I'm certainly not very knowledgeable in the science of head/brain injuries. I just recall the worst concussion or pcs-type recovery I had was when I had a had a hard second bump a few days after the first and had a foggy feeling where I had trouble staying awake afterwards and could only think about sleeping. It took at least a month for the lingering light sensitivity issues and daily headaches to go away at that time and most bumps since have not produced that level of trouble except for the time I fell backwards and my head bounced off the wall - roughly 3-4 months after the 'bad' concussion. I've also read of people on table tennis forums who reported of hitting their head during a similar stroke and 'seeing stars.'

Perhaps none since have even been subconcussive. The latest episode kind of had me confused since I'd never heard a loud pitched ringing immediately after a head hit and I didn't know if it was what is referred to as 'getting your bell rung.'