What Causes Numb Left Foot After Surgery For Severe Spinal Stenosis?

My mother recently underwent emergency surgery for severe spinal stenosis and removal of a herniated disc (lumbar). She continues to have a numb left foot and loss of proprioceptive sense in the left foot. The surgeon said from a surgical standpoint she did great but it is unusual to see this loss of proprioception with lumbar surgery. I am concerned that 11 days post op she is still not able to walk and has no awareness of her foots position in space. Should we be looking for answers other than spinal cord related (CNS)