Thymectomy for myasthenia gravis

 

Thymectomy, a surgical procedure to remove the thymus gland, is one of the therapeutic options available for myasthenia gravis (MG).

MG is an autoimmune disease caused by self-reactive antibodies mistakenly attacking the proteins involved in nerve-muscle communication.

While it’s not known why the self-reactive antibodies develop in MG, their production is associated with irregularities in the thymus gland, which plays a part in the body’s immune system.

The goal of removing the thymus gland is to reduce the symptoms caused by MG by decreasing the production of the self-reactive antibodies.

While there is not a cure for MG, there are a number of MG treatments, in addition to thymectomy, that may help with MG symptoms. These include medications, plasmapheresis, and intravenous immunoglobulin infusions.

What is a thymectomy?

A thymectomy is the removal of the thymus gland by a surgeon.

The thymus gland is located in the upper part of the chest. It produces and trains white blood cells, which are important for the body to recognize and protect against infection and disease.

Once these cells have matured in the thymus, they travel throughout the body to support the immune system in keeping a person healthy.

The thymus gland is an important part of the immune system’s development in children, but becomes redundant around puberty.

The exact mechanism(s) by which thymectomy is a benefit to people with MG is not completely understood.

Who should have a thymectomy?

A thymectomy is frequently recommended for people living with MG who are younger than 60 with moderate to severe muscle weakness.

It also is recommended for people of any age who have a thymoma (a tumor in the thymus gland). As many as 15% of people with MG have a tumor in the thymus. Another 60% to 75% have an enlargement of the thymus gland.

Thymectomy is sometimes recommended for people with relatively mild weakness, especially if there is weakness of the muscles involved in breathing or swallowing. But it is not usually recommended for treating weakness that is limited to the eye muscles (ocular myasthenia gravis).

Factors such as age, specific MG symptoms, and whether there is a thymoma all may play a role in the decision about whether to have a thymectomy.

Potential benefits of thymectomy for people with MG

Thymectomy is a long-term treatment — it does not cause an immediate change in symptoms. While medications for MG are still needed after surgery, the hope is that eventually the dosage will be reduced or treatment will stop completely, depending on symptoms.

One of the potential benefits of thymectomy is disease remission. This is when symptoms significantly ease or even disappear, allowing a person with MG to live with minimal medications or medical interventions.

According to the Cleveland Clinic, about 70% of people with MG are able to significantly reduce their medications or go fully into remission within a year of having a thymectomy.

A 2022 study of the short- and long-term outcomes following thymectomy found the rates of remission within the first year after the surgery are higher than the rates of long-term remission in people with MG. A decrease in the levels of self-reactive antibodies after surgery has been associated with a higher chance of disease remission in the first year. However, half of the people in the study who had sustained remission in the first year relapsed at some later point.

How is a thymectomy performed?

Prior to surgery, a person with MG will be given a series of tests to assess their physical condition. This may include a CT scan to view the size of the thymus gland and a pulmonary function test to assess lung function and respiratory strength.

During a thymectomy, the surgeon removes the thymus gland and any existing thymomas (tumors).

There are a number of surgical options for removing the thymus:

Transsternal thymectomy

This has been typically the most recommended approach, where an incision is made through the breastbone (sternum) to reach the thymus.

Transcervical thymectomy

This surgical technique is done through a small incision made in the neck, instead of a larger chest incision. It is minimally invasive and typically has a shorter recovery time.

Robotic thymectomy

This is a minimally invasive approach that involves small incisions in the chest. It  is done with the assistance of robotic instruments that are controlled by the surgeon. The technique allows for precision and reduced scarring, when compared to traditional transsternal thymectomy, and a shorter hospital stay.

Video-assisted thoracoscopic surgery

This is a minimally invasive approach, like the robotic thymectomy, but uses a tiny camera to guide the surgeon. It also has the advantage of greater precision during surgery and less time recovering in the hospital.

Potential thymectomy side effects

As with any surgical procedure, thymectomy has risks, especially for people whose MG makes it difficult for them to breathe. However, with advances in minimally invasive surgical techniques, the procedure is generally considered safe.

Potential thymectomy side effects include infections, myasthenic crisis (an episode of severe breathing difficulty that requires hospitalization), and injury to the nerves in the throat.

How long does it take to recover from a thymectomy?

The amount of recovery time in the hospital varies, depending on the surgical approach and the person’s condition. Hospital stays for some minimally invasive thymectomy procedures are generally shorter than in-hospital recovery time for more traditional procedures.

After being discharged from the hospital, it’s important to follow the healthcare provider’s instructions for postoperative care — including restrictions on mobility and physical activity, and how to care for the surgical wound. The recovery period may last several months to a year, depending on the surgical approach.

Follow-up appointments will be scheduled to monitor progress and address any concerns.

Results of a thymectomy

The ideal goal of a thymectomy is a lasting remission that includes the complete elimination of weakness and no need for medications for MG. However, some people still may have residual muscle weakness and need to continue taking medications.

Ongoing medical monitoring after a thymectomy is important as MG symptoms can fluctuate and may reappear.

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