Did you know about the rare disorder that affects nearly 20 per 100,000 people worldwide? Our family here at Laparo Obeso Centre aims in guiding and educating you about this uncommon but severe disorder, Myasthenia Gravis.
What is Myasthenia Gravis ?
It is an autoimmune condition where the body attacks the muscle receptors that control the voluntary muscles, limiting the ability of the brain to control muscle movements. It is best described as a neuromuscular junction disorder with skeletal muscle weakness.
Relation between Thymus gland and myasthenia Gravis
Thymus gland is situated behind the sternum or the chest bone and is in very close relation with heart, important vessels and stays in the midline space between two lungs.In the early age, thymus gland serves the purpose of developing the immune system
As the age grows, Thymus shrinks and stays as a pad fat in the same area.In adults with myasthenia gravis, the thymus gland is larger and abnormal, usually diagnosed on a CT scan of the chest.Such gland may contain active lymphoid follicles. The gland can grow into a tumour called thymoma.It is believed that such gland may impair the body's immune system and form antibodies which eventually affect muscle actions.
Thymectomy advised for the treatment of Myasthenia gravis or thymoma
Neuro physicians advise thymectomy or surgical removal of thymus gland so as to control the disease in some patients. Early diagnosis and thymectomy within a year after diagnosis is known to give the best results in combination with medications. In some patients, thymectomy is the main part of the treatment of the disease.
How is thymectomy for myasthenia gravis performed?
Since the gland is situated in the chest, the thymectomy used to be performed by splitting the chest in the centre, just like open heart surgery. However, it is more invasive and has more chances of person requiring ventilation after surgery, especially since the muscles are already weak.It is still reserved for very large tumours.
What are the advances in thymectomy
Minimally invasive Thymectomy Thoracoscopic Thymectomy
Thymectomy can be performed through an endoscope through three small(1 to 2 cm) incisions over the chest . It is also called thoracoscopic thymectomy. Since the chest is not opened, the recovery is faster and chances of the person being on a ventilator after surgery are minimum.
It is the most preferred method since the risks are reduced with the same result. It should be performed by surgeons with experience in performing this procedure.
Dr Shashank Shah from LOC has published his innovative technique of thoracoscopic thymectomy for myasthenia gravis or thymoma in the SAGES video library. He has been performing this procedure since 2002 and has a vast experience of over 100 thymectomies performed successfully. He was also honoured by the neurology association for the same.
How are muscles contracted in patients with Myasthenia Gravis?
Since, Myasthenia Gravis is an autoimmune disease, the antibodies that are made by the body, attacks the nicotinic acetylcholine receptors. The same antibodies can also attack a similar protein called muscle, a specific kinase (MuSK) which is involved in forming nerve muscular junctions. Therefore since the antibodies attack the receptors involved in transmission of a nerve impulse to a muscle, which is basically attacking voluntary muscles that are under our control, the resulting effect for the same causes muscle weakness in our body.
Thus, Myasthenia Gravis is a disease of impaired transmission of motor nerve impulses characterized by episodic muscle weakness and easy fatigability due to autoimmune destruction of the acetylcholine receptors.
Types of Myasthenia Gravis as per their level of severity can be classified as :
We have classified Myasthenia Gravis under the severity ranges/ stages and under the age of occurrence we have discussed in details the following :
Class I : eye muscle weakness (possibly ptosis) but no other weak muscle in the body,
Class II : severe eye muscle weakness added with mild weakness of other muscles
Class II a :mainly affecting limb and axial (bones along body’s long axis) muscles
Class II b : respiratory muscles and the muscles of bulbar region (muscles of the throat and mouth)
Class III : severe eye muscle weakness and an increased weakness of other muscles
Class III a : severe effect on limb and axial muscles
Class III b : mainly attacking the respiratory and bulbar muscles more severely
Class IV : excessive weakness of the eye muscle as well as other body muscles
Class IV a : severity of limb and axial muscle weakness
Class IV b : excess severity of weakness in the respiratory and bulbar muscles
Class V : intubation to help move air in and out of the lungs thus helps in maintaining proper airway as this stage is very severe and may cause breathing troubles.
What are the causes of Myasthenia Gravis? / What are the risk factors of Myasthenia Gravis?
The risk factors or the causes can be divided into several heads like :
Antibodies and receptors :The immune system of Myasthenia Gravis produces antibodies that block and destroy the muscle receptor sites. Since the muscles receive fewer nerve signals, the resulting effect is weakness.
Thymus gland : The thymus gland maintains the production of antibodies to block acetylcholine.It is situated at the upper chest portion under the breastbone and is a part of the immune system of the body. This gland which is generally small in healthy individuals enlarges in people with Myasthenia Gravis. Added to enlargement of the thymus gland, some people may also have benign tumors in the gland called thymomas.
Negative antibodies : In some cases Myasthenia Gravis is not caused due to acetylcholine blocking or the muscle specific receptor tyrosine kinase in their blood serum. But it is caused when antibodies go against lipoprotein. This condition is called seronegative (or antibody negative) Myasthenia Gravis.
- Inheritance :Although not genetically suspected, Myasthenia Gravis have some genetic factors to it. The cluster of genes through generations is linked to the MuSK antibody positive myasthenia. Thus it can be concluded that people with a relative affected by Myasthenia Gravis are at a suspected rate of the disease.
- Other factors : Individuals already suffering from other autoimmune diseases (thyroid disease, rheumatoid arthritis etc) are at a higher risk of developing Myasthenia Gravis.
What are the symptoms of Myasthenia Gravis? / Can Myasthenia Gravis be detected early?
Myasthenia Gravis which arises from blocking and transmission of the nerve impulse leading to the symptoms as follows :
- It starts with ptosis of drooping eyelids and lazy eyes (or amblyopia)
- Slow speech due to weakness of muscles involved in speech
- Difficulty in chewing and swallowing due to weakness of muscles in mastication
- Facial weakness characterized with hanging mouth and drooping head to one side
- Breathing troubles since the respiratory muscles become too heavy making the patient out of breath.
What are the muscles affected during Myasthenia Gravis?
- The muscle of the eye or the extraocular muscle is attacked. This is generally the primary sign in every patient causing the eyelids to droop in one or both eyes. It also causes double vision due to impaired alignment. (We will further study about ocular myasthenia in detail.)
- Another common effect is the weakness of the throat muscle making the voice hoarse, chewing an effort and difficulty swallowing.
- Myasthenia Gravis also spreads weakened muscles towards the legs and arms.
What are the diagnosis of Myasthenia Gravis? / Can Myasthenia Gravis be diagnosed?
The heads of tests or diagnostics done to come to conclusion about the type and severity of Myasthenia Gravis, which helps in deciding the line of treatment for the surgeons, are as follows:
Physical examinations : This includes reviewing one’s medical history and then conducting physical and neurological examinations. Eyes are tested by checking their weaknesses on one of them or both. The patient is given certain physical activities to perform to examine their fatigability. The test results of physical examinations are quite variable in nature.
Neurological tests : Key tests are performed as in curtain tests where the affected drooped eyelid is manually lifted. Another eye (healthy one) droops too in Myasthenia Gravis patients.
Ice test : This test uses a cold pack on the eye fold for two to five minutes in the drooping or the lazy eye. With myasthenia patients the previously drooped eye will open up and appear normal. To distinguish it from a healthy individual, in the latter one there will be no difference.
Electromyography (EMG) : A single fiber electromyography is conducted to detect the motor nerve to muscle transmission and measure the electrical potential of the muscle cells. In myasthenia patients, the muscle fibers do not respond well to the electrical stimulations unlike unaffected people.
Blood tests : Special blood tests are done to examine the presence of acetylcholine receptor antibodies. In myasthenia patients the antibodies are excessively elevated. Along with these antibodies, MuSK is also found in patients with seronegative Myasthenia Gravis.
However in people with ocular myasthenia disease, the blood test does not show the presence of any such antibodies.
Edrophonium test : Where Edrophonium chloride is used for a short relief the weakness of muscle in myasthenia patients. This drug injection helps in blocking the breakdown of the acetylcholine thus temporarily increasing the levels of acetylcholine in the junction.
Imaging : In this test the thymomas is needed to locate for examine its size enlargement. The tests performed are plain chest radiograph and chest computed tomography.
Breathing tests :The pulmonary breathing test function is performed to predetermine the possibility of a respiratory fail and myasthenia attack.
What are the health risks associated with Myasthenia Gravis?
The autoimmune disorder of Myasthenia Gravis comes with other health issues and complications. Some of the detected side effects of the disorder are :
- Thymus gland tumors : The tumor present in most of the thymus gland of the Myasthenia Gravis patients are benign which is non cancerous. However in rare cases it may also take a malignant (cancerous) turn.
- Autoimmune diseases :As discussed earlier people with Myasthenia Gravis disease are more prone to other autoimmune disease. This makes their immune system weaker thus making it totally dependent on medications and steroids
What are the treatments available for Myasthenia Gravis? / Is there any treatment for Myasthenia Gravis?
Individuals affected with Myasthenia Gravis have many options open to them for temporary or short term relief from the symptoms and pain that come with the disorder. Some of them are :
Medications :Medicines can help in the process of treating Myasthenia Gravis.
Thymectomy : This surgery is performed in order to remove the excess enlarged thymus i.e. thymomas present
Acetylcholinesterase (AChE) inhibitors : This set of medicine ensures to inhibit the function of acetyl esterase, which in turn prevents the acetylcholine neurotransmitter to break down frequently thus helps in transmission of impulse from nerve to the muscle.
Soliris : For adult individuals with seronegative Myasthenia Gravis who are anti AchR and antibody positive.
Immunosuppressive steroids :or drugs also known as anti – rejection drugs are used as well to lower the inability to fight against other diseases and infection.
Surgeries : The surgical method mainly aims to remove the thymus. However while one surgery removes the gland, another removes the antibody
Plasmapheresis : A method of plasma transplant done by removing the circulating humoral factor. This surgery ensures the remission of the antibodies which attack the receptors. This procedure is usually executed in patients with severe disorder of Myasthenia Gravis.
Physical therapy : This is a very important aspect of treatment available for Myasthenia Gravis patient wherein the patient is guided to perform breathing exercises, certain physical exercises and also correction of body postures. Although Myasthenia Gravis is a disorder which improves with rest and worsens with activity, it is advisable to involve in certain activities for making the muscles strong for performing daily activities.
What are the long term consequences from the medications of Myasthenia Gravis?
The long term use of steroids as medicine for change of the immune system in Myasthenia Gravis patients has its own disadvantages and risks. Some of the possible complications are
- Weakness and Fatigue : lack of muscle strength and feeling of extreme tiredness or extreme lack of energy.
- Osteoporosis : a condition where bones become fragile and weak.
- Cataracts : cloudy and foggy covering in the lens of the eye
- Hyperglycemia : or high blood sugar
- Hypertension : or high blood pressure
- Other complications : weight gain (overweight), gastritis, death of bone tissue due to lack of blood supply, ulcers and other adaptable infections.
Can Myasthenia Gravis be prevented?
Since there are no preventable measures available for Myasthenia Gravis, from our team at Laparo Obeso Centre, it is suggested to maintain a healthy and proper hygiene for avoiding infection and get regular checkups and also involve in exercises along with proper rest.
Few facts about Myasthenia Gravis:
- It is a lifetime disease, since it is non curable, however there are surgeries and medications available to reduce the symptoms for a short period of time.
- Myasthenia Gravis can affect human beings from every gender and ethnicity. The usual age when it occurs to female is under 40 years old and to male under 60 years of age. But it can occur at any age including childhood.
- The life expectancy of Myasthenia Gravis is highly variable. While some patients lives a normal life with continued treatment or remission of antibodies by surgeries, other patients undiagnosed and diagnosed have poor prognosis approach.