My understanding of this video
Pusher syndrome
is a 18 degree lean to the left or right due to brain damage in a specific region
It is treated by having the patient look in a mirror while sitting still & trying to adjust their posture so that they do not lean
Next is trying to do likewise with a mirror while standing
Next while moving or interacting with objects such as picking them up
The mirror is removed in each stage to see if they can adjist without a mirror