Myasthenia gravis

Myasthenia gravis e.smith.bodie Wed, 03/25/2020 - 13:55

Anti-cholinesterase medication

The first specific form of treatment is anti-cholinesterase drugs (usually one called Pyridostigmine), which prevent the breakdown of acetylcholine and so improve the efficiency of the chemical signal at the neuromuscular junction. The benefits of Pyridostigmine occur within 30-60 minutes, but wear off in three to four hours, so tablets should be taken at regular intervals throughout the day. People may develop colicky abdominal pain and diarrhoea on Pyridostigmine because the medication also increases nerve and muscle action in the intestine. If this occurs, the dose can be reduced, or alternatively Propantheline can be taken 30 minutes before each Pyridostigmine dose to counteract the effects on the bowel. For some, myasthenia gravis symptoms disappear with Pyridostigmine alone, but most require additional treatments, which vary from person to person.

Thymectomy

Since the thymus can be abnormal in people with myasthenia gravis, surgical removal of the thymus (thymectomy) is recommended for some. Following thymectomy, symptoms do not usually improve in patients with a thymoma, but may improve in young patients with an enlarged thymus. In these patients, about one in four is cured by thymectomy, two in four have significant improvement, but one in four does not improve. Improvement following thymectomy is usually apparent in the first year, but may take up to three years. If the patient recovers, or improves significantly following thymectomy, then they may not need any additional therapy. But many will need further treatments.

Immunosuppression

  • Steroids: People who do not respond to thymectomy, or do not undergo a thymectomy, are treated with steroids. They are usually started on a low dose of steroids, which is gradually increased over the next few weeks to reach the fulldose. During this period, they are often kept in hospital as symptoms sometimes deteriorate before they improve. Once the symptoms are controlled, the dose of steroids is gradually reduced to find the minimum dose at which the symptoms remain under control. Patients then remain on that dose.There are several side-effects associated with steroids, some of which can be prevented by taking additional medication. Thinning of the bones (osteoporosis) can occur and so patients will have a bone densitometry (DEXA) scan and will have medication to protect the bones if appropriate. Patients should never stop taking steroids suddenly, as this can result in a serious condition because the body has become used to regular steroids. All patients should carry a ‘steroid card’ so that in an emergency other doctors will know they require regular steroids.
  • Steroid-sparing agents: Although steroids are extremely effective in controlling myasthenia gravis, there are potential side-effects. Therefore, additional drugs are often used which allow the doctors to reduce the dose of steroids required and may even allow the patient to stop steroids completely. These drugs also suppress the immune system but they act in a different way from the steroids, take longer to work and have different side-effects. Thus by using a small dose of steroids and one of these other medications, the side-effects are kept to a minimum, while maximising the immunosuppressive effect. Azathioprine is the only steroid-sparing agent that has been tested formally and found to be beneficial in treating myasthenia gravis. However for those who cannot take Azathioprine, alternatives such as Methotrexate or Cyclosporin appear to be effective. Patients taking steroids or steroid-sparing agents are at increased risk of infection, so they should consult their doctors before having any vaccinations (live vaccines should be avoided), or engaging in unusual activities that could put them at risk of contracting infections.

Emergency treatments

If a person is very weak or having trouble breathing or swallowing, then they are usually admitted to hospital for more aggressive treatments such as plasma exchange or intravenous immunoglobulin (IVIg). These treatments can produce a rapid improvement in symptoms but the benefits only last for about six weeks. They are reserved for situations when symptoms need to be controlled quickly, and they are not appropriate long-term treatments.

What can people do themselves?

It is important for people to use common sense and avoid things that would put them in danger if their weakness suddenly increased (for instance swimming on their own). Taking medications regularly is the key to maintaining the lowest possible levels of symptoms.

https://mduk-resources-stage.s3.eu-west-1.amazonaws.com/pdf/factsheets/Myasthenia-gravis.pdf