Is it Myasthenia or MSA (Shy-Drager)

I am 58 years old Female. History of FMS and Hypothyroid, Arthritis, Sleep Apnea and Elevated Cholesterol among a few other things. For over a year I have been experiencing first, weakness of particularly the upper torso with chest, neck and throat fatigue. My arms show some weakness too as well as it is more difficult to open jars etc. with my hands. Usually I have more energy in the beginning of the day as my strength diminishes as the day goes by. Then I started having shortness of breath upon climbing the stairs. I live on the second floor and have to go to the basement to do laundry. In the last 7 months I now have difficulty with my throat. At times I am hoarse and my words won't come out. I love to sing and some of my notes/words will not come out at all. When I am the most weak I have difficulty just talking. I feel like it takes too much energy. I saw a Neurologist who seems to think that it is Myasthenia Gravis and has given me Mestinon 60mg. to take up to 4 times per day. It has greatly improved my speech and singing voice but I still am weak in the chest, arms and hands. I am also experiencing some jerking motions perhaps maybe from the medication. I did not have the jerking prior to med. Antibodies for Acetylcholine are negative. Awaiting Musk Antibody test. EMG pretty much negative. Chest xray Ok in the Thymus. If the Musk comes back positive then Ok, its probably MG but if not then what? And why does the mestinon help my voice issues only? Is there a chance this could be Multi-System Atrophy instead?                       Thank you for any help you can give and answers to my questions.

[Christopher R Newey, DO]

Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with a doctor.

Without the ability to examine and obtain a history, I can not tell you what the exact cause of the symptoms is. However I will try to provide you with some useful information.

Myasthenia gravis is an autoimmune disease in which the body makes antibodies that attack a receptor located at the junction of the nerve and muscle. This causes impaired neural transmission leading to weakness of muscles. There are various forms of myasthenia gravis. These include ocular (affecting eyes predominantly), generalized (affecting the arms/legs/trunk predominantly), or mixed.  The typical symptoms of myasthenia are double vision, drooping eyelid, difficulty talking and swallowing, and weakness of the shoulders or hips. The weakness usually worsens as the day progresses. It is usually managed with immunsuppressants such as steroids or azathioprine. Other treatment options include IVIG or plasmapheresis. Medicines such as mestinon are used for symptomatic treatment.

Multiple system atrophy (MSA) has several forms. These include predominantly parkinsonian (tremor, rigidity, etc), cerebellar (i.e., incoordination), and autonomic (i.e., difficulties with urinating, sweating, etc). MSA would not improve with mestinon.

In your workup for myasthenia gravis, did you have an EMG with repetitive nerve stimulation or single fiber EMG? If not, I would suggest at least the single fiber EMG. Antibodies can be negative in up to 20% of patients with myasthenia gravis. The anti-MuSK may increase yield, but there will be some patients with negative antibodies even still.

You should discuss with your neurologist the efficacy of your medication, if you feel that you have had minimal response. You are on a small dose.

Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck!