📋 In This Article
Autonomic dysreflexia is a sudden, potentially life-threatening spike in blood pressure that affects people with spinal cord injuries at T6 and above. Unlike many secondary conditions that develop slowly, AD can escalate to stroke, cardiac arrest, or death within minutes. This guide covers everything you need to recognise an episode, identify the trigger, and act fast.
The autonomic nervous system (ANS) controls everything your body does automatically — heart rate, blood pressure, digestion, temperature, sweating, and hundreds of other functions. It has two balancing sides: the sympathetic system (speeds things up — fight or flight) and the parasympathetic system (slows things down — rest and digest).
After a spinal cord injury above T6, that balance breaks down. When something irritating or noxious happens below the level of injury, the sensory nerves send a signal upward — but the brain’s correcting message can’t fully get back down through the damaged cord. Instead, the sympathetic nervous system fires a massive, uncontrolled burst of activity throughout the body. Blood pressure surges dangerously high. The parasympathetic system tries to counteract above the injury level but cannot stop the storm below. This is autonomic dysreflexia.
AD is a Medical Emergency
Because the ANS is automatic, you cannot consciously control or stop an AD episode. Emergency treatment must begin immediately. Do not wait to see if it passes on its own.
⚡ Sympathetic (Fight or Flight)
Raises heart rate and blood pressure
Dilates airways, increases respiration
Constricts blood vessels
Triggers sweat and goosebumps
🌿 Parasympathetic (Rest & Digest)
Slows heart rate and lowers blood pressure
Supports digestion and bowel function
Promotes rest and recovery
Controls bladder and sexual function
Any injury or disease affecting the upper motor neurons — located in the brain and upper spinal cord — creates the conditions for AD. The most well-known risk group is people with spinal cord injury at T6 and above, but the population is broader than many realise.
Spinal Cord Injury
PRIMARY RISK GROUP
Injury at T6 and above. Some research also shows risk in injuries as low as T10 due to anatomical variation and extended trauma zones.
Brain Injury & Stroke
UPPER MOTOR NEURON DAMAGE
Paroxysmal sympathetic hyperactivity (PSH) is a specific form seen in brain injury, with fever, tachycardia, high BP, and sweating.
Multiple Sclerosis
PROGRESSIVE NEUROLOGICAL
Upper motor neuron involvement in MS can trigger AD episodes; onset may occur at an unknown stage of disease progression.
Guillain-Barré & Others
OTHER NEUROLOGICAL CONDITIONS
Any disease or injury disrupting the autonomic nervous system can produce AD episodes, even without a formal SCI diagnosis.
Not Everyone with These Diagnoses Will Develop AD
It is not fully understood why some people develop AD and others do not, or why some experience more severe episodes. There are rare cases of AD with no identified neurological cause at all.
Symptoms vary significantly between individuals. Some people experience one symptom; others experience many. Even mild symptoms must never be ignored — any symptom can indicate a dangerous blood pressure elevation. The pounding headache is the most commonly cited sign, but AD can occur without it.
Blood Pressure Monitoring is Essential
Elevated blood pressure above your personal baseline — even without obvious symptoms — can lead to stroke, cardiac arrest, seizures, retinal haemorrhage, pulmonary oedema, and death if untreated.
⬆️ ABOVE Level of Injury
Hypertension — BP rise of 20–40 mmHg systolic above usual
Bradycardia or tachycardia (slow or fast heart rate)
Pounding headache
Apprehension, anxiety, or uneasy feeling
Changes in vision
Nasal congestion, sweating, flushed skin
Goosebumps and tingling sensation
⬇️ BELOW Level of Injury
Nausea
Chills without fever
Clammy, cool, and pale skin
⬆️ ABOVE Level of Injury
BP rise of 15 mmHg (children) or 15–20 mmHg (adolescents) systolic
Bradycardia or tachycardia
Big headache, feeling nervous or scared
Red cheeks, neck, or shoulders
Blurry vision, stuffy nose, sweating, goosebumps, tingling
⬇️ BELOW Level of Injury
Upset stomach or nausea
Chills without fever
Clammy, cool, pale skin
Silent AD is one of the most dangerous — and underrecognised — forms of autonomic dysreflexia. Blood pressure rises to dangerous levels, but the person feels no symptoms at all. There is no headache, no flushing, no warning. Silent AD has been detected during sleep monitoring, bladder assessments, and routine bowel programmes.
During Sleep
Blood pressure monitored during sleep has revealed silent AD episodes with no waking symptoms.
Bladder Assessments
Urodynamic testing and cystoscopy can trigger silent AD episodes that require BP monitoring throughout.
Bowel Programmes
Routine bowel care has been found to silently elevate blood pressure to AD-level thresholds.
Monitor Routinely — Even Without Symptoms
Studies show silent AD affects 42.9–63.6% of people with SCI at T6 and above. During routine activities and procedures, blood pressure should be actively monitored. Any elevation should be immediately reported to a healthcare professional for evaluation.
There is no blood test or imaging scan that detects AD directly. Diagnosis is based on blood pressure assessment at the time of symptoms. Knowing your personal baseline BP is critical — because SCI often lowers resting blood pressure over time, a reading that looks “normal” may actually represent a dangerous spike for you.
Adults: Rise of 20–40 mmHg systolic above personal baseline
Adolescents: Rise of 15–20 mmHg systolic above personal baseline
Children: Rise of 15 mmHg systolic above personal baseline
Note: Adults with SCI at T6 and above often have a resting BP of 90–110 mmHg systolic — lower than the pre-injury norm. This baseline must be established and documented so any dangerous rise is caught early.
A trigger is anything the body perceives as noxious or irritating below the level of injury. Because sensation is reduced or absent in that zone, the body can’t correct the problem normally — so it fires the AD response instead. The three most common trigger sources are the bladder, bowel, and skin.
#1 — Bladder (Most Common)
Blocked, kinked, or clogged catheter; bladder overdistension; spasms; detrusor sphincter dyssynergia (DSD); bladder stones or infection; urodynamic testing; overfull or heavy leg bag; tight leg bag straps; wet containment garments.
#2 — Bowel
Constipation, impaction, incomplete bowel programme, gas, overzealous digital stimulation, enemas, manual removal; also diarrhoea, diverticulitis, Crohn’s disease, fissures, and haemorrhoids.
#3 — Skin & Clothing
Pressure injuries (any stage), rashes, cuts, bruises, ingrown toenails, sitting on a wrinkle; constrictive clothing — tight socks, jeans rivets, ill-fitting shoes, belts, bras, or even an air current over skin.
Temperature changes — fever, chills, hot or cold environment
Spasticity anywhere in the body
Internal organ issues — gallstones, appendicitis, ulcers, ovarian cysts
Sexual function, menstruation, pregnancy, or childbirth
DVT or pulmonary embolism
Heterotopic ossification, pain, eye strain from screens or sunlight
AD is a Medical Emergency — Act Immediately
Do not wait. Do not see if it passes. Call 911 without hesitation if the trigger cannot be found or if blood pressure does not come down after correcting known triggers.
Sit bolt upright immediately. Torso and hips at 90°. Ask for help if needed. This uses orthostatic hypotension to cause a sudden blood pressure drop as blood rushes away from your head.
Monitor blood pressure every 2–3 minutes until it returns to your normal range.
Loosen all tight or restrictive items — belts, clothing, leg bag straps, shoes — while getting into the sitting position.
Search for the trigger. In this order: (1) Check urine flow — catheterise if little or no output. (2) Check bowel — disimpact if stool is present. (3) Check skin — remove wrinkles, constrictions, and tight clothing. If your usual trigger is known, address it first.
Administer prescribed medication if available. Common options include Nitro Paste (½” under 13 yrs; 1″ age 13+), applied topically above the level of injury every 30 minutes — washed off once BP stabilises. Or Nifedipine (immediate release, sublingual or chewed). Never administer IV antihypertensives outside a monitored ICU setting. Consult your prescriber about which medication is right for you.
Continue monitoring for at least two hours after blood pressure stabilises.
Call 911 immediately if trigger cannot be found, or if blood pressure remains elevated after corrections. Risk of stroke, cardiac arrest, seizures, retinal haemorrhage, pulmonary oedema, and death is real without medical intervention.
Managing AD is a team effort. The moment you suspect an episode is starting, begin treatment by sitting up — then call for help. Every member of your care network should know about your AD, because in a severe episode you may not have time to explain.
Physiatrist / Neurologist / GP
Provides diagnosis, prescribes medications, and adjusts treatment plans as episodes evolve or triggers change.
Rehabilitation Registered Nurse
Educates you and your caregivers on identifying AD, performing emergency treatment, and responding to crises in hospital and community settings.
Urologist
Addresses bladder-specific triggers — numbing agents, catheter selection, sphincterotomy, and urodynamic assessment strategies that minimise AD risk.
Home Caregivers
Often the first responders during an episode at home — monitoring BP, helping into a sitting position, calling 911, and assisting with trigger identification.
Tell Everyone Who Cares for You
This includes therapists, teachers (for children), support workers, and any healthcare professional who may encounter you during a procedure. Download and carry the Reeve Foundation’s free Autonomic Dysreflexia Wallet Card — available in multiple languages at christopherreeve.org/cards.
Reeve Foundation — Information Specialists
Mon–Fri, 9am–8pm ET · Toll-free: 800-539-7309
AD Wallet Card (Adults, Children, Multi-language)
christopherreeve.org/cards — free download or call for a print copy
Consortium for SCI Medicine — Clinical Guidelines (2nd Ed.)
Acute Management of Autonomic Dysreflexia — Paralyzed Veterans of America
Washington State DOH — Trauma Rehabilitation Clinical Guideline
Reeve Foundation Fact Sheets Repository
Hundreds of topics on secondary conditions and state resources
AD is a medical emergency — elevated blood pressure from a missed trigger can cause stroke, cardiac arrest, or death within minutes. Never wait to see if it resolves on its own.
The first action in any episode is to sit bolt upright immediately. This alone can begin to lower blood pressure using orthostatic hypotension.
The three most common triggers are the bladder, bowel, and skin. Always check these in order when searching for the cause of an episode.
Silent AD — elevated blood pressure with no symptoms — affects 42.9–63.6% of people with SCI at T6 and above. Regular blood pressure monitoring during routine activities is essential.
Know your personal baseline blood pressure — people with SCI often run lower than the general population, so a reading that looks normal may actually represent a dangerous rise for you.
Everyone in your care circle — caregivers, therapists, teachers, and all healthcare providers — must be aware of your AD and how to respond. Carry the Reeve Foundation wallet card at all times.
Content adapted from the Christopher & Dana Reeve Foundation National Paralysis Resource Center · christopherreeve.org · 800-539-7309 © 2026 AccessLife
