I think the term 'spontaneous recovery' applies to the 85% or so of concussion victims who never make it to this forum. They may have concussion symptoms for a few days to a few weeks but they resolve before the person starts to see major impacts on their everyday life. They may consider these recoveries as full recoveries.

Most of my concussions resulted in spontaneous recovery. Only four resulted in ongoing symptoms. The very first which was severe, resulting in hospitalization for three days, appeared to recover within a short time. My last three have all left me with permanent symptoms, each one causing more severe symptoms. The ten between, all recovered within a short period.