Difficulties in the diagnosis of autonomic dysfunction in multiple sclerosis

Immune and autonomic nervous system interactions in multiple sclerosis: clinical implications

Multiple sclerosis is characterized by a wide spectrum of clinical manifestations, among which dysfunction of the autonomic nervous system represents an important cause of multiple sclerosis-related disability. The aim of this review is to provide an overview of autonomic dysfunction in people with multiple sclerosis, and to discuss the interactions between the immune and autonomic nervous systems and the effects of these interactions on various aspects of multiple sclerosis. Autonomic dysfunction in people with multiple sclerosis can be demonstrated clinically and on a molecular level. Clinically, it can be demonstrated by measuring autonomic symptoms with the Composite Autonomic Symptom Score (COMPASS-31), and neurophysiologically, with different autonomic nervous system tests. Both symptomatic and objectively determined autonomic dysfunction can be associated with increased risk of multiple sclerosis disease activity. Further supporting these clinical observations are molecular changes in immune cells. Changes in the sympathetic autonomic system, such as different expression of dopaminergic and adrenergic receptors on immune cells, or modulation of the cholinergic anti-inflammatory pathway over different subunits of the nicotinic acetylcholine receptor in the peripheral immune system, may mediate different effects on multiple sclerosis disease activity.

Metaboreflex activity in multiple sclerosis patients

PURPOSE

The muscle metaboreflex activation has been shown essential to reach normal hemodynamic response during exercise. It has been demonstrated that patients with multiple sclerosis (MS) have impaired autonomic functions and cardiovascular regulation during exercise. However, to the best of our knowledge, no previous research to date has studied the metaboreflex in MS patients. The purpose of this study was to investigate the hemodynamic response to metaboreflex activation in patients with MS (n = 43) compared to an age-matched, control group (CTL, n = 21).

METHODS

Cardiovascular response during the metaboreflex was evaluated using the post-exercise muscle ischemia (PEMI) method and during a control exercise recovery (CER) test. The difference in hemodynamics between the PEMI and the CER test was calculated and this procedure allowed for the assessment of the metaboreflex response. Hemodynamics was estimated by impedance cardiography.

RESULTS

The MS group showed a normal mean blood pressure (MBP) response as compared to the CTL group (+6.5 ± 6.9 vs. +8 ± 6.8 mmHg, respectively), but this response was achieved with an increase in systemic vascular resistance, that was higher in the MS with respect to the CTL group (+137.6 ± 300.5 vs. -14.3 ± 240 dyne · s(-1) cm(-5), respectively). This was the main consequence of the MS group's incapacity to raise the stroke volume (-0.65 ± 10.6 vs. +6.2 ± 12.8 ml, respectively).

CONCLUSION

It was concluded that MS patients have an impaired capacity to increase stroke volume (SV) in response to low level metaboreflex, even if they could sustain the MBP response by vasoconstriction. This was probably a consequence of their chronic physical de-conditioning.

Ultrasonographic evaluation of cerebral arterial and venous haemodynamics in multiple sclerosis: a case-control study

Objective

Although recent studies excluded an association between Chronic Cerebrospinal Venous Insufficiency and Multiple Sclerosis (MS), controversial results account for some cerebrovascular haemodynamic impairment suggesting a dysfunction of cerebral autoregulation mechanisms. The aim of this cross-sectional, case-control study is to evaluate cerebral arterial inflow and venous outflow by means of a non-invasive ultrasound procedure in Relapsing Remitting (RR), Primary Progressive (PP) Multiple Sclerosis and age and sex-matched controls subjects.

Material and Methods

All subjects underwent a complete extra-intracranial arterial and venous ultrasound assessment with a color-coded duplex sonography scanner and a transcranial doppler equipment, in both supine and sitting position by means of a tilting chair. Basal arterial and venous morphology and flow velocities, postural changes in mean flow velocities (MFV) of middle cerebral arteries (MCA), differences between cerebral venous outflow (CVF) in clinostatism and in the seated position (ΔCVF) and non-invasive cerebral perfusion pressure (CPP) were evaluated.

Results

85 RR-MS, 83 PP-MS and 82 healthy controls were included. ΔCVF was negative in 45/85 (52.9%) RR-MS, 63/83 (75.9%) PP-MS (p = 0.01) and 11/82 (13.4%) controls (p<0.001), while MFVs on both MCAs in sitting position were significantly reduced in RR-MS and PP-MS patients than in control, particularly in EDSS≥5 subgroup (respectively, 42/50, 84% vs. 66/131, 50.3%, p<0.01 and 48.3±2 cm/s vs. 54.6±3 cm/s, p = 0.01). No significant differences in CPP were observed within and between groups.

Conclusions

The quantitative evaluation of cerebral blood flow (CBF) and CVF and their postural dependency may be related to a dysfunction of autonomic nervous system that seems to characterize more disabled MS patients. It's not clear whether the altered postural control of arterial inflow and venous outflow is a specific MS condition or simply an “epiphenomenon” of neurodegenerative events.

Arterial Compliance in Multiple Sclerosis: A Pilot Study

A reduction in arterial compliance in patients with autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus has been previously reported. It is caused by the effect that systemic inflammation has on the cardiovascular system. Multiple sclerosis (MS), an immune-mediated disease that exclusively affects the central nervous system (CNS), has a significant inflammatory component that is limited to that compartment. The potential effects of its inflammatory mediators in the cardiovascular system are largely unknown. Purpose: To examine large (C1) and small arterial compliance (C2) in patients with MS and compare them with healthy age-matched controls. To also determine whether any differences in C1 and C2 indices between participants diagnosed with relapsing remitting MS (RR-MS), secondary progressive MS (SP-MS), and controls exist. Methods: A total of 26 men and women between the ages of 18 and 64 diagnosed with MS and 25 healthy controls volunteered for this study. Arterial compliance was measured by using pulse contour analysis (PCA), which records and analyzes the blood pressure waveform data from the Arterial Pulse Wave Sensors. Results: Significant differences in C1 and C2 were found between young RR-MS and healthy young controls (P < .05), with the MS group showing lower arterial C1 and C2 compliance. No significant differences (P > .05) were seen for C1 or C2 values between older RR-MS, SP-MS, and healthy controls. Conclusion: Arterial compliance is significantly compromised in young individuals with MS, compared with age-matched controls, but not for older individuals, suggesting a systemic effect of an inflammatory process that predominantly affects the CNS.