Dr Arun Prasad, MS, FRCS, FRCSEd Senior Consultant, Surgeon, Minimal Access Surgery, Apollo Hospital, New Delhi, India
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New Delhi , India is one of the few places where Thoracoscopic removal of Thymus Gland is being done as a surgical treatment of Myasthenia Gravis. Other terms used to describe this modality of treatment are Minimal access/ minimal invasive surgery, VATS (Video Assisted Thoracic Surgery). Dr Arun Prasad is the senior thoracoscopic surgeon doing this at Apollo Hospital.
Following is a brief introduction of the disease, treatment options and views of some of the experienced surgeons around the world. I hope it answers most of the questions. If there are any unanswered questions or doubts, please email to me at firstname.lastname@example.org .
Warning!! Please note that the management of this disease is complicated and should be carefully planned with an expert team of Neurologist and Surgeon.
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Myasthenia Gravis is a greek word ( myo = muscle + asthenia = weakness & gravis = serious ). In other words a serious weakness of muscles / muscle weakness that is grave !!
The condition affects muscles that are controlled voluntarily. Muscles that are not controledl voluntarily, such as the heart muscles, are not affected.
Most commonly affected the muscles are those that control eye and eyelid movement, facial expression, chewing, swallowing and talking, and the arms and legs. Less often, the muscles involved in breathing may be affected. The muscle weakness is usually made worse by physical activity and improved by rest.
HOW DOES THIS HAPPEN ?
It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.
Normally when impulses travel down the nerve, the nerve endings release a neurotransmitter substance called acetylcholine. Acetylcholine travels from the neuromuscular junction and binds to acetylcholine receptors which are activated and generate a muscle contraction.
In myasthenia gravis, antibodies block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents the muscle contraction from occurring. These antibodies are produced by the body's own immune system. Myasthenia gravis is an autoimmune disease because the immune system—which normally protects the body from foreign organisms—mistakenly attacks itself.
What is the role of the thymus gland in myasthenia gravis?
The thymus gland, which lies in the chest area beneath the breastbone, plays an important role in the development of the immune system in early life. Its cells form a part of the body's normal immune system. The gland is somewhat large in infants, grows gradually until puberty, and then gets smaller and is replaced by fat with age.
In adults with myasthenia gravis, the thymus gland remains large and is abnormal. It contains certain clusters of immune cells indicative of lymphoid hyperplasia—a condition usually found only in the spleen and lymph nodes during an active immune response. Some individuals with myasthenia gravis develop thymomas (tumors of the thymus gland). Thymomas are generally benign, but they can become malignant.
The relationship between the thymus gland and myasthenia gravis is not yet fully understood. Scientists believe the thymus gland may give incorrect instructions to developing immune cells, ultimately resulting in autoimmunity and the production of the acetylcholine receptor antibodies, thereby setting the stage for the attack on neuromuscular transmission.
WHAT ARE THE FEATURES OF THIS DISEASE ?
In most cases, the first noticeable symptom is weakness of the eye muscles. In others, difficulty in swallowing and slurred speech may be the first signs. The degree of muscle weakness involved in MG varies greatly among patients, ranging from a localized form that is limited to eye muscles (ocular myasthenia), to a severe and generalized form in which many muscles - sometimes including those that control breathing - are affected. Symptoms, which vary in type and severity, may include asymmetrical ptosis (a drooping of one or both eyelids), diplopia (double vision) due to weakness of the muscles that control eye movements, an unstable or waddling gait, weakness in arms, hands, fingers, legs, and neck, a change in facial expression, dysphagia (difficulty in swallowing), shortness of breath and dysarthria (impaired speech, often nasal due to weakness of the velar muscles).
In myasthenic crisis a paralysis of the respiratory muscles occurs, necessitating assisted ventilation to sustain life. In patients whose respiratory muscles are already weak, crises may be triggered by infection, fever, an adverse reaction to medication, or emotional stress. Since the heart muscle is only regulated by the autonomic nervous system, it is generally unaffected by MG.
WHAT TESTS ARE NEEDED ?
• Acetylcholine receptor antibodies (may be present in the blood)
• CT or MRI scan of the chest (may show a tumor in the thymus)
• Repetitive stimulation (a type of nerve conduction study, may be more sensitive)
• Single-fiber EMG (may be very sensitive)
There are four basic therapies used to treat myasthenia gravis
• Symptomatic treatments (anticholinesterase agents)
• Chronic immunomodulating treatments (glucocorticoids and other immunosuppressive drugs)
• Rapid immunomodulating treatments (plasma exchange and intravenous immune globulin)
• Surgical treatment (thymectomy) => Click picture on right to see site about the 3 mehods to do so =>
Medicines known as cholinesterase inhibitors (such as pyridostigmine) can block the action of the chemical that normally makes the muscles relax once they have contracted. These medicines work best with mild myasthenia gravis, and can improve muscle contractions and muscle strength in the affected muscles.
Cholinesterase inhibitors sometimes cause side effects, such as stomach cramps and nausea.
Steroids (such as prednisolone) or immunosuppressant drugs (such as azathioprine) can alter the body's immune system and reduce the production of the antibodies that cause myasthenia gravis. Generally, steroids take a month to work. Azathioprine takes at least three to six months to work.
Although it may take several months, this medication can reduce or even completely relieve myasthenia gravis symptoms. It is often prescribed to people who cannot have a thymectomy, or to those whose symptoms have not been improved by a thymectomy.
Plasmapheresis and immunoglobulin therapy
If myasthenia gravis muscle weakness becomes so severe that it causes life-threatening breathing or swallowing problems, plasmapheresis or intravenous immunoglobulin therapy can be given in hospital:
• In plasmapheresis, your blood is routed through a machine that removes the plasma containing the harmful antibodies, and replaces it with antibody-free plasma before returning it to your body.
• In intravenous immunoglobulin therapy, you are injected with normal antibodies that change the way your immune system acts.
Both of these treatments can produce a rapid improvement in myasthenia gravis symptoms, but the benefits only last for a few weeks, so they are not suitable as long-term treatments and are usually used only if you are seriously ill.
The thymus is a gland located in the chest area that helps the immune system develop. A thymectomy is the removal of the thymus gland. The thymus is removed as a treatment of Myasthenia Gravis in the hope of increasing the chance of remission (absence of symptoms and no need of medication) from the disease. It is thought that in some patients removal of the thymus reduces the production of antibodies against the nerve-muscle junction, which are producing the disease.
The exact mechanism by which thymectomy produces benefits in MG is uncertain. The possible mechanisms include:
(1) removal of the thymus may eliminate a source of continued antigen stimulation;
(2) thymectomy may remove a reservoir of B cells secreting acetycholine-receptor antibody; and
(3) thymectomy may in some way correct a disturbance of immune regulation in MG.
Surgical removal of the thymus gland (thymectomy) improves the symptoms of myasthenia gravis in more than 70% of those who have it. Symptoms disappear completely in about 30% of people. However, the improvement may take some time to appear. It is usually seen within the first year, but may take up to three years.
Thymectomy is recommended for all individuals with thymoma (tumour of the thymus gland).
When should a thymectomy be done?
Most experts and some studies suggest that a thymectomy be done early in treatment. Most experts do not recommend thymectomy for purely Ocular Myasthenia Gravis, but there are differences in opinion. Patients with immune MG tend to respond similarly to thymectomy whether they have antibodies to the acetylcholine receptors or not, but there is disagreement, with some experts thinking that patients without antibodies against the receptor do not benefit from thymectomy.
A thymectomy is generally only recommended for people under the age of 60.
What are the methods for this surgery ?
There are 3 approaches to this surgery based on the training and experience of the surgeon.
1. The transcervical approach involves a small incision above the breastbone across the neck.
2. The transsternal approach involves going through the breastbone to remove the thymus gland. Most surgeons prefer this method as it is easy and ensures complete removal. The transsternal approach does produce a larger scar, is painful and the recovery period is long.
3. Since the begining of 21st century, Thoracoscopic ( a video-assisted technique - VATS), which uses smaller incisions, has been developed. It is done through 3 small keyholes in the chest. Pain is less, recovery quick and paitent is able to go home in 2-3 days. This procedure is being done at selected centres around the world. Video on the left shows the steps of this surgery in brief. ( Video is uploaded for surgeons who intend to learn this procedure )
4. Robotic surgery has taken thymectomy to unprecidented heights with its accuracy and precision. RATS or robotic assisted thoracic surgery is now soon going to become the gold standard for this surgery. This method is expensive both for the patient and the hospital hence very few centres are offering it. Also a trained robotic surgeon with good thoracoscopic surgery experience is needed. Brief video of Robotic Thymectomy is shown in the clip below.
BENEFITS OF ROBOTIC SURGERY
Some major advantages of robotic surgery are precision, miniaturization, smaller incisions, decreased blood loss, less pain, and quicker healing time. Further advantages are articulation beyond normal manipulation and three-dimensional magnification, resulting in improved ergonomics. Robotic techniques are also associated with reduced duration of hospital stays, blood loss, transfusions, and use of pain medication.
In addition, surgeons no longer have to stand throughout the surgery and do not tire as quickly. Naturally occurring hand tremors are filtered out by the robot’s computer software. Finally, the surgical robot can continuously be used by rotating surgery teams.
By providing surgeons with superior visualization, enhanced dexterity, greater precision and ergonomic comfort, the da Vinci Surgical System makes it possible for more surgeons to perform minimally invasive procedures involving complex dissection or reconstruction.
Complications of surgery
Thymectomy is a major surgery and there are risks of bleeding, collapsed lung, and post-operative infections. Pain in the region of the incision and the back should be expected from surgery. Because of anesthesia and the stress of surgery, patients with MG may become temporarily weaker after surgery. In addition, a patient with other medical problems may have more complications. The surgeon, anesthetist and neurologist will discuss these issues with you prior to surgery.
One of the largest series in the world is from University of California, Los Angeles, School of Medicine.
This study states the following:
There were no operative deaths, but one late death occurred at 5 months. During a mean followup of 3.6 years, 67 patients (80%) benefited from operation with remission achieved in 30 (36%) and improvement noted in 37 (44%). Acetylcholine receptor site antibody was present in 43 patients, of whom 19 (44%) achieved remission in contrast to 9 (27%) of the 33 patients without antibody. Hyperplasia of the excised thymus in 38 patients was associated with remission in 20 (53%) in contrast to remission in 7 (20%) of the 35 patients whose glands were "normal" or atrophic. The best prognosis was found in the 23 patients who had both receptor site antibody and thymic hyperplasia, as remission occurred in 15 of them (65%) in contrast to only 6 (27%) of the 22 patients who had neither factor. Remission rates (remissions per 1,000 patient-months of follow-up) for the present series (84 patients), the previous group (249 patients), and the overall group (333 patients) are 9.95, 6.13, and 6.62, respectively.
( In simple English, it means 8 out of 10 patients were happy with the results of the surgery )
Another study from
Department of Neurology, The Institute of Neurological Sciences, CARE Hospital, Exhibition Road, Nampally, Hyderabad - 500 001 India
In conclusion the balance of evidence currently favors thymectomy for generalized nonthymomatous MG (level of evidence 2; recommendation grade B). In the absence of thymoma, the current practice is generally not to recommend thymectomy for patients over age 60 (level of evidence 3; recommendation grade D). Thymectomy is mostly considered scarcely effective in anti-MuSK-positive MG; however, at present, no firm conclusions can be drawn on its role in the treatment of this form of MG. In thymomatous MG, thymectomy should always be performed.
Video-assisted thoracoscopic surgery or transsternal thymectomy in the treatment of myasthenia gravis?
a Imperial College London, South Kensington Campus, London SW7 2AZ, UK
b Department of Thoracic Surgery, Guy's Hospital, Great Maze Pond, London SE1 9RT, UK
A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was how video-assisted thoracoscopic surgery (VATS) compares to median sternotomy in the surgical management of patients with myasthenia gravis (MG)? Overall 74 papers were found using the reported search, of which 15 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results are tabulated. We conclude that VATS produces equivalent postoperative mortality and complete stable remission (CSR) rates, with superior results in terms of hospital stay, operative blood loss and patient satisfaction at the expense of a doubling of operative time.
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