Definition and Overview
Autonomic dysreflexia (AD) is a potentially life-threatening condition in patients with spinal cord injury at the level of the 6th thoracic vertebra (T6) or higher, in which the sympathetic nervous system is uncontrollably overactivated by noxious stimulation below the damaged area, accompanied by a variety of autonomic symptoms centered on a rapid increase in blood pressure.
Because the T6 level corresponds to the upper limit of the spinal sympathetic outflow tract, damage above this level deprives the entire visceral sympathetic nervous system of descending inhibition from higher centers. Autonomic dysreflexia is reported in 48-90% of patients with spinal cord injury above T6.
pathophysiology
Normal autonomic control
Normally, when a noxious stimulus occurs below the spinal cord injury site, the sympathetic nerves are activated through the spinal cord, but at the same time, descending inhibitory signals are transmitted from the upper brainstem and hypothalamus, thereby limiting the increase in blood pressure. The baroreflex also induces a compensatory response through reduced heart rate and vasodilation.
Pathophysiology after spinal cord injury
When the spinal cord is damaged above T6, the descending inhibitory pathway is blocked. If noxious irritation occurs below the site of injury:
1. Sympathetic nerve transmission pathways within the spinal cord are activated reflexively. 2. The visceral blood vessels and blood vessels of the lower extremities constrict, causing a rapid rise in blood pressure. 3. In response to an increase in blood pressure recognized by the brain, the baroreceptor reflex is triggered, resulting in bradycardia via the vagus nerve. 4. However, due to spinal cord damage, the sympathetic nerve inhibitory signals below the level of damage are not transmitted, and hypertension persists.
As a result, a characteristic pattern occurs where vasodilation and sweating appear above the damaged area, and vasoconstriction and skin pallor appear simultaneously below the damaged area.
Causes and triggers
The trigger for autonomic dysreflexia can be any noxious stimulus below the level of injury.
- Bladder problems (75-85%): urinary blockage, bladder overcapacity, urinary tract infection, cystoscopy
- Intestinal problems: constipation, fecal impaction, irritation of the intestinal mucosa
- Skin problems: bedsores, pressure, abrasions, tight clothing
- Others: fractures, surgical procedures, menstruation, sexual activity, autonomic nervous system disturbances
symptoms
Symptoms of autonomic dysreflexia occur suddenly and are distributed as follows:
Abnormal area of spinal cord injury (vasodilator response)
- Pulsatile headache (the most common symptom)
- Redness and sweating of the face, neck, and shoulders
- stuffy nose
- Blurred vision, visual deviation
- anxiety, nervousness
Area below spinal cord injury (vasoconstrictor response)
- Pale skin, goosebumps
- no sweating
cardiovascular response
- Systolic blood pressure: increase of 20 to 40 mmHg or more compared to baseline
- Bradycardia (caused by vagal reflex, but tachycardia is also possible)
- Risk increases if high blood pressure persists above 150 mmHg systolic
diagnosis
The diagnosis of autonomic dysreflexia is made clinically.
Diagnostic criteria
- Patients with spinal cord injury T6 or higher
- Systolic blood pressure rises by more than 20 mmHg above baseline
- Accompanied by symptoms such as headache, sweating, and flushing
Since the resting blood pressure of patients with spinal cord injury is often lower than that of normal people (90 to 100 mmHg systolic), even a systolic level of 150 mmHg or more may be considered severe hypertension in this patient group.
Differential diagnosis
- Hypertensive crisis of other causes
- autonomic storm
- malignant hypertension
treatment
Immediate treatment (first aid procedures)
1. Lower blood pressure by having the patient sit down or raise the bed to maintain an upright seated position. 2. Immediately check for and remove tight clothing, abdominal compression straps, and urinary lines. 3. If the urine line is absent or blocked, catheterization should be performed immediately. 4. If fecal impaction is suspected, apply lidocaine gel and perform a digital rectal examination. 5. Monitor blood pressure by measuring it every 2 to 5 minutes.
medication
If systolic blood pressure persists above 150 mmHg or symptoms are severe even after the cause has been removed, antihypertensive medication is administered.
- Nifedipine 10 mg sublingually
- Nitroglycerin ointment or spray
- Captopril 25 mg sublingually
preventive treatment
In patients with recurrent autonomic dysreflexia, doxazosin, famotidine, etc. can be used for preventive purposes after the cause has been removed.
Complications and Prognosis
Untreated autonomic dysreflexia can lead to serious complications, including:
- Cerebral hemorrhage and stroke
- hypertensive encephalopathy
- Cardiac arrhythmias such as ventricular fibrillation
- seizure
- death
If the cause is quickly removed and appropriate treatment is provided, blood pressure usually normalizes within a few minutes. However, repeated occurrence increases the risk of chronic complications, so prevention through education of patients and guardians is most important.
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This information is provided for medical educational purposes and is not a substitute for individual medical care or treatment. If you have any symptoms, be sure to seek professional advice. Inquiries: Osang Neurosurgery 1599-5453 | osns.co.kr