From the Guidelines
For a patient with myasthenia symptoms including ptosis that worsens after sustained upward gaze, the next appropriate step would be to check for acetylcholinesterase inhibitor response, such as administering a short-acting acetylcholinesterase inhibitor like edrophonium (Tensilon test) or neostigmine, as this test serves as both a diagnostic tool and can confirm the diagnosis of myasthenia gravis before proceeding to more invasive or expensive tests, including checking for thymoma 1. The Tensilon test is a valuable diagnostic tool, with a sensitivity of 95% for generalized myasthenia and 86% for ocular myasthenia, and it works by temporarily increasing acetylcholine concentration at the neuromuscular junction, improving neuromuscular transmission and muscle strength in myasthenic patients 1. Some key points to consider when performing the Tensilon test include:
- It should be performed by a practitioner experienced with proper intravenous administration, as associated muscarinic activity can occur 1
- The test should be performed in a monitored setting, and atropine should be available for potential administration 1
- The presence of antiacetylcholine receptor antibody (AChR-Ab-binding, blocking, or modulating) can confirm the diagnosis, although about 20% of patients with generalized myasthenia and about half of those with ocular myasthenia are seronegative 1 Other diagnostic tests, such as repetitive nerve stimulation testing and single fiber electromyography, may also be useful in confirming the diagnosis of myasthenia gravis, with single fiber EMG being considered the gold standard for diagnosis in many centers 1. While checking for thymoma is an important part of the workup for myasthenia gravis, as 10-15% of patients have thymomas, it typically follows confirmation of the diagnosis with acetylcholinesterase inhibitor testing and serologic testing for acetylcholine receptor antibodies 1. Thymectomy may be indicated in certain cases, particularly in the presence of thymoma, and may substantially reduce clinical symptoms in specific age-based and immune-based characteristics 1. Overall, the next step in evaluating a patient with myasthenia gravis symptoms, including worsening ptosis after looking up, should prioritize checking for acetylcholinesterase inhibitor response, followed by further diagnostic testing and potential treatment with thymectomy or other management strategies as needed.
From the Research
Evaluating Myasthenia Gravis Symptoms
To evaluate a patient with myasthenia gravis (MG) symptoms, specifically worsening ptosis after looking up, the next steps would involve:
- Checking for thymoma: Thymoma is a common association with MG, and its presence can impact treatment decisions 2, 3, 4.
- Investigating Acetylcholinesterase abnormalities: Acetylcholinesterase inhibitors, such as pyridostigmine, are commonly used to treat MG symptoms 2, 5, 6.
- Conducting serologic testing: Testing for anti-acetylcholine receptor (AChR) antibodies, anti-muscle specific kinase (MuSK) antibodies, and other antibodies can help classify MG and guide treatment 5, 6.
- Performing additional tests: Repetitive nerve stimulation, single fiber EMG, and the ice pack test can aid in diagnosing MG 5.
Thymoma Evaluation
When evaluating for thymoma, consider the following:
- Thymoma is more common in patients with AChR-positive MG 5, 3.
- Thymectomy is recommended for patients with thymoma-associated MG 2, 3.
- Thymectomy can improve symptoms and reduce the need for immunosuppressive therapy 3.
Acetylcholinesterase Abnormalities
When investigating Acetylcholinesterase abnormalities, consider the following:
- Acetylcholinesterase inhibitors can help control MG symptoms 2, 5, 6.
- Patients with MuSK-positive MG may respond poorly to acetylcholinesterase inhibitors and require alternative treatments 6.
- Monitoring for adverse responses to acetylcholinesterase inhibitors is essential, particularly in patients with MuSK-positive MG 6.