I had 'the' concussion that brought about my PCS 8 months ago now. After 3 months I had a month of remission where I was free of daily headaches, the fatigue improved significantly etc. I relapsed on month 4 after playing football/soccer and the problems came back (in retrospect I still can't tell if it was a relapse or another concussion from shoulder-barging).

In the past 4 months following the relapse/setback I've gradually improved again and for the past month again my headaches had significantly improved.

Two weeks ago I finally decided to go to a 'concussion clinic' in the capital where I was given ocular and vestibular exercises by a... physio-therapist.

One of the vestibular exercises was this gaze stabilization exercise where you shake your head side to side while focusing on a letter chart in front of you.

The therapist recommended starting with slow head shakes and progressively increasing speed up until 180 beat/m on a metronome.

This Wednesday I finally got to 180 beat/m with disastrous results. I did it for a couple of minutes and immediately stopped after I got a strange sensation in my head, not dizziness but the feeling that my brain was hitting the sides of my skull in my head (which it obviously was given the movements)... I think I may have concussed myself by violently shaking my head side to side...

I developed nausea not too long after that exercise and only stopped myself going to the ED because the nausea subsided after an hour. Since yesterday I've been experienced something akin to the first few weeks of my first concussion - sound and light sensitivity, terrible headaches, crippling mental fatigue, fogginess etc etc

My question is how are we supposed to tell whether we have a bad case of setback/relapse or a new concussion? It seems ridiculous that we can get concussed from shoulder barging in soccer or fast head turning but I have read cases of individuals with PCS who were fainting after relatively light accidental bumps on their head from a stray elbow so who knows, maybe a PCS brain can have a concussion threshold of a few gs.