If you have nerve damage, the myelin sheath is not at 100%, it never heals at 100%. which means the transfer of communication, or electrical impulses are not as efficient as they could be.

When fasting, you begin to lose electrolytes + sleep quality , which aid in these electrical impulses and in a normal person, they wouldn’t have nerve symptoms because it doesn’t effect it that dramatically assuming they have a healthy sheath.

However, considering your nerve transmission is already less than optimal, the lack of electrolytes creates an even more noticeable effect and you will get more of the symptoms you have associated with that damage.

This is a more simplified non scientific version of explaining it, but that’s the cause. This is why people with heavy nerve damage like people with MS often claim they experience a “relapse”, when fasting but it’s not really a relapse, it’s their damaged nerves having trouble due to the explained above.

Dr. valter longo has seen fasting improve density of the myelin sheath and help repair damage, but I believe if it’s long term damage, it might be too late. That hasn’t really been confirmed, but overtime it does become scar tissue and considered unrepairable.