I am also not aware of a treatment for the Horner's syndrome, once the underlying cause (in this case, the tumor) is treated. It is possible that the nerves will regenerate, and the upper lid droop and the lack of sweating will improve. If the lid does not return to its original position after 6-12 months, ptosis surgery (to lift the upper lid) could be considered. I don't know that vitamins would help, but a good multivitamin and fish oil certainly couldn't hurt. I know of no exercises which would help.
The neurologist sent me to rehabilitation. It's going to be 15 sessions of laser, electrostimulation and some exercises. It will start next Thursday, doctor said that I could expect for good results.
Thank you. I have an appointment with the neurologist today, I still don't know exactly at which point of the nerves is the injury caused by surgery. I am takin a multivitamin and fish oil. Other doctor recommended me to take Vitamin B Complex. I will be patient to wait for some results.