Oooo, head trauma.
Yes, it can take years to regain a sense of normalcy, physically and moreso mentally, even with proper care. Kyle has progressed remarkably fast from a medical standpoint, I'd be very willing to guess.
To add to that, it's not just physical trauma we're talking about. If the reports are true... he almost died. That is definitely a situation in which someone could suffer emotional trauma, which could theoretically continue just as long if not longer than any effects of the direct physical damage. Although, yeah, the brain. Neuropsychology or whatever. It's all physical, but the healing process is different between getting hit in the head and suffering from the 'hey, I almost died and left my kids without their father' type of trauma. I hope that makes any modicum of sense.
Either way, it's showed on the ice too. He looks considerably better out there. More aware, gaining better control of the puck, and is actually starting to score. Good for him, I hope his recovery continues at this pace.