Neuromuscular Junction and Myasthenia Gravis

Study Notes

Neuromuscular junction diseases impact the site where nerves and muscles connect, crucial for muscle contraction.
Myasthenia Gravis (MG) is a notable autoimmune disease impacting this junction, characterized by muscle weakness.

Primarily affects women, demonstrating a significant gender disparity.
Autoantibodies primarily target acetylcholine receptors on muscle cells, disrupting normal signaling.

Muscle weakness intensifies with physical activity and improves with rest.
Common initial symptoms include:
- Droopy eyelids (ptosis)
- Double vision (diplopia)
Can also affect bulbar muscles leading to difficulties in:
- Speech
- Chewing
- Swallowing

Often associated with abnormalities of the thymus gland, such as hyperplasia or the presence of a thymoma.

Diagnosis involves:
- Nerve conduction studies
- Single fiber EMG to assess muscle response
Key findings include:
- Decremental response in nerve conduction studies
- Increased jitter observed in EMG tests

Medications:
- Acetylcholinesterase inhibitors (e.g., pyridostigmine) augment acetylcholine availability at the neuromuscular junction.
Immunosuppressants:
- Steroids, azathioprine, or methotrexate address the autoimmune component.
Other Therapies:
- Intravenous immunoglobulin (IVIG) and plasmapheresis utilized in severe cases or crisis situations.
Surgical Intervention:
- Thymectomy, or removal of the thymus, is considered, especially in patients with thymoma.