understanding dysautonomia glossary

Short Definition:
Continuous BP recording over a full day and night.

Long Definition + Context:
Captures daytime surges and nocturnal “dipping” (or lack thereof), helping distinguish supine hypertension (common in PAF/MSA) from labile BP in POTS or OH. Useful when office readings don’t match patient symptoms.

Short Definition
A sudden challenge to blood pressure regulation when moving from lying/sitting to standing.

Long Definition + Context
Activities like standing quickly, standing in a hot shower, or rising after surgery can acutely overwhelm baroreflexes. In susceptible individuals, this may provoke lightheadedness, palpitations, or fainting. Learning to stand slowly, use support maneuvers, and warm‐to‐cool transitions can mitigate these stressors.

Short Definition
A distressing sensation of not getting enough air or an urge to breathe more deeply, even when breathing normally.

Long Definition & Context
Air hunger is a form of dyspnea characterized by the subjective feeling of “unsatisfied inspiration” — as if your lungs aren’t filling despite the effort to breathe. In POTS, this often stems from autonomic dysregulation and dysfunctional breathing patterns (e.g., shallow, chest-only breaths or chronic hyperventilation). When standing triggers sympathetic over-drive, lowered carbon dioxide levels can further disrupt the body’s respiratory drive, amplifying that persistent urge to gasp or yawn without relief. Addressing air hunger in POTS typically involves breathing retraining (diaphragmatic exercises, paced breathing) and dysautonomia management strategies to restore more balanced respiratory control.

Short Definition
A rare, antibody-mediated attack on autonomic ganglia causing widespread autonomic failure.

Long Definition + Context
Anti–ganglionic acetylcholine receptor antibodies disrupt signaling in autonomic neurons, producing severe orthostatic hypotension, anhidrosis, GI dysmotility, and fixed pupils. Rapid recognition and treatment with IVIG or plasmapheresis can partially restore function. AAG illustrates how autoimmunity can underlie sudden, multifaceted dysautonomia.

Short Definition
Damage to autonomic nerves impairing involuntary functions.

Long Definition + Context
Seen in diabetes, amyloidosis, or infectious causes; leads to gastroparesis, anhidrosis, orthostatic hypotension, and neurogenic bladder. Skin biopsy and QSART can confirm small-fiber involvement.

Short Definition
An automatic feedback loop that stabilizes blood pressure via stretch receptors in arteries.

Long Definition + Context
When arterial walls stretch (high BP) or slacken (low BP), baroreceptors in the carotid sinus and aortic arch adjust sympathetic/parasympathetic outflow to normalize pressure. Impaired baroreflex sensitivity is common in POTS and orthostatic hypotension, leading to exaggerated heart rate swings or inadequate vascular tone on standing.

Short Definition
Medications that slow heart rate by blocking β-adrenergic receptors.

Long Definition + Context
Low-dose propranolol, metoprolol, or bisoprolol are mainstays in hyperadrenergic POTS to reduce tachycardia, tremor, and anxiety. They blunt sympathetic overactivity but require careful titration to avoid hypotension or fatigue. Beta blockers can also help neurocardiogenic syncope by tempering excessive vagal reflexes.

Short Definition
Excess accumulation of blood in the legs or abdomen upon standing.

Long Definition & Context
Blood pooling happens when gravity causes blood vessels in the lower body to hold more blood than the heart can pump back upward. In dysautonomia, insufficient vasoconstriction exacerbates this, reducing cardiac output and triggering symptoms like leg swelling, cool extremities, and orthostatic intolerance. Compression garments and physical counter-maneuvers can help mitigate pooling.

Short Definition
A resting heart rate below 60 beats per minute.

Long Definition & Context
Bradycardia describes a slower-than-normal heart rate. While less common in POTS, certain dysautonomia subtypes (such as neurocardiogenic syncope) can produce episodic bradycardia when vagal tone surges. Patients may feel weak, dizzy, or experience near-fainting during these slow-heart-rate episodes.

Short Definition
Loss of cardiovascular fitness from prolonged inactivity.

Long Definition + Context
Bedrest or sedentary lifestyle reduces plasma volume, stroke volume, and vascular tone, mimicking or worsening POTS/OI. Graded recumbent exercise programs aim to reverse deconditioning.

Short Definition
Inability of the heart to raise its rate appropriately during exertion.

Long Definition + Context
Some dysautonomia patients can’t increase HR with activity (despite resting tachycardia), leading to exercise intolerance. Diagnosed on exercise stress testing; may be managed with tailored pacing and sometimes pacemaker placement in severe cases.

Short Definition
Difficulty concentrating, memory lapses, or a general sense of mental cloudiness.

Long Definition & Context
Brain fog in dysautonomia reflects transient cerebral hypoperfusion and neurochemical imbalances driven by autonomic dysfunction. Patients report slowed thinking, poor short-term memory, and mental fatigue, often worsened by upright posture or exertion. Addressing hydration, blood volume, and breathing patterns can improve cognitive clarity.

Short Definition
Broad term for any disorder of the autonomic nervous system (ANS).

Long Definition + Context
Encompasses conditions in which involuntary processes—heart rate, blood pressure, digestion, temperature control—are dysregulated. Primary (idiopathic) forms like POTS arise on their own; secondary forms follow diabetes, EDS, MCAS, or neurodegeneration. Symptoms span dizziness, GI distress, sweat anomalies, and exercise intolerance, reflecting multi-system ANS involvement.

Short Definition
A subjective sensation of difficult, uncomfortable, or labored breathing.

Long Definition & Context
Dyspnea is the clinical term for breathlessness—the feeling that it’s hard to inhale or exhale enough air. It can range from mild tightness in the chest to overwhelming air hunger. In POTS and other dysautonomia conditions, dyspnea often arises from altered autonomic control of the heart and lungs, dysfunctional breathing patterns (shallow or rapid breaths), and changes in blood flow when standing. Managing dyspnea in this context typically involves breathing retraining (e.g., paced diaphragmatic breathing), optimizing hydration and circulation, and treating underlying autonomic imbalances.

Short Definition
A synthetic mineralocorticoid that increases salt and water retention.

Long Definition + Context
By mimicking aldosterone, fludrocortisone boosts plasma volume in hypovolemic POTS and orthostatic hypotension. Typical doses (0.1–0.2 mg) support a high-salt regimen but require potassium monitoring. It’s one of the first pharmacologic steps to address low fill-volume before adding vasoconstrictors.

Short Definition
A nuclear medicine test measuring how fast food moves through the stomach.

Long Definition + Context
Gastroparesis is common in dysautonomia and MCAS; delayed emptying causes nausea, bloating, erratic blood sugars, and worsened orthostatic symptoms. Management includes dietary modifications (small, low‐fat meals), prokinetic agents (metoclopramide), and gastric pacing in refractory cases.

Short Definition
Abnormal movement of food through the digestive tract, causing symptoms like bloating or constipation.

Long Definition & Context
GI dysmotility arises from impaired autonomic regulation of smooth muscle contractions in the stomach and intestines. In dysautonomia, patients may experience gastroparesis (delayed stomach emptying), irritable-bowel-type symptoms, or rapid transit leading to diarrhea. Dietary modifications, prokinetic medications, and small frequent meals are common management approaches.

Short Definition
Beat-to-beat fluctuation in heart rate reflecting autonomic balance.

Long Definition + Context
Higher HRV indicates robust parasympathetic (vagal) tone; low HRV suggests sympathetic dominance or ANS impairment. In dysautonomia patients, blunted HRV during deep breathing tests or daily wearables correlates with symptom severity. Monitoring HRV can guide pacing, relaxation techniques, and track treatment response.

Short Definition
A POTS subtype with excessive standing norepinephrine or adrenaline.

Long Definition + Context
Characterized by upright norepinephrine >600 pg/mL, pronounced tremor, hypertension spikes, and flushing. Often treated with low-dose beta blockers, clonidine, or methyldopa. Screening must exclude pheochromocytoma. Patients may feel “wired” on standing, distinguishing them from hypovolemic or neuropathic POTS.

Short Definition
POTS driven by low circulating blood volume.

Long Definition + Context
Many POTS patients have 10–20% below-normal blood volume. Compensation via tachycardia leads to classic symptoms. Management focuses on aggressive hydration (2–3 L/day), high-salt intake, and fludrocortisone; severe cases may benefit from periodic IV saline infusions to “jump-start” volume before exercise reconditioning.

Short Definition
An α₁-agonist that raises standing blood pressure by vasoconstriction.

Long Definition + Context
Taken in 2.5–10 mg doses, midodrine combats orthostatic pooling in OH and neuropathic POTS. Peak action occurs 1 hour post-dose, lasting 3–4 hours. Patients must avoid supine positions post-dose to prevent hypertension. It’s often used “as needed” for high-symptom situations (outings, hot weather).

Short Definition
A neurodegenerative disease causing severe autonomic failure plus motor signs.

Long Definition + Context
Also known as Shy-Drager syndrome, MSA combines profound OH, bladder dysfunction, cerebellar ataxia or parkinsonism, and poor levodopa response. Prognosis is poor (mean survival ~10 years). Although rare in our community, any adult with new, progressive dysautonomia warrants evaluation for MSA.

Short Definition
Reflex-mediated faint (“vasovagal”) from sudden bradycardia and vasodilation.

Long Definition + Context
Triggered by prolonged standing, emotional distress, or pain, NCS causes nausea, sweating, then abrupt hypotension and slowing of the heart via a vagal surge. Treatment includes trigger avoidance, counter-pressure maneuvers (leg crossing, handgrip), and sometimes medications like midodrine or low-dose beta blockers when episodes are frequent.

Short Definition
Impaired bladder control due to autonomic nerve dysfunction.

Long Definition + Context
Presents with urgency, frequency, retention, or incontinence. Urodynamic studies characterize detrusor over- or underactivity. Management ranges from timed voiding and pelvic floor therapy to intermittent catheterization.

Short Definition
POTS subtype due to partial sympathetic denervation in the legs.

Long Definition + Context
Damaged vasoconstrictor nerves fail to squeeze leg vessels on standing, causing pooling and reflex tachycardia. Signs include cold, mottled lower limbs and relatively normal norepinephrine levels. Compression garments, midodrine, and—if immune-mediated—IVIG can improve symptoms. Small fiber neuropathy workup (QSART, skin biopsy) often reveals the underlying nerve injury.

Short Definition
A sustained ≥20 mmHg systolic or ≥10 mmHg diastolic BP drop within 3 minutes of standing.

Long Definition + Context
Causes dizziness, weakness, and syncope. Etiologies range from dehydration and medications to diabetic or neurogenic autonomic failure (PAF, MSA). Management parallels POTS (fluids, salt, compression, midodrine) but often prioritizes vasoconstrictors due to the predominant BP drop.

Short Definition
Symptoms of dizziness, weakness, or palpitations relieved by recumbency.

Long Definition + Context
An umbrella term covering POTS (tachycardic OI), OH (hypotensive OI), and NMH (delayed hypotension). OI explains why simple acts—standing in line, showering, or cooking—can be disabling. Core therapies (fluid/salt loading, gradual exercise, compression) support all OI subtypes.

Short Definition
The “rest-and-digest” branch of the ANS that slows heart rate and promotes digestion.

Long Definition + Context
Mediated chiefly by the vagus nerve, parasympathetic activity counters sympathetic arousal. In dysautonomia, parasympathetic withdrawal (or unopposed sympathetic tone) can exacerbate tachycardia, GI dysmotility, and anxiety. Therapies like deep breathing and biofeedback aim to augment vagal tone and restore ANS balance.

Short Definition
A dysautonomia defined by a ≥30 bpm HR rise (or >120 bpm) within 10 minutes of standing, without hypotension.

Long Definition + Context
Symptoms include lightheadedness, palpitations, fatigue, brain fog, and sometimes syncope. Onset is often in adolescence or early adulthood, frequently succeeding viral illness or surgery. First-line management: increased fluids/salt, compression, recumbent exercise, and tailored pharmacotherapy (beta blockers, ivabradine, fludrocortisone, midodrine). POTS can coexist with EDS and MCAS, forming the “autonomic triad.”

Short Definition
A sensation of near-fainting marked by lightheadedness, dizziness, or blurred vision without complete loss of consciousness.

Long Definition & Context
Presyncope occurs when blood flow to the brain temporarily dips (often from standing too quickly or autonomic imbalance), triggering warning signs like sweating, nausea, or tunnel vision. It’s common in POTS, orthostatic hypotension, and vasovagal reactions. Recognizing these early symptoms allows use of counter-pressure maneuvers (leg crossing, handgrip), sitting or lying down, and fluid/salt intake to prevent a full faint.

Short Definition
A peripheral neurodegenerative dysautonomia causing severe orthostatic hypotension and anhidrosis.

Long Definition + Context
Predominantly in older adults, PAF spares central motor and sensory functions but yields profound BP instability, reduced HR variability, and sweat dysfunction. Treatment centers on midodrine, droxidopa, and supportive measures (head-up sleep, small meals). PAF contrasts with MSA by lacking parkinsonism or cerebellar signs.

Short Definition
A test measuring sweat output to assess small-fiber autonomic function.

Long Definition + Context
By applying acetylcholine iontophoresis, QSART quantifies sweat gland response in forearm or leg skin. Diminished or asymmetric sweat reflects sudomotor nerve damage, common in neuropathic POTS, diabetic autonomic neuropathy, or small-fiber neuropathies. QSART guides subtype classification and helps direct therapies such as IVIG in immune causes.

Short Definitionz
Assessments of sweat gland activity to evaluate sympathetic cholinergic function.

Long Definition + Context
Includes QSART (quantitative), thermoregulatory sweat test (whole‐body acetylcholine spray), and silicone pod methods. Abnormalities help subtype POTS (neuropathic) or diagnose small-fiber neuropathy.

Short Definition
Elevated blood pressure when lying down.

Long Definition + Context
Common in OH and PAF, aggravated by midodrine or fludrocortisone. Patients must sleep with head elevated and avoid late-day vasoconstrictors. Balancing OH therapy with supine BP control is a key challenge.

Short Definition
A transient loss of consciousness and muscle tone caused by reduced blood flow to the brain.

Long Definition & Context
In dysautonomia, syncope often results from improper autonomic control: blood pressure or heart rate can suddenly drop (as in vasovagal syncope or orthostatic hypotension), briefly depriving the brain of oxygen. Patients may feel lightheaded, nauseated, or sweaty before fainting and recover quickly when lying flat. Diagnosis commonly uses a tilt-table test to reproduce symptoms under monitoring. Management includes trigger avoidance (e.g., standing slowly, counter-pressure maneuvers), volume expansion, compression garments, and medications tailored to the underlying cause.

Short Definition
The “fight-or-flight” ANS branch increasing heart rate, constricting vessels, and mobilizing energy.

Long Definition + Context
Overactivity causes tachycardia, tremor, and high BP; underactivity yields pooling and hypotension. Dysautonomia reflects imbalances—either hyperadrenergic states (hyper-POTS) or sympathetic failure (OH, PAF). Medications modulate sympathetic tone: beta blockers and clonidine reduce it; midodrine and droxidopa augment it.

Short Definition
A resting heart rate above 100 beats per minute.

Long Definition & Context:
Tachycardia is an elevated heart rate at rest. In POTS, patients experience a rise of 30 bpm or more (40 bpm in adolescents) within 10 minutes of standing, often reaching rates well above 100 bpm. This compensatory rapid heartbeat tries to maintain blood flow when venous return is impaired but can cause palpitations, anxiety, and fatigue.

Short Definition
Inability to maintain normal body temperature, resulting in excessive heat or cold sensitivity.

Long Definition & Context
Dysautonomia can disrupt sweat gland control and peripheral vasomotor responses, so patients may overheat easily, feel cold in warm environments, or vice versa. Heat intolerance can exacerbate orthostatic symptoms and tachycardia, while cold intolerance may lead to chills and discomfort. Environmental adjustments and clothing choices are key strategies.

Short Definition
A diagnostic procedure to provoke and record orthostatic responses under controlled tilt.

Long Definition + Context
Patients are strapped to a motorized table and tilted upright (usually ~70°) while continuous ECG and BP monitoring detect POTS (tachycardia without hypotension), OH (rapid BP drop), or NCS (sudden BP/HR crash). Provocative agents (isoproterenol, nitroglycerin) enhance test sensitivity. Despite patient discomfort, it remains the gold standard for dysautonomia subtyping.

Short Definition
A forced exhalation against a closed airway used to test autonomic reflexes.

Long Definition + Context
Phases I–IV produce predictable BP/HR changes. Blunted or delayed responses indicate baroreflex failure. It’s a standard part of autonomic reflex screening alongside tilt testing and QSART.