Trevor, Don't try to over diagnose yourself or make complicated assumptions. It usually leads to anxiety. The simple fact is your brain took quite a beating. The sense of your brain moving is more likely a vestibular issue.

The subtle neck injuries common to PCS rarely show up on imaging, unless the x-rays are taken by an upper cervical chiro. A PT can sometimes help with gentle traction and mobilization. Then, good sleep posture and being a bit protective with day to day activities, no extreme head/neck angles, and such for an extended period can help things settle down. Some do neck strengthening exercises. Avoiding range of motion exercises early in the process is good for some.