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Myasthenia Gravis

Why is MG so hard to diagnose?

05/18/2009

Question:

I have had dysphagia to solid foods for a couple of years. I can swallow only liquids. It has been progressing slowly for over 5 years. My throat muscles fatigue easily when chewing or speaking. My face is not very expressive any more. My voice tends to weaken and become raspy as the day goes on, requiring more effort to get enough air across my vocal cords to speak intelligibly. My thigh muscles and upper arm muscles feel tired after exertion, especially when it is hot. I am best in the morning, but symptoms increase as the day goes by and are worse in the evening. Now, for the last 3 months I have had an annoying tick in my right eyelid. I am taking Requip for RLS. My neurologist saw indications of myopathy in my facial muscles during an EMG and suspected Myasthenia Gravis. I have had a single-fiber EMG, deltoid biopsy, nerve conduction test, AchR antibody test, serum CK, and a DNA test for GCG trinucleotide expansions in the PABP2 gene. All tests except for the EMG appear normal. I have not had the MuSK antibody test performed yet. My question is, if not MG, what can this be? If it is MG, why might it be so difficult to firm up a diagnosis?

Answer:

It can be difficult to diagnose a case such as yours. In fact, it can defy diagnosis. It sounds like your neurologist has been very thorough and thus far has not found serious abnormalities. That is encouraging. I would suggest two choices:

1) Continue to work with your current neurologist and maintain an active life as he/she follows your case

OR

2) Get a second opinion from a neuromuscular specialist. I must say it is not unusual for patients to have complaints such as yours and have very good test results. With reassuring test results, as long as you do not have problems with weight loss or pneumonias, and you have good follow up and remain active, the prognosis is good.

For more information:

Go to the Myasthenia Gravis health topic, where you can:

Response by:

John G Quinlan, MD John G Quinlan, MD
Professor of Neurology
College of Medicine
University of Cincinnati