Why can't quadriplegics move neck down?

Quadriplegics typically experience paralysis due to damage to the spinal cord, often at the cervical level, which disrupts the communication between the brain and the body. This injury affects the nerves that control movement and sensation in the arms, legs, and torso. As a result, individuals may retain some function in their neck and head but lack the ability to move or control muscles below that level. The extent of paralysis can vary based on the severity and location of the spinal cord injury.