It may be okay to say it in speech, but it's to be avoided when writing, because it is ambiguous.

"Tedavi ile nöbetlerim azaldı" can also (and does normally) mean: "My treatments as well as my seizures decreased." It would be understood as the shortened form of: "tedavilerim ve nöbetlerim azaldı".

Furthermore, for me, it just sounds better to put the adverbial part "tedavi ile" next to the verb.

added now

it is a very weird word order. Maybe you can hear it in a poem but not in a normal sentence. Place your verbs at the end