Myasthenia gravis is an autoimmune disorder affecting the skeletal neuromuscular system. Auto-antibodies are produced against the nicotinic acetylcholine postsynaptic receptors of skeletal neuromuscular junction resulting in skeletal muscle weakness. The characteristic feature of myasthenia gravis is fluctuating muscle weakness with fatigue that exacerbates with increased activity and alleviates with rest. Therefore, its symptoms are better in the morning and worse by the evening or night. The commonly affected muscles are the eye muscles, oropharyngeal muscles, and proximal skeletal muscles. In about 85% of the patients, ocular symptoms of double vision and drooping eyelids are present. Oropharyngeal weakness affects chewing, swallowing, speech, and breathing, while other proximal skeletal muscle weakness leads to limb weakness causing difficulty in sitting, rising from a chair, climbing stairs and fatigue with prolonged walking.
What Is The Best Treatment For Myasthenia Gravis?
Although, there is no consensus in treatment or no tested treatment, myasthenia gravis is a highly treatable condition. Myasthenia gravis is managed keeping in mind various factors, such as age of onset of disease, distribution of weakness, severity of the disease, progression of disease, presence or absence of thymic pathology, and serology profile. Various myasthenia gravis treatment methods include symptomatic treatment, cholinesterase inhibitors, immunomodulators, immunosuppressants, plasmapheresis and thymectomy.
Acetylcholine esterase (AChE) inhibitors and immunomodulators form the standard for treatment of myasthenia gravis. AChE inhibitors include pyridostigmine and neostigmine. Pyridostigmine is used for maintenance therapy and symptomatic treatment only; it does not cure the underlying condition. Neostigmine is used in circumstances where pyridostigmine is not available. The effective dose of AChE inhibitors depends on the severity of the condition and other factors that might affect cholinergic transmission (such as certain medications or impaired renal function).
Those patients who have generalized symptoms benefit from immunomodulating agents. Immunomodulation is acquired by corticosteroids and non-steroid immunosuppressants, such as azathioprine, cyclosporine, mycophenolate mofetil, rituximab, cyclophosphamide and other immune therapies include PLEX and IVIg. Non-steroid immunosuppressants are used when corticosteroids are not indicated and they can be used in combination with steroids when there is risk of steroid side-effect. The immunosuppressants should be tapered gradually once remission is achieved. However, these agents are not effective in managing ocular symptoms. PLEX and IVIg are reserved for severe cases, including refractory cases or myasthenia crisis.
Plasmapheresis is used as an adjunct to immunosuppressants in the management of myasthenia crisis or refractory cases. It is thought to remove circulating humoral factors, such as anti-AChR antibodies and immune complexes from circulation. It is an effective treatment, but the effects of plasmapheresis are short lived lasting only 2 months; therefore, long term regular plasmapheresis is required on weekly or monthly basis to manage the condition, if other methods fail to keep the disease in check.
Patients with generalized myasthenia gravis have thymic hyperplasia in 85% cases and thymoma in 10-15% cases. These patients are anti-AChR-ab positive; therefore, thymectomy is indicated in patients with thymoma or without thymoma who have generalized myasthenia gravis. Thymectomy is the first line treatment for patients with generalized myasthenia. However, in late onset myasthenia gravis and thymoma, thymectomy has no effect on the course of disease. Thymectomy has a potential to induce remission in selective patients.
Patients are also advised on diet and activity modification. They are advised to follow a diet low in carbohydrate, sodium, and high in protein to avoid excessive weight gain. Since, they suffer from dysphagia and chewing difficulty, they are also advised to eat soft food and avoid meats and hard foods that are difficult to chew. In addition, liquids should be given in thickened form to avoid regurgitation. They are also educated regarding the fluctuating nature of the disease and recommended to avoid strenuous activities that might increase fatigue and to rest in between activities.
Therefore, there is no best or specific treatment of myasthenia gravis. The treatment is highly individualized and varies from patient to patient depending on the presenting clinical features and severity of the disease.
- Aydin Y, Ulas AB, Mutlu V, Colak A, Eroglu A. Thymectomy in Myasthenia Gravis. Eurasian J Med. 2017;49(1):48–52.