Autonomic hyperreflexia

Definition

Autonomic hyperreflexia is a reaction of the autonomic (involuntary) nervous system to over-stimulation. This reaction may include high blood pressure, change in heart rate, skin color changes (pallor, redness, blue-grey coloration), and excessive sweating.

Causes

The most common cause of autonomic hyperreflexia is spinal cord injury. Stimuli which are otherwise tolerated in healthy people (such as filling of the urinary bladder) create an excessive response from the patient's nervous system.

Other causes include medication side effects, use of illegal stimulants such as cocaine and amphetamine, Guillain-Barre syndrome (a severe form of paralysis which can lead to respiratory failure), subarachnoid hemorrhage (a form of brain bleeding), severe head trauma, and other brain injuries.

The following conditions share many similar symptoms with autonomic hyperreflexia, but have a different cause:

• Carcinoid syndrome -- a disease caused by abnormalities of cells of the lungs and gut that produce hormones
• Thyroid storm -- a condition caused by too much production of thyroid hormone
• Neuroleptic malignant syndrome -- a condition characterized by muscle stiffness, high fever, and drowsiness, which can be caused by some antipsychotic medications and anesthetic agents
• Serotonin syndrome -- an abnormal release of serotonin, a brain chemical