Myasthenia gravis
"The prognosis is positive and in most cases tends to stabilize with treatment".
DR. VICENTE GAJATE GARCÍA
SPECIALIST. NEUROLOGY DEPARTMENT
Myasthenia gravis is an autoimmune disease of the neuromuscular junction, which means that it is our own organism that attacks the muscle cell, specifically the acetylcholine receptors and related structures, thus hindering muscle activation.
The main symptom is weakness with fatigue, i.e., it worsens as we do physical activity and throughout the day, improving with rest.
It is a pathology that appears in two different age groups. It can appear in young people (<40 years) being more frequent in this case in women, but also in people older than this age, being here equally frequent in men and women.
It is a disease with highly variable clinical manifestations which in severe cases can affect the respiratory muscles and pose a risk to the patient. However, it is currently treatable and new drugs are being developed for more effective treatment.
Only the striated or voluntary musculature is affected, and not the involuntary musculature such as the cardiac or intestinal muscles.
What are the symptoms of myasthenia gravis?
Although myasthenia gravis may manifest itself differently in each patient, the clinical picture is characterized by muscle weakness and fatigue, i.e. worsening with physical activity. Worsening throughout the day and clinical improvement with rest is also common.
It is important to bear in mind that general fatigue or asthenia is not the same as the weakness with fatigue that characterizes this disease, given that in this pathology not only fatigue appears with activity, but loss of strength in the affected musculature or alterations in vision or the eyelid can also be observed.
This weakness can initially manifest itself by exclusive involvement of the musculature at the eye level (ocular) with drooping eyelid (eyelid ptosis), double vision (diplopia) which is also fatiguable, becoming worse as the day goes by. But it can begin at a general level, with weakness in the muscles of the extremities or throat producing difficulty in pronouncing (dysarthria) or swallowing (dysphagia), chewing and even breathing (dyspnea). Weakness asymmetry is frequent in this disease.
The disease progresses without treatment in a progressive manner in some patients, but usually reaches its maximum expression after 2 years. There are patients who have the disease limited to the eye musculature exclusively, but there are also cases (10-20%) in which the pathology can spontaneously self-resolve.
The most common symptoms are:
- Muscle weakness and fatigue.
- Drooping eyelids.
- Double vision.
The severe part of myasthenia is especially evident when the weakness involves the respiratory muscles. In these cases dyspnea and acute respiratory failure may occur, requiring hospital admission. This situation is called myasthenic crisis.
Do you have any of these symptoms?
You may have myasthenia gravis
What causes myasthenia gravis?
Nowadays it is considered to be an autoimmune disease, which means that our own immune defense system, by mistake, is able to recognize as foreign, attack and destroy some component of the tissues of our own organism. There are several antibodies described as causative, especially the anti-acetylcholine receptor antibody.
This disease is also frequently associated with pathology at the level of the thymus (thymoma in 10% of cases and thymic hyperplasia in 70%). This is an immunological organ that is important in childhood and with time disappears. It can also be associated with other autoimmune diseases and other autoantibodies such as hypothyroidism.
Who can get myasthenia gravis?
It is a rare disease and although it can appear at any age, it usually begins to manifest itself between the second or third decade of life.
Sometimes, children born to non-myasthenic mothers present symptoms due to genetic defects that affect neuromuscular transmission. This is known as congenital myasthenia.
It affects predominantly women, especially when it starts below the age of 40 and there is no racial predominance.
How is myasthenia gravis diagnosed?
If myasthenia gravis is suspected on the basis of the clinical picture and physical examination, the diagnosis should be confirmed by performing complementary examinations:
- Electrophysiological studies: There are two tests: repetitive stimulation test and isolated fiber electromyogram, the latter being very sensitive, i.e., if the result is normal in the affected musculature, it practically rules out this pathology. The electrophysiological study is the main diagnostic test. In addition, it can help to rule out other pathologies that may clinically simulate this disease.
- Determination of antibodies: the most frequent are anti-acetylcholine receptors. They are positive in up to 50% of patients with ocular myasthenia and in >80% of cases of generalized myasthenia. However, two others occur less frequently: anti-MUSK and anti-LPR4.
- Administration of anticholinesterase drugs: The edrophonium test (Tensilon®) consists of achieving a rapid antimyasthenic effect. However, nowadays it is no longer used since it must be done with monitoring and we have other techniques such as electrophysiological studies that provide more information and without risks.
Myasthenia gravis is associated with other pathologies as mentioned above, therefore, a thymus tumor (thymoma) should always be ruled out by thoracic CT, thyroid function should be studied and the presence of other autoimmune diseases should be ruled out.
How is myasthenia gravis treated?
The treatment of myasthenia gravis can be divided into symptomatic (or symptomatic) treatment and treatment of the autoimmune disease (immunosuppressive).
Symptomatic treatment drugs do not act on the cause of the disease and therefore do not resolve it. However, if they act on the symptoms of weakness and fatigue, they improve them. Among these are the anticholinesterase drugs, whose action consists of blocking the degradation of acetylcholine by means of the cholinesterase enzyme. This type of drug helps to make more acetylcholine available for the muscle to work better.
The drugs that actually treat the disease are immunosuppressants. They act by decreasing the immune response of our organism to prevent it from attacking the neuromuscular junction, whose lesion is responsible for the symptoms. Mainly we have: corticosteroids, azathioprine, cliklophosphamide, monoclonal antibodies such as rituximab, etc. The choice of one or the other will depend on the clinical characteristics of the patient's disease and possible side effects. More and more drugs are being developed that act on other targets such as the complement system, so that more therapeutic tools are available.
In case of an abrupt worsening or severe life-threatening situations for the patient, other immunomodulatory treatments with more immediate action are necessary. There are mainly two: intravenous immunoglobulins or plasmapheresis.
In patients with thymoma, surgical removal of the thymus is necessary and also in certain patients, especially with positive anti-acetylcholine receptor antibodies, surgical removal of the thymus may be indicated.
What clinical trials do we have on Myasthenia gravis?
Where do we treat it?
IN NAVARRA AND MADRID
The Department of Neurology
of the Clínica Universidad de Navarra
The Neurology Department has extensive experience in the diagnosis and multidisciplinary treatment of neurological diseases.
We offer a diagnosis in less than 72 hours, along with a proposal for personalized treatment and post-consultation follow-up of the patient by our specialized nursing team.
We have the most advanced technology for an accurate diagnosis with cutting-edge equipment such as HIFU, deep brain stimulation devices, video EEG, PET and epilepsy surgery, among others.
Why at the Clinica?
- State-of-the-art diagnostic assistance with great work in research and teaching.
- Specialized nursing team.
- We work together with the Sleep Unit.
Our team of professionals
