Is fatigue in patients with multiple sclerosis related to autonomic dysfunction?

Abstract

Time-dependent frequency decomposition of fluctuations in cardiovascular signals (heart rate [HR], blood pressure, and blood flow) provides noninvasive and quantitative evaluation of autonomic activity during transient and steady-state conditions. This method was applied during a change of position from supine to standing in patients with multiple sclerosis (MS) who experienced unexplained fatigue and in age-matched control subjects. No difference in response to standing, as reflected in the time domain parameters (mean HR, mean blood pressure, and mean blood flow), was observed between patients with MS and control subjects. Moreover, no difference was observed in very-low-frequency and low-frequency (related to sympathetic activity) content of HR, blood pressure, blood flow, or high-frequency content of HR (related to parasympathetic activity). The only spectral estimates that showed a significant difference between groups were the ratio of low-frequency to high-frequency content of HR and low-frequency content of HR normalized to total power. Both these parameters provide an estimate of the sympathovagal balance. A significant increase in these two estimates on standing was observed in control subjects only, indicating possible impairment of the sympathovagal balance response to standing in patients with MS who experienced fatigue. The authors observed a significant age dependence between close age subgroups, which occurred in the MS group only and was observed in some of the investigated spectral estimates that reflect vagal activity. Therefore, the authors assumed that age-related reduction in vagal activity occurred earlier in patients with MS who experienced fatigue. This reduction could also explain the lack of increase in the sympathovagal balance on standing. To validate this enhanced age dependence, further investigation should be performed in a larger group of subjects with a wider age range.

Transcutaneous Electrical Nerve Stimulation (TENS) Improves Upper GI Symptoms and Balances the Sympathovagal Activity in Scleroderma Patients

“…Reduced sympathovagal balance has been associated with increased risk of death [51,52] and the improvement in patient sympathovagal balance after cardiac transplantation was associated with improved QOL and survival [53]. Additionally, impaired sympathovagal balance was related to fatigue in multiple sclerosis patients [54]. We believe that normalization of the sympathovagal balance might lead to or reflect physiologically relevant improvements of our patients' activity or mobility, an important goal in the therapy in this disabling disease.…”

Autonomic dysfunction in multiple sclerosis

“…An interesting hypothesis was postulated by Keselbrener et al who found that age-related reduction in vagal activity occurred earlier in MS patients complaining of fatigue, assuming that this form of AD may well be the pathological cause of fatigue [17].…”

Sedentary Behavior and Blood Pressure in Patients with Multiple Sclerosis

“…All BP measurements were collected after 10 minutes of quiet rest lying down and were recorded in the supine position, rather than sitting or standing, to yield a stabilized, steady-state value. 22 Blood pressure can be measured in either the seated or supine position. We measured BP in the supine position because other outcomes were measured concurrently.…”