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.

Prevalence of Autonomic Dysfunction in Patients with Multiple Sclerosis

“…7,14,15 The percentage of patients complaining about gastrointestinal symptoms was the highest of all domains. This finding supported former studies showing that gastrointestinaldysfunction is a common feature in MS patients, who tend to have slowergastric emptying rate16 as well as bowel symptoms 17,18 Previous evidence showed that orthostatic intolerance can be present in up to 50% of MS patients 19 and in our study it affected around 60%. Furthermore, more than half of the patients from this group had secretomotor symptoms, such as trouble with general body sweating, dry eyes or dry mouth, which is consistent with sudomotor regulation failure found in other studies.…”

No cerebrocervical venous congestion in patients with multiple sclerosis

“…Consistent with this finding, the decrease of the BVF in patients was less pronounced after moving from a lying to an upright position. We hypothesize that this finding might reflect vascular dysregulation, perhaps due to MS affecting the autonomous nervous system, 31 and this result warrants further investigation. If anything, however, higher BVF in patients should suggest a better than normal cerebral venous drainage (at least in an upright position) in MS. Our results therefore call into question the existence of CCSVI-certainly in a large proportion of patients with MS-and do not underpin a role of cerebral venous congestion leading to reflux of blood into the CNS in the pathophysiology of MS.…”

Arterial Compliance in Multiple Sclerosis: A Pilot Study

“…8 Other documented effects include orthostatic intolerance, 27,33 disease duration, 28 increased Expanded Disability Status Score, 26 progression of clinical disability 6,34 as well as severity of MS. 29 The main limitation of this study is the crosssectional design, which does not establish a cause and effect relationship between arterial compliance and MS. Another limitation is that the PCA is a noninvasive measure of C1 and C2, and an invasive measure would be more precise.…”