia gravis, Myasthenia gravis paralytica, Myasthenia gravis NOS (disorder), Myasthenia Gravis [Disease/Finding], myasthenia gravis (MG), myasthenia gravis disorder, Erb-Goldflam disease, Myasthenia gravis, MG - Myasthenia gravis, Myasthenia gravis (disorder), Erb-Goldflam, Goldflam-Erb, gravis; myasthenia, myasthenia; gravis
Dutch myasthenia gravis paralytica, gravis; myasthenie, myasthenie; gravis, myasthenia gravis, Myasthenia gravis
French Myasthénie grave pseudo-paralytique, Myasthénie grave, Myasthénie, Myasthénie auto-immune, Myasthénie autoimmune
German Myasthenia gravis paralytica, Myasthenia gravis
Italian Miastenia gravis paralitica, Miastenia grave
Portuguese Miastenia grave paralítica, Miastenia grave, Miastenia Grave, Miastenia Gravis
Spanish Miastenia gravis paralítica, Myasthenia gravis, enfermedad de Erb - Goldflam, miastenia grave, miastenia gravis (trastorno), miastenia gravis, SAI (trastorno), miastenia gravis, SAI, miastenia gravis, Miastenia gravis, Miastenia Gravis
Japanese 麻痺性重症筋無力症, ｼﾞｭｳｼｮｳｷﾝﾑﾘｮｸｼｮｳ, ﾏﾋｾｲｼﾞｭｳｼｮｳｷﾝﾑﾘｮｸｼｮｳ, 重症筋無力症, 筋無力症, 筋無力症-重症
Swedish Myasthenia gravis
Czech myasthenia gravis, Myasthenia gravis, Myastenia gravis
Finnish Myasthenia gravis
Russian MIASTENIIA GREVIS, MIASTENIIA TIAZHELAIA PSEVDOPARALITICHESKAIA, ERBA-GOL'DFLAMA BOLEZN', MIASTENIIA, MYASTHENIA GRAVIS, МИАСТЕНИЯ, МИАСТЕНИЯ ГРЭВИС, МИАСТЕНИЯ ТЯЖЕЛАЯ ПСЕВДОПАРАЛИТИЧЕСКАЯ, ЭРБА-ГОЛЬДФЛАМА БОЛЕЗНЬ
Korean 중증 근육무력증
Croatian MIASTENIJA GRAVIS
Polish Nużliwość mięśni rzekomoporaźna, Miastenia
Hungarian Myasthenia gravis paralytica, Myasthenia gravis
Sources
Derived from the NIH UMLS (Unified Medical Language System)


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