Just a follow-up. I am 9 days after the bump, and I now have little doubt that I sustained a concussion that night, most likely by bumping my head against the headboard (without waking up). I have been feeling terrible since then with almost no improvement. I am used to having relapses after small hits or bumps, but these usually last for a few days and the symptoms are much less severe than now. This time is clearly different.

I am writing this to convey the information that it is unfortunately possible to give oneself a concussion while sleeping, and without waking up. I would not have believed that 10 days ago, and I perfectly understand why some of you considered my story with skepticism (I would have reacted in the same way).

As Mark sometimes writes, "wise people learn from others' mistakes". I thus strongly encourage you to make some arrangements in order to avoid hitting your head in your sleep - for instance, by placing pillows against the headboard.

Best wishes to all of you.