Myasthenia Gravis Clinical Features
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Questions and Answers

What is the characteristic electromyographic finding in inflammatory muscle diseases?

  • Absence of fibrillation potentials
  • Decreased incidence of polyphasic potential
  • Decreased duration and amplitude of action potential (correct)
  • Increased duration and amplitude of action potential

    • What is the primary muscle involved in neck muscle involvement in dermatomyositis?

  • Trapezius muscle
  • Sternocleidomastoid muscle
  • Scalene muscle
  • Not specified in the text (correct)

    • What is the percentage of dermatomyositis cases associated with malignancies?

  • 10-15%
  • 20-25%
  • >20% (correct)
  • 15-20%

    • What is the dose of prednisolone used in the treatment of inflammatory muscle diseases?

    <p>60 mg/day</p> Signup and view all the answers

    What is the purpose of immune suppression in the treatment of inflammatory muscle diseases?

    <p>To combine with prednisolone for 1-2 years</p> Signup and view all the answers

    What is the laboratory finding that indicates muscle damage in inflammatory muscle diseases?

    <p>Increased levels of CPK</p> Signup and view all the answers

    What is the characteristic feature of muscle involvement in Myasthenia Gravis?

    <p>No wasting of muscles and normal or brisk reflexes</p> Signup and view all the answers

    What is the diagnostic test used to detect Myasthenia Gravis?

    <p>All of the above</p> Signup and view all the answers

    What is the characteristic feature of Myotonic muscle disorders?

    <p>Delayed relaxation of skeletal muscles after contraction</p> Signup and view all the answers

    What is the mode of inheritance of Myotonia congenita?

    <p>Autosomal dominant</p> Signup and view all the answers

    What is the investigation of choice to detect Thymoma in Myasthenia Gravis?

    <p>CT chest</p> Signup and view all the answers

    What is the electrophysiological feature of Myasthenia Gravis?

    <p>Decreased amplitude and decrementing response in CMAP</p> Signup and view all the answers

    What is the characteristic clinical feature of Myotonia congenita?

    <p>Slowness in relaxation of the hand grip</p> Signup and view all the answers

    What is the underlying defect in Myotonia congenita?

    <p>Altered Na+ and K+ channels</p> Signup and view all the answers

    What is the primary cause of Myasthenia gravis?

    <p>Production of auto antibodies against Ach receptors by the thymus gland</p> Signup and view all the answers

    What is the characteristic feature of the action potential in Electromyography (EMG) study of muscular dystrophy?

    <p>Increased polyphasic action potential with short duration and low amplitude</p> Signup and view all the answers

    What is the primary treatment for Myasthenia gravis?

    <p>No specific drug treatment is available</p> Signup and view all the answers

    What is the association between Myasthenia gravis and other autoimmune diseases?

    <p>There is a close relation between Myasthenia gravis and other autoimmune diseases</p> Signup and view all the answers

    What is the characteristic feature of muscle weakness in Myasthenia gravis?

    <p>Descending march course</p> Signup and view all the answers

    What is the temporary treatment for Myasthenia gravis?

    <p>Methylprednisolone 1mg/kg/day</p> Signup and view all the answers

    What is the association between Myasthenia gravis and certain drugs?

    <p>Certain drugs can produce myasthenic features</p> Signup and view all the answers

    What is the inheritance pattern of Myasthenia gravis?

    <p>It is not inherited</p> Signup and view all the answers

    Study Notes

    Myasthenia Gravis (MG)

    • A chronic disease due to disorder of transmission at the myoneural junction as a result of formation of circulating autoantibodies against acetylcholine (Ach) receptors.
    • Characterized by muscular fatigability, may be restricted to a group of muscles, with descending march course and tendency to relapse and remission.
    • In later stages, associated with permanent weakness.
    • Thymus gland is usually hyperplastic or site of neoplasm.

    Clinical Features of Myasthenia Gravis

    • Fatigability appears on repeated or sustained movements, e.g., counting, talking, or upgaze.
    • Involvement of:
      • Ocular muscles: diplopia, drooping eyelids.
      • Facial and bulbar muscles: dysphonia, dysarthria, dysphagia, and nasality of voice.
      • Limbs: proximal weakness.
    • No wasting of muscles and reflexes are normal or brisk.

    Diagnosis of Myasthenia Gravis

    • Clinical diagnosis: ask patient to count up to 50, talk continuously for 5 minutes, or do upgaze for 5 minutes to demonstrate fatigability.
    • Therapeutic test: inject 2mg of tensilon (anticholine esterase) IV to observe rapid improvement of fatigue.
    • Detection of serum anti-Ach receptor antibodies.
    • X-ray chest and CT chest to detect thymoma.
    • EMG study: decreased amplitude and decrementing response in the amplitude of CMAP in response to repeated stimulation.

    Myotonic Muscles Disorders

    • Primary muscle disease characterized by myotonic phenomena: delayed relaxation of a skeletal muscle after contraction.
    • Clinically:
      • Slowness in relaxation of the hand grip.
      • Persisting dimpling after sharp blow on a muscle belly (e.g., tongue, thenar muscles, or deltoid muscle).
    • Hereditary syndromes of myotonia:
      • Genetically determined AD inheritance.
      • Low chloride conductance, alteration of K+ and Na+ channels.

    Inflammatory Muscle Diseases

    • Clinical diagnosis.
    • EMG study:
      • Decreased duration and amplitude of action potential.
      • Increased incidence of polyphasic potential.
      • Detection of fibrillation potentials.
    • Histopathologically:
      • Muscle fiber necrosis, phagocytosis, and regeneration.
      • Interstitial, perivascular, and perifascicular inflammatory cell infiltration.
    • Laboratory: increased levels of CPK and transaminase.

    Treatment of Inflammatory Muscle Diseases

    • Prednisolone orally 60 mg/day or 120 mg every other day.
    • Immune suppression (azathioprine 2-2.5 mg/kg/day) combined with prednisolone.
    • IV methylprednisolone in severe cases.
    • IV immunoglobulin and plasmapheresis.

    Muscular Dystrophy

    • Definition: Lack of dystrophin in muscle fibers.
    • EMG study:
      • Increased polyphasic action potential.
      • Short duration of action potential.
      • Decreased amplitude of mean action potential.
    • DNA studies and genetic counseling.
    • Treatment:
      • No specific drug treatment.
      • Supportive treatment (e.g., vitamins, physiotherapy, wearing light spinal supports, ventilatory support, and psychological support).
      • Infrequent course of methylprednisolone (1mg/kg/day) for transient improvement of power.
      • Dealing with complications (e.g., bed sores, pneumonia).
      • Genetic counseling before marriage.

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    Description

    This quiz covers the clinical features of Myasthenia Gravis, including the effects of muscle involvement on the eyes, face, and limbs. It also touches on the role of the thymus gland.

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