My cat fell and may have a mild concussion.

A cat concussion can cause changed gait, occasional twitching, dilated pupils, slow breathing, thin pulse, drooling, vomiting, and reduced or lost reflexes from central nerve damage, even unconsciousness; get a brain CT promptly to assess damage and receive professional treatment. If suspected, go to a vet at once; if brain swelling is suspected, mannitol may be given to reduce edema, and faster care raises survival odds. A mild concussion generally needs pain relief, anti-inflammation, and quiet rest for 1-2 weeks.