Seizures
"Brain rot. I have been on dilantin for over 40 years. Have just discovered dilantin is cause to numbness in legs, feet, balance and walking control. How so?&quot; It&#039;s called cerebellum atrophy.  Thats where your cerebellum shrinks (my case about 40%) 
It will get worse if I continue to take it, putting me in a wheel chair. Only one medicine does that to you- Dilantin. DO NOT TAKE IT. If you are on it, get off it (as I am about to do) It was also considered at one time the most toxic medicine out there. Look it up in PDR. Did it stop seizures? yes. Do I want to be a cripple and eventually have to be fed. No. Get off it."