Cardiovascular autonomic dysfunction in multiple sclerosis: correlation with orthostatic intolerance
ABSTRACT 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.
SourceAvailable from: Helmut Hildebrandt[Show abstract] [Hide abstract]
ABSTRACT: Background: Fatigue is a common symptom in Multiple Sclerosis (MS) and body cooling may be an important non-pharmacological treatment strategy for fatigue by, for instance, reducing the loss of axonal conduction efficiency due to Uhthoff's phenomenon. However, up to now, no studies have demonstrated such a treatment effect for mentally induced fatigue. Methods: In this single-blinded randomized placebo controlled cross-over design we studied the effects of cooling on cognitive fatigue and autonomic functioning (heart rate variability and sympathovagal balance measures) during a vigilance task in 31 MS patients and 10 controls. Results: Task performance, fatigue and sympathovagal balance did not differ between verum-and placebo condition after controlling for depressive mood. MS patients showed more omissions on the vigilance test than controls; their performance declined during the task and this correlated significantly with cognitive fatigue. Cardiac sympathetic drive remained unchanged during vigilance testing in MS patients, but it increased significantly in controls. Conclusion: Cooling has no impact on experienced cognitive fatigue and on cognitive performance in MS patients. Vigilance testing seems to be an appropriate behavioural measure of cognitive fatigue. Cardiac sympathetic drive to compensate for mental strain is reduced in MS patients, indicating an autonomic dysfunction.
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ABSTRACT: Multiple sclerosis (MS), a progressive neurological disease, can result in autonomic dysfunction. Impairments in the autonomic control of cardiovascular and thermoregulatory function during exercise have been observed in MS. Attenuated elevations in blood pressure during exercise in MS patients can negatively impact blood flow to skeletal muscle. Diminished sweating during exercise may impair heat dissipation likely limiting the exercise intensity that can be performed before detrimental core temperatures are reached. Further understanding the physiologic mechanisms of autonomic dysfunction during exercise in MS may lead to the development of novel therapeutic strategies targeted at improving quality of life in individuals with this disease. Copyright © 2014. Published by Elsevier B.V.Autonomic neuroscience: basic & clinical 10/2014; 188. DOI:10.1016/j.autneu.2014.10.017 · 1.82 Impact Factor
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ABSTRACT: The definition of cardiovascular autonomic dysfunction in patients with multiple sclerosis is controversial. Thus, its true prevalence is unknown. We performed a systematic review and meta-analysis to compare the proportion of patients with multiple sclerosis that would be diagnosed with cardiovascular dysautonomia using a definition of at least one abnormal cardiac autonomic test vs. at least two abnormal studies. We searched PubMed, Embase, and Scopus from 1980 to December 2013 for publications reporting abnormal autonomic tests in patients with multiple sclerosis. We performed random-effects meta-analyses for calculating the proportion of patients diagnosed with autonomic dysfunction with both definitions. We included 16 studies comprising 611 patients with multiple sclerosis, assessing ≥3 cardiovascular autonomic tests. The proportion of patients with autonomic dysfunction was two-fold higher (p=0.006) when using the definition of only one abnormal autonomic test (42.1%) compared to that using at least two abnormal results (18.8%). We found a wide variation in the proportion of patients with multiple sclerosis diagnosed with cardiovascular dysautonomia by using the two definitions. Consensus is needed to define autonomic dysfunction in patients with multiple sclerosis. In the meantime, we encourage investigators to report results using both thresholds. Copyright © 2015 Elsevier B.V. All rights reserved.02/2015; 4(2). DOI:10.1016/j.msard.2015.02.002