Has Riley had a stroke?

[Sarah]

Oh dear,   I am simply horrified with my findings of one my much loved gerbils, Riley. He was fine yesterday, as active and curious as usual. This evening when going to take him out he seems unwell.   The first thing I noticed was he was squinting (nearly closing) his left eye. I took him out and he didn't move much. Very lethargic in my hand, and obvious balance problems on his left side. Putting him back in his cage and he didn't move at all. Picking him back up, he wouldn't move when I held him in my hands. After a few minutes he began to move, but seemed as if he was walking circles in my hand.   10 minutes later he is now in his cage, he was acting normal, maybe 5 minutes. And again stood perfectly still lethargic like for 2/3 minutes.   Now he seems fine, chewing the tp roll I gave him.   Advice, or answers?   Sarah and her dear Riley