Medical Surgical Nursing | Neuromuscular Disorders | Myasthenia Gravis |

 

Myasthenia Gravis:


Definition
Myasthenia Gravis (MG) is a chronic autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of voluntary muscles due to a defect in the transmission of nerve impulses to the muscles. This occurs because antibodies block or destroy acetylcholine receptors at the neuromuscular junction.

Causes

  1. Autoimmune Response:
    • The body's immune system produces antibodies that attack acetylcholine receptors or related proteins like muscle-specific kinase (MuSK), disrupting nerve-muscle communication.
  2. Thymus Gland Disorders:
    • Abnormalities in the thymus gland, such as hyperplasia or thymomas, may trigger autoimmune activity.
  3. Genetic Factors:
    • A family history of autoimmune diseases can increase susceptibility.
  4. Triggering Factors:
    • Infections, stress, certain medications (e.g., beta-blockers, quinine), and surgeries.

Signs and Symptoms

  1. Muscle Weakness:
    • A hallmark feature, worsening with activity and improving with rest.
  2. Specific Symptoms:
    • Ocular Symptoms: Ptosis (drooping eyelids), diplopia (double vision).
    • Facial Symptoms: Difficulty smiling, chewing, or swallowing.
    • Limb Weakness: Weakness in arms and legs, affecting mobility.
    • Respiratory Symptoms: In severe cases, respiratory muscles may weaken, leading to respiratory failure (myasthenic crisis).
  3. Fluctuating Symptoms:
    • Weakness worsens as the day progresses or with exertion.

Pathophysiology

  1. Normal Mechanism:

    • Acetylcholine (ACh) is released at the neuromuscular junction and binds to ACh receptors, stimulating muscle contraction.

  2. In Myasthenia Gravis:

    • Autoantibodies attack ACh receptors or related proteins, reducing receptor availability.
    • This impairs the transmission of nerve impulses to the muscles, causing reduced muscle activation and weakness.
    • Persistent immune activity leads to receptor degradation, further exacerbating the condition.

Investigations

  1. Serological Tests:
  2. Electromyography (EMG):
    • Measures electrical response of muscles to stimulation.
    • Repetitive nerve stimulation shows a decline in muscle response.
  3. Edrophonium Test (Tensilon Test):
    • Temporary improvement of muscle strength after administering edrophonium chloride, which inhibits acetylcholinesterase.
  4. Imaging:
    • CT or MRI to detect thymoma or thymic hyperplasia.
  5. Pulmonary Function Tests:
    • Assess respiratory muscle strength in severe cases.

Medications

  1. Acetylcholinesterase Inhibitors:
    • Pyridostigmine (Mestinon): Improves communication between nerves and muscles.
  2. Immunosuppressants:
    • Corticosteroids: Prednisone to reduce immune response.
    • Non-steroid Immunosuppressants: Azathioprine, mycophenolate mofetil, or cyclosporine.
  3. Plasmapheresis or Intravenous Immunoglobulin (IVIG):
    • Removes or neutralizes circulating antibodies during acute exacerbations or myasthenic crises.
  4. Monoclonal Antibodies:
    • Eculizumab (Soliris): For refractory MG.
  5. Other Treatments:
    • Antibiotics or antivirals for infections triggering MG exacerbation.

Nursing Management

  1. Assessment:

    • Monitor muscle strength, especially respiratory muscles, and assess for signs of fatigue.
    • Watch for complications like aspiration or myasthenic crisis.

  2. Medication Administration:

    • Ensure timely administration of pyridostigmine.
    • Observe for side effects of immunosuppressants and anticholinesterase medications.

  3. Patient Education:

    • Teach energy conservation techniques.
    • Instruct patients to avoid triggers like infections, stress, and certain medications.
    • Educate on proper medication usage and the importance of compliance.

  4. Airway Management:

    • Keep emergency equipment (e.g., ventilator) ready for respiratory crises.
    • Position patient to facilitate breathing and prevent aspiration.

  5. Dietary Modifications:

    • Provide soft, easy-to-chew foods to reduce the risk of choking.

  6. Emotional Support:

    • Offer psychological support and counseling for dealing with chronic illness.

Rehabilitation

  1. Physical Therapy:

    • Encourage mild exercises to maintain muscle strength and flexibility without overexertion.

  2. Speech Therapy:

    • For patients with difficulties in swallowing or speaking.

  3. Occupational Therapy:

    • Assist in adapting to daily activities with tools and strategies to conserve energy.

  4. Support Groups:

    • Connect patients with groups to share experiences and gain emotional support.

  5. Follow-Up Care:

    • Regular check-ups to monitor disease progression, medication effectiveness, and side effects.


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