How can a person with MS have symptoms if their lesions are inactive ?

Here is My Question:
I just sent you a question about "inactive lesions" on my MRI. But I told you about certain things I was still experiencing. One was memory. Well, I just remembered, fatigue is a very big complaint. How can I have these symptoms if my lesions are inactive. I guess I just don't understand this. Sorry to bother you again, but I wanted to be clear. 

Answer:
You ask a great question. To paraphrase, How can a person with MS have symptoms if their lesions are inactive?

There are 4 explanations that come readily to my mind:

1. When MS affects areas of your brain, there is always some degree of permanent damage that remains after the inflammatory response has resolved. Remember, Multiple Sclerosis literally means Multiple Scars in your brain. These inactive areas or scars cause variable persistent symptoms and problems

2. Partially affected regions in your brain, both visible and invisible on MRI scans, may no longer function as well as previously. Conduction of electric currents through these partially affected regions—your nervous system functions through these complex electrical circuits— may falter with the slight increase in body temperature which occurs in us everyday during the afternoon and evening as part of our normal circadian rhythm. This is why people with MS most often report that their daily symptoms emerge or worsen in the afternoon and evening. This is also the reason we recommend cooling vests, hats and collars or exercising in a swimming pool with cool water.

3.  Other medical problems, such as diabetes, or mood states, such as depression and anxiety, directly or indirectly exacerbate many symptoms of MS. This is why we spend so much time focusing on these issues in the clinic

4. Lastly, many medications often make MS symptoms worse. This possibility should always be considered in any patient complaining of new or worsening symptoms

Hope this helps

Revere (Rip) Kinkel MD
Director of the Multiple Sclerosis Program
Director of Hillcrest Neurology
Professor of Clinical Neurosciences
University of California San Diego