I am still feeling awful 48 hours after that, so I think I indeed hit my head fairly hard during the night, most likely against the headboard, and did not wake up - or do not remember that.

I wish I had taken some prevention measures to avoid that, this is so stupid... Now my mattress is on the floor, far away from any hard surface.

What I learn from this event is that I should have organized every little aspect of my life to minimize the risk of impacts, including these unlikely ones. I should simply have avoided sleeping on a bed with a headboard. I had thought about it but rejected this idea, since it sounded silly and paranoid, and I wanted to live as normally as possible without developping irrational or obsessive fears.

But the consequences of a hit are so undesirable for us that I think it makes sense to be overly cautious. I had made a fairly good recovery after 14 months of PCS, was starting to enjoy work/hobbies again, and all this has to be redone now.

Sorry for publicly wallowing in self-pity. If you are struggling with PCS, please consider making these kind of adjustments, as long as it does not develop into an obsession. Thanks again to Mark and Jo*mar for the advice, and my best wishes to all of you.