Abstract
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.
Highlights
We studied the effects of neck mobilization on the eye stabilization reflexes as part of the oculomotor system in healthy subjects
cervico-ocular reflex (COR) recording failed in two participants, and vestibulo-ocular reflex (VOR) recording failed in another participant, in both interventions due to technical reasons
In one participant the COR and VOR recording failed in the hyperkinesia condition and in one other participant, VOR recording failed in the hyperkinesia condition
Summary
In patients with neck pain and Whiplash Associated Disorders (WAD) oculomotor disturbances have been describedThe trial is registered in the ISRCTN registry with trial ID ISRCTN55660633.(Heikkilä and Wenngren 1998; Kelders et al 2005; Storaci et al 2006; Montfoort et al 2006, 2008; Treleaven et al 2011; Ischebeck et al 2016), which may be attributed to altered cervical functioning (Treleaven et al 2006; Falla and Farina 2007; Kristjansson and Treleaven 2009; Hodges 2011). In patients with neck pain and Whiplash Associated Disorders (WAD) oculomotor disturbances have been described. We studied the effects of neck (im-) mobilization on the eye stabilization reflexes as part of the oculomotor system in healthy subjects. To guarantee clear vision the vestibulo-ocular reflex (VOR) and the cervico-ocular reflex (COR) work in conjunction to stabilize the visual image on the retina. The VOR receives input from the vestibulum, responding to movements of the head in space. The COR receives input from the mechanoreceptors, mainly the muscle spindles and joint sensors, of the upper cervical spine (Hikosaka and Maeda 1973). The COR responds to movements of the head relative to the trunk
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