Quadriplegia (or Tetraplegia) is the partial or complete paralysis of both arms and legs. The spinal cord and the brain are the main parts of the central nervous system, which sends messages throughout the body. The spinal cord is the nerve system encased in the vertebrae and discs that comprise the spine. The primary cause of quadriplegia is spinal cord injury. Spinal cord injury resulting in quadriplegia can occur at any age, including at birth or after cervical spine trauma in later childhood. Quadriplegia occurs when the neck area of the spinal cord is injured and the brain is unable to properly communicate through it; therefore, sensation and movement are impaired. The location of the spinal cord injury and the extent of damage determine the resultant level of impairment.
Conditions such as cerebral palsy can cause similar paralysis. Spastic quadriplegia/spastic tetraplegia is a subcategory of spastic cerebral palsy that affects all four limbs. It is generally caused by brain injury either before, during, or shortly after birth, and can result from many factors such as fetal infections, maternal infections, exposure to toxins, or medical negligence. Spastic tetraplegia affects the entire body and causes spasticity of the limbs rather than the strict paralysis associated with complete quadriplegia. It is different from other forms of cerebral palsy as those with spastic quadriplegia display stiff, jerky movements stemming from abnormally high levels of muscle tone or tension of the muscles.