The state of confusion that is produced by entering a shopping mall wherein one forgets the reason they came, their place in the world, and possibly their very identity.
Girlfriend: What shirt did you buy for the wedding at the mall?
Boyfriend: I must have come down with mallzheimers, cause all I got was this puppy!
The phenomenon that occurs when one walks out of a store in the mall and has no idea which way they came from, blocking mall traffic with their paralysis.
I hate going shopping with my mom: she gets such bad mallnesia and walks the wrong way every time!