If the electrolytes are way out of balance (which happens with extreme kidney failure) seizures result. Epilepsy is also possible in
which medication can be used to control seizures. In
terms of cancer
if its the case, I would be concerned with brain or spinal cancer. Unlike stated above, cancer is NOT contagious, not even to other cats. There is a condition called Feline Leukemia which is confusing because humans have a cancer called Leukemia. However, Feline Leukemia is NOT a cancer.