### Date : 2024-06-08 13:46 ### Topic : Myasthenia Gravis #neurology #medicine ---- ### Myasthenia Gravis: An Overview **Myasthenia gravis (MG)** is a chronic autoimmune neuromuscular disorder characterized by weakness and rapid fatigue of voluntary muscles. It occurs when the immune system produces antibodies that block or destroy many of the muscles' receptor sites for acetylcholine, a neurotransmitter essential for muscle contraction. #### Pathophysiology - **Autoimmune Response:** The body’s immune system produces antibodies that interfere with the transmission of nerve signals to muscles by attacking the acetylcholine receptors at the neuromuscular junction. - **Thymus Gland:** The thymus gland is often abnormal in patients with MG, sometimes developing tumors (thymomas). The thymus may give incorrect instructions to developing immune cells, causing the autoimmune response. #### Symptoms Symptoms can vary in type and severity and may include: - **Muscle Weakness:** Typically worsens with activity and improves with rest. Commonly affected muscles include those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing. - **Ptosis:** Drooping of one or both eyelids. - **Diplopia:** Double vision. - **Dysphagia:** Difficulty swallowing. - **Dysarthria:** Difficulty speaking. - **Weakness in the limbs and neck:** Can lead to difficulty in holding up the head or maintaining posture. #### Diagnosis Diagnosis involves a combination of clinical evaluation, laboratory tests, and imaging studies: 1. **Clinical Evaluation:** Detailed history and physical examination focusing on muscle strength and fatigue. 2. **Edrophonium Test:** Short-acting anticholinesterase (edrophonium) is administered to see if muscle strength temporarily improves. 3. **Blood Tests:** Detection of anti-acetylcholine receptor (AChR) antibodies or anti-muscle-specific kinase (MuSK) antibodies. 4. **Electromyography (EMG):** Measures electrical activity between the brain and muscle. Repetitive nerve stimulation tests can show characteristic decremental response. 5. **Imaging:** CT or MRI of the chest to check for thymomas. #### Treatment Treatment focuses on managing symptoms and improving muscle function. Options include: 1. **Medications:** - **Anticholinesterase Agents:** Pyridostigmine (Mestinon) improves communication between nerves and muscles. - **Immunosuppressants:** Prednisone, azathioprine, mycophenolate mofetil, cyclosporine, and tacrolimus reduce immune system activity. 2. **Intravenous Therapy:** - **Plasmapheresis:** Removes antibodies from the blood. - **Intravenous Immunoglobulin (IVIG):** Provides the body with normal antibodies, which can modify the immune response. 3. **Surgery:** - **Thymectomy:** Surgical removal of the thymus gland, which can result in symptom improvement in some patients. 4. **Lifestyle Adjustments:** - **Rest:** Frequent rest breaks to manage fatigue. - **Safety Measures:** Use of assistive devices as needed to prevent falls and ensure safety. ### Patient Example **Patient:** Jee Hoon Ju, 32-year-old female **Presentation:** Jane presents to the clinic with complaints of double vision and drooping eyelids that worsen in the evening. She also reports difficulty swallowing and generalized muscle weakness that improves with rest. **History:** - Symptoms started 3 months ago, gradually worsening - No significant past medical history **Examination:** - Ptosis of the left eyelid - Weakness in ocular muscles causing diplopia - Mild facial muscle weakness - Normal deep tendon reflexes **Investigations:** - **Edrophonium Test:** Positive, with temporary improvement in muscle strength. - **Blood Tests:** Elevated levels of anti-acetylcholine receptor antibodies. - **EMG:** Shows a decremental response to repetitive nerve stimulation. - **CT Chest:** No evidence of thymoma. **Management:** - **Medications:** Pyridostigmine to improve muscle strength. - **Immunosuppressants:** Prednisone to control autoimmune response. - **Lifestyle Adjustments:** Advised to take frequent rest breaks, avoid strenuous activities, and eat soft foods to help with swallowing difficulties. **Follow-Up:** - Regular monitoring of symptoms and medication side effects. - Referral to a neurologist for specialized care. **Outcome:** With treatment, Jane experiences significant improvement in muscle strength and a reduction in symptoms, allowing her to resume most of her daily activities.