What Is Myasthenia Gravis? Key Facts Every Biology Student Should Know
Myasthenia Gravis Meaning
So, what is myasthenia gravis? Myasthenia Gravis refers to a chronic neuromuscular disease which leads to fatigue and fluctuating muscle weakness. Myasthenia Gravis symptom is visible degrees of weakness in skeletal muscles. Myasthenia Gravis meaning is derived from a Latin word which means 'grave muscle weakness.' Myasthenia Gravis meaning includes the circulation of antibodies which cause nicotinic acetylcholine receptors to be blocked at the postsynaptic neuromuscular joint. These antibodies deter motor neurons from signaling the contraction of muscles. Muscle weakness is also a form of a genetic defect in some part of the neuromuscular junction that is inherited at birth. This is another myasthenia Gravis cause.
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Myasthenia Gravis Symptoms
Now that we are familiar with myasthenia gravis meaning let us take a look at the symptoms. The primary myasthenia Gravis symptom is the weakness in voluntary skeletal muscles which control muscles in the area. The muscles fail to contract since they become unresponsive to nerve impulses. In the absence of impulse transmission of impulses, communication between nerve and muscles are blocked. The various myasthenia gravis symptoms include double vision, difficulty in talking. Drooping of eyelids, problems in lifting objects, difficulty breathing, difficulty in talking or chewing. The myasthenia gravis definition states that this condition could affect any voluntarily controlled muscle where some are affected more than others. Some of them include eye muscles causing double vision or drooping of eyelids. When this condition affects the face and throat muscles altered speaking, difficulty in chewing and swallowing and limited expressions may occur. These are the types of myasthenia gravis.
Myasthenia Gravis Causes
There are a few myasthenia gravis causes. The primary cause is when regular communication between nerve and muscle is interrupted at the neuromuscular joint where the connection of nerve cells and the place they control. The leading myasthenia gravis cause is that the neuromuscular joint is affected with acetylcholine which causes muscle contraction that no longer produces contractions required in muscle movement. These are the myasthenia gravis causes.
Diagnosis of Myasthenia Gravis
Since we have understood the myasthenia gravis meaning, we should understand how such a condition can be diagnosed. This is a long term and autoimmune condition which results in muscular weakness. The symptoms may get worse with age if proper treatment is not received. The first test for myasthenia gravis is a blood test that tests for any antibody which is stopping the signals between muscles and nerves. A high level of antibodies indicates that the person has the condition. Another test for myasthenia gravis is a nerve test which is done if the blood test results are negative. The test is known as electromyography in which small needles are inserted into the muscles for measuring electrical activity. The needles are generally inserted in the eyes or forehead. The electrical recordings indicate whether the condition is present or not. If nothing else a CT scan or MRI scan of the chest helps to assess the size of the thymus. An edrophonium test may also be done.
Myasthenia Gravis Treatment
There are various myasthenia gravis treatment methods, including both medication and therapy. The disorder is caused by the malfunction of the immune system and attacks body tissues and hence this a non-curable condition. The goal of the treatment is to deal with symptoms and control activity of the immune system. Medications include cholinesterase inhibitors, corticosteroids and immunosuppression that help to control the symptoms of the condition and bring them into manageable proportions. Intravenous therapy aims to treat the condition in the short term or treat the worsening of symptoms before conducting surgery or any other therapy. Another treatment method is surgery which is done in case of tumour in the thymus gland. A thymectomy is done through open surgery and minimally invasive therapy. Rest is also recommended to reduce muscle weakness.
Solved Examples
1. What is Myasthenia Gravis?
Answer: Myasthenia gravis is the name of a chronic neuromuscular disease that causes a fluctuation of muscles leads to weakness and fatigue. The disorder is primarily caused by the circulation of antibodies that block nicotinic acetylcholine receptors.
Did You Know?
Myasthenia gravis is a form of autoimmune disease. Autoimmune disease refers to a set of diseases in which the immune system attacks the person's own body. The immune system serves typically to protect the body from diseases and infections. These disorders cause abnormally low activity or overactivity of the immune system, which causes the body to attack and damage its tissues. Immune deficiency decreases the body's ability to fight invaders and cause vulnerability to various infections.
FAQs on Myasthenia Gravis Explained: Symptoms, Causes, and Treatment
1. What is Myasthenia Gravis (MG)?
Myasthenia Gravis is a chronic autoimmune disorder that affects the neuromuscular junction—the point where nerve cells communicate with the muscles they control. This condition leads to fluctuating muscle weakness and fatigue that worsens with activity and improves with rest. It most commonly affects the voluntary muscles of the body, particularly those controlling the eyes, face, throat, and limbs.
2. What is the underlying cause of Myasthenia Gravis symptoms?
The primary cause of Myasthenia Gravis is an autoimmune error where the body's immune system produces antibodies that block, alter, or destroy the acetylcholine (ACh) receptors on muscle cells. Acetylcholine is a neurotransmitter essential for muscle contraction. When these receptors are damaged, the communication between nerves and muscles is impaired, resulting in the characteristic muscle weakness.
3. What are the most common early symptoms of Myasthenia Gravis?
The earliest symptoms of Myasthenia Gravis often involve the eye muscles. Common signs include:
Ptosis: Drooping of one or both eyelids.
Diplopia: Double vision, which can be horizontal or vertical.
Weakness in facial muscles, leading to a changed facial expression.
Difficulty in swallowing (dysphagia) or slurred speech (dysarthria).
4. How does Myasthenia Gravis differ from Muscular Dystrophy?
Myasthenia Gravis and Muscular Dystrophy both cause muscle weakness, but they are fundamentally different. Myasthenia Gravis is an autoimmune disorder where nerve-muscle communication is blocked. In contrast, Muscular Dystrophy is a group of genetic disorders caused by mutations in genes responsible for muscle structure and protein, leading to progressive degeneration of muscle fibres themselves.
5. Can you explain the pathophysiology of Myasthenia Gravis in simple terms?
The pathophysiology of Myasthenia Gravis is a communication breakdown at the neuromuscular junction. Normally, nerves release a chemical called acetylcholine (ACh), which binds to receptors on the muscle to signal a contraction. In MG, the immune system's antibodies attack these receptors. With fewer receptors available, the muscle receives a weaker signal, leading to incomplete contraction and the feeling of fatigable weakness. The more a muscle is used, the less ACh is available, making the weakness more pronounced.
6. Why do the symptoms of Myasthenia Gravis typically worsen with activity and improve with rest?
This occurs due to the reduced number of functioning acetylcholine receptors. During activity, nerve endings deplete their stores of acetylcholine faster. In a healthy individual, enough receptors are available to catch the remaining ACh. In MG, the supply of ACh quickly becomes insufficient to stimulate the few available receptors, causing increased weakness. Rest allows time for acetylcholine to be replenished at the nerve ending, temporarily improving muscle strength.
7. How is Myasthenia Gravis diagnosed?
Diagnosis typically involves several methods to confirm the condition:
Blood Test: To detect the presence of abnormal acetylcholine receptor antibodies or other specific antibodies like MuSK.
Nerve Conduction Studies: Tests like Repetitive Nerve Stimulation (RNS) show a decreasing muscle response with repeated nerve stimulation, a hallmark of MG.
Edrophonium (Tensilon) Test: Involves injecting a drug that briefly increases ACh levels. A temporary improvement in muscle strength can indicate MG.
Imaging: A CT scan or MRI of the chest may be done to check the thymus gland for abnormalities like hyperplasia or a thymoma.
8. What are the main treatment options for Myasthenia Gravis?
While there is no cure, treatments effectively manage symptoms. Key options include:
Cholinesterase Inhibitors: Medications like pyridostigmine increase the amount of acetylcholine available at the neuromuscular junction, improving muscle strength.
Immunosuppressants: Corticosteroids and other drugs are used to suppress the immune system and reduce the production of harmful antibodies.
Thymectomy: Surgical removal of the thymus gland can improve symptoms and may lead to remission in some patients.
Plasmapheresis and IVIg: These are short-term treatments for severe symptoms or a myasthenic crisis, where the blood is filtered to remove antibodies or donor antibodies are administered.
9. Is Myasthenia Gravis a fatal disease?
With modern treatments, most individuals with Myasthenia Gravis have a normal or near-normal life expectancy. While the condition itself is not typically fatal, a severe episode known as a myasthenic crisis can be life-threatening. This involves extreme weakness of the respiratory muscles, requiring immediate medical intervention and mechanical ventilation. However, such crises are manageable with proper medical care.
10. Why is the thymus gland important in Myasthenia Gravis?
The thymus gland, located in the chest, is a central part of the immune system. In many patients with Myasthenia Gravis, the thymus is abnormal—it may be enlarged (thymic hyperplasia) or contain tumours (thymomas). It is believed to be a primary site where immune cells are incorrectly programmed to produce the antibodies that attack acetylcholine receptors. This is why its surgical removal, a thymectomy, is often a recommended part of the treatment plan.
