Yes, there is. We use 'off the cuff' to refer to comments made without any thought behind them or a speech given without preparation. For example, 'an off-the-cuff remark'. We use 'off the top of .... head' to refer to the retrieval of information. It's about knowledge which you have 'at your fingertips'. For example, if someone asks you to name all the capitals in Europe, you might say that you could name about eight 'off the top of your head', but you'd have to check Wikipedia for the others.

Personally I would say "off the top of my head" should be used when you are trying to recall something from memory. For example, if someone asked you 'What is the capital of Zimbabwe?', it would make sense to say 'Off the top of my head, I don't know'. To say 'Off the cuff, I don't know', would sound a little weird. "Off the cuff" is more to do with preparedness for something. If you make a speech at a wedding without preparation, you are doing it "off the cuff". However, they are really similar terms and if you use them interchangeably people would still understand what you meant. Let me know if this doesn't make sense :)