Research Review By Dr. Ceara Higgins©

Audio:

Download MP3

Date Posted:

November 2016

Study Title:

Cervico-ocular reflex is increased in people with nonspecific neck pain

Authors:

de Vries J, Ischebeck BK, Voogt LP et al.

Author's Affiliations:

Erasmus MC, Rotterdam, the Netherlands; Rotterdam University of Applied Sciences, Rotterdam, the Netherlands; Spine and Joint Centre, Rotterdam, the Netherlands; Erasmus University College, Rotterdam, the Netherlands.

Publication Information:

Physical Therapy 2016; 96(8): 1190–1195.

Background Information:

Visual disturbances have been reported in individuals with neck pain and may be related to deficits in oculo-motor control (2). Because afferent information from the cervical muscles converges with information regarding head movements relayed from the visual and vestibular systems in the vestibular nuclei (3), inconsistencies among the cervical, vestibular, and visual systems are likely associated with dizziness and decreased postural stability (4). As well, cervical afferents are involved in the cervico-ocular reflex (COR), which stabilizes your eyes in response to movement of the head on the trunk (5) through proprioceptive input from the cervical facet joints as well as the deep neck musculature. In an ideal scenario, the COR works in harmony with the vestibulo-ocular reflex (VOR), which stabilizes your eyes in response to vestibular input. In this relationship, if the VOR goes down, the COR typically increases to compensate. An increase in the COR is generally seen in those over 60 years of age as a compensation for the sensory loss in the vestibulum (VOR decreases, COR increases). By comparison, in those with whiplash-associated disorders (WAD), the COR also generally increases without a compensatory drop in the VOR (this could theoretically lead to cervicovestibular dysfunction).

This study looked at the COR and VOR in individuals with non-specific neck pain, who could be expected to have deficits in neck proprioception (6), and compared them to healthy controls. The authors expected to see differences in the COR but none in the VOR in the non-specific neck pain group (thus, they hypothesized that neck pain patients would demonstrate a similar pattern as WAD patients).

Pertinent Results:

The study included 37 participants with neck pain and 30 healthy controls. In participants with neck pain, a higher COR and an unaltered VOR was found when compared to the control group. These results were similar to those of a previous study involving individuals with WAD (2), which suggests that an increased COR is not specific to patients with specific types of neck pain (rather, it could be a general characteristic of those with any sort of neck pain). This increase could be due to altered afferent information from the cervical spine, as suggested by previous MRI studies showing the widespread presence of fatty infiltrates in the neck muscles of individuals with chronic whiplash (9) and, to a lesser extent, individuals with idiopathic neck pain (10). As well, the exceptionally high density of muscle spindles in the cervical spine make it likely that altered afferent information from the cervical spine would likely affect the COR. The tendency of individuals with neck pain to avoid movements in their end ranges of motion may also affect this afferent information. This was also demonstrated in this study where individuals in the non-specific neck pain group showed reduced range of motion in the vertical plane. This reduction could also, however, be due to the non-specific neck pain group being generally older.

Clinical Application & Conclusions:

This study suggests that VOR does not appear to compensate for increases in COR in individuals with non-specific neck pain. This incongruity could lead to visual disturbances (1), dizziness (12), or disturbances in postural control (12). Because it is not possible to deliberately influence the COR, it could be used as an objective outcome measure of oculomotor function in a clinical setting. (REVIEWER’S NOTE: While it is possible that testing COR could give you clinical information, the testing required is likely too costly and complicated to practically pursue in a clinical setting. Having said that, there are some simple clinical testing procedures that can help point clinicians toward dysfunction in the relationship among a patient’s vestibular, ocular and cervical proprioceptive systems. Identifying such dysfunction may then assist in prescription of rehabilitation exercises or even direct manual therapy interventions in the suboccipital or upper cervical region.)

Study Methods:

The authors undertook a cross-sectional study following the guidelines of the STROBE statement (STrengthening the Reporting of OBservational Studies in Epidemiology) (7). Participants with neck pain were recruited from physical therapy practices in Rotterdam via personal invitation from their physiotherapists. Healthy controls were recruited from Erasmus MC and the Rotterdam University of Applied Sciences through an information letter.

Inclusion Criteria for Non-Specific Neck Pain Patients:
  • Between the ages of 18 and 65 years
  • Fluent in Dutch
  • Experiencing non-specific neck pain (mild to moderate pain and discomfort in the neck area with possible radiation to the thoracic spine and one or both shoulders) for less than 1 year
  • Physically able to sit immobilized in a chair for 30 minutes in order to undergo COR and VOR testing
Exclusion Criteria for Non-Specific Neck Pain Patients:
  • Use of medication that influences alertness or balance
  • Any neurological disorder or vestibular or visual problems
  • A history of neck trauma
Inclusion Criteria for Healthy Controls:
  • Between the ages of 18 and 65 years
  • Fluent in Dutch
  • No complaints of the cervical spine (including cervicogenic headaches and dizziness) in the past 5 years
  • No history of neck trauma
All participants filled in demographic questionnaires, and individuals with neck pain also rated their pain intensity using a numeric pain rating scale (NPRS), filled in the Neck Disability Index (NDI) to evaluate functional disability and the Dizziness Handicap Inventory (DHI) to evaluate perceived handicap due to dizziness. All participants then had cervical range of motion (CROM) measured using a CROM device, consisting of a magnet and three compass-like instruments positioned to measure the maximum range of motion (in degrees) in rotation, flexion/extension, and lateral flexion. Next, infrared video-oculography was used to record left eye positions (8) during either cervical or vestibular stimulation in complete darkness. Participants were seated in a chair attached to a motor and secured to the chair at shoulder level by a double-belt system and by a custom-made biteboard (set so the axis of rotation was under the midpoint of the interaural line) to fix head position. In both situations, participants were asked to keep their eyes open and look at a position directly in front of the setup that was briefly indicated by a laser dot.

During COR stimulation, the biteboard was mounted to the floor to keep the position of the head fixed in space and ensure the rotation of the chair produced pure cervical stimulation. During VOR stimulation, the biteboard was mounted to the chair so chair rotation produced pure vestibular stimulation.

Study Strengths / Weaknesses:

Weaknesses:
  • Eye movements need to measured with precision and accuracy which may be technically difficult.
  • Video-oculography is quite expensive, so may not be readily available in most clinical practice environments.
  • Only group effects were observed.

Additional References:

  1. Treleaven J, Takasaki H. Characteristics of visual disturbances reported by subjects with neck pain. Man Ther 2014; 19: 203-207.
  2. Kelders WP, Kleinrensink GJ, van der Geest JN, et al. The cervico-ocular reflex is increased in whiplash injury patients. J Neurotrauma 2005; 22: 133-137.
  3. Corneil BD, Olivier E, Munoz DP. Neck muscle responses to stimulation of monkey superior colliculus, II: gaze shift initiation and volational head movements. J Neurophysiol 2002; 88: 2000-2018.
  4. Kristjansson E, Treleaven J. Sensorimotor function and dizziness in neck pain: implications for assessment and management. J Ortho Sports Phys Ther 2009; 39: 364-377.
  5. Barany R. Augenbewgungen durch Thoraxbewegungen ausgelost. Zentralbl Physiol 1906; 20: 298-302.
  6. Strimpakos N. The assessment of the cervical spine, part 1: range of motion and proprioception. J Bodywork Mov Ther 2011; 15: 114-124.
  7. von Elm E, Altman DG, Egger M, et al. The strengthening the reporting of observational studies in epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet 2007; 370: 1453-1457.
  8. van der Geest JN, Frens MA. Recording eye movements with video-oculography and scleral search coils: a direct comparison of two methods. J Neurosci Methods 2002; 114: 185-195.
  9. Elliott JM. Are there implications for morphological changes in neck muscles after whiplash injury? Spine 2011; 36: S205-S210.
  10. Elliott JM, Pedler AR, Jull GA, et al. Differential changes in muscle composition exist in traumatic and nontraumatic neck pain. Spine 2014; 39: 39-47.
  11. Liu JX, Thornell LE, Pedrosa-Domellof F. Muscle spindles in the deep muscles of the human neck: a morphological and immunocytochemical study. J Histochem Cytochemistry 2003; 51: 175-186.
  12. Treleaven J. Dizziness, unsteadiness, visual disturbances and postural control: implications for the transition to chronic symptoms following a whiplash trauma. Spine 2011; 36(25 suppl): S211-S217.