Six months ago I had a BAD reaction to rolling twice in a week...then a half pill the day after that. In addition to a LOT of other horrible symptoms, one that I remember quite clearly is precisely what you describe.
For days after this I had a buzzing feeling around the back of my head/neck. It was very unpleasant. It seemed to 'tickle' the nerves on the back of my scalp. Calling it a 'dizzy' feeling is not a good enough description. It was almost like 'room-spinning' when you are way too drunk, especially when eyes are closed. But even this description lacks aptitude.
The best analogy I came up with is this: When you are in a car as a passenger...and the driver stops at a red light....suddenly a truck next to you starts moving forward before you do...and you actually feel like you are in reverse! For just a moment, your whole body feels like it is in movement even though you are completely still. In the car, this is caused by a visual illusion.
With MDMA, this 'spatial' distortion is caused by changes in serotonin.
And it lasted for HOURS. Every time I would stand up, I would expect to lose my balance, but somehow I would not. This went on for days. After the first two weeks it went away completely, even though many of my other symptoms persisted for much longer.
When your serotonin levels drop to extremely low levels, blood flow to certain regions of the brain is reduced. Serotonin is known to have a direct effect upon blood distribution, regardless of MDMA use. So when MDMA or other serotonergic drugs cause changes in blood flow, certain regions of the brain will 'up-regulate' its serotonin receptors to compensate. This will steal blood from the rest of the brain while serotonin is limited.
The visual cortex is known to be rich in serotonin receptors, and it has been proven in animal research to respond with 'compensatory up-regulation' following toxic MDMA doses. This is likely the cause of HPPD, which causes some people to have visual distortions. Not hallucinations....more like your eyes are 'set back' in your skull, further away from the world...and what you are seeing looks almost like it were being played on a movie screen. This can be quite disconcerting, so many people tie it to anxiety. While anxiety can make it worse, anxiety is not the cause - 'compensatory up-regulation' is.
This change in the occipital lobe as well as other regions of the brain are likely responsible for the 'twitching' you are feeling on the back of your head. The good news: this 'spatial distortion' seems to be one of the first symptoms to disappear. Certain regions of the brain are able to correct serotonin innervation quickly, while others are not. The bad news: you may discover new symptoms as time goes on.
If you are not feeling major anxiety, I wouldn't worry too much. That seems to be universal in toxic cases. However, with LSD - many former users have suffered long-lasting/permanent alterations in their vision. This includes color blindness and visual snow. Typically these people get used to it and can tolerate it, even if for the rest of their lives. But it goes to show how complex and vulnerable the visual cortex really is.
The anecdotal AND scientific evidence is clear: Re-Dosing carries the highest risk. Do NOT roll two days in a row. Do NOT roll two weekends in a row. Although some will claim to be fine, it is NOT worth finding out they are wrong.
Space your rolls by three months or more, and keep your doses reasonable. Use anti-oxidants and keep your body temperature low!
Hope the information helped.
