symptoms of a feline concussion?

My sister's male Siamese just ran full force head first into a closed glass door. Hit so hard his collar flew off.

What are symptoms for potential head injury or concussion? Are they roughly the same as with humans? Uneven pupils, lack of coordination, vomiting, etc.?

My sister is keeping an eye on him - I told her not to let him go to sleep and watch him closely - what signs to look for prior to bringing to e.r. vet?

She said he's walking around and watching fireflies at the moment. Was hiding for a bit but is out now.

Don't want to be an alarmist, just careful...

Thanks for suggestions.

I'm not a vet, but I would think problems would have shown up pretty quickly if it was a bad head injury.

Whenever my cat wants in/out of a closed room, she bangs her head repeatedly into the door. I have to put a cushion in front of my bedroom door to keep her from doing it . I do worry about her getting a concussion, but she seems fine in spite of doing this over and over...I suspect your sister's cat is fine, too.