the exaggerated activity of the autonomic nervous system caused by a spinal-cord injury at or above the sixth thoracic vertebra. It may be caused by irritation, pain, or similar stimulation of the nervous system below the area of the injury. In some cases this may be fatal. Symptoms include the sudden onset of a bad headache and hypertension- there may also be bradycardia, sweating, dilated pupils, blurred vision, nasal stuffiness, flushing, and goose bumps. Also known as autonomic hyperreflexia.