On the play in question, Cottam caught a pass and almost did a flip but landed on his head. He got up, and walked away just fine. X-rays later revealed that he had a cracked cervical vertebra.
The following day, Chiefs head coach Todd Haley said Cottam had a successful surgery.
"[S]aw the doc today and should be out of the neck brace in 2 months," he wrote.
From what I've heard, he'll make a complete recovery, which is excellent news.
While he'll be out of his neck brace in two months, the timetable on his return to the field isn't known at this point.