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Autonomic testing may reveal, apneusis which can be associated with dizzy spells.

This is an example of a Valsalva-like activity (straining) inducing dizziness and headaches. Autonomic testing showed excessive increase of cerebral blood flow velocity during Phase 4 of the Valsalva maneuver, which is consistent with cerebral hyperemia. Valsalva-induced headaches are usually indomethacin-responsive.

Postural tachycardia syndrome (POTS) patients exhibit signs of cerebral hypoperfusion, which is related to a decline in cerebral blood flow velocity (CBFv). End tidal CO2 has profound effects on CBFv. A decline in CBFv in POTS is mainly due to hypocapnia. This is a common finding in POTS.

Tilt test showed a typical orthostatic cerebral hypoperfusion syndrome (OCHOS). The OCHOS pattern is characterized by reduced orthostatic cerebral blood flow velocity (CBFv) without orthostatic hypotension, tachycardia, or hypocapnia and no evidence of adrenergic autonomic failure.

Autonomic failure manifesting as neurogenic orthostatic hypotension and supine hypertension are common manifestations of cardiovascular dysautonomia in Parkinson’s disease. Depending on the cerebral blood flow, neurogenic orthostatic hypotension can be either compensated (with stable orthostatic cerebral blood flow) and noncompensated (with reduced flow).

The patient has history of mast cell activation syndrome (MCAS), as well as Ehlers-Danlos (EDS) syndrome. This study was indicative of mild postural tachycardia syndrome (POTS), most likely a hyperadrenergic variant which is associated with elevated orthostatic catecholamines. Both EDS and MCAS syndromes are clustered with dysautonomia.

Paroxysmal dysautonomia can be responsible for transient dizziness and postural tachycardia syndrome (POTS).

Orthostatic symptoms in postural tachycardia syndrome (POTS) (shortness of breath, lightheadedness, fatigue, and others) are due cerebral hypoperfusion associated with reduced cerebral blood flow velocity (CBFv), which is induced by hyperventilation. Immunomodulatory therapy using immune globulins may be effective in small fiber neuropathy with a positive antibody against the P/Q-type calcium channel.

The tilt test showed orthostatic cerebral hypoperfusion syndrome (OCHOS) with intermittent reduction in cerebral blood flow velocity and vision loss. OCHOS is associated with reduced orthostatic cerebral blood flow velocity without orthostatic hypotension or arrhythmia.

Autonomic testing is useful to differentiate between postural tachycardia syndrome (POTS) and inappropriate sinus tachycardia (IST). IST can be comorbid with orthostatic cerebral hypoperfusion syndrome.

Patient experienced symptoms of orthostatic intolerance due to cerebral hypoperfusion and to hypocapnic hyperventilation, which is typical for hypocapnic cerebral hypoventilation. (HYCH). Voluntary hyperventilation in supine position reproduced symptoms and findings.

Preload failure can be associated with small fiber neuropathy, hypocapnic cerebral hypoperfusion, and dysautonomia.

This case demonstrates severe autonomic failure associated with autoimmune small fiber neuropathy that was positive for elevated voltage-gated potassium channel (VGKC) antibodies. Adrenergic autonomic failure is associated with orthostatic hypotension. Low cerebral blood flow velocity during the tilt was associated with cerebral vasoconstriction.

This patient showed evidence of mild but widespread autonomic dysfunction. These findings are nonspecific and can be seen in variety of central (α‎-synucleinopathies) and peripheral (autonomic neuropathy/ganglionopathy) disorders. Clinical workup for neuropathy showed elevated acetylcholine ganglionic neuronal antibodies. Immunotherapy with intravenous immunoglobulins for suspected autoimmune autonomic neuropathy was recommended.

The patient presents with fatigue, postprandial nausea, diarrhea, food allergies, and nighttime tachycardia. She was diagnosed with mast cell syndrome (MCAS). Autonomic testing has shown anxiety; mild postural tachycardia syndrome (POTS), neuropathic form; and small fiber neuropathy, mixed, length-dependent.

The tilt test reproduced several of a patient’s complaints, including dizziness and palpitations. Her symptomatic episodes were positive for elevated cerebral blood flow velocity (CBFv), with prominent oscillations, but tilt did not show tachycardia or hypotension.

In this patient, the initial decline in blood pressure at the tilt onset was physiologic since it was accompanied by the decline in cerebral blood flow velocity and heart rate responses. The testing revealed normal autonomic functions. It is important always to check the raw data. Blood pressure from the finger cuff is not always accurate.

Low cerebral blood flow velocity (CBFv) can be associated with signs of cerebral hypoperfusion with dizziness in concussion. The tilt test with CBFv monitoring can be helpful to differentiate this from other causes of dizziness.

This chapter lists the main syndromes and patterns seen during autonomic testing, based on classification according to physiology and/or functional anatomy. Although the classification is arbitrary, it is useful in that it allows the diagnostician to see classify patterns in test results that assist in the correct interpretation of the results. Presented in a series of easy to access lists, the most common patterns are autonomic failure, autonomic overactivity, paroxysmal dysautonomia orthostatic hypotension syncope, hyperventilation, cerebral hypoperfusion, cerebral blood flow velocity, and cerebral autoregulation disorders.

Postural tachycardia syndrome and small fiber neuropathy can be associated with polycystic ovary syndrome or with the use of metformin.

Small fiber neuropathy, mixed, length-dependent, is associated with antibodies against the N-type calcium channel. Tilt showed hypocapnic cerebral hypoperfusion.

It is of paramount importance to recognize artifacts since they can mimic various abnormalities, such as high or low blood pressure or even syncope.

This case presents syncope, neurally mediated, and mixed. Small fiber neuropathy (SFN) presented as sensory and length-dependent, and the typical hyperventilatory response with a decline of end tidal CO2 just before the syncope was absent.

Autonomic testing with cerebral blood flow velocity monitoring can be useful to evaluate psychogenic dizziness.

Autonomic testing may reveal combined initial orthostatic hypotension and orthostatic hypotension due to a combination of volume depletion and adrenergic failure, presyncope with prominent vasodepressor component, and small fiber neuropathy.

Autonomic testing can be useful to evaluate a mixed pattern consisting of postural tachycardia syndrome, cerebral autoregulatory failure, pseudosyncope, and syncope.

Postural tachycardia syndrome (POTS) without evidence of autoimmunity or neuropathy has a good prognosis. Early blood pressure decline at the beginning of tilt may provide early warning of impending syncope or other abnormalities during the tilt. Hypocapnic hyperventilation is a common occurrence in POTS.

Severe anxiety and severe postural tachycardia syndrome (POTS) may coexist, and both require adequate therapy. Autonomic testing can be useful in the evaluation of dizziness in anxious patients.

Short episodes confusion, dizziness, and shortness of breath can be associated with intermittent declines in cerebral blood flow velocity (CBFv). CBFv decline without orthostatic hypotension or decline in end tidal CO2 can be seen in orthostatic cerebral hypoperfusion syndrome (OCHOS) associate with abnormal cerebral vasoconstriction due to cerebral autoregulatory failure.

This case illustrates severe generalized autonomic failure associated with frontotemporal dementia (FTD) and hypothermia. The tilt test provoked severe sustained orthostatic hypotension associated with reduced heart rate response and a decline in cerebral blood flow velocity. Thermoregulation is a vital function of autonomic nervous system.

In this patient, testing showed several findings including small fiber neuropathy, orthostatic hypertension, and hypocapnic cerebral hypoperfusion. Elevated orthostatic blood pressure is commonly seen in painful neuropathies.

This patient showed severe generalized autonomic failure associated with compensated orthostatic hypotension, which is consistent with multiple system atrophy (MSA). Cerebral autoregulatory failure was associated with low supine cerebral blood flow velocity, which remained stable during the tilt. Small fiber neuropathy, biopsy-proven, mixed, was affecting both sensory and autonomic fibers.

This case describes neuropathic postural tachycardia syndrome (POTS) with striational antibodies that can be associated with small fiber neuropathy and respond to IVIG.

Syncopal reaction can mimic postural tachycardia syndrome.

This chapter describes posttreatment Lyme disease syndrome (PLDS) that can be associated with mild adrenergic failure, small fiber neuropathy, and hypocapnic cerebral hypoperfusion during the tilt.

An older patient presents with fatigue, exertional dyspnea, exertional chest tightness, and palpitations. Cardiopulmonary exercise testing (CPET) showed low biventricular filling pressure and poor peripheral oxygen extraction as a cause of dyspnea, consistent with preload failure. Tilt test demonstrated postural tachycardia syndrome (POTS), neuropathic form.

This case illustrates autonomic failure in painful post-Lyme disease syndrome. Autonomic testing has shown supine hypertension, orthostatic hypotension, and hypocapnic cerebral hypoperfusion (HYCH). Small fiber neuropathy was painful, affecting sensory fibers. Patient noted improvement in the pain by about 40% after 12 month of intravenous immune globulins.

Cervical spine injury may result in postural tachycardia syndrome and autonomic dysreflexia.

Postural tachycardia syndrome (POTS), syncope, and small fiber neuropathy is associated with hypermobile Ehlers-Danlos syndrome.

Autonomic testing is useful to differentiate between postural tachycardia syndrome (POTS) and inappropriate sinus tachycardia. Inappropriate sinus tachycardia and orthostatic cerebral hypoperfusion syndrome may coexist.

Patient experienced symptoms of orthostatic intolerance, most likely due to mild cerebral hypoperfusion due to hypocapnic hyperventilation and normal heart rate responses, which is typical for hypocapnic cerebral hypoperfusion (HYCH). In addition, there was significant small fiber cholinergic neuropathy affecting predominantly autonomic fibers, biopsy-proven.

This case demonstrates severe autonomic failure with orthostatic hypotension affecting cardiovagal and sympathetic adrenergic fibers and associated with small fiber neuropathy. Small fiber neuropathy is severe, mixed, and affecting sensory and autonomic fibers, non–length-dependent. Orthostatic cerebral blood flow velocity was reduced throughout the tilt, indicative of autoregulation failure.

Patient presents with frequent spells of passing out. Tilt test provoked two episodes of neurally mediated syncope, mixed type. Although rare, neurally mediated syncope can occur in the supine position. A second syncope can follow the first syncope almost immediately.

This chapter describes the main characteristics of laboratory equipment used in autonomic testing.

Cerebral blood flow velocity monitoring can be useful to diagnose psychogenic unresponsiveness.

Postural tachycardia syndrome (POTS) can be associated with mixed small fiber neuropathy in which both epidermal and autonomic fibers are affected. Damage of sensory fibers leads to sensory symptoms (pain, numbness) while dysfunction of autonomic fibers (in this case, with adrenergic dysfunctions as detected by the Valsalva maneuver and sudomotor deficit as detected by sudomotor testing and confirmed by abnormal sweat gland nerve fibers on the skin biopsy) leads to POTS. Hypocapnia is common in POTS and reduces the cerebral blood flow velocity due to its vasoconstrictive effect.

Dizziness, numbness, and pain can be associated with small fiber neuropathy and hypocapnic hyperventilation. Lyme disease can be the underlying cause.

Autonomic testing is useful to assess inappropriate sinus tachycardia (ISA).

Episodic decrease in cerebral blood flow velocity triggered by a deep breath can be associated with dizziness.

This patient had diagnoses of multiple autoimmune disorders including Sjögren syndrome, rheumatoid arthritis, and systemic lupus erythematosus. Sjögren syndrome can be accompanied by severe painful neuropathy and dysautonomia. Orthostatic intolerance was due to cerebral autoregulatory failure.