I have never had a squirrel undergo abdominal surgery but I wanted to chime in since (my) Sidekick's thread was linked. Sidekick was a wild squirrel found in the middle of a busy highway, not doubts about a concussion... and top teeth knocked out.

I fear your little one's problem is more likely MBD than concussion.

As far as him (what is his name BTW?) "hating" the Henry's block, especially the picky formulation, he is not eating it because he has been provided the option of not eating it. Remove the option. Think of it like offering a toddler a bowl of broccoli and a bowl of cotton candy then saying they hate broccoli because they eat all the cotton candy and leave the broccoli untouched. It should be no surprise they choose the cotton candy. It's already been mentioned this requires "tough love", and especially so when they are older, but they need to be trained they have to eat the block before they get the goodies. Block, then lots of veggies (and the natural foods you do provide)... a bit of fruit and nuts as a treat (and no treats if one has not eaten their blocks and veggies first).

I have posted this analogy frequently, but once they learn they get other goodies after (and only after) eating the block they will line up to eat their block like kids at an ice cream truck (and it it just as fast!).

So the MBD Protocol for now and work on introducing block to his diet, increasing the veggies, decreasing the fruit and limiting nuts to rare treats.