I've read that Topamax can cause "sensory sensitivity." For you that could be excessive sensitivity to smells.

Drugs in the same class as Topamax can also interfere with the body's ability to properly absorb some nutrients. Zinc deficiency can cause a person to suffer terribly from perceptions of malodor all around. There are other drugs in the same class as Topamax that may provide you with the same or better positive effect without the unpleasant side effect.

Unfortunately, when it comes to this class of drugs, it's often a trial and error process to find which one is right for a particular individual. I speak from personal experience. Maybe your doctor can switch you to something that does not have this unpleasant side effect.

I googled Topamax and smell and there seemed to be many people with a complaint similar to yours, although it is not emphasized as a side effect on the official Topamax site.