Influence of sympathetic nervous system on sensorimotor function: whiplash associated disorders (WAD) as a model

Abstract

There is increasing interest about the possible involvement of the sympathetic nervous system (SNS) in initiation and maintenance of chronic muscle pain syndromes of different aetiology. Epidemiological data show that stresses of different nature, e.g. work-related, psychosocial, etc., typically characterised by SNS activation, may be a co-factor in the development of the pain syndrome and/or negatively affect its time course. In spite of their clear traumatic origin, whiplash associated disorders (WAD) appear to share many common features with other chronic pain syndromes affecting the musculo-skeletal system. These features do not only include symptoms, like type of pain or sensory and motor dysfunctions, but possibly also some of the pathophysiological mechanisms that may concur to establish the chronic pain syndrome. This review focuses on WAD, particular emphasis being devoted to sensorimotor symptoms, and on the actions exerted by the sympathetic system at muscle level. Besides its well-known action on muscle blood flow, the SNS is able to affect the contractility of muscle fibres, to modulate the proprioceptive information arising from the muscle spindle receptors and, under certain conditions, to modulate nociceptive information. Furthermore, the activity of the SNS itself is in turn affected by muscle conditions, such as its current state of activity, fatigue and pain signals originating in the muscle. The possible involvement of the SNS in the development of WAD is discussed in light of the several positive feedback loops in which it is implicated.

The rapid and progressive degeneration of the cervical multifidus in whiplash: A MRI study of fatty infiltration

“…49 Altered SNS activation is centrally programmed and has shown to exert a number of actions at the level of the muscle cell. 49 In a state of prolonged stress, as might be expected in some cases of whiplash, excessive sympathetic outflow could result in hypoxia and toxaemia under which, intramyocellular oxidative stresses may affect the contractility of skeletal muscle, and possibly the MFI observed in this and another study. 5 Further research investigating SNS activity in those who develop MFI and post-traumatic stress following whiplash is important to better understand the underlying mechanisms of persistent WAD.…”

Neck motion, motor control, pain and disability: A longitudinal study of associations in neck pain patients in physiotherapy treatment

“…Due to the connections between mechanoreceptors (muscle spindles), vision, and the vestibular system, altered afferent information from the mechanoreceptors in neck pain conditions may cause mismatch between afferent signals and thus lead to disturbances in neck motor control and sensorimotor dysfunctions like dizziness, visual disturbances and altered postural control (Treleaven andTakasaki, 2014, Treleaven, 2008a). Proprioceptive information is important for head motor control (Shaikh et al, 2013), and pain may alter this information through activation of the sympathetic nervous system in addition to altering nociceptive information (Passatore andRoatta, 2006, Radovanovic et al, 2015). Subjects with chronic neck pain may exhibit alterations in sympathetic activity in response to physical activity compared with healthy controls (Hallman et al, 2015), underlining that neck pain is associated with a dysregulation in central processes.…”

Effects of Heart Rate Variability Biofeedback in Subjects with Stress-Related Chronic Neck Pain: A Pilot Study

“…The autonomic nervous system (ANS) is an important factor in pathogenesis of chronic muscle pain (Passatore & Roatta 2006;Johansson et al 2003;Maekawa et al 2002). Elevated sympathetic activity may alter pain perception/sensitivity by increasing muscle tension (Roatta et al 2008;Larsman et al 2009) and impairing local microcirculation in the affected muscle (Larsson 1995).…”