Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-Week Longitudinal Study With a Healthy Control Group Comparison

The impact of subclinical neck pain and laterality on vertical goal directed upper limb movements

Subclinical neck pain (SCNP) is a subset of the recurrent neck pain population for which individuals have not received treatment. Individuals with SCNP have been shown to have altered cerebellar processing. The cerebellum integrates sensorimotor information to refine and update internal models necessary for reaching movements. The impact of SCNP on sensorimotor integration and motor behavior has not been fully elucidated in the context of goal-directed reaching movements. Therefore, our study investigated the role of SCNP on these processes by comparing upper limb reaching movements to controls with the dominant and non-dominant hands using light and heavy styli in the vertical plane. The results show that those with SCNP have quicker reaction times and end their primary movement closer to the target compared to controls. This is likely to allow for greater central visual processing, thus illustrating the tendency for those with SCNP to rely more on visual feedback in order to compensate for an altered body schema.

Neuroplastic Responses to Chiropractic Care: Broad Impacts on Pain, Mood, Sleep, and Quality of Life

OBJECTIVES

This study aimed to elucidate the mechanisms of chiropractic care using resting electroencephalography (EEG), somatosensory evoked potentials (SEPs), clinical health assessments (Fitbit), and Patient-reported Outcomes Measurement Information System (PROMIS-29).

METHODS

Seventy-six people with chronic low back pain (mean age ± SD: 45 ± 11 years, 33 female) were randomised into control (n = 38) and chiropractic (n = 38) groups. EEG and SEPs were collected pre and post the first intervention and post 4 weeks of intervention. PROMIS-29 was measured pre and post 4 weeks. Fitbit data were recorded continuously.

RESULTS

Spectral analysis of resting EEG showed a significant increase in Theta, Alpha and Beta, and a significant decrease in Delta power in the chiropractic group post intervention. Source localisation revealed a significant increase in Alpha activity within the Default Mode Network (DMN) post intervention and post 4 weeks. A significant decrease in N30 SEP peak amplitude post intervention and post 4 weeks was found in the chiropractic group. Source localisation demonstrated significant changes in Alpha and Beta power within the DMN post-intervention and post 4 weeks. Significant improvements in light sleep stage were observed in the chiropractic group along with enhanced overall quality of life post 4 weeks, including significant reductions in anxiety, depression, fatigue, and pain.

CONCLUSIONS

These findings indicate that many health benefits of chiropractic care are due to altered brain activity.

The cervico-ocular reflex changes following treatment in individuals with subclinical neck pain: a randomized control trial

Individuals with subclinical neck pain (SCNP) exhibit altered cerebellar processing, likely due to disordered sensorimotor integration of inaccurate proprioceptive input. This association between proprioceptive feedback and SMI has been captured in cervico-ocular reflex (COR) differences where SCNP showed higher gain than healthy participants. Previous neurophysiological research demonstrated improved cerebellar processing in SCNP participants following a single treatment session, but it is unknown whether these neurophysiological changes transfer to cerebellar function. In a parallel group, randomized control trial conducted at Ontario Tech University, 27 right-hand dominant SCNP participants were allocated to the 8-week chiropractic care (n = 15; 7M & 8 F) or 8-week control (n = 12; 6M & 6 F) group. COR gain (ratio of eye movement to trunk movement) was assessed using an eye-tracking device at baseline and at post 8-weeks (treatment vs. no treatment). COR gain (10 trials): participants gazed at a circular target that disappeared after 3 s, while a motorized chair rotated their trunk at a frequency of 0.04 Hz, with an amplitude of 5º, for 2 minutes. A 2 × 2 repeated measures ANOVA was performed. COR gain was significantly reduced following 8-weeks of chiropractic care compared to the SCNP control (8-weeks of no treatment) group (p = 0.012, ηp2 = 0.237). The decrease in COR gain following treatment is likely due to normalized proprioceptive feedback from the neck, enabling improved processing and integration within the flocculonodular lobe of the cerebellum.

Impact of subclinical neck pain on eye and hand movements in goal-directed upper limb aiming movements

Individuals with untreated, mild-to-moderate recurrent neck pain or stiffness (subclinical neck pain (SCNP)) have been shown to have impairments in upper limb proprioception, and altered cerebellar processing. It is probable that aiming trajectories will be impacted since individuals with SCNP cannot rely on accurate proprioceptive feedback or feedforward processing (body schema) for movement planning and execution, due to altered afferent input from the neck. SCNP participants may thus rely more on visual feedback, to accommodate for impaired cerebellar processing. This quasi-experimental study sought to determine whether upper limb kinematics and oculomotor processes were impacted in those with SCNP. 25 SCNP and 25 control participants who were right-hand dominant performed bidirectional aiming movements using two different weighted styli (light or heavy) while wearing an eye-tracking device. Those with SCNP had a greater time to and time after peak velocity, which corresponded with a longer upper limb movement and reaction time, seen as greater constant error, less undershoot in the upwards direction and greater undershoot in the downwards direction compared to controls. SCNP participants also showed a trend towards a quicker ocular reaction and movement time compared to controls, while the movement distance was fairly similar between groups. This study indicates that SCNP alters aiming performances, with greater reliance on visual feedback, likely due to altered proprioceptive input leading to altered cerebellar processing.

Development of the Sensory-Motor Dysfunction Questionnaire and Pilot Reliability Testing

Both chronic and recurrent spinal pain alter sensorimotor integration (SMI), which is demonstrated using complex neurophysiological techniques. Currently, there is no patient-reported outcome measure that documents and/or assesses SMI in populations with spinal problems. The purpose of this study was to develop the Sensory-Motor Dysfunction Questionnaire (SMD-Q) and assess its test-retest reliability and internal consistency in individuals with recurrent spinal pain. The SMD-Q was developed based on the existing literature on motor control disturbances associated with disordered SMI. The initial SMD-Q drafts underwent review by two separate panels of subject matter experts and a focus group with subclinical spine pain. Their suggestions were incorporated into the questionnaire prior to reliability testing. The questionnaire was administered twice at a seven-day interval using QualtricsTM. A total of 20 participants (14 females and 6 males; 20.95 ± 2.46 years of age) completed the study. Quadratic weighted kappa (Kw) was used to assess test-retest reliability and Cronbach's alpha (α) was used to assess internal consistency. Four items had a Kw < 0.40, seven had a 0.40 < Kw < 0.75, and one had a Kw > 0.75 (excellent agreement), with excellent internal consistency (α > 0.90). The pilot SMD-Q appears to reliably measure altered SMI, suggesting that revisions and testing with a larger sample are worth pursuing.

Cervico-Ocular and Vestibulo-Ocular Reflexes in Subclinical Neck Pain and Healthy Individuals: A Cross-Sectional Study

Alterations in neck sensory input from recurrent neck pain (known as subclinical neck pain (SCNP)) result in disordered sensorimotor integration (SMI). The cervico-ocular (COR) and vestibulo-ocular (VOR) reflexes involve various neural substrates but are coordinated by the cerebellum and reliant upon proprioceptive feedback. Given that proprioception and cerebellar processing are impaired in SCNP, we sought to determine if COR or VOR gain is also altered. COR and VOR were assessed using an eye-tracking device in 20 SCNP (9 M and 11 F; 21.8 (SD = 2.35) years) and 17 control (7 M and 10 F; 22.40 (SD = 3.66) years) participants. COR gain (10 trials): A motorized chair rotated the trunk at a frequency of 0.04 Hz and an amplitude of 5° while participants gazed at a circular target that disappeared after three seconds. VOR gain (30 trials): Rapid bilateral head movements away from a disappearing circular target while eyes fixated on the last observed target. Independent t-tests on COR and VOR gain were performed. SCNP had a significantly larger COR gain (p = 0.006) and smaller VOR gain (p = 0.487) compared to healthy controls. The COR group differences suggest an association between proprioceptive feedback and SMI, indicating COR may be a sensitive marker of altered cerebellar processing.

Comparison of the Impacts of Under-Treated Pain and Opioid Pain Medication on Cognitive Impairment

Purpose: To guide clinicians in balancing the risks and benefits of opioids when treating pain, we conducted two systematic reviews: 1) the impact of pain on cognitive function, and 2) the impact of opioids on cognitive function.

Methods: Part one addressed the impact of pain on cognitive impairment; Part two considered the impact of opioids on cognitive impairment. PubMed was used to search for eligible articles. For part one, 1786 articles were identified, of which 23 met our eligibility criteria. For part two, among 584 articles, 18 were found eligible.

Results: For part one, 16 studies concluded that patients with chronic pain showed impaired cognitive function; six studies found that chronic pain does not worsen cognitive function; one study concluded that the impact of pain on cognitive function differs based on the underlying cognitive status. For part two, 15 studies found that using opioids to control pain did not cause significant cognitive impairment, while three studies concluded the opposite. Studies evaluating older subjects did not observe different results from those in the whole population for both reviews.

Conclusion: The published literature indicates that moderate to severe pain can impair cognitive function, and that careful use of opioid analgesics in such subjects does not necessarily worsen cognition. Although our results are insufficient to support clear guidance due to heterogeneity of cohorts and outcomes, this study may assist primary care providers by rendering explicitly the factors to be considered by providers caring for this population with pain when opioids are considered.

Non-invasive brain stimulation in modulation of mental rotation ability: A systematic review and meta-analysis

Mental rotation, the ability to manipulate mental images, is an important function in human cognition. This systematic review and meta-analysis investigates the potential of non-invasive brain stimulation in modulation of this component of visuo-spatial perception. The PubMed database was reviewed prior to 31 September 2020 on randomized controlled trials investigating the effects of repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and transcranial alternating current stimulation (tACS) on the mental rotation ability in healthy persons. A total of 17 studies (including 485 subjects) matched our inclusion criteria. Within their scope, overall, 46 sham-controlled experiments were performed. Methodology and results of each experiment are presented in a meta-analysis. The data show a large variety of methods and effects. The influence of (1) stimulation-technique (tDCS, tACS, and rTMS), (2) stimulation protocol (anodal, cathodal, bilateral tDCS, tACS, high-frequency rTMS, low-frequency rTMS, paired pulse rTMS, and theta burst stimulation), (3) stimulation timing (preconditioning and simultaneous), (4) stimulation location (left, right hemisphere, frontal, and parietal area), and (5) stimulus type (bodily and non-bodily) is discussed. The data indicate a beneficial effect of anodal tDCS and of tACS and no effect of cathodal tDCS on the mental rotation ability. Bilateral tDCS protocols both improved and worsened the parameters assessed. The small effect sizes obtained in mostly rTMS experiments require cautious interpretation.

The contemporary model of vertebral column joint dysfunction and impact of high-velocity, low-amplitude controlled vertebral thrusts on neuromuscular function

Purpose

There is growing evidence that vertebral column function and dysfunction play a vital role in neuromuscular control. This invited review summarises the evidence about how vertebral column dysfunction, known as a central segmental motor control (CSMC) problem, alters neuromuscular function and how spinal adjustments (high-velocity, low-amplitude or HVLA thrusts directed at a CSMC problem) and spinal manipulation (HVLA thrusts directed at segments of the vertebral column that may not have clinical indicators of a CSMC problem) alters neuromuscular function.

Methods

The current review elucidates the peripheral mechanisms by which CSMC problems, the spinal adjustment or spinal manipulation alter the afferent input from the paravertebral tissues. It summarises the contemporary model that provides a biologically plausible explanation for CSMC problems, the manipulable spinal lesion. This review also summarises the contemporary, biologically plausible understanding about how spinal adjustments enable more efficient production of muscular force. The evidence showing how spinal dysfunction, spinal manipulation and spinal adjustments alter central multimodal integration and motor control centres will be covered in a second invited review.

Results

Many studies have shown spinal adjustments increase voluntary force and prevent fatigue, which mainly occurs due to altered supraspinal excitability and multimodal integration. The literature suggests physical injury, pain, inflammation, and acute or chronic physiological or psychological stress can alter the vertebral column’s central neural motor control, leading to a CSMC problem. The many gaps in the literature have been identified, along with suggestions for future studies.

Conclusion

Spinal adjustments of CSMC problems impact motor control in a variety of ways. These include increasing muscle force and preventing fatigue. These changes in neuromuscular function most likely occur due to changes in supraspinal excitability. The current contemporary model of the CSMC problem, and our understanding of the mechanisms of spinal adjustments, provide a biologically plausible explanation for how the vertebral column’s central neural motor control can dysfunction, can lead to a self-perpetuating central segmental motor control problem, and how HVLA spinal adjustments can improve neuromuscular function.

The Potential Mechanisms of High-Velocity, Low-Amplitude, Controlled Vertebral Thrusts on Neuroimmune Function: A Narrative Review

The current COVID-19 pandemic has necessitated the need to find healthcare solutions that boost or support immunity. There is some evidence that high-velocity, low-amplitude (HVLA) controlled vertebral thrusts have the potential to modulate immune mediators. However, the mechanisms of the link between HVLA controlled vertebral thrusts and neuroimmune function and the associated potential clinical implications are less clear. This review aims to elucidate the underlying mechanisms that can explain the HVLA controlled vertebral thrust--neuroimmune link and discuss what this link implies for clinical practice and future research needs. A search for relevant articles published up until April 2021 was undertaken. Twenty-three published papers were found that explored the impact of HVLA controlled vertebral thrusts on neuroimmune markers, of which eighteen found a significant effect. These basic science studies show that HVLA controlled vertebral thrust influence the levels of immune mediators in the body, including neuropeptides, inflammatory markers, and endocrine markers. This narravtive review discusses the most likely mechanisms for how HVLA controlled vertebral thrusts could impact these immune markers. The mechanisms are most likely due to the known changes in proprioceptive processing that occur within the central nervous system (CNS), in particular within the prefrontal cortex, following HVLA spinal thrusts. The prefrontal cortex is involved in the regulation of the autonomic nervous system, the hypothalamic-pituitary-adrenal axis and the immune system. Bi-directional neuro-immune interactions are affected by emotional or pain-related stress. Stress-induced sympathetic nervous system activity also alters vertebral motor control. Therefore, there are biologically plausible direct and indirect mechanisms that link HVLA controlled vertebral thrusts to the immune system, suggesting HVLA controlled vertebral thrusts have the potential to modulate immune function. However, it is not yet known whether HVLA controlled vertebral thrusts have a clinically relevant impact on immunity. Further research is needed to explore the clinical impact of HVLA controlled vertebral thrusts on immune function.

The Effects of Spinal Manipulation on Motor Unit Behavior

Over recent years, a growing body of research has highlighted the neural plastic effects of spinal manipulation on the central nervous system. Recently, it has been shown that spinal manipulation improved outcomes, such as maximum voluntary force and limb joint position sense, reflecting improved sensorimotor integration and processing. This study aimed to further evaluate how spinal manipulation can alter neuromuscular activity. High density electromyography (HD sEMG) signals from the tibialis anterior were recorded and decomposed in order to study motor unit changes in 14 subjects following spinal manipulation or a passive movement control session in a crossover study design. Participants were asked to produce ankle dorsiflexion at two force levels, 5% and 10% of maximum voluntary contraction (MVC), following two different patterns of force production (“ramp” and “ramp and maintain”). A significant decrease in the conduction velocity (p = 0.01) was observed during the “ramp and maintain” condition at 5% MVC after spinal manipulation. A decrease in conduction velocity suggests that spinal manipulation alters motor unit recruitment patterns with an increased recruitment of lower threshold, lower twitch torque motor units.

The Influence of Subclinical Neck Pain on Neurophysiological and Behavioral Measures of Multisensory Integration

Multisensory integration (MSI) is necessary for the efficient execution of many everyday tasks. Alterations in sensorimotor integration (SMI) have been observed in individuals with subclinical neck pain (SCNP). Altered audiovisual MSI has previously been demonstrated in this population using performance measures, such as reaction time. However, neurophysiological techniques have not been combined with performance measures in the SCNP population to determine differences in neural processing that may contribute to these behavioral characteristics. Electroencephalography (EEG) event-related potentials (ERPs) have been successfully used in recent MSI studies to show differences in neural processing between different clinical populations. This study combined behavioral and ERP measures to characterize MSI differences between healthy and SCNP groups. EEG was recorded as 24 participants performed 8 blocks of a simple reaction time (RT) MSI task, with each block consisting of 34 auditory (A), visual (V), and audiovisual (AV) trials. Participants responded to the stimuli by pressing a response key. Both groups responded fastest to the AV condition. The healthy group demonstrated significantly faster RTs for the AV and V conditions. There were significant group differences in neural activity from 100-140 ms post-stimulus onset, with the control group demonstrating greater MSI. Differences in brain activity and RT between individuals with SCNP and a control group indicate neurophysiological alterations in how individuals with SCNP process audiovisual stimuli. This suggests that SCNP alters MSI. This study presents novel EEG findings that demonstrate MSI differences in a group of individuals with SCNP.

Association of Subclinical Neck Pain With Altered Multisensory Integration at Baseline and 4-Week Follow-up Relative to Asymptomatic Controls

OBJECTIVE

The purpose of this study was to test whether people with subclinical neck pain (SCNP) had altered visual, auditory, and multisensory response times, and whether these findings were consistent over time.

METHODS

Twenty-five volunteers (12 SCNP and 13 asymptomatic controls) were recruited from a Canadian university student population. A 2-alternative forced-choice discrimination task with multisensory redundancy was used to measure response times to the presentation of visual (color filled circles), auditory (verbalization of the color words, eg, red or blue), and multisensory (simultaneous audiovisual) stimuli at baseline and 4 weeks later.

RESULTS

The SCNP group was slower at both visual and multisensory tasks (P = .046, P = .020, respectively), with no change over 4 weeks. Auditory response times improved slightly but significantly after 4 weeks (P = .050) with no group difference.

CONCLUSIONS

This is the first study to report that people with SCNP have slower visual and multisensory response times than asymptomatic individuals. These differences persist over 4 weeks, suggesting that the multisensory technique is reliable and that these differences in the SCNP group do not improve on their own in the absence of treatment.

Increased Voluntary Activation of the Elbow Flexors Following a Single Session of Spinal Manipulation in a Subclinical Neck Pain Population

To investigate the effects of a single session of spinal manipulation (SM) on voluntary activation of the elbow flexors in participants with subclinical neck pain using an interpolated twitch technique with transcranial magnetic stimulation (TMS), eighteen volunteers with subclinical neck pain participated in this randomized crossover trial. TMS was delivered during elbow flexion contractions at 50%, 75% and 100% of maximum voluntary contraction (MVC) before and after SM or control intervention. The amplitude of the superimposed twitches evoked during voluntary contractions was recorded and voluntary activation was calculated using a regression analysis. Dependent variables were analyzed with two-way (intervention × time) repeated measures ANOVAs. Significant intervention effects for SM compared to passive movement control were observed for elbow flexion MVC (p = 0.04), the amplitude of superimposed twitch (p = 0.04), and voluntary activation of elbow flexors (p =0.03). Significant within-group post-intervention changes were observed for the superimposed twitch (mean group decrease of 20.9%, p < 0.01) and voluntary activation (mean group increase of 3.0%, p < 0.01) following SM. No other significant within-group changes were observed. Voluntary activation of the elbow flexors increased immediately after one session of spinal manipulation in participants with subclinical neck pain. A decrease in the amplitude of superimposed twitch during elbow flexion MVC following spinal manipulation suggests a facilitation of motor cortical output.

Laterality judgment performance between people with chronic pain and pain-free individuals. A systematic review and meta-analysis

Background: Treatment of chronic pain is challenging and there is often failure of recovery, with the need to look at different approaches in its management. Central mechanisms may contribute to chronicity (i.e. disturbance in body schema). Laterality judgment is dependent on body schema and can determine affected central mechanisms. Objective: This review aimed to determine whether there are laterality judgment differences between chronic pain and pain-free individuals. Methods: A search was done of various databases, using combinations of keywords, and reference lists of full-text articles. Articles were considered from inception until February 2018. Eighteen studies were included. Methodological quality was assessed by two reviewers using the JBI Critical Appraisal Checklist. Studies were analyzed broadly then divided into subgroups. A meta-analysis or narrative review was done. Results: There was high heterogeneity for broad outcome measures, complex regional pain syndrome (CRPS1), and upper limb pain. Analysis for accuracy in lower limb conditions showed a medium significant effect size (0.59) and significant 95%CI (0.11-1.07). Low back and cervical pain results could not be pooled into meta-analysis (due to different methods of reporting). Conclusions: Laterality judgment impairment was shown in CPRS1, upper limb pain, hand and wrist pain, carpal-tunnel syndrome, facial pain, knee osteoarthritis, and leg pain. No conclusions could be drawn in low back pain, due to the low-quality evidence and differing results. There was no impairment in whiplash-associated disorders and nonspecific cervical pain showed conflicting evidence.

Chiropractic Manipulation Increases Maximal Bite Force in Healthy Individuals

Recent research has shown that chiropractic spinal manipulation can alter central sensorimotor integration and motor cortical drive to human voluntary muscles of the upper and lower limb. The aim of this paper was to explore whether spinal manipulation could also influence maximal bite force. Twenty-eight people were divided into two groups of 14, one that received chiropractic care and one that received sham chiropractic care. All subjects were naive to chiropractic. Maximum bite force was assessed pre- and post-intervention and at 1-week follow up. Bite force in the chiropractic group increased compared to the control group (p = 0.02) post-intervention and this between-group difference was also present at the 1-week follow-up (p < 0.01). Bite force in the chiropractic group increased significantly by 11.0% (&plusmn;18.6%) post-intervention (p = 0.04) and remained increased by 13.0% (&plusmn;12.9%, p = 0.04) at the 1 week follow up. Bite force did not change significantly in the control group immediately after the intervention (&minus;2.3 &plusmn; 9.0%, p = 0.20), and decreased by 6.3% (&plusmn;3.4%, p = 0.01) at the 1-week follow-up. These results indicate that chiropractic spinal manipulation can increase maximal bite force.

The effects of a single session of spinal manipulation on strength and cortical drive in athletes

Purpose

The primary purpose of this study was to investigate whether a single session of spinal manipulation (SM) increases strength and cortical drive in the lower limb (soleus muscle) of elite Taekwondo athletes.

Methods

Soleus-evoked V-waves, H-reflex and maximum voluntary contraction (MVC) of the plantar flexors were recorded from 11 elite Taekwondo athletes using a randomized controlled crossover design. Interventions were either SM or passive movement control. Outcomes were assessed at pre-intervention and at three post-intervention time periods (immediate post, post 30 min and post 60 min). A multifactorial repeated measures ANOVA was conducted to assess within and between group differences. Time and session were used as factors. A post hoc analysis was carried out, when an interactive effect was present. Significance was set at p ≤ 0.05.

Results

SM increased MVC force [F(3,30) = 5.95, p < 0.01], and V-waves [F(3,30) = 4.25, p = 0.01] over time compared to the control intervention. Between group differences were significant for all time periods (p < 0.05) except for the post60 force measurements (p = 0.07).

Conclusion

A single session of SM increased muscle strength and corticospinal excitability to ankle plantar flexor muscles in elite Taekwondo athletes. The increased MVC force lasted for 30 min and the corticospinal excitability increase persisted for at least 60 min.