Myasthenia GravisMyasthenia Gravis“Grave muscle weakness”“Grave muscle weakness”

YASHWANT KUMAR DILLI YASHWANT KUMAR DILLI BABU-GROUP:8BABU-GROUP:8

Myasthenia Gravis• Autoimmune disease affecting the

neuromuscular junction

• Not a brain disorder – brain functions normally

• Characterized by fluctuating muscle weakness and fatigability

• Disease may be generalized or ocular specific

NeuroMuscularJunction(NMJ)

Pathophysiology• Antibodies attack Acetylcholine (ACH)

receptors at the motor end plate

• Decreased number of (ACH) receptor sites at neuromuscular junction

• Prevents neurotransmitter (ACH) from attaching and stimulating muscle contraction

• Resulting in loss of muscle strength

Causes•No single cause has been identified •Abnormal thymus tissue found in most patients with MG • Thymic tumors found in 15% of patients •Virus infections have been found in some cases and are a suspected cause

Genetic Factors• Myasthenia Gravis is not a genetically

inherited disease

• Some families appear to carry a gene that increases the risk for developing the disease

• No specific gene has been identified and

there are no tests for genetic screening

Signs and Symptoms• Affects any of the muscles that can be

controlled voluntarily, certain muscle groups are more commonly affected than others• Eye, face, throat, neck, limb muscles

• Difficulty speaking (dysarthria)

• Difficulty swallowing (dysphagia),

• Drooping eyelids (ptosis)

Signs and Symptoms• Double vision (diplopia)

• Nasal-sounding speech and weak neck muscles that give the head a tendency to fall forward or backward. 

• Symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease

• Worsening muscle weakness with repeat activity

Complications Myasthenic crisis: A life-threatening condition, which

occurs when the muscles that control breathing become too weak to do their jobs. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people recover from myasthenic crisis, so they can again breathe on their own.

Thymus tumors: About 15 percent of the people who have myasthenia gravis have a tumor in their thymus, a gland under the breastbone that is involved with the immune system. Most of these tumors are noncancerous.

Underactive or overactive thyroid: The thyroid gland, located in the neck, secretes hormones that regulate metabolism. If thyroid is underactive, body uses energy more slowly. An overactive thyroid makes body use energy too quickly.Lupus: Disease of immune system. Common symptoms include painful or swollen joints, hair loss, extreme fatigue and a red rash on the face.Rheumatoid arthritis: Caused by problems with immune system. It is most conspicuous in the wrists and fingers, and can result in joint deformities that make it difficult to use hands.

Complications

Prognosis• Chronic disease with periods of exacerbation

and sometimes remissions

• Disease course is highly variable

• Symptoms respond well to treatment and in most cases the patient can live a normal or nearly normal life

• Ocular Myasthenia has the best prognosis

Diagnosis•Edrophonium test (Tensilon) •Blood analysis •Repetitive nerve stimulation •Single-fiber electromyography (EMG) • Imaging scans

Edrophonium test: Injection of the chemical edrophonium (Tensilon) may result in a sudden, although temporary, improvement in muscle strength — an indication that you may have myasthenia gravis. Edrophonium acts to block an enzyme that breaks down acetylcholine, the chemical that transmits signals from nerve endings to muscle receptor sites.Blood analysis: A blood test may reveal the presence of abnormal antibodies that disrupt the receptor sites where nerve impulses signal muscles to move.

Repetitive nerve stimulation: Is a type of nerve conduction study, in which electrodes are attached to skin over the muscles to be tested. Small pulses of electricity are sent through the electrodes to measure the nerve's ability to send a signal to muscle. To diagnose MG, the nerve will be tested many times to see if its ability to send signals worsens with fatigue.Single-fiber electromyography (EMG): EMG measures the electrical activity traveling between brain and muscle. It involves inserting a very fine wire electrode through skin and into a muscle. In single-fiber EMGs, a single muscle fiber is tested. Imaging scans: CT scan or an MRI to confirm a tumor or other abnormality in thymus.

CT-SCAN SINGLE FIBER EMG

Exacerbation Trigger Factors

• Infection

•Stress

• Fatigue

•Cathartics (laxatives)

•Heat (sauna, hot tubs, sunbathing)

Medications/Treatment

•Plasmapheresis• Immunoglobulin Therapy•Thymectomy•Corticosteroids•Yoga exercises (Pranayama)

Medications/Treatment

• Immunosuppressive Therapy• Prednisone• Azathioprine

•Acetylcholinesterase Inhibitors• First line of therapy • Neostigmine bromide (Pyridostigmine)• Edrophonium chloride (Tensilon)

Thymectomy - surgical removal of the thymus gland. The role of the thymus gland in MG is not fully understood, and the thymectomy may or may not improve a patient's symptoms.

Plasmapheresis - a procedure that removes abnormal antibodies from the blood and replaces the patient's blood with normal antibodies through donated blood. Extent of the problems is dependent on the severity of the condition and the presence of other problems that could affect the patient.

Surgery

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