Myasthenia Gravis Signs and Symptoms

Myasthenia gravis (MG) is a chronic autoimmune disease that causes severe weakness in muscles throughout the body, including muscles that control the eyes, face and neck movements, limbs, and breathing. 

Myasthenia gravis is caused by your immune system's antibodies mistakenly attacking the neuromuscular junction, which is where your nervous system and muscles connect. This immune dysfunction hinders your body from transmitting acetylcholine, a neurotransmitter that regulates muscle function. Neurotransmitters are messengers that help your brain and body communicate.

Symptoms of myasthenia gravis appear suddenly and vary widely in severity from person to person. Symptoms usually start out mildly and worsen over time. Symptoms tend to worsen with increased physical activity but can improve after periods of rest and treatment with medications. There is currently no cure for myasthenia gravis, but it is possible for symptoms to go into remission for periods of time.

Myasthenia gravis affects 20 in every 100,000 people in the United States, and is the most common neurological disease that affects communication between nerves and muscles.

Common Symptoms of Myasthenia Gravis

Muscle weakness caused by myasthenia gravis can affect multiple parts of the body at the same time. The most common symptoms people with myasthenia gravis experience are:

• Eye muscle weakness
• Face and neck muscle weakness
• Difficulty swallowing (dysphagia)
• Weakness in the limbs (arms, legs, fingers, hands)

Symptoms of myasthenia gravis usually fluctuate throughout the day and are commonly worse at the end of the day after periods of work or exercise. The consistent variation and changes in muscle weakness symptoms from mild to severe usually help healthcare providers differentiate between myasthenia gravis and other similar diseases like multiple sclerosis.

While there are multiple subtypes of myasthenia gravis, the two primary clinical classifications are ocular myasthenia gravis and generalized myasthenia gravis. These classifications are defined by their differing presenting symptoms.

Ocular Myasthenia Gravis Symptoms

Ocular myasthenia gravis is the most common form of the disease. Ocular means "eye," and this type of MG is characterized by eye-related symptoms. Ocular symptoms of myasthenia gravis include:

• Ptosis: Ptosis is weakness of the muscles in the upper eyelid which causes them to droop. This can affect one or both eyes. It can also switch from one eye to the other over time. In some cases, the drooping eyelid can obstruct your vision.
• Diplopia: General ocular muscle weakness can cause diplopia, better known as “double vision." Images might start out as blurry and then develop into double images that might appear horizontally or vertically.

Around 85% of people with myasthenia gravis will experience some form of ptosis or diplopia, or both at the same time.

Generalized Myasthenia Gravis Symptoms

The symptoms of generalized myasthenia gravis can affect most areas of your body. Some of the symptoms seen in generalized myasthenia gravis include:

• Neck muscle weakness: Neck muscle weakness can cause your head to feel heavy, People experiencing this symptom can have a hard time keeping their head steady.
• Limb weakness: Limb weakness in can affect your arms, legs, and fingers. Arm weakness is the most common version of this symptom. Limb weakness can also result in generalized fatigue and tiredness.
• Facial expression: Weak facial muscles cause changes in facial expression, making it difficult for you to move your mouth. This can result in presenting an “expressionless” face.
• Dysarthria: Dysarthria is having difficulty speaking due to weak mouth and facial muscles. Dysarthria usually causes speech that is low and nasally.
• Dysphagia: Dysphagia means difficulty swallowing. Muscle weakness that causes dysphagia makes it hard to swallow food, medications, and liquids.
• Respiration muscle weakness: Weakness in the muscles that control breathing can occur, making it more difficult for you to breathe. This is the most severe and life-threatening symptom of generalized myasthenia gravis. Respiratory failure caused by weakness of the respiratory muscles is known as “myasthenic crisis.” Around 15% of people with myasthenia gravis will experience at least one “myasthenic crisis” event.
  

Symptoms in Children

Childhood myasthenia gravis is very uncommon in Western countries and more common in Asia. Approximately 50% of Asian individuals who present with myasthenia gravis symptoms are 15 years or younger. In North America, about 10 to 15% of myasthenia gravis cases affect children. 

In general, children with myasthenia gravis experience ocular symptoms like ptosis and diplopia.

Some children develop neonatal myasthenia gravis. This is a type of myasthenia gravis that develops in the womb, where the fetus receives antibodies from a parent who has myasthenia gravis. Neonatal myasthenia gravis is temporary and symptoms disappear two or three months after birth.

Symptoms In Men/Women

There are no differences in how symptoms of myasthenia gravis develop in men and women. There is, however, a difference in when symptoms present themselves.

Women with myasthenia gravis tend to begin experiencing symptoms between ages 20 to 40. Men generally start experiencing symptoms later in life, with the incidence of cases peaking between the ages of 60 and 80. 

More studies need to be conducted in order to identify the cause of these sex-based differences.  

When to Contact a Healthcare Provider

Myasthenia gravis can be a difficult condition to diagnose due to the fact that muscle weakness is a common symptom of other disorders like multiple sclerosis, botulism, thrombosis, and many others. 

Because the symptoms of myasthenia gravis can occur suddenly, you should contact a healthcare provider if you are experiencing the condition's hallmark symptoms. These include: 

• Weakness in eye muscles (drooping eyelids)
• Double vision or blurry vision
• Face and neck muscle weakness
• Consistent changes in the severity of muscle weakness symptoms

In addition to MG, sudden and severe facial drooping is a common symptom of stroke and Bell's palsy.

If you have already been diagnosed with myasthenia gravis and notice that you are having trouble breathing, you should seek immediate medical attention in order to address a potential case of myasthenic crisis and avoid respiratory failure. Timely medical assistance can treat cases of myasthenic crisis. Currently, the myasthenic crisis mortality rate is 4.4%.

A Quick Review

Myasthenia gravis is a neuromuscular disorder that causes muscle weakness throughout your body. Symptoms of myasthenia gravis include drooping eyelids, double vision, difficulty swallowing, and weakness in the muscles of the face, neck, and other parts of the body. In severe cases, weakness in muscles that control breathing can cause shortness of breath and significant breathing difficulties.

Symptoms of myasthenia gravis can begin suddenly and are known to vary widely from person to person. Additionally, symptoms tend to be worse at the end of the day after prolonged physical activity or exercise.

You should contact your healthcare provider if you or a loved one are experiencing the hallmark symptoms of myasthenia gravis in order to begin treatment and learn to manage symptoms.