Expandable interspinous process spacer with lateral support and method for implantation

An interspinous process spacer and method of implanting same is provided for maintaining separation between adjacent spinous processes of adjacent vertebrae. The spacer has two lateral portions and a medial portion therebetween, the medial portion adapted to reside between the adjacent superior and inferior spinous processes in the deployed configuration and the lateral portions each comprise a superior lateral portion and an inferior lateral portion adapted to reside on the lateral side of the respective superior and inferior spinous process in the deployed configuration to maintain positioning of the interspinous process spacer between the two adjacent vertebrae. The lateral portions each comprise an expandable lateral member.