What is Neuromuscular Junction Disorder ?
Nerves connect with muscles at the neuromuscular junction. These junctions contain receptors that enable the muscle to respond to acetylcholine, a chemical messenger (neurotransmitter) released by the nerve to transmit a nerve impulse across the neuromuscular junction.
Which are neuromuscular junction disorders ?
- Myasthenia gravis
- Eaton-Lambert syndrome
What is Myasthenia Gravis ?
Myasthenia gravis is most common neuromuscular disorder which leads to weakness in skeletal muscles. In myasthenia gravis, antibodies (immune proteins) block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents the muscle from contracting. These antibodies are produced by the body's own immune system. The thymus is a gland that controls immune function and maybe associated with myasthenia gravis. It most commonly impacts young adult women (under 40) and older men (over 60).
Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often (but not always) involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.
What are the symptoms of Myasthenia Gravis ?
- Drooping of one or both eyelids (ptosis)
- Blurred or double vision (diplopia) due to weakness of the muscles that control eye movements
- A change in facial expression
- Difficulty swallowing
- Impaired speech (dysarthria)
- Shortness of breath
- Weakness in the arms, hands, fingers, legs, and neck.
How is Myasthenia Gravis diagnosed ?
- Neurological examination
- Ice pack test
- Edrophonium test
- Blood test - Acetylcholine receptor antibodies or Anti-MuSK antibody
- Electrodiagnostics - Repetitive nerve stimulation (RNST)
- Diagnostic imaging - Computed tomography (CT) chest for thymoma
How is Myasthenia Gravis treated ?
- Anticholinesterase medications – Symptomatic treatment with Pyridostigmine
- Immunosuppressive drugs - prednisone, azathioprine, mycophenolate mofetil, tacrolimus, and rituximab
- Plasmapheresis and intravenous immunoglobulin – Used in life threatening condition called myasthenic crisis