Autonomic hyperreflexia

Autonomic hyperreflexia


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.


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


Symptoms can include any or all of the following:

  • Fever
  • Goose bumps
  • Flushing
  • Lightheadedness or dizziness
  • Bladder or bowel dysfunction
  • Headache
  • Profuse sweating
  • Blurry vision
  • Anxiety
  • Nasal congestion
  • Muscle spasm

Sometimes, despite a dangerous rise in blood pressure, no symptoms are present.

Exams and Tests

  • High blood pressure
  • Slow pulse or fast pulse

A complete neurological and medical examination must be performed. Patients must provide an accurate medication and drug history in order to help determine which tests are necessary.

Tests may include:

  • Brain pictures including head CT or MRI
  • Spine pictures, particularly MRI
  • Lumbar puncture
  • Blood and urine tests
  • Toxicology screening (tests for any drugs, including medications, in the patient's bloodstream)
  • X-rays
  • EKG (measurement of the heart's electrical activity)
  • Tilt-table testing (testing of blood pressure regulation as body position changes)


Treatment depends on the cause. Offending medications or drugs must be discontinued. Any underlying illness that is causing the symptoms needs to be treated. If a substantial slowing of the heart rate is shown to produce symptoms, some drugs called anticholinergics (such as atropine) may be tried.

Very high blood pressure needs to be treated rapidly but carefully, as it may be quite unpredictable, falling abruptly. Commonly-used, emergency drugs include: Nifedipine (Procardia), Nitroglycerine, Phenoxybenzamine hydrochloride (Dibenzyline), Mecamylamine (Inversine), and Diazoxide (Hyperstat).

A pacemaker may be required for certain unstable heart-related situations.

In patients with spinal cord injury, autonomic hyperreflexia may be caused by pain, fecal impaction, bladder distension, pressure sores, or suctioning. Careful attention to the patient's needs can prevent these problems.

Outlook (Prognosis)

The outlook depends on the underlying cause. People with autonomic hyperreflexia due to medications usually recover when the offending medications are stopped. Recovery when the condition is caused by other factors depends on the success of treating the underlying disease.

Possible Complications

Complications may occur as a result of side effects of medications. Severe reduction of the pulse rate may result in a cardiac arrest.

Prolonged, severe high blood pressure may result in seizures or stroke.

When to Contact a Medical Professional

Call your health care provider if you have symptoms of autonomic hyperreflexia.


Prevention of autonomic hyperreflexia includes avoiding medications that cause this condition or make it worse. In the spine-injured patient, attention to voiding habits, skin condition, and pain level may prevent autonomic hyperreflexia.

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