CT scans

So I went to the ER for dizziness and head pressure and they did a CT scan on my head and it was normal. Fast forward to now I saw a neurologist yesterday from some different issues and he wants me to do an MRI on my brain. Issues are related to my balance, neck pain, sharp pains in head, etc But I forgot to mention to him I had a ct not long ago. I know MRI is more in-depth but what are the chances something changed this quickly? Also MRI is like $300 and I’m struggling financially so yeah.