Hi MissP,
I've been taking Topamax for mood swings for almost 3 years now. I was on Neurontin which wasn't working, and was switched to the Topamax, which has worked great. I take 200 mgs, 100 mgs in the am, 100 mgs at bedtime.
The only side-effect I experienced from it is pretty common, called cognitive dulling. Or, a case of the stupids as my wife called it with me

. Your doc should start you pretty low and titrate up slowly until you hit your target dose. You should discuss that target dose with him/her ahead of time, along with how much to increase and how often.
The dulling effect happened when I started the med, and at each increase. It would last for a day or two each time. What happened is I couldn't remember simple things like how to spell words or math problems, forgot phone numbers, people's names, stuff like that. But like I said, it went away after a day or two, and after I hit my target dose, it went away and never came back. Also, it might make you a little drowsy at first.
I think that's it, but if you have any questions, please let me know. I hope this helped.
Greg
"Beauty is truth, truth is beauty - that is all you know on earth, and all you need to know"