To diagnose myasthenia gravis (MG), healthcare professionals use a combination of clinical examination and specific tests:
- Clinical Evaluation:
- The doctor reviews your medical history and symptoms
- A neurological exam assesses muscle strength, tone, reflexes, coordination, balance, and eye movements
- Look for characteristic signs like muscle weakness that worsens with activity and improves with rest, eyelid drooping (ptosis), and double vision
- Ice Pack Test:
- If you have a droopy eyelid, placing an ice pack on the eyelid for about 2 minutes and observing improvement can support the diagnosis
- Blood Tests:
- Detect antibodies against acetylcholine receptors (AChR) or muscle-specific kinase (MuSK), which interfere with nerve-muscle communication
- Elevated antibody levels confirm MG in many cases, but some patients with MG, especially ocular MG, may test negative
- Electrodiagnostic Tests:
- Repetitive Nerve Stimulation (RNS): measures muscle response to repeated nerve stimulation; a decline in response suggests MG
- Single-Fiber Electromyography (SFEMG): a very sensitive test measuring electrical activity between nerves and muscles, detecting impaired transmission indicative of MG
- Imaging:
- CT or MRI scans of the chest to check the thymus gland for tumors or abnormalities associated with MG
- Pulmonary Function Tests:
- To assess if muscle weakness is affecting breathing
- Occasionally, an edrophonium test (using a medication that temporarily improves muscle strength) may be used, but it is rare due to potential side effects
The diagnosis relies on a combination of these tests along with clinical evaluation to confirm MG and rule out other conditions with similar symptoms.
