Eye stabilization reflexes in traumatic and non-traumatic chronic neck pain patients

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.

Neck muscle activation in response to eye movement depends on sitting posture and is modified in whiplash associated disorders: Cross-sectional study

BACKGROUND

Activity of specific neck muscles is modulated by eye movement. This activity modulation is exaggerated in people with whiplash associated disorders (WAD), but it is unknown whether it is impacted by sitting posture.

OBJECTIVE

This study investigated; (i) whether activity of cervical muscles differs with spinal posture; (ii) whether the effect of eye gaze direction (horizontal/vertical) on neck muscle activity differs between postures, and (iii) whether these effects differ between individuals with and without WAD.

METHODS

In three seated postures (normal relaxed, head forward, sit tall) electromyography (EMG) was recorded right obliquus capitis inferior (OI), multifidus (MF), splenius capitis (SP) and left sternocleidomastoid (SCM) with fine-wire and surface electrodes in ten healthy controls and nine with WAD. Electro-oculography recorded eye movements.

RESULTS

In controls, EMG was less for extensor muscles in Sit Tall than Head Forward, but higher in SCM. Only SC EMG modulated with eye movement. When WAD participants adopted similar sitting postures several responses were different; compared to Normal Relaxed posture OI EMG was less in Head Forward; MF EMG was less in Sit Tall; and SC was less in Head Forward and Sit Tall. Neck muscles in WAD were generally more sensitive to eye movement, except SC which did not modulate.

CONCLUSIONS

These finding support the hypothesis that neck muscle activity is influenced by spinal posture and eye movement. In WAD, this relationship is distorted and the response to eye movement is increased.

SIGNIFICANCE

These observations have potential implications for clinical management of individuals with WAD.

Post-Traumatic Craniocervical Disorders From a Postural Control Perspective: A Narrative Review

Mild traumatic brain injury (mTBI) and whiplash injury (WI) may lead to long-term disabling consequences known as post-concussive syndrome (PCS) and whiplash-associated disorders (WADs). PCS and WAD patients commonly complain of conditions encompassing dizziness, vertigo, headache, neck pain, visual complaints, anxiety, and neurocognitive dysfunctions. A proper medical work-up is a priority in order to rule out any acute treatable consequences. However investigations may remain poorly conclusive. Gathered in the head and neck structures, the ocular sensorimotor, the vestibular, and the cervical proprioceptive systems, all involved in postural control, may be damaged by mTBI or WI. Their dysfunctions are associated with a wide range of functional disorders including symptoms reported by PCS and WAD patients. In addition, the stomatognathic system needs to be specifically assessed particularly when associated to WI. Evidence for considering the post-traumatic impairment of these systems in PCS and WAD-related symptoms is still lacking but seems promising. Furthermore, few studies have considered the assessment and/or treatment of these widely interconnected systems from a comprehensive perspective. We argue that further research focusing on consequences of mTBI and WI on the systems involved in the postural control are necessary in order to bring new perspective of treatment.

Modification of Eye-Head Coordination With High Frequency Random Noise Stimulation

The vestibulo-ocular reflex (VOR) plays an important role in controlling the gaze at a visual target. Although patients with vestibular hypofunction aim to improve their VOR function, some retain dysfunction for a long time. Previous studies have explored the effects of direct current stimulation on vestibular function; however, the effects of random noise stimulation on eye–head coordination have not previously been tested. Therefore, we aimed to clarify the effects of high frequency noisy vestibular stimulation (HF-nVS) on eye–head coordination related to VOR function. Thirteen healthy young adult participants with no serious disease took part in our study. The current amplitude and density used were 0.4 mA and 0.2 mA/cm², respectively, with a random noise frequency of 100–640 Hz. The electrodes were located on both mastoid processes. The stimulus duration and fade in/out duration were 600 and 10 s, respectively. Subjects oscillated their head horizontally, gazing at the fixation point, at 1 Hz (0.5 cycles/s) for 30 repetitions. The coordination of eye–head movements was measured by eye-tracking and a motion capture system. Peak-to-peak angles for eye and head movement and deviation of the visual line from the fixation target revealed no significant differences between HF-nVS and sham. The lag time between the eye and head movement with HF-nVS post-stimulation was significantly shorter than that of the sham. We found that HF-nVS can reduce the lag time between eye and head movement and improve coordination, contributing to a clear retinal image. This technique could be applied as a form of VOR training for patients with vestibular hypofunction.

Misperception of Visual Vertical in Peripheral Vestibular Disorders. A Systematic Review With Meta-Analysis

OBJECTIVE

The main aim was to assess the misperception of visual verticality (VV) in patients with peripheral vestibular disorders (PVD) in comparison with healthy controls. As secondary objectives, we checked if vestibular, visual, and somatosensory postural pathways can be affected in patients with PVD as well as the characteristics of PVD that could influence on the VV perception.

METHODS

A systematic review with meta-analysis was carried out. The bibliographic search was performed in January, 2020 in PubMed, Scopus, Web of Science (WOS), CINAHL, SciELO. Two reviewers selected the studies that met the inclusion criteria, extracted data, and assessed the methodological quality using the Newcastle-Ottawa Scale (NOS). The VV perception was assessed in two meta-analysis according the used test: The Subjective Visual Vertical test (SVV) or the Rod and Frame Test (RFT) in comparison with healthy subjects. The Standardized Mean Difference (SMD) and its 95% Confidence Interval (95% CI) was used to estimate the pooled effect. Publication bias was assessed using the Egger's test and Trim and Fill Method.

RESULTS

Thirty-four studies were included reporting 3,524 participants. PVD patients showed a misperception of the VV with SVV (SMD = 1.510; 95%CI: 1.190-1.830) and the RFT (SMD = 0.816; 95% CI: 0.234-1.398) respect healthy controls. A subgroup of patients in the acute phase (SMD = 2.5; 95%CI: 2.022-2.978) and who underwent a vestibular surgery (SMD = 2.241; 95%CI: 1.471-3.011) had the greater misperception of VV.

CONCLUSION

Patients with PVD show an alteration in the perception of VV, being greater in the acute phase and after a vestibular surgery. Laryngoscope, 131:1110-1121, 2021.

Variability of the helical axis during active cervical movements in people with chronic neck pain

BACKGROUND

Recent work described parameters of the helical axis in asymptomatic people with potential for investigating kinematic changes in the cervical region. This approach could provide novel information on movement variability in people with neck pain, however this has never been investigated. This study aimed to investigate movement variability during active neck movements performed at different speeds in people with and without chronic neck pain.

METHODS

This observational case-control study examined 18 participants with chronic neck pain of either idiopathic or traumatic origin and 18 gender-matched asymptomatic participants. Cervical kinematics were captured with 3D motion capture as people with and without chronic neck pain performed flexion-extension, bilateral lateral flexion and bilateral rotation at different speeds (natural, slow, and fast). The mean distance and mean angle parameters of the helical axis were extracted to describe 3D motion and quantify movement variability.

FINDINGS

A smaller mean distance was observed in those with neck pain compared to the asymptomatic participants during flexion-extension (P = 0.019) and rotation movements (P = 0.007). The neck pain group displayed smaller values for the mean angle during rotation movements with different speeds (P = 0.01). These findings indicate less variable movement for those with neck pain relative to the asymptomatic participants. No difference in the mean angle was observed between groups for flexion-extension and lateral flexion.

INTERPRETATION

The findings reiterate the importance of data derived from kinematic measures, and its potential for providing clinicians with further insight into the quality of active neck movements in people with chronic neck pain.

The influence of cervical movement on eye stabilization reflexes: a randomized trial

To investigate the influence of the amount of cervical movement on the cervico-ocular reflex (COR) and vestibulo-ocular reflex (VOR) in healthy individuals. Eye stabilization reflexes, especially the COR, are changed in neck pain patients. In healthy humans, the strength of the VOR and the COR are inversely related. In a cross-over trial the amplitude of the COR and VOR (measured with a rotational chair with eye tracking device) and the active cervical range of motion (CROM) was measured in 20 healthy participants (mean age 24.7). The parameters were tested before and after two different interventions (hyperkinesia: 20 min of extensive active neck movement; and hypokinesia: 60 min of wearing a stiff neck collar). In an additional replication experiment the effect of prolonged (120 min) hypokinesia on the eye reflexes were tested in 11 individuals. The COR did not change after 60 min of hypokinesia, but did increase after prolonged hypokinesia (median change 0.220; IQR 0.168, p = 0.017). The VOR increased after 60 min of hypokinesia (median change 0.155, IQR 0.26, p = 0.003), but this increase was gone after 120 min of hypokinesia. Both reflexes were unaffected by cervical hyperkinesia. Diminished neck movements influences both the COR and VOR, although on a different time scale. However, increased neck movements do not affect the reflexes. These findings suggest that diminished neck movements could cause the increased COR in patients with neck complaints.