From the Guidelines
Encephalopathy in myasthenia gravis can occur due to several causes, including cholinergic crisis, myasthenic crisis with respiratory failure, immunosuppressive treatments, plasma exchange or intravenous immunoglobulin (IVIG) treatments, thymectomy, concurrent autoimmune disorders, and infections. The most common cause is cholinergic crisis resulting from excessive acetylcholinesterase inhibitor medication (like pyridostigmine, neostigmine), which can lead to central nervous system effects 1. Myasthenic crisis with respiratory failure may cause hypoxic encephalopathy if not promptly treated with ventilatory support. Immunosuppressive treatments used for myasthenia, such as corticosteroids (prednisone), azathioprine, or cyclosporine, can occasionally cause metabolic disturbances or direct neurotoxicity leading to encephalopathy. Plasma exchange or intravenous immunoglobulin (IVIG) treatments may rarely cause aseptic meningitis or other neurological complications. Thymectomy, a surgical procedure often performed in myasthenia patients, carries risks of post-operative complications including encephalopathy. Additionally, concurrent autoimmune disorders that frequently coexist with myasthenia (like thyroid disease) can contribute to encephalopathic states. Infections may develop due to immunosuppression and cause infectious encephalopathy. Some key points to consider in the management of encephalopathy in myasthenia gravis include:
- Careful medication management to avoid cholinergic crisis
- Monitoring for respiratory insufficiency to prevent myasthenic crisis
- Prompt recognition of neurological changes to initiate early treatment
- Consideration of immunosuppressive treatments and their potential side effects
- Awareness of the risks of plasma exchange or IVIG treatments
- Monitoring for post-operative complications after thymectomy
- Management of concurrent autoimmune disorders
- Prevention and treatment of infections to avoid infectious encephalopathy, as recommended by the American Society of Clinical Oncology clinical practice guideline 1. It is essential to note that the management of encephalopathy in myasthenia gravis requires a comprehensive approach, taking into account the various potential causes and risk factors, as well as the need for careful monitoring and prompt treatment, as outlined in the guideline update 1.
From the Research
Causes of Encephalopathy in Myasthenia Gravis (MG)
There is limited information available on the causes of encephalopathy in Myasthenia Gravis (MG) from the provided studies. However, some studies mention the following factors that may contribute to encephalopathy or severe exacerbations of MG:
- Infections, which can trigger myasthenic crisis and disease exacerbation 2
- Certain medications, including antibiotics, which can exacerbate weakness and lead to respiratory decompensation 3
- Respiratory tract infections, which can lead to MG exacerbations and precipitate an MG crisis 4
Risk Factors for Myasthenic Crisis and Disease Exacerbation
The following factors have been identified as independent risk factors for myasthenic crisis and disease exacerbation in MG patients:
- Disease severity at diagnosis (quantitative MG score or Myasthenia Gravis Foundation of America class) 2
- Presence of thymoma and anti-muscle specific tyrosine kinase-antibodies 2
- Older age, higher MGFA class before and at admission, and lower vital capacity before and at admission, which are associated with worse outcome in myasthenic crisis 2
Treatment and Management of MG
The treatment and management of MG involve a range of options, including:
- Acetylcholinesterase inhibitors, such as pyridostigmine, for symptom control 5
- Corticosteroids and immunosuppressive therapies, such as azathioprine, for inducing remission 5
- Thymectomy, which has been shown to be beneficial in patients with acetylcholine receptor (AChR) antibody positive generalized MG 5
- Intravenous immunoglobulin and plasma exchange, which are core treatments for severe MG exacerbations 4