eMedicine Specialties > Physical Medicine and Rehabilitation > Spinal Cord Injury

Autonomic Dysreflexia in Spinal Cord Injury

Author: Denise I Campagnolo, MD, MS, Director of Multiple Sclerosis Clinical Research and Staff Physiatrist, Barrow Neurology Clinics, St Joseph's Hospital and Medical Center; Investigator for Barrow Neurology Clinics; Director, NARCOMS Project for Consortium of MS Centers
Contributor Information and Disclosures

Updated: Jul 2, 2009

Introduction

Background

Autonomic dysreflexia (AD) is a syndrome of massive imbalanced reflex sympathetic discharge occurring in patients with spinal cord injury (SCI) above the splanchnic sympathetic outflow (T5-T6). Anthony Bowlby first recognized this syndrome in 1890 when he described profuse sweating and erythematous rash of the head and neck initiated by bladder catheterization in an 18-year-old patient with SCI. Guttmann and Whitteridge completed a full description of the syndrome in 1947. This condition represents a medical emergency, so recognizing and treating the earliest signs and symptoms efficiently can avoid dangerous sequelae of elevated blood pressure. SCI patients, caregivers, and medical professionals must be knowledgeable about this syndrome and its management. (See image below and Image 1.)

Pathophysiology

This phenomenon occurs after the phase of spinal shock in which reflexes return. Individuals with injury above the major splanchnic outflow may develop autonomic dysreflexia (AD). Below the injury, intact peripheral sensory nerves transmit impulses that ascend in the spinothalamic and posterior columns to stimulate sympathetic neurons located in the intermediolateral gray matter of the spinal cord. The inhibitory outflow above the SCI from cerebral vasomotor centers is increased, but it is unable to pass below the block of the SCI. This large sympathetic outflow causes release of various neurotransmitters (norepinephrine, dopamine-b-hydroxylase, dopamine), causing piloerection, skin pallor, and severe vasoconstriction in arterial vasculature.¹ The result is sudden elevation in blood pressure and vasodilation above the level of injury. Patients commonly have a headache caused by vasodilation of pain sensitive intracranial vessels.

Vasomotor brainstem reflexes attempt to lower blood pressure by increasing parasympathetic stimulation to the heart through the vagus nerve to cause compensatory bradycardia. This reflex action cannot compensate for severe vasoconstriction, explained by the Poiseuille formula, where pressure in a tube is affected to the fourth power by change in radius (vasoconstriction) and only linearly by change in flow rate (bradycardia). Parasympathetic nerves prevail above the level of injury, which may be characterized by profuse sweating and vasodilation with skin flushing.

Cameron and colleagues have found that site-directed genetic manipulation of fiber sprouting in the spinal dorsal horns in a cord compression rat model could alter the extent of hyperreflexia after bowel distention, indicating that endogenous spinal cord circuitry/neural sprouting plays a role in the pathophysiology of AD.²

Frequency

United States

Reported prevalence rates vary, but the generally accepted rate is 48-90% of all individuals who are injured at T6 and above. Some incidence has been reported in SCI as low as T10. Autonomic dysreflexia (AD) occurs during labor in approximately two thirds of pregnant women with SCI above the level of T6. The occurrence of AD increases as the patient evolves out of spinal shock. With the return of sacral reflexes, the possibility of AD increases.³

Mortality/Morbidity

Sex

The male-to-female ratio for sustaining SCI is 4:1; therefore, autonomic dysreflexia is primarily a male phenomenon.

Age

No specific relationship has been documented between autonomic dysreflexia and age.

Clinical

History

The patient with autonomic dysreflexia generally gives a history of blurry vision, headaches, and a sense of anxiety. Feelings of apprehension or anxiety over an impending physical problem commonly are exhibited.

Physical

A patient with autonomic dysreflexia (AD) may have 1 or more of the following findings on physical examination:

• A sudden significant rise in systolic and diastolic blood pressures, usually associated with bradycardia, can appear. The normal systolic blood pressure for SCI above T6 is 90-110 mm Hg. Blood pressure 20-40 mm Hg above the reference range for such patients may be a sign of AD.
• Profuse sweating above the level of lesion, especially in the face, neck, and shoulders, may be noted, but it rarely occurs below the level of the lesion because of sympathetic cholinergic activity.
• Goose bumps above, or possibly below, the level of the lesion may be observed.
• Flushing of the skin above the level of the lesion, especially in the face, neck, and shoulders, frequently is noted.
• The patient may report blurred vision.
• Spots may appear in the patient's visual fields.
• Nasal congestion is common.
• No symptoms may be observed, despite elevated blood pressure.

Causes

Episodes of autonomic dysreflexia (AD) can be triggered by many potential causes.⁴ Essentially any painful, irritating, or even strong stimulus below the level of the injury can cause an episode of AD. Although the list is not comprehensive, the following events or conditions all can cause episodes of AD:

• Bladder distension
• Urinary tract infection
• Cystoscopy
• Urodynamics
• Detrusor-sphincter dyssynergia⁵
• Epididymitis or scrotal compression
• Bowel distension
• Bowel impaction
• Gallstones
• Gastric ulcers or gastritis
• Invasive testing
• Hemorrhoids
• Gastrocolic irritation
• Appendicitis or other abdominal pathology trauma
• Menstruation
• Pregnancy, especially labor and delivery
• Vaginitis
• Sexual intercourse
• Ejaculation
• Deep vein thrombosis
• Pulmonary emboli
• Pressure ulcers
• Ingrown toenail
• Burns or sunburn
• Blisters
• Insect bites
• Contact with hard or sharp objects
• Temperature fluctuations
• Constrictive clothing, shoes, or appliances
• Heterotopic bone
• Fractures or other trauma
• Surgical or diagnostic procedures
• Pain

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