THANKS FOR THE QUERY
Let me explain you that lesions in MRI
brain or in brain could be so many things like infection, demyelination
and cancer and so on. The duration of steroid
treatment depends upon the exact diagnosis. Generally speaking, the shorter the duration of steroid use the better. How ever, it is difficult to avoid steroid in certian patients. In these patients, it is better to use the minimum possible dose which will decrease the side effects. I will suggest you to get the opinion of the treating neurologist
who will tell you the diagnosis and the duration of steroid use.
Hope this helps