I've been tested for everything but my MRI is always normal...what could this be?

Here is My Question:
I need advice. I have a unusual story, Six years ago I had unusual episode. Numbness, tremor, mostly on right side. It all resolved in a month. For the next five years I had stiffness in legs. My right leg would be weak if I walked too much. My rightt arm would be weak if I reached high for something. I saw doctors over the years and had MRIs that were all normal.

Last Christmas my arms felt like 50lb weights were on them and I couldn’t use them as much. I keep having episodes like this but my MRIs are always normal.

I've been tested for lupus, B12, ALS...I've had every test you can think of. I am 52 years old, can I have PPMS? This mimics MS I have so many same symptoms plus I feel like I have had flares.

Where do I go from here I am getting worse and scared to have another episode. In November I was on a rowing machine working on my arm strength to get it back and a treadmill. I can’t even lift my arms well or lift my ankle up . Please help me I need help!

Answer:
It is very difficult to establish a diagnosis based on the history of symptoms you provide. I can tell you that it is rare for MRI scans to remain normal for over 6.5 years in people with MS of any type. There are many causes of waxing and waning weakness and fatigue including disorders of the muscle, neuromuscular junction, and peripheral nerves. I would begin by getting a second or third neurological evaluation, perhaps at an academic  neurology clinic.
Good luck

​Revere P (Rip) Kinkel, MDProfessor of Clinical Neurosciences
Director of the Multiple Sclerosis Program
Clinical Neurosciences Director
University of California San Diego