NUR4581: Myasthenia Gravis & Guillain-Barré

Myasthenia Gravis

• Definition: An autoimmune disease affecting the myoneural junction, causing fluctuating weakness in skeletal muscles.

  • Mechanism: Antibodies interfere with acetylcholine receptors, reducing receptor availability and impairing impulse transmission.

  • Symptoms: Muscle weakness worsens with activity.

• Clinical Types:

  • Ocular MG: Involves eye muscles leading to diplopia and ptosis.

  • Generalized MG: Affects all extremities and may involve respiratory muscles, leading to a myasthenic crisis (risk of respiratory failure).

• Diagnosis:

  • Tensilon Test: Administered edrophonium (an anticholinesterase drug) temporarily improves muscle strength if MG is present. Adverse effects include bradycardia and bronchoconstriction, needing atropine as an antidote.

  • Ice Test: Applicable if the patient has a history of asthma or cardiac issues.

  • Additional Tests: Blood tests for acetylcholine receptor antibodies, MRI for thymus size, and EMG for muscle strength assessment.

• Management: No cure exists; treatment focuses on improving function and reducing antibody production:

  • Anticholinesterase Medications: First-line treatment (e.g., Pyridostigmine bromide) improves muscle contraction by enhancing acetylcholine action.

  • Immunosuppressive Therapy: Corticosteroids to decrease antibody production.

  • IVIG: Administers pooled human gamma-globulin for short-term improvements.

  • Therapeutic Plasma Exchange: Filters out antibodies to help in exacerbations.

  • Thymectomy: Surgical removal of thymus can lead to significant improvements, especially in younger patients.

• Myasthenic Crisis: Severe weakness can cause respiratory failure necessitating ICU monitoring. Common triggers include infections and surgery.

• Cholinergic Crisis: Rare condition from overdose of medications, presenting similarly to myasthenic crisis.

  • Complications: Respiratory failure demands intubation or positive-pressure ventilation.

Guillain-Barré Syndrome (GBS)

• Definition: An acute autoimmune attack on peripheral nerve myelin, leading to rapid demyelination, often following a viral infection.

  • Mechanism: Immune response misidentifies nerve myelin as foreign, causing inflammation and damage.

• Types of GBS:

  • Ascending GBS: Begins in the lower extremities and may progress to respiratory failure.

  • Purely Motor: No sensory symptoms are experienced.

  • Descending GBS: Affects head and neck, harder to diagnose.

  • Miller-Fisher Variant: Characterized by ocular paralysis, ataxia, and areflexia.

• Clinical Manifestations:

  • Symmetrical weakness and diminished reflexes starting in lower limbs, potentially progressing to paralysis.

  • Autonomic dysfunction presents with unstable cardiovascular parameters (tachycardia, bradycardia, blood pressure fluctuations).

• Diagnosis and Progression: Rapid progression (within 4 weeks) is essential; slower progression indicates chronic conditions.

• Management: GBS is a medical emergency:

  • Respiratory Support: Possible need for intubation and mechanical ventilation.

  • Therapeutic Plasma Exchange and IVIG: Reduce circulating antibodies and enhance recovery time.

  • Monitoring: Continuous ECG for autonomic dysfunction; manage hypotension with increased IV fluids.

• Nursing Interventions: Prioritize:

  • Monitoring respiratory function.

  • Enhancing mobility to prevent DVT.

  • Administering nutritional support.

  • Ensuring safe swallowing to prevent aspiration.

  • Individualizing communication plans for patients.

  • Providing psychological support to alleviate fear and anxiety related to condition.