MG Diagnosis?

[flakyone]

My wife was in her late 50's when she was clinically diagnosed with MG in November, 2003. She is one of those special people who is seronegative and musk negative. The CT scan in 2005 showed the thymus was fine. The neuro later also diagnosed her with fibromyalgia. She has severe allergies and is a universal delayed reactor. Her PCP, allergist, and other doctors are in agreement with the MG diagnosis. There is little ptosis but she has is increasing double vision, and her eyes occasionally "pop in and out of focus." There are increasing problems with swallowing. General activity tires her and rest helps. Her presentation is typical MG. We recently saw a reputable MDA neurologist at a large clinic who did a clinical evaluation, and an RNS which was normal. Many blood tests were run and all were normal. He said she does not have MG. Neuropothy was diagnosed but with no recommendations for treatment. He wants her to discontinue the prednisone and prograf (which seems to be helping) so he can do a single fiber test in four months. Can you help with the confusion about the MG diagnosis? How likely is it that the single fiber test will be definitive? The research I have done seems to indicate an MGer who is seronegative and musk negative may be more difficult to diagnose, and may be less likely to experience an MG crisis. Is this correct?

[CCF-Neuro-M.D.-SH]

First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.
   Myastenia Gravis (MG) is caused by an immune reaction to the components of the neuro-muscular junction.  This immune response stops effective delivery of acetyl-choline (the neuro transmitter) to muscles cells and thus causes weakness.  The most common forms of MG involve immune response in the form of antibodies to the acetyl-choline receptors (binding, blocking and modulating).  If these antibodies are negative the patient is called 'seronegative', and were initially a mystery. Antibodies against MUscle Specific Tyrosine Kinase (MUSK) were also discovered to cause MG and these antibodies were found to be positive in 40-70% of seronegative patients in some studies.  These MUSK+ patients tend to have more bulbar complaints such as speech problems, problems swallowing, drooling etc, rather that breathing problems and generalized fatigue.  There are still a group of patients with MG that are seronegative and MUSK negative (with an unknown immune response against the neuro-muscular junction).  In addition to the antibody tests, MG is also diagnosed with neuro-physiological tests such as EMG, RNS (Repetitive nerve stimulation) and SFEMG (single fiber EMG).  Seronegative patients that are also MUSK- tend to have more abnormal RNS and SFEMG tests.  The treatment for MG incldues long term immune suppression with agents such as cellcept, imuran, etc; prednisone (usually more short term due to side effects); and intermittent plasma exchange and/or IVIG.  Mestinon is also used for some symptoms relief.  Stopping predinsone and prograf to obtain a quality diagnostic study is a wise move.  You want to be sure of a diagnosis before you undertake therapies that have risk associated with them (prednisone has many side effects, all immunosuppressants make you more vulnerable to infections).  I would suggest that you have the SFEMG done, then continue your therapy.  Some cases of MG are linked to a cancer of the Thymus gland (Thymoma) which is the reason to get the CT scan (Seronegative patients tend to have a lower incidence of thymoma).  Seropostive and seronegative MG patients can have similar levels of clinical severity and the treatment for all remains the same.
I hope this has been helpful.

[korky]

To my knoledge I have had all the tests available in the u.k for the diagnosis of occular m.g.I first started getting double vision when I was playing football about 15years ago,I had a scan and the 3rd disc in my spine was compressing my cord.I had the operation and everything seemed to be ok.My double vision returned a couple of months later.I regularly train and even run marathons with no problems except double vision.I have no muscle weakness  at all and every test says I have not got occular m.g.I really dont know what else I can do.I have had another scan and my disc in my spine are ok