What's your cycling like? How long does it take to get from a high to low, and back again? How long do you stay in either of those states?

The lexapro could indeed be the cause of the weird "top of the head" feeling, but it's more likely to be due to your mood state itself.

I don't know a lot about your physical condition. If you're overweight, you're more likely to develop irregular blood sugar responses, either hypo or hyper glycemic. You could have temporary electrolyte disturbances that affect peripheral nerves. Do you watch what you eat? Take vitamins? Minerals? Other supplements?

Is there anything that you associate with this weird feeling, other than the mood state? Does your appetite and food intake change during those periods? Activity level? Caffeine intake?

I'm posing a lot of questions because you're the expert on you, and I'm hoping that you have some intuition about what you might want to consider trying, so that you might become more stable.

Lar