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edriscoll
Anaesthesia
Postural orthostatic tachycardia syndrome: anesthetic implications in the obstetric patient:
http://www.ncbi.nlm.nih.gov/pubmed/17179264?dopt=AbstractPlus

Anaesthetic management of a parturient with the postural orthostatic tachycardia syndrome: a case report:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16698864&query_hl=1&itool=pubmed_docsum
Preoperative considerations in a patient with orthostatic intolerance syndrome:
http://journals.lww.com/anesthesiology/pages/articleviewer.aspx?year=2000&issue=08000&article=00041&type=fulltext
Autonomic dysfunction - anaesthetic management
http://www.anaesthetist.com/anaes/patient/ans.htm
Baroreflex
Abnormal baroreflex responses in patients with idiopathic orthostatic intolerance:
http://www.ncf-net.org/library/freeman-OI-2000.htm
Baroreflex control of muscle sympathetic nerve activity in postural orthostatic tachycardia syndrome:
http://ajpheart.physiology.org/cgi/content/full/289/3/H1226 
Catecholamines
The broader view: catecholamine abnormalities:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=12102462&dopt=Abstract
Endothelial NO Synthase Polymorphisms and Postural Tachycardia Syndrome:
http://pt.wkhealth.com/pt/re/dyslipidaemia/pdfhandler.00004268-200511000-00008.pdf;jsessionid=LnhQwG11yV0fKLVmTywMzWdZLQfyhxRq1HLnJ9
1n7vhQ2rxnX4yv!-2048123402!181195628!8091!-1
Chiari malformation/spinal cord involvement
Watch a presentation by physicians at The Chiari Institute and NIH as they discuss the possible connection between POTS, Ehlers-Danlos syndrome and Chiari Malformation: (click on the Ehlers-Danlos National Foundation link)
http://www.thechiariinstitute.com/
Cerebral syncope in a patient with spinal cord injury:
http://www.ncbi.nlm.nih.gov/pubmed/11990670?dopt=Abstract

Chiari Malformation:
http://www.dizziness-and-balance.com/disorders/central/cerebellar/chiari.html
Chiari, fibromyalgia, gastrointestinal problems, gulf war syndrome, multiple chemical sensitivities/environmental illness, orthostatic intolerance:
http://www.cfids.org/about-cfids/orthostatic-intolerance.asp
Sinus arrhythmia and pupil size in Chiari I malformation: evidence of autonomic dysfunction:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8314116&dopt=Abstract
The Chiari Institute:
http://www.chiariinstitute.com/chiari_malformation.html
Autonomic nervous system disorders in 230 cases of basilar impression and arnold-chiari deformity:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1494411&dopt=Abstract
Chiari I malformation as a cause of orthostatic intolerance symptoms: a media myth?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11705431&dopt=Abstract
No increased herniation of the cerebellar tonsils in a group of patients with orthostatic intolerance:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12598952&dopt=Abstract
Orthostatic intolerance and syncope associated with Chiari type I malformation:
http://jnnp.bmj.com/cgi/content/full/76/7/1034
Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology:
http://www.nature.com/sc/journal/v44/n6/full/3101855a.html
Chronic fatigue syndrome
The importance of orthostatic intolerance in the chronic fatigue syndrome:
http://www.ncf-net.org/library/orthostaticreview.htm
MEDLINEplus health information on chronic fatigue syndrome:
http://www.nlm.nih.gov/medlineplus/chronicfatiguesyndrome.html
Chronic fatigue syndrome: A hypothesis focusing on the autonomic nervous system:
http://cs.portlandpress.com/cs/096/0117/0960117.pdf
Dental Considerations
Postural Orthostatic Tachycardia Syndrome: Dental Treatment Considerations by John K. Brooks, DDS; Laurie A. P. Francis, RDH: 
http://jada.ada.org/cgi/reprint/137/4/488.pdf
Diabetes and autonomic neuropathy
Chronic administration of pharmacologic doses of vitamin E improves the cardiac autonomic nervous system in patients with type 2 diabetes:
http://www.ajcn.org/cgi/content/full/73/6/1052
Value of scintigraphy using meta-iodo-benzyl-guanidine (MIBG) in the investigation of cardiac autonomic neuropathy in diabetic patients. Comparison with Ewing tests:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9404408&dopt=Abstract
Abnormal cardiovascular reflexes in juvenile diabetics as preclinical signs of autonomic neuropathy:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7346309&dopt=Abstract
Response of the autonomous nervous system of the heart in diabetes mellitus:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=529862&dopt=Abstract
MEDLINEplus health information on diabetes:
http://www.nlm.nih.gov/medlineplus/diabetes.html
Disability
Blood volume perturbations in the postural tachycardia syndrome:
PubMed

Quality of life in patients with postural tachycardia syndrome:
http://www.ncbi.nlm.nih.gov/pubmed/12059122 
Ehlers-Danlos Syndrome (Joint Hypermobility Syndrome)
Ehlers Danlos Syndrome. University of Washington, Seattle:
http://www.orthop.washington.edu/uw/ehlersdanlos/tabID__3376/ItemID__32/PageID__1/Articles/Default.aspx
Ehlers-Danlos National Foundation:
http://www.ednf.org/
Ehlers-Danlos syndrome, classical type:
http://ghr.nlm.nih.gov/condition=ehlersdanlossyndromeclassicaltype 
Ehlers-Danlos syndrome, hypermobility type:
http://ghr.nlm.nih.gov/condition=ehlersdanlossyndromehypermobilitytype
Joint hypermobility syndrome: a complex constellation of symptoms:
http://www.reumatologia-dr-bravo.cl/para%20medicos/HIPERLAXITUD/
www_jointandbone_org_RODGRAH.htm
Connective tissue disorders with spontaneous spinal cerebrospinal fluid leaks and intracranial 
hypotension: a prospective study:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=14683542&dopt=Abstract
Association Between Joint Hypermobility Syndrome and Panic Disorder:
http://ajp.psychiatryonline.org/cgi/content/full/155/11/1578
Is joint hypermobility related to anxiety in a nonclinical population also?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15345789
Neurological manifestations of Ehlers-Danlos syndrome:
http://www.neurologyindia.com/article.asp?issn=0028-3886;year=2005;volume=53;issue=3;spage=339;epage=341;aulast=Mathew
Your eyes and Ehlers-Danlos Syndrome:
http://www.totaleyecare.com/ocular-complication-ehlers-danlos-syndrome-1.html?_ga=1.14621751.1418931888.1390611040
Exercise
The prevalence and significance of post-exercise (postural) hypotension in ultramarathon runners:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8614313&dopt=Abstract
Fainting
Certain cardiovascular indices predict syncope in the postural tachycardia syndrome:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8902319&dopt=Abstract
Fibromyalgia
National Fibromyalgia Research Association:
http://www.nfra.net/
MEDLINEplus health information on fibromyalgia:
http://www.nlm.nih.gov/medlineplus/fibromyalgia.html
Elusive syndromes: Treating the biologic basis of fibromyalgia and related syndromes:
http://www.ccjm.org/pdffiles/Clauw1001.pdf
Hormones
Influence of the menstrual cycle on sympathetic activity, baroreflex sensitivity, and vascular
transduction in young women:
http://circ.ahajournals.org/cgi/content/full/101/8/862
Hypovolemia
Hypovolemia in syncope and orthostatic intolerance role of the renin-angiotensin system:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9274896&dopt=Abstract
Is this patient hypovolemic?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10086438&dopt=Abstract
Idiopathic hypovolemia: a self perpetuating autonomic dysfunction?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9869552&dopt=Abstract
Lipodystrophy
Partial lipodystrophy in a boy:
http://www.indianpediatrics.net/jan2000/case3.htm
Magnesium
Erythrocyte magnesium in symptomatic patients with primary mitral valve prolapse: relationship to symptoms, mitral leaflet thickness, joint hypermobility and autonomic regulation:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1844553&dopt=Abstract
Cardiovascular consequences of magnesium deficiency and loss: pathogenesis, prevalence and manifestations. Magnesium and chloride loss in refractory potassium repletion:
http://www.mgwater.com/cardio.shtml
Magnesium and therapeutics:
http://www.mgwater.com/dur01.shtml
Magnesium deficiency in the pathogenesis of mitral valve prolapse:
http://www.mdheal.org/magnesiu.htm
Review and hypothesis: Might patients with the chronic fatigue syndrome have latent tetany 
of magnesium deficiency:
http://www.mgwater.com/clmd.shtml
The magnesium web site - Links to over 300 articles discussing magnesium and magnesium 
deficiency:
http://www.mgwater.com/index.shtml

Medications/Treatments
Web Site for Cardiovascular and Autonomic Pharmacology:
http://courses.washington.edu/chat543/cvans/
Drug protects against nervous system failure:
http://www.news.harvard.edu/gazette/1997/04.17/DrugProtectsAga.html

Treatment of orthostatic hypotension with erythropoietin:
http://content.nejm.org/cgi/content/absract/329/9/611

Effects of long-term clonidine administration on the hemodynamic and neuroendocrine postural 
responses of patients with dysautonomia:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6295714&dopt=Abstract
Cardiac vagal response to water ingestion in normal human subjects:
http://cs.portlandpress.com/cs/103/0157/cs1030157.htm
Medicinal uses of licorice through the millennia: the good and plenty of it:
http://fkogserver.bmc.uu.se/course/B/Liquorice.pdf
Licorice root. A natural sweetener and an important ingredient in Chinese medicine:
http://www.iupac.org/publications/pac/2002/pdf/7407x1189.pdf
Licking latency with licorice root:
http://www.jci.org/cgi/content/full/115/3/591
Adverse drug reactions related to drugs used in orthostatic hypotension: a prospective and systematic pharmacovigilance study in France:
http://www.ncbi.nlm.nih.gov/pubmed/15991040?dopt=Abstract
Mitochondrial disease and dysautonomia
Mitochondrial cytopathy in adults: what we know so far:
http://www.ccjm.org/pdffiles/COHEN701.PDF

Mitochondrial encephalomyopathies presenting with features of autonomic and visceral dysfunction:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8736411&dopt=Abstract
A case of mitochondrial encephalomyopathy with peripheral neuropathy and autonomic symptoms:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=7605684&dopt=Abstract
Neurologic presentations of mitochondrial disorders
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10641610&dopt=Abstract
Mitral valve prolapse
The phenomenon of dysautonomia and mitral valve prolapse:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8003350&dopt=Abstract
Exercise response in young women with mitral valve prolapse:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=2805839&dopt=Abstract
Multiple system atrophy/shy-drager syndrome
SDS/MSA support group:
http://www.shy-drager.org/
Web site full of links to other sites about MSA/SDS:
 http://www.corwin-millman.com/shy-drager/links.html

Norepinephrine transporter
Genetic or acquired deficits in the norepinephrine transporter: current understanding of clinical 
implications:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=168695
Orthostatic intolerance is not necessarily related to a specific mutation (Ala457Pro) in the human norepinephrine transporter gene:
http://www.ncbi.nlm.nih.gov/pubmed/12589229?dopt=Abstract

Phenotypical evidence for a gender difference in cardiac norepinephrine transporter function: 
http://ajpregu.physiology.org/cgi/content/full/286/5/R851
The Nutcracker phenomenon
Does severe nutcracker phenomenon cause pediatric chronic fatigue?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10749295&dopt=Abstract
Nutcracker phenomenon demonstrated by three-dimensional computed tomography:
http://www.medonline.com.br/nutpn.pdf
Diagnosis of the nutcracker phenomenon using two-dimensional ultrasonography:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=9491284&dopt=Abstract
Magnetic resonance angiography in nutcracker phenomenon:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10230562&dopt=Abstract
An effective "transluminal balloon angioplasty" for pediatric chronic fatigue syndrome with nutcracker phenomenon:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10661488&dopt=Abstract
Nutcracker phenomenon treated with left renal vein transposition: a case report:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10331171&dopt=Abstract
The nutcracker syndrome: its role in the pelvic venous disorders:
http://www.ncbi.nlm.nih.gov/pubmed/11700480?dopt=Abstract
Outlook
Orthostatic hypotension in organic dementia: relationship between blood pressure, cortical blood flow and symptoms:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8924753&dopt=Abstract
Neurocardiovascular instability, hypotensive episodes, and MRI lesions in neurodegenerative dementia:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10818535&dopt=Abstract
Orthostatic hypotension in Alzheimer's disease: result or cause of brain dysfunction?
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=10476310&dopt=Abstract
Orthostatic hypotension as a risk factor for stroke:
http://stroke.ahajournals.org/cgi/pmidlookup?view=full&pmid=11022055
Orthostatic hypotension
Orthostatic hypotension:
http://www.dizziness-and-balance.com/disorders/medical/orthostatic.html
Cardiovascular Causes of Falls by Brian J. Carey and John F. Potter:
http://ageing.oxfordjournals.org/cgi/reprint/30/suppl_4/19.pdf
Orthostatic Hypotension by Bradley JG, Davis KA.
http://www.aafp.org/afp/20031215/2393.pdf
Paraneoplastic syndromes
Immunological and endocrinological abnormalities in paraneoplastic disorders with involvement of the autonomic nervous system:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=9241563&dopt=Abstract
Pheochromocytoma
Biochemical diagnosis of pheochromocytoma:
http://www.angelfire.com/hi/Pheochromocytoma/biodiag.html
MEDLINEplus health information on pheochromocytoma:
http://www.nlm.nih.gov/medlineplus/pheochromocytoma.html
Germ-line mutations in nonsyndromic pheochromocytoma:
http://content.nejm.org/cgi/content/abstract/346/19/1459
Porphyria
Diagnosis and management of porphyria:
http://bmj.bmjjournals.com/cgi/content/full/320/7250/1647
Postural orthostatic tachycardia syndrome/orthostatic intolerance
Medscape: Postural Tachycardia Syndrome:
http://www.medscape.com/viewarticle/705183
The Postural Tachycardia Syndrome (POTS): Pathophysiology, Diagnosis & Management
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1501099/
Orthostatic intolerance:
http://www.nymc.edu/fhp/centers/syncope/chronic_orthostatic_intolerance.htm
A review of the classification, diagnosis, and management of autonomic dysfunction syndromes associated with orthostatic intolerance:
http://publicacoes.cardiol.br/abc/2000/7406/74060008i.pdf
Clinical disorders of the autonomic nervous system associated with orthostatic intolerance: an overview of classification, clinical evaluation and management:
http://www.ndrf.org/PDF%20Files/disorders.PDF
The neuropathic postural tachycardia syndrome:
http://content.nejm.org/cgi/content/abstract/343/14/1008
Hereditary dysautonomias: Current knowledge and collaborations for the future:
Oct 3, 2002 http://www.familialdysautonomia.org/NIH_OCT3.pdf 
Oct. 4 2002 http://www.familialdysautonomia.org/NIH_OCT4.pdf
Effects of head-up tilting on baroreceptor control in subjects with different tolerances to orthostatic stress:
http://cs.portlandpress.com/cs/103/0221/cs1030221.htm
Vascular perturbations in the chronic orthostatic intolerance of the postural orthostatic tachycardia syndrome:
http://jap.physiology.org/cgi/content/full/89/4/1505
American Autonomic Society: (be sure to visit the autonomic news section for information on the latest research)
www.americanautonomicsociety.org/
Postural tachycardia syndrome and anxiety disorders:
http://jnnp.bmj.com/content/80/3/339.abstract/reply#jnnp_el_4620
Pregnancy
Postpartum Postural Orthostatic Tachycardia Syndrome in a Patient with the Joint Hypermobility Syndrome:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2778448/
Postural orthostatic tachycardia syndrome: anesthetic implications in the obstetric patient:
http://www.ncbi.nlm.nih.gov/pubmed/17179264?dopt=%20AbstractPlus
Research Studies
ClinicalTrials.gov
http://www.clinicaltrials.gov/
DINET studies page:
http://dinet.org/index.php/information-resources/studies
NDRF clinical research page:
http://www.ndrf.org/dysautonomia_clinic_resea.htm
Support
12 More Pages:
http://www.12morepages.com
STARS US (Syncope Trust and Reflex Anoxic Seizures)
http://www.stars-us.org/
STARS - syncope trust and reflex anoxic seizures:
www.stars.org.uk
National Dysautonomia Research Foundation:
www.ndrf.org
Dysautonomia Youth Network of America (DYNA) (devoted to youth with dysautonomia)
http://www.dynainc.org/
Syringomyelia
NINDS syringomyelia information page:
http://www.ninds.nih.gov/health_and_medical/
disorders/syringomyelia_short.htm
Postural tachycardia syndrome in syringomyelia: response to fludrocortisone and beta-blockers:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=11710800&dopt=Abstract
Involvement of the autonomic nervous system in patients with syringomyelia - a study with the sympathetic skin response:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8654321&dopt=Abstract
Hyperhidrosis as the presenting symptom in post-traumatic syringomyelgia: (hyperhidrosis is excessive sweating)
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=8090551&dopt=Abstract
Cardiovascular reflexes in syringomyelia:
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=
Retrieve&db=PubMed&list_uids=7139257&dopt=Abstract
MEDLINEplus health information on syringomyelia:
http://www.nlm.nih.gov/medlineplus/syringomyelia.html
Tests
The fainting patient: value of the head-upright tilt-table test in adult patients with orthostatic intolerance:
http://www.cmaj.ca/cgi/content/full/164/3/372
Autonomic diseases: clinical features and laboratory evaluation:
http://jnnp.bmjjournals.com/cgi/content/full/74/suppl_3/iii31
Syncope Care & Treatment:
http://my.clevelandclinic.org/heart/disorders/electric/syncope.aspx
Videos 
The Dysautonomia Information Network presents the first full length documentary about Postural Orthostatic Tachycardia Syndrome.
http://dinet.org/index.php/information-resources/pots-place/pots-video
POTS - Mayo Clinic:
http://www.youtube.com/watch?v=CatWlEGPqG4&feature=related
POTS syndrome - Mayo Clinic:
http://www.youtube.com/watch?v=iJ9bv7jx-Ls&feature=channel
The Woman who Kept Falling Down - Mystery Diagnosis - Part 1:
http://www.youtube.com/watch?v=NN3PB6N6oGY

The Woman who Kept Falling Down - Mystery Diagnosis - Part 2:
http://www.youtube.com/watch?v=I40-r3RpFjs&NR=1 

The Woman who Kept Falling Down - Mystery Diagnosis - Part 3:
http://www.youtube.com/watch?v=PHydjGdg4XQ&NR=1

edriscoll

Neurocardiogenic Syncope Info

By edriscoll, in NCS,

What is Neurocardiogenic Syncope?
Neurocardiogenic syncope is a temporary loss of consciousness associated with a drop in arterial blood pressure, quickly followed by a slowed heart rate (Grubb & McMann, 2001, p. 133).
Neurocardiogenic syncope (NCS) is also referred to as vasovagal syncope or neurally mediated syncope. The terms are used interchangeably throughout this web page. 

What are the symptoms of NCS?
Neurocardiogenic fainting usually occurs while standing. Emotional stress, stressful condition and pain may trigger an episode, especially among the young (Shah, Gupta & Lokhandwala, 2003). The onset may be abrupt or associated with warning symptoms such as fatigue, weakness, nausea, sweating, pallor, visual disturbances, abdominal discomfort, headache, pins-and-needles, lightheadedness or vertigo (Deering, 2003). Presyncopal patients may also complain of palpitations, vomiting, disorientation, and difficulty speaking clearly or coherently (Grubb & McMann, 2001, p. 60.). Other symptoms that may present before a faint include feeling either warm or cold, tremors, yawning and having a bluish/purple or red coloring to the skin (Alboni, Brignole, Menozzi, Raviele, Del Rosso, Dinelli, Solano & Bottoni, 2001).
During the faint "seizure-like" activity may occur (Grubb, Gerard & Roush, 1991). This convulsive activity is thought to be distinct from a seizure disorder.
Patients are sometimes symptomatic after a faint as well. Patients may complain of symptoms including nausea, clamminess, lightheadedness, headache and malaise (Deering, 2003). Patients may also experience vomiting, abdominal discomfort, weakness, tremors, cold or warm feelings and confusion (Alboni et al., 2001). Patients who experience frequent neurocardiogenic syncope may report symptoms between faints as well, such as chronic fatigue, headache, chest pain, exercise intolerance, heart "flip flops" and an inability to tolerate prolonged standing.
Mechanisms and Causes of NCS
When a person stands up, the pull of gravity causes blood to pool in the lower extremities. This can result in a lack of blood supply to the upper body, including the heart and brain. Normally, the body automatically adjusts to the lack of blood supply by increasing vascular tone, heart rate and cardiac output. Blood vessels contract, heart rate increases, systolic blood pressure remains about the same or drops slightly while diastolic pressure rises slightly (Brunner & Suddarth, 2000, p. 546).
In those with neurocardiogenic syncope this compensatory mechanism does not always work correctly. The exact mechanisms of NCS are not completely understood, and several theories have been proposed. Many physicians hold a general consensus as to what is happening during NCS as follows:
The strong contractions of the ventricle walls are thought to cause a response in the mechanoreceptors, which misinterpret what is happening and send a message to the brain that the blood pressure is actually high. In response, the sympathetic portion of the cardiovascular center reduces its impulses to the heart and blood vessels while the parasympathetic division increases its impulses (Grubb & McMann, 2001, p. 61-62). This abnormal nervous system reflex causes the heart to slow and the blood vessels to dilate (open up), further lowering blood pressure (North American Society of Pacing and Electrophysiology, 1999). Because of this faulty adjustment, NCS patients may experience intermittent fainting.
A 2004 research publication suggests patients may awaken from sleep with symptoms of forthcoming neurocardiogenic syncope (Krediet, Jardine, Cortelli, Visman & Wieling, 2004). This suggestion may seem to contradict current teachings on this disorder. However, research shows that transient autonomic mechanisms that predispose to vasovagal syncope may occur during sleep (Shneerson, 2000, p. 1-15).
Findings from a 2008 neurocardiogenic syncope study seem to contradict current beliefs regarding what happens during a fainting episode as well. The results did not show an increase in ventricular contractility before tilt-induced syncope, or in presence of a valuable increase of sympathetic activity. Instead, the researchers observed a reduction of atrial contractility, which they believe may be a contributory component in the pathogenesis of vasovagal syncope .
There are several other factors that may be contributory components in the pathogenesis of vasovagal syncope as well.  Differential changes in plasma levels of epinephrine, renin, endothelin, vasopressin, cortisol, prolactin, beta endorphins and substance P have been reported by some investigators either prior to or during a syncopal episode in patients with vasovagal syncope (Ellenbogen, Morillo, Wood, Gilligan, Eckberg & Smith, 1997). Further research has shown that galanin may play a role in one's ability to adapt to orthostatic stress. Patients may have a genetic susceptibility to NCS as well.
Some researchers have suspected that serotonin might be involved in the pathogenesis of NCS. Studies in animals have shown that the withdrawal of sympathetic impulses correlates with a higher level of serotonin being present in the central nervous system, the brain and the spinal cord (Grubb & McMann, 2001, p. 57). However a later study of NCS patients found no differences in serotonin activity at the time of fainting, but did show a lower serotonin level in patients during the early phase of tilt table testing (Mitro, Hijova & Mudrakova, 2006).
Another study showed that young women who had vasovagal syncope with a positive tilt test result had a greater sensitivity to insulin. Insulin, in addition to its known metabolic effects, has sympatho-excitatory and vasodilatory actions on muscular blood vessels. The authors of this study conclude that insulin hypersensitivity could be one of the predisposing factors for vasovagal episodes (Ruiz, Calvar, Hermes, Rivadeneira, Bengolea, Chirife, Tentori & Gelpi, 2003).
How is NCS diagnosed?
Tilt table testing is often used to diagnose NCS. However, tilt table testing can have false-negative and false-positive results (Levine, 1999).
How is NCS treated?
There are a variety of non-pharmacutical methods used to control and prevent neurocardiogenic syncope. No single therapy has been found to be effective in all patients. Non-pharmacutical therapies used to treat NCS include the following:
Cardioneuroablationreportedly has helped some neurocardiogenic syncope patients, although the study reporting this was small and patients had only been followed up for 9 months at the time of publishing (Pachon, Pachon, Pachon, Lobo, Pachon, Vargas & Jatene, 2005). Further investigation is warranted.
Counter-maneuvers may help some patients with neurocardiogenic syncope. Research has shown that physical counterpressure maneuvers are a risk-free, effective, and low-cost treatment for patients with vasovagal syncope and recognizable prodromal symptoms, and should be advised as first-line treatment in these patients (van Dijk, Quartieri, Blanc, Garcia-Civera, Brignole, Moya & Wieling, 2006).
Isometric arm counter-pressure maneuvers can increase systolic blood pressure and prevent fainting in some patients with NCS (Brignole, Croci, Menozzi, Solano, Donateo, Oddone, Puggioni & Lolli, 2002). Patients can perform isometric arm counter-pressure maneuvers by gripping one had with the other and pushing both arms away from their chest.  
Leg crossing combined with muscle tensing at the onset of prodromal symptoms can postpone, and in some instances prevent, vasovagal syncope (Krediet, van Dijk, Linzer, van Lieshout & Wieling, 2002).
Sitting with the head between the knees often is an effective means of preventing syncope (Mathias, 2003).
One patient has reported success in warding off a fainting episode by gently but briskly stepping in place for a short time, bringing the knees a little upward and puffing out the exhale with each rep. Pumping the arms and fists during this counter-maneuver has helped her as well.
Increasing dietary salt and fluid intake may help prevent symptoms associated with neurocardiogenic syncope (Bloomfield, 2002).
Orthostatic self-training and tilt training may help select patients with NCS (Abe, Kondo, Kohshi, Nakashima, 2002). It is of greatest benefit to younger patients and those who faint frequently (Zeng, Ge, Zhang, Wang, & Guo, 2008). Orthostatic self-training involves standing against a wall, without moving, twice a day for a planned duration of up to 30 minutes. The results of orthostatic self-training studies have been mixed, with one study concluding it ineffective in reducing the positive response rate of head-up tilt test in patients with recurrent neurally mediated syncope (On, Park, Huh, & Kim, 2007).

Tilt training involves inclining patients on a tilt table each day. Some patients have to continually be inclined for this therapy to be effective. This therapy will not be effective in all patients. However, one study showed that in 19 patients who abandoned tilt training after about 1 year, none of them reported fainting during daily life. The authors of this study hypothesize that the disturbed autonomic reflex activity may have been restored in these patients (Reybrouck, Heidbuchel, Van De Werf & Ector, 2002).
Paced breathing may help to prevent vasovagal syncope induced by head-up tilt test. Researchers who studied the effects of paced breathing believe respiratory training could be useful in the prevention of vasovagal syncope (Jauregui-Renaud, Marquez, Hermosillo, Sobrino, Lara, Kostine & Cardenas, 2003).

Removal or avoidance of agents that predispose to hypotension or dehydration can lessen the occurance of neurocardiogenic syncope (Bloomfield, 2002). Situations that can predispose an individual to syncope are listed on the POTS Place "What to Avoid" page.
There are a variety of medications and medical treatments that may help prevent neurocardiogenic syncope as well. These include the following:
ACE inhibitors may prevent NCS, presumably through inhibition of sympathetic system activation and the peripheral hypotensive effect (Zeng, Zhu, Liu, Hu, Wang, Yang, Wang, He & Tan, 1998).
Alpha-agonists increase venous tone and decrease pooling, which may prevent activation of mechano-receptors. They also counteract the arteriolar vasodilation produced by the triggering of the vasovagal reflex (Raviele, Themistoclakis & Gasparini, 1996, p. 115). Midodrine is an example of an alpha-agonist that is used to treat NCS. Midodrine has been shown to significantly improve orthostatic tolerance during head-up tilt in patients with recurrent neurally mediated syncope (Kaufmann, Saadia & Voustianiouk, 2002). Researchers have also found Midodrine to be effective in both treating and preventing vasovagal syncope in children (Qingyou, Z., Junbao, D. & Chaoshu, T., 2006). 
Beta blockers have been reported in many studies to be effective in treating neurocardiogenic syncope. Presumably, these agents exert their effects through their negative inotropic actions, which are felt to diminish the degree of cardiac mechano-receptor activation or by acting elsewhere to oppose the high levels of circulating epinephrine (Raviele, Themistoclakis & Gasparini, 1996, p. 114). However, studies of the efficacy of beta blockers in treating NCS have had mixed results. One study showed that propranolol, nadolol and placebo were all equally effective in treating vasovagal syncope (Flevari, Livanis, Theodorakis, Zarvalis, Mesiskli & Kremastinos, 2002). The physicians conducting this study concluded that beta blockers are no better than placebo at reducing neurocardiogenic syncope.
Another study showed nonselective beta blockers to be more effective than beta-1-selective blockers in preventing tilt-induced syncope (Dendi & Goldstein, 2002).
Calcium Channel Blockers may be effective in some patients with NCS. However, in a study comparing verapamil (a calcium channel blocker) to metoprolol (a beta blocker), verapamil was found to be less effective in the management of neurocardiogenic syncope (Jhamb, Singh, Sharda, Kaul, Goel, Talwar & Wasir, 1996).
Disopyramide has negative inotropic and anticholinergic effects that may be potentially beneficial in preventing vasovagal syncope by decreasing ventricular contractibility and counteracting parasympathetic activity (Raviele, Themistoclakis & Gasparini, 1996, p. 114).

Fludrocortisone is sometimes used to prevent neurocardiogenic syncope. There is considerable clinical experience and a consensus suggesting that fludrocortisone is effective (Bloomfield, 2002).
Pacemakers are a somewhat controversial treatment for neurocardiogenic syncope. Many studies have suggested the efficacy of pacemakers. However, a double-blind randomized trial showed that pacing therapy did not reduce the risk of recurrent syncope in patients with vasovagal syncope. The authors of this study concluded that pacemaker therapy should not be recommended as a first-line therapy for patients with recurrent vasovagal syncope (Connolly, Sheldon, Thorpe, Roberts, Ellenbogen, Wilkoff & Morillo, 2003).
Scopolamine may be effective in reducing the high vagal tone that occurs during syncopal episodes (Raviele, Themistoclakis & Gasparini, 1996, p. 115).
Serotonin Reuptake Inhibitors may prevent NCS by reducing the sympathetic impulses that signal the heart to contract more strongly (Grubb & McMann, 2001, p. 115).
Theophylline is an adenosine receptor blocker. It may prevent NCS, although patients sometimes discontinue theophylline because of adverse reactions (Nelson, Stanley, Love, Coyne & Schaal, 1991). Theophylline is not generally used as a first line treatment for NCS.
Patients sometimes need a combination of medications to prevent recurrent neurocardiogenic syncope.
To read more on NCS, please visit our neurocardiogenic syncope links page.
References
    1. Abe, H., Kondo, S., Kohshi, K., Nakashima, Y. (2002). Usefulness of   orthostatic self-training for the prevention of neurocardiogenic syncope.   Pacing & Clinical Electrophysiology, 25(10), 1454-1458. Pubmed     2. Alboni, P., Brignole, M., Menozzi, C., Raviele, A., Del Rosso, A., Dinelli, M.,    Solano, A.,  & Bottoni N. (2001). Diagnostic value of history in patients     with syncope with or without heart disease. Journal of the American    College of Cardiology, 37, 1921-1928. PubMed     3. Bloomfield, D. M. (2002). Strategy for the management of vasovagal syncope.   Drugs & Aging, 19(3), 179-202.     4. Brignole, M., Croci, F., Menozzi, C., Solano, A., Donateo, P., Oddone, D.,   Puggioni, E. &  Lolli, G. (2002). Isometric arm counter-pressure maneuvers   to abort impending vasovagal syncope. Journal of the American College   of Cardiology, 40(11), 2053-2059. PubMed     5. Brunner, L. S. & Suddarth, D. S. (2000). Assessment of cardiovascular   function. In S. C. Smeltzer & B. G. Bare (Eds.), Brunner and Suddarth's   textbook medical-surgical nursing (pp. 532-563). Philadelphia, PA:   Lippincott Williams and Wilkins.     6. Connolly, S. J., Sheldon, R., Thorpe, K. E., Roberts, R. S., Ellenbogen, K. A.,   Wilkoff, B. L.,  Morillo, C., & Gent, M. (2003). Pacemaker therapy   for prevention of syncope in patients with recurrent severe vasovagal   syncope: Second Vasovagal Pacemaker Study (VPS II): a randomized trial.   Journal of the American Medical Association, 289(17), 2224-2229.   PubMed     7. Deering, A. (2003). Cheltenham Syncope Clinic. Retrieved May 15, 2003.   http://www.syncope.co.uk/     8. Dendi, R., & Goldstein, D. S. (2002). Meta-analysis of nonselective versus   beta-1 adrenoceptor- selective blockade in prevention of tilt-induced   neurocardiogenic syncope. American Journal of Cardiology, 89(11),   1319-1321. PubMed     9. Ellenbogen, K. A., Morillo, C. A., Wood, M. A., Gilligan, D. M., Eckberg,   D. L., Smith, M. L. (1997). Neural monitoring of vasovagal syncope.   Pacing & Clinical Electrophysiology. 20(3 Pt 2), 788-794. PubMed     10. Flevari, P., Livanis, E. G., Theodorakis, G. N., Zarvalis, E., Mesiskli, T.,   Kremastinos, D. T. (2002). Vasovagal syncope: a prospective, randomized,   crossover evaluation of the effect of propranolol, nadolol and placebo   on syncope recurrence and patients' well-being. Journal of the American   College of Cardiology, 40(3), 499-504. PubMed     11. Grubb, B. P., Gerard, G., Roush, K. (1991 ). Differentiation of convulsive   syncope and epilepsy with head up tilt table testing. Annals of Internal   Medicine, 117, 871-876. PubMed     12. Grubb, B. P. & McMann, M. C. (2001). The fainting phenomenon:   Understanding why people faint and what can be done about it. New   York: Futura Publishing Company, Inc.     13. Jauregui-Renaud, K., Marquez, M. F., Hermosillo, A. G., Sobrino, A., Lara,   J. L.,  Kostine, A., Cardenas, M. (2003). Paced breathing can prevent   vasovagal syncope during head-up tilt testing. Journal Canadien de   Cardiologie, 19(6), 698-700. PubMed     14. Jhamb,  D. K., Singh, B., Sharda, B., Kaul, U., Goel, P., Talwar, K. K.,   Wasir, H. S. (1996). Comparative study of the efficacy of metoprolol and   verapamil in patients with syncope and positive head-up tilt test response.   American Heart Journal, 132(3), 608-611. PubMed     15. Kaufmann, H., Saadia, D., Voustianiouk, A. (2002). Midodrine in neurally   mediated syncope: a double-blind, randomized, crossover study.   Annals of Neurology, 52(3), 342-345. PubMed     16. Krediet, C. T., van Dijk, N., Linzer, M., van Lieshout, J. J., Wieling, W.   (2002). Management of vasovagal syncope: controlling or aborting faints by   leg crossing and muscle tensing. Circulation, 106(13), 1684-1689.   PubMed     17. Krediet, C. T., Jardine, D. L., Cortelli, P., Visman, A. G., Wieling, W.   (2004). Vasovagal syncope interrupting sleep? Heart, 90(5), e25. PubMed     18. Levine, M. M. (1999). Neurally mediated syncope in children: results of tilt   testing, treatment, and long-term follow-up. Pediatric Cardiology, 20(5),   331-335. PubMed     19. Mathias, C. J. (2003). Autonomic diseases: management. Journal of   Neurology, Neurosurgery & Psychiatry. 74 Suppl 3:iii, 42-47.   Full Text: http://jnnp.bmjjournals.com/cgi/content/full/74/suppl_3/iii42     20. Mitro, P., Hijova E. & Mudrakova K. (2006). Role of the peripheral   serotoninergic system in the pathogenesis of vasovagal syncope.   Bratisl Lek Listy. 107(6-7), 248-52. PubMed     21. Nelson, S. D., Stanley, M., Love, C. J., Coyne, K. S., Schaal, S.F. (1991).   The autonomic and hemodynamic effects of oral theophylline in patients   with vasodepressor syncope.Archives of Internal Medicine, 151(12),   :2425-2429. PubMed     22. North American Society of Pacing and Electrophysiology. (1999). Other   tests: tilt table test. Retrieved June 17, 2003, from NASPE Heart Rhythm   Society. No longer available.     23. On, Y. K., Park, J., Huh, J., & Kim,  J. S. (2007). Is home orthostatic   self-training effective in preventing neurally mediated syncope?   Pacing Clin Electrophysiol. 30(5), 638-643. PubMed     24. Pachon M. J. C., Pachon, M. E. I., Pachon, M. J. C., Lobo, T. J., Pachon,   M. Z., Vargas, R. N. & Jatene, A. D. (2005). "Cardioneuroablation" -   new treatment for neurocardiogenic syncope, functional AV block and   sinus dysfunction using catheter RF-ablation. Europace. 7(1), 1-13.   PubMed     25. Qingyou, Z., Junbao, D. & Chaoshu, T. (2006). The efficacy of midodrine   hydrochloride in the treatment of children with vasovagal syncope.   J Pediatr, 149(6), 777-780. PubMed     26. Raviele, A., Themistoclakis, S. & Gasparini, G. (1996). Drug treatment of   vasovagal syncope. In J. J. Blanc and D. Benditt (Eds.), Neurally   mediated syncope: pathophysiology, investigations, and treatment   (pp. 113-117). Armonk, NY: Futura Publishing Co.     27. Reybrouck, T., Heidbuchel, H., Van De Werf, F., Ector, H. (2002).   Long-term follow-up results of tilt training therapy in patients with recurrent   neurocardiogenic syncope. Pacing & Clinical Electrophysiology, 25(10),   1441-1446. PubMed     28. Ruiz, G. A., Calvar, C., Hermes, R., Rivadeneira, D., Bengolea, V., Chirife,   R., Tentori, M. C., & Gelpi, R. J. (2003). Insulin sensitivity in young   women with vasovagal syncope. American Heart Journal, 145(5),   834-840. PubMed     29. Shah, J. S., Gupta, A. K. & Lokhandwala, Y. Y. (2003). Neurally mediated   syncope: an overview and approach. Journal of the Association of   Physicians of India. 51, 805-810.     30. Shneerson, J. M. (2000). Handbook of sleep medicine. Oxford: Blackwell   Science.     31. van Dijk, N., Quartieri, F., Blanc, J. J., Garcia-Civera, R., Brignole, M.,   Moya, A. & Wieling, W. (2006). Effectiveness of physical counterpressure   maneuvers in preventing vasovagal syncope: the Physical Counterpressure   Manoeuvres Trial (PC-Trial). J Am Coll Cardiol. 48(8), 1652-1657.     32. Zeng, C., Zhu, Z., Liu, G., Hu, W., Wang, X., Yang, C., Wang, H., He, D.,   & Tan, J. (1998). Randomized, double-blind, placebo-controlled trial of oral   enalapril in patients with neurally mediated syncope. American Heart   Jounal, 136(5), 852-858. PubMed     33. Zeng, H., Ge, K., Zhang, W., Wang, G., & Guo, L. (2008) The effect of orthostatic   training in the prevention of vasovagal syncope and its influencing factors.   Int Heart J. 49(6), 707-712.

edriscoll

What Causes POTS?

By edriscoll, in POTS,

POTS symptoms can occur due to many different abnormalities in the body. Some disorders associated with POTS symptoms have been identified. Many of the causes of POTS still remain unknown. It can be difficult to distinguish between the causes and effects of this disorder, which further complicates matters.  
There are a multitude of disorders that can produce POTS-like symptoms. It is important that physicians attempt to find possible causes of a patient's orthostatic intolerance, as many secondary disorders are treatable. Some of the entities that may be contributing to one's orthostatic intolerance include: 
Adrenal disorders, such as Addison's disease,can produce symptoms that mimic POTS. 
Anemia patients sometimes exhibit the symptoms of POTS (Nand, Mohan, Khosla & Kumar, 1989). Some patients may have folic acid deficiency, which is contributing to their anemia and POTS symptoms. 
POTS patients may have a form of hidden anemia where the standard tests, such as hemoglobin and hematocrit, are relatively normal even though the patient has a severe anemia (Raj, Biaggioni, Yamhure, Black, Paranjape, Byrne & Robertson, 2005). A formal radioisotope dilution assessment of blood volumes was required to discover the red blood cell volume deficit documented in a 2005 study of POTS patients (Raj, et. al, 2005). The authors of this study state that it is possible a deficit in erythropoietin production might play a pathophysiological role in POTS, although this is not yet clear.
Angiotensin II has been found to be increased in some people with postural orthostatic tachycardia syndrome. The results from one study imply impaired catabolism of Angiotensin II through the angiotensin-converting enzyme 2 pathway. Vasoconstriction in POTS may result from a reduction in Ang-(1-7) and an increase in angiotensin II (Stewart, Ocon, Clarke, Taneja & Medow, 2009).
The angiotensin II type I receptor gene may be responsible for some orthostatic disorders.The NIH has researched vascular responsiveness in subjects with polymorphisms of the angiotensin II type I receptor gene. Angiotensin II is a hormone that constricts blood vessels by attaching to a protein on the blood vessels. People can have a variety of forms of this protein. Researchers have looked for differences in the gene that makes this protein to determine if these genetic differences have any effect on blood pressure.
Autoimmune disorders,such as Guillain-Barre (Singh, Jaiswal, Misra & Srivastava, 1987) and lupus are suspected of causing POTS symptoms in some individuals. 
Researchers have discovered an antibody to neuronal nicotinic acetylcholine receptors of autonomic ganglia (Vernino, Low, Fealey, Stewart, Farrugia & Lennon, 2000).  Some people with POTS have an antibody titer test that is positive to this antibody. Patients with orthostatic intolerance, anhidrosis, constipation, urinary dysfunction, sicca syndrome and pupillary dysfunction had higher antibody titers than subjects that did not (Gibbons & Freeman, 2009). Patients with the highest levels of these ganglionic-receptor-binding antibodies have the most severe autonomic dysfunction. Physicians have discovered that antibody levels lower as some patients improve, which suggests a cause and effect relationship. Patients interested in being tested for the ganglionic antibody should have their physician contact:
Mayo Medical Laboratories
1-800-533-1710
mml@mayo.edu
Cardiac atrophy has been pinpointed as the cause of orthostatic intolerance in astronauts. Research has shown that astronauts' hearts actually shrink and stiffen due to the reduced blood volume caused by microgravity (Mitka, 2002). Researchers want to find out if the cardiac atrophy is entirely reversible, and if the loss of mass can reach a point where it leads to catastrophic consequences (Healthline Scripts: Cardiac Atrophy, 1998). This finding may have implications for people who develop orthostatic intolerance due to being bedridden. Whether or not the finding can be applied to a percentage of patients who develop orthostatic intolerance for other reasons has yet to be proven. 
Cardiac disease can cause POTS symptoms. Most physicians are quick to rule cardiac disease out.
Cardiac electrophysiologic property abnormalities may be occurring in some POTS patients. Data from one study suggests abnormalities of atrioventricular conduction and ventricular repolarization in some patients with POTS (Singer, Shen, Opfer-Gehrking, McPhee, Hilz, & Low, 2003). The investigating physicians of this study concluded that these findings may reflect intrinsic cardiac electrophysiologic abnormalities or may be secondary due to abnormalities of cardiac autonomic innervation.
Another study suggested a primary sinus node abnormality could be present in a subset of POTS patients (Singer, Shen, Opfer-Gehrking, McPhee, Hilz & Low, 2002). Abnormal rate-dependent P-wave axis behavior has been observed in a small subset of POTS patients. This could be interpreted as a primary sinus node abnormality. However, several publications caution against ablating POTS patients.
A Mayo clinic study reported short-term success in five of seven ablated patients with inappropriate sinus tachycardia and postural orthostatic tachycardia features (Shen, Low, Jahangir, Munger, Friedman, Osborn, Stanton, Packer, Rea & Hammill, 2001). However, long-term outcomes were disappointing in these patients. None of the patients experienced complete eradication of symptoms. A follow-up evaluation showed no vast improvement in symptoms, despite better heart rate control. A later publication states "in our laboratory, sinus node modification, total sinus node ablation, or atrioventricular nodal ablation is not recommended for patients with inappropriate sinus tachycardia who have autonomic evidence of postural orthostatic tachycardia" (Shen, 2002).
Ablations have reportedly been detrimental to some POTS patients who were misdiagnosed as having inappropriate sinus tachycardia. After the apparently successful elimination of their "sinus tachycardia", they were left with profound orthostatic hypotension (Grubb & Karas, 1999).
Cervical stenosis is a condition in which the spinal canal is too narrow, causing compression of the spinal cord and nerve roots. It was once reported that POTS patients with cervical stenosis may benefit from craniovertebral decompression (Rosner, D'Amour & Rowe, 1999). A few patients have reported a decrease or resolution in POTS symptoms after undergoing surgery to correct this condition. Yet other patients have not had any decrease in POTS symptoms after undergoing surgery to correct cervical stenosis. Some physicians are convinced that cervical stenosis can cause POTS, others debate the relationship.
Chemical exposure may cause POTS symptoms in some individuals. Researchers at Johns Hopkins University have tested Gulf War vets to see if they have neurally mediated hypotension or POTS. The study aimed to find out if environmental factors such as pesticides, vaccinations or infections are associated with having POTS.
Chiari malformation is a condition in which the cerebellar tonsils protrude down into the spinal cord. This can restrict the flow of cerebral spinal fluid. The symptoms of Chiari are similar to those of POTS. A number of Chiari patients have reported being diagnosed with POTS. Some of these patients proclaim a decrease or resolution in POTS symptoms after undergoing surgical correction of their Chiari malformation. Other POTS patients with Chiari malformation have not experienced any benefits from corrective surgery. Some physicians are convinced that Chiari malformation is a cause of POTS, others doubt the relationship.
Physicians from the NIH and The Chiari Institute believe their is a connection between Ehlers-Danlos syndrome, POTS and Chiari 1 malformation. Read More
Diabetes can produce the symptoms of POTS (Llamas, Garcia, Gaos, Jimenez, Villavicencio, Cueto & Arriaga, 1985). There are different types of diabetes, including diabetes insipidus, that are associated with POTS symptoms. Read more 
Ehlers-Danlos Syndrome (EDS), a connective tissue disorder,is found in some POTS patients. Physicians propose that these syndromes occur together due to abnormal connective tissue in dependent blood vessels in those with EDS, which permits veins to distend excessively in response to ordinary hydrostatic pressures (Rowe, Barron, Calkins, Maumenee, Tong & Geraghty, 1999). Simply put, this connective tissue abnormality allows excessive amounts of blood to pool in these patients' lower limbs when they stand up.
There are a variety of types of Ehlers-Danlos syndrome. Classical and type III EDS were originally reported in orthostatic intolerance patients (Rowe et al., 1999). Many POTS patients with EDS have type III (Grubb, 2002).
The classical form of Ehlers-Danlos syndrome (types I and II) is characterized by soft, hyperextensible skin; easy bruising; poor wound healing; thin, atrophic scars; hypermobile joints; varicose veins and prematurity of affected newborns (Wenstrup & Hoechstetter, 2001). Mutations in type V collagen are a major cause of the classical type of Ehlers-Danlos syndrome.
Clinical features associated with EDS III include soft skin and large and small joint hypermobility (Wenstrup & Hoechstetter, 2001). Skin may be stretchy but scarring tends to be normal. POTS patients with EDS III are often hypermoblie/hyperflexable, double jointed, pale, female and tend to have blond hair and blue eyes (Grubb, 2002). The genetic basis for EDS III is unknown.
A wide variety of medical complications may occur with the classical and hypermobile types of EDS. Mitral valve prolapse can occur in all types of EDS and delayed gastric emptying has been observed in type III (personal observations, Wenstrup & Hoechstetter, 2001). A significant number of individuals with both the classical form and the hypermobile form have dilation and/or rupture of the ascending aorta (Wenstrup & Hoechstetter, 2001). Hiatal hernia has been widely reported in adults with EDS (Steinman, Royce & Superti-Furga, 1993). As previously stated, premature rupture of the membranes in pregnancy (primarily classical type) and poor wound healing (particularly with severe classical type) may occur. Other complications include a mild to moderate increase in peripartum bleeding, joint dislocations, chronic pain (most common in the hypermobile type), surgical complications and intraoperative problems (more common in the classical than hypermobile type), diverticulitis, problems associated with fragile skin (particularly with the classical type) and motor delay (Wenstrup & Hoechstetter, 2001).
One study on patients with "joint hypermobility syndrome", a disorder similar if not identical to EDS III, showed that 78% had signs of dysautonomia, such as orthostatic hypotension, postural orthostatic tachycardia syndrome and uncategorized orthostatic intolerance (Gazit, Nahir, Grahame, & Jacob, 2003). These patients also had evidence of a-adrenergic and B-adrenergic hyperresponsiveness. The authors of this study note that patients with the joint hypermobility syndrome have apparently intact vagal control of heart rate with disturbed sympathetic function. They further state that "the sympathetic dysregulation associated with joint hypermobility syndrome may have several explanations, such as peripheral neuropathy, blood pooling in the lower limbs, impaired central sympathetic control, or deconditioning due to muscle disuse through pain or fear of pain".
Another study of one hundred and seventy women with joint hypermobility syndrome concluded that non-musculoskeletal symptoms are common in patients with joint hypermobility syndrome, and that individuals with these symptoms may express more fatigue, anxiety, migraine, flushing, night sweats, and poor sleep than their peers (Hakim & Grahame, 2004). Read more
Electrical injury has reportedly occurred prior to the development of POTS in a couple of cases (Kanjwal, Karabin, Kanjwal & Grubb, 2009).
Gastric bypass surgery may cause orthostatic intolerance in some individuals.
Lesions of the autonomic nervous system might be causing POTS in some individuals. Research shows that animals become dysautonomic by selectively lesioning postganglionic sympathetic neurons (Carson, Appalsamy, Diedrich, Davis & Robertson, 2001).
Lipodystrophy a rare metabolic disorder, has been associated with POTS symptoms (Bernstein, Pierson, Ryan & Crespin, 1979).
Liver disease may contribue to orthostatic intolerance. Compensated Cirrhosis is a condition in which the liver is damaged but is able to compensate for it. This condition coincides with hypovolemia and vasodilation. POTS, as well as peripheral blood pooling and decreased arterial tone, has been found in some patients (Hartleb, Rudzki, Karpel, Becker, Waluga, Boldys, Nowak & Nowak, 1979). 
Mast-cell activation disorders may play a role in the development of POTS in some individuals. Some patients with orthostatic intolerance suffer from episodes of flushing, palpitations, shortness of breath, chest discomfort, headache, lightheadedness, hypotension or hypertension and occasionally syncope (Jacob & Biaggioni, 1999). Exercise may trigger an attack (Shibao, Arzubiaga, Roberts, Raj, Black, Harris & Biaggioni, 2005). Patients may complain of increased fatigue, sleepiness, increased urination and/or diarrhea after an attack (Jacob & Biaggioni, 1999). Symptoms of orthostatic intolerance often worsen after an episode. An increase in urinary methylhistamine, a marker of mast-cell activation, can be found in these patients.
Mast-cell activation results in the release of the vasodilator histamine, which may contribute to symptoms of POTS. Other mast cell mediators, such as plasma prostaglandin 2, may contribute to symptoms as well. Urinary histamine is often measured in the evaluation of flushing, but it is less specific than methylhistamine and not useful in the diagnosis of mast-cell activation (Shibao et al., 2005). Patients should be instructed to collect urine for a 4-hour period immediately after a severe spontaneous flushing episode. Urinary methylhistamine is usually normal between episodes in patients with mast-cell activation disorders, although the patients may experience chronic fatigue and orthostatic intolerance between episodes, which can lead to a disabling condition (Shibao et al., 2005).
Beta blockers should be used with caution, if at all, in those with mast-cell activation disorders (Shibao et al., 2005). Beta blockers may trigger mast-cell activation.
Mitochondrial disease is sometimes found in patients who present with autonomic dysfunction. Read more
Neuropathy may be involved in the development of POTS in some individuals. One study showed that POTS may be, in part, a manifestation of autonomic cardiac neuropathy (Haensch, Lerch, Schlemmer, Jigalin & Isenmann, 2009). Sympathetic denervation of the legs might be the cause of POTS in some patients as well. 
Nitric Oxide deficit may play a role in POTS symptoms. Nitric Oxide (NO) is a very simple molecule whose job it is to control blood vessel size with changes in blood flow, changes in blood vessels during inflammation and blood vessel leakiness (Stewart, 2005). Some POTS patients have a deficit of nitric oxide (Stewart, Taneja, Glover & Medow, 2008.). This deficit may relate to the nitric oxide synthase molecule called nNOS, but it also has a compelling relationship with the hormone angiotensin-II.Together angiotensin-II and  NO may help to regulate sympathetic nerve activity in the brain and also in certain peripheral nerves (such as the splanchnic circulation). Moreover, angiotensin-II can result in increased oxidative stress which can itself reduce NO (Dr. Julian Stewart, personal communication, November 28, 2007).
Researchers have found that NO levels can be increased by blocking the most important receptor for angiotensin-II. This may lead to treatments in the future in select groups of POTS patients.
Norepinephrine transporter deficiency is thought to cause POTS in some patients. These patients have an abnormality in the clearance of norepinephrine from the synaptic cleft. The body normally recycles norepinephrine. The protein that recycles norepinephrine doesn't work well in people with the norepinephrine transporter deficiency (Grubb, 2002). Excessive amounts of norepinephrine is spilled over. These people soon become depleted of norepinephrine if the neuron is continually stimulated (Grubb, 2002). They go from having excessive amounts of norepinephrine to having no norepinephrine, at which point they crash. Read More
Other researchers have reportedly discovered hypermethylation of the norepinephrine transporter (NET) gene promoter in POTS patients (Esler, Alvarenga, Pier, Richards, El-Osta, Barton, Haikerwal, Kaye, Schlaich, Guo, Jennings, Socratous & Lambert, 2006) In these patients, the gene for the protein that transports norepinephrine (NET) is turned off because its promoter is turned off. Further studies are being conducted to determine whether hypermethylation of the NET gene promoter is a mechanism or cause of POTS.
The nutcracker phenomenon has reportedly produced POTS symptoms in some individuals. Nutcracker phenomenon (NC) is the congestion of the left renal vein due to its compression by the aorta and the superior mesenteric artery (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The main and common findings of one study on pediatric NC patients were chronic fatigue associated with orthostatic hypotension and/or postural tachycardia (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The authors of this study point out that "the originally reported symptom of NC is renal bleeding. However, reported 'renal bleeding' patients, including ours, have no complaints of chronic fatigue and our 'chronic fatigue' (NC) patients have no renal bleeding". Some of these patients did report fibromyalgia type pain. Some patients had proteinuria, others had no urinary abnormalities. 
The authors of this study explain the various ways in which NC might affect autonomic function: First, severe congestion in the kidney may cause the expansion of the renal venous bed, which would affect the renin-angiotensin system. Secondly, severe congestion in the adrenal medulla, which is innervated by sympathetic nerves, may disturb a complex set of central neural connections controlling the sympathoadrenal system. On the other hand, overproduction or night retention of catecholamines might be responsible for the various symptoms of pediatric chronic fatigue syndrome (Takahashi, Ohta, Sano, Kuroda, Kaji, Matusuki & Matsuo, 2000). The nutcracker phenomenon occurs in adults as well as children. Transluminal balloon angioplasty has successfully been used to treat compression of the left renal vein between the aorta and superior mesenteric artery (Takahashi, Sano & Matsuo, 2000). 
The methods used to diagnose nutcracker phenomenon include Doppler US, MRI and three-dimensional helical computed tomography. Dr. Takahashi (personal communication, September 8, 2002) explains the procedures for testing as follows: Conventional ultrasound requires patients to be examined for left renal vein obstruction in 4 positions: supine, semisitting, upright and prone. Nonvisualization of the left renal vein lumen or absence of the left renal vein wall between the aorta and superior mesenteric artery is regarded as signifying left renal vein obstruction. Doppler color flow imaging can be used to locate a blue-colored blood stream flowing to the dorsal direction. This is a collateral vein flowing from the left renal vein into the paravertebral vein. With MRI, oblique coronal images along the left renal vein, and also axial images, are recommended to visualize the collateral veins around the left renal vein. Read more
Nutritional deficiencies can lead to autonomic dysfunction. The B vitamins 1, 3, 6, and 12 have been reportedly linked to dysautonomia symptoms (Autonomic Dysfunction, 2000). Folic acid deficiency (B9) can also cause POTS symptoms.
Other neurological conditions, such as multiple sclerosis, are sometimes associated with autonomic dysfunction.
Parasites can transmit diseases, such as Chagas, that can cause POTS symptoms. Some patients report developing POTS after having Lyme disease. 
Porphyrias have been associated with POTS symptoms (Stewart & Hensley, 1981). Porphyrias are rare, mainly genetic disorders that affect the body's ability to make hemoglobin. They are caused by deficiencies in enzymes involved in the synthesis of heme. Porphyria patients are often overly sensitive to sunlight. 
It is important for physicians to rule out porphyrias before prescribing medication to POTS patients. Some medications that are considered unsafe for porphyria patients are used to treat dysautonomia. Read more
Syringomyelia is a condition in which a cyst grows within the spinal cord. POTS can occur in patients with this condition. Syringomyelia is similar to POTS in that it usually occurs between the ages of 25 and 40, it can have a sudden onset, some patients have Chiari malformation and some patients may experience long periods of stability. The symptoms of syringomyelia can worsen with straining or any activity that causes cerebrospinal fluid to fluctuate. Many POTS patients also report a worsening of symptoms upon straining. Partial sympathetic denervation of the legs in those with syringomyelia might explain the occasional occurrence of postural tachycardia syndrome (NINDS Syringomyelia Information Page, 2001). Read more
Tumors can lead to autonomic dysfunction. Tumors, such as pheochromocytoma and neuroblastoma, can secrete catecholamines that affect the autonomic system. Pelvic ganglioneuroma is another type of tumor that has also been associated with autonomic dysfunction (Gentile, Rainero, Luda & Pinessi, 2001). Tumors can cause compression, which directly affects the autonomic nervous system. Tumors are also capable of having a paraneoplastic effect on the ANS by producing autoantibodies against acetylcholine receptors in the autonomic ganglia (Grubb, Kanjwal & Kosinski, 2006). 
Thyroid disease can cause symptoms that are similar to those of POTS.
Viruses are thought to be the provoking factor in approximately 50% of POTS patients (Low & Schondorf, 1997, p. 279). There are reports of dysautonomia occurring after the Epstein-Barr virus (Itoh, Oishi, Ohnishi, Murai & Imawatari, 1993). Viruses may directly affect the autonomic nervous system or lead to an immune pathogenesis (Grubb, 2000). Roughly one-half of post-viral POTS patients will make a good practical recovery over a 2-5 year period (Grubb, Kanjwal & Kosinski, 2006).
These are but a few of the possible causes of POTS symptoms. More information on causes of autonomic dysfunction can be located at the National Dysautonomia Research Foundation.


References
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edriscoll

POTS Myths

By edriscoll, in POTS,

As with many disorders that have received little research, there are numerous false assumptions made about POTS. Many of these assumptions stem from the lack of information available about this disorder. This page was created in hopes of clarifying some of these false assumptions. Suggestions for this page can be sent to: Dysautonomia Information Network
Myth: POTS symptoms only occur while standing.
Many patients report symptoms occurring while sitting or lying down. Standing does exacerbate symptoms.
Myth: Everyone with POTS faints.
Many people with POTS have never fainted.
Myth: POTS symptoms are present at all times.
The symptoms of POTS can vary greatly from day to day and hour to hour.  
Myth: Most doctors will be competent in treating POTS patients.
Some doctors have never even heard of POTS. It is essential to one's well being to seek out a specialist.
Myth: People get POTS because they are lazy and deconditioned.
People can get POTS symptoms due to prolonged bed rest, however the symptoms should diminish as the person becomes more active. The origins of chronic orthostatic intolerance are certainly distinct from laziness or deconditioning.

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