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Query: UMLS:C0012833 (dizziness)
 9,689 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Autonomic dysfunction is frequently observed in patients with multiple sclerosis (MS), but clinical studies disagree on the frequency and type of abnormalities in autonomic function tests. Orthostatic dizziness (OD) has been reported in up to 49% of patients, but the pathophysiological mechanisms are poorly understood. This study investigated cardiovascular reflex tests and their association with OD in patients with MS in order to examine the hypothesis that the sympathetic nervous system is specifically involved in these patients. Forty patients with clinically active relapsing-remitting (n = 27) and secondary progressive MS (n = 13), aged 35.0+/-8.5 years, were studied by parasympathetic (heart rate responses to the Valsalva maneuver, deep breathing, and active change in posture) and sympathetic function tests (blood pressure responses to active change in posture and sustained handgrip), and by spectral analysis of heart rate variability during rest and during standing. Results were compared to those obtained in 24 healthy volunteers, aged 29.4+/-7.2 years. A standardized questionnaire was used to evaluate symptoms of orthostatic intolerance. Abnormal responses on at least one cardiovascular reflex test were observed in 40% of MS patients, compared to 17% of the control group, with a statistically significant involvement of the sympathetic vasomotor system. Orthostatic intolerance was reported in 50% of patients (controls: 14%, P<0.006). Subgroup comparison of patients with and without OD suggests that orthostatic intolerance results from impaired sympathetic vasoconstriction. These results provide further evidence that the sympathetic nervous system is involved in patients with MS.
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PMID:Cardiovascular autonomic dysfunction in multiple sclerosis: correlation with orthostatic intolerance. 1046 60

Orthostatic intolerance (OI) is a cause of significant disability in otherwise healthy women seen by gynecologists. Orthostatic tachycardia is often the most obvious hemodynamic abnormality found in OI patients, but symptoms may include dizziness, visual changes, discomfort in the head or neck, poor concentration, fatigue, palpitations, tremulousness, anxiety, and, in some cases, fainting (syncope). It is the most common disorder of blood pressure regulation after essential hypertension, and patients with OI are traditionally women of childbearing age. Estimates suggest that at least 500,000 Americans suffer from some form of OI, and such patients comprise the largest group referred to centers specialized in autonomic disorders. This article reviews recent advances made in the understanding of this condition, potential pathophysiological mechanisms contributing to orthostatic intolerance, and therapeutic alternatives currently available for the management of these patients.
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PMID:Orthostatic intolerance: a disorder of young women. 1075 21

Orthostatic intolerance affects an estimated 1 in 500 persons and causes a wide range of disabilities. After essential hypertension, it is the most frequently encountered dysautonomia, accounting for the majority of patients referred to centers specializing in autonomic disorders. Patients are typically young females with symptoms such as dizziness, visual changes, head and neck discomfort, poor concentration, fatigue, palpitations, tremulousness, anxiety, and, in some cases, syncope. Syncope is the most hazardous symptom of orthostatic intolerance, presumably occurring because of impaired cerebral perfusion and in part to compensatory autonomic mechanisms. The etiology of this syndrome is still unclear but is heterogeneous. Orthostatic intolerance used to be characterized by an overall enhancement of noradrenergic tone at rest in some patients and by a patchy dysautonomia of postganglionic sympathetic fibers with a compensatory cardiac sympathetic activation in others. However, recent advances in molecular genetics are improving our understanding of orthostatic intolerance, such as several genetic diseases (such as Ehler-Danlos syndrome and norepinephrine transporter deficiency) presenting with symptoms typical of orthostatic intolerance. Future work will include investigation of genetic functional mutations underlying interindividual differences in autonomic cardiovascular control, body fluid regulation, and vascular regulation in orthostatic intolerance patients. The goal of this review article is to describe recent advances in understanding the pathophysiological mechanisms of orthostatic intolerance and their clinical significance.
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PMID:Orthostatic intolerance: potential pathophysiology and therapy. 1561 27

Orthostatic intolerance (OI) syndromes are frequent and share symptoms like dizziness and orthostatic syncope. Their pathophysiology however seems to be different. The aim of our work was to evaluate autonomic and hemodynamic behaviour in patients with familial amyloidotic polyneuropathy and neurally mediated syncope in supine position and after acute orthostatic passive stress. We studied 12 patients with autonomic failure (group A), 12 patients with neurally mediated syncope (group B) and 16 aged matched normal controls (group C), in supine position and during the first 10 min of head-up tilt test (HUTT). Beat-by-beat blood pressure and heart rate were continuously monitored and digitised at 500 Hz. The baroreceptor alfa-index gain (vagal reflex-BRG), high frequency of RR variability (HFRR, vagal tonus) and low frequency of systolic arterial pressure variability (LFSAP, sympathetic tone) were calculated. Catecholamines, plasma brain (BNP) and atrial natriuretic (ANP) peptides were also measured. Hemodynamic data were derived and calculated by the non-invasive modelflow method. During supine position, cardiac output (CO) and stroke volume (SV) were similar in all groups. Mean arterial pressure (MAP) and BNP were higher in group A. Noradrenaline (NOR), BRG, HFRR and LFSAP were extremely low in this group. BRG and adrenaline (ADR) were higher in group B than in controls. Within the first 10 min of HUTT, there was a huge drop of CO, SV and MAP in group A, maintenance of very low levels of neurohormones and lack of autonomic function. HR, LFSAP and ADR had a higher rise at HUTT in group B compared with controls (p<0.01) but a significant decrease of BRG was noted (p<0.05). ANP or BNP did not change with tilt in any group. Different orthostatic intolerance syndromes may show important hormonal, autonomic and hemodynamic differences during supine rest and enhanced after passive orthostatism.
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PMID:Hemodynamic, autonomic and neurohormonal behaviour of familial amyloidotic polyneuropathy and neurally mediated syncope patients during supine and orthostatic stress. 1684 44

We report on two previously healthy patients who developed severe form of postural orthostatic tachycardia syndrome (POTS) following an electric injury. Both the patients developed symptoms of orthostatic intolerance in the form of dizziness, fatigue, lightheadedness, and palpitations, weeks to months after electrical injury. Orthostatic intolerance produced considerable functional impairment in these patients. Early recognition of POTS when it occurs after an electrical injury allows for prompt evaluation and management to occur.
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PMID:Postural orthostatic tachycardia syndrome: a rare complication following electrical injury. 2001 31