Paralysis can be either partial or complete. Paralysis of both the arms and legs has been traditionally been called quadriplegia. Quad comes from the Latin for four and plegia comes from the Greek for inability to move. Currently the term tetraplegia is becoming more popular, but it means the same thing. Tetra is from the Greek for inability to move.
The primary cause of quadriplegia is a spinal cord injury, but other conditions such as cerebral palsy and strokes can cause a similar appearing paralysis. The amount of impairment resulting from a spinal cord injury depends on the part of the spinal cord injured and the amount of damage done. Injury to the spinal cord can be devastating because the spinal cord and the brain are the main parts of the central nervous system, which sends messages throughout your body.
When the spinal cord is injured the brain cannot properly communicate with it and so sensation and movement are impaired. The spinal cord is not the spine itself; it is the nerve system encased in the vertebrae and discs which make up the spine.