Myasthenic Crisis vs. Cholinergic Crisis

Introduction

• Part of an NCLEX review series on the neuro system.
• Conditions can arise from Myasthenia Gravis (MG).
• Related lecture on MG covering pathophysiology, signs, symptoms, interventions, and medications.
• Myasthenia Gravis (MG): An autoimmune neuromuscular disease.

Pathophysiology of Myasthenia Gravis (MG)

• Neuromuscular Junction: Key Interest
  • Nerve (cholinergic fiber) meets muscle fiber.
  • Central Nervous System stimulates the nerve.
• Acetylcholine (ACh): Neurotransmitter
  • Released by cholinergic fibers to receptors (nicotinic acetylcholine receptors) on muscle fibers causing contraction.
• Myasthenia Gravis (MG): Issue at the Junction
  • Immune system creates antibodies attacking the receptors.
  • Result: Less ACh reaches receptors = Muscle weakness.
• Acetylcholinesterase (enzyme)
  • Breaks down ACh for recycling to continue muscle fiber stimulation.
  • Treatment for MG: Anti-cholinesterase medications to inhibit acetylcholinesterase.

Myasthenic Crisis

• Cause: Low/no stimulation of neuromuscular junction by ACh.
• Result: Severe muscle weakness → Respiratory failure.
• Affected Areas:
  • Voluntary muscles in face, throat, respiratory system.

Cholinergic Crisis

• Cause: Excessive stimulation at the neuromuscular junction by ACh.
• Result: Severe muscle weakness → Respiratory failure.
• Mechanism:
  • Excessive ACh overstimulating receptors causing muscle fatigue.
  • Simulates overdrive of the parasympathetic system.

Causes of Each Crisis

• Myasthenic Crisis Causes:
  • Insufficient anti-cholinesterase medication.
  • Acute exacerbation (stress, surgery, respiratory infection).
• Cholinergic Crisis Causes:
  • Excessive anti-cholinesterase medication.

Signs and Symptoms

• Myasthenic Crisis:
  • Dilated pupils.
  • Increased heart rate & blood pressure.
  • No cough/gag reflex, risk for aspiration.
  • Incontinence of bowel and bladder.
• Cholinergic Crisis:
  • Increased gastric motility (vomiting, diarrhea, abdominal cramping).
  • Constricted pupils, increased salivation, and tears (blurred vision).
  • Increased respiratory secretions.
  • Muscle fasciculations, eventually leading to flaccid paralysis.
  • Decreased heart rate & blood pressure.

Diagnosis

• Tensilon Test (edrophonium administration):
  • Myasthenic Crisis: Improvement of signs/symptoms → Positive test result.
  • Cholinergic Crisis: Worsening signs/symptoms → Negative test result.

Treatment

• Myasthenic Crisis:
  • Increase anti-cholinesterase medication.
• Cholinergic Crisis:
  • Atropine as an antidote.
  • Hold further doses of anti-cholinesterase medication.

Conclusion

• Complete lecture on Myasthenic vs. Cholinergic Crisis.
• Free quiz and subscription for more videos recommended.