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Background

Assessment of sensorimotor function is useful for classification and treatment evaluation of neck pain disorders. Several studies have investigated various aspects of cervical motor functions. Most of these have involved slow or self-paced movements, while few have investigated fast cervical movements. Moreover, the reliability of assessment of fast cervical axial rotation has, to our knowledge, not been evaluated before.

Methods

Cervical kinematics was assessed during fast axial head rotations in 118 women with chronic nonspecific neck pain (NS) and compared to 49 healthy controls (CON). The relationship between cervical kinematics and symptoms, self-rated functioning and fear of movement was evaluated in the NS group. A sub-sample of 16 NS and 16 CON was re-tested after one week to assess the reliability of kinematic variables. Six cervical kinematic variables were calculated: peak speed, range of movement, conjunct movements and three variables related to the shape of the speed profile.

Results

Together, peak speed and conjunct movements had a sensitivity of 76% and a specificity of 78% in discriminating between NS and CON, of which the major part could be attributed to peak speed (NS: 226 ± 88 °/s and CON: 348 ± 92 °/s, p < 0.01). Peak speed was slower in NS compared to healthy controls and even slower in NS with comorbidity of low-back pain. Associations were found between reduced peak speed and self-rated difficulties with running, performing head movements, car driving, sleeping and pain. Peak speed showed reasonably high reliability, while the reliability for conjunct movements was poor.

Conclusions

Peak speed of fast cervical axial rotations is reduced in people with chronic neck pain, and even further reduced in subjects with concomitant low back pain. Fast cervical rotation test seems to be a reliable and valid tool for assessment of neck pain disorders on group level, while a rather large between subject variation and overlap between groups calls for caution in the interpretation of individual assessments.

The effect of neck/shoulder pain on the performance in a hand laterality motor imagery test was studied. Responses to the Cooper and Shepard (1975, Journal of Experimental Psychology: Human Perception and Performance 104 48–56) hand laterality test were explored in twenty-four individuals with chronic non-specific neck pain and twenty-one subjects with chronic neck pain of traumatic origin (whiplash-associated disorder). Twenty-two controls were also included in the study. Digitalised right- or left-hand stimuli were presented at five different stimulus angles (0°, 45° laterally, 90° laterally, 135° laterally, and 180°). The experimental task was to decide the laterality as fast and accurately as possible. The performance, both reaction time (RT) and accuracy, of the two experimental groups was contrasted with that of the control group. The main results revealed that the subjects afflicted with whiplash injury on the average exhibited a faster response pattern than symptom-free healthy controls. Despite their musculoskeletal deficits and experience of pain these volunteers also exhibited a preserved speed–accuracy tradeoff. Longer duration of time with symptoms of neck pain was, moreover, associated with progressively faster RTs. These results point to perceptual learning and may reflect different stages of adaptation to neck pain.

Chronic neck pain is a widespread problem that causes individual suffering as well as large costs for the society. The knowledge about the pathophysiology is poor and therefore specific diagnosis and causal treatment are rare. Important knowledge for characterization of the disorders has been gained from research on sensorimotor functions in people with neck pain. Moreover, rehabilitation regimes including sensorimotor exercises indicate promising results.

The main objectives of this thesis were to extend the knowledge on sensorimotor dysfunctions in chronic neck pain, and to develop a new exercise method for improving sensorimotor functions of the neck. The studies focused on aspects of postural control and movements of the arm and neck. These are vital functions for many activities of daily living. People with chronic (>3 months) neck pain were compared to healthy controls (CON). Neck pain related to trauma was referred to as whiplash associated disorders (WAD), while neck pain without association to trauma was referred to as non-specific (NS).

Arm-functioning was assessed in a pointing task. WAD and NS had reduced pointing precision compared to CON. The reduced precision was associated with self-rated difficulties performing neck movements, physical functioning, and in WAD, also pain and balance disturbances.

Postural control was assessed in quiet standing on a force platform without vision. The center of pressure signal was decomposed into it’s slow and fast components. WAD and NS were compared to CON. The results revealed an effect of age on the magnitude of the fast sway component, but no effect of group. The magnitude of the slow component was elevated in both WAD and NS. This increase was associated with self-rated balance disturbance, arm-functioning, difficulties to run and sensory alterations in WAD, while in NS, the increase in the slow sway component was associated with concurrent low back pain.

Neck movements were assessed in a cervical axial rotation test with maximal speed. In total 8 variables representing basic kinematics, including variables reflecting movement smoothness and conjunct motions were calculated. NS were compared to CON. Linear discriminant modelling indicated Peak Speed and conjunct motions as significant classification variables that together had a sensitivity of 76.3% and specificity of 77.6%. Retest reliability was good for Peak Speed but poor for the measure of conjunct motions. Peak Speed was slower in NS compared to CON, and even slower in a sub-group of NS with concurrent low back pain. Reduced Peak Speed was associated with self-rated difficulties performing neck movements, car driving, running, sleeping disturbances and pain.

The clinical applicability of a novel method for neck coordination exercise was assessed in a pilot study on persons with NS. The results supported the applicability and indicated positive effects of the exercise: reduced postural sway in quiet standing and increased smoothness in cervical rotations. Indications on improvement in self-rated disability and fear of movement were seen at six months follow up.

In conclusion, sensorimotor functions can be altered in chronic neck pain, particularly in neck disorders with concurrent low back pain and WAD. The discriminative ability and clinical validity displayed in pointing precision, postural sway and cervical axial rotation speed imply that such tests can be valuable tools in the assessment of chronic neck pain patients, and for selecting and evaluating treatment interventions. Indications of improvements seen in the pilot-study support a future RCT.

BACKGROUND: Chronic neck pain is a common problem and is often associated with changes in sensorimotor functions, such as reduced proprioceptive acuity of the neck, altered coordination of the cervical muscles, and increased postural sway. In line with these findings there are studies supporting the efficacy of exercises targeting different aspects of sensorimotor function, for example training aimed at improving proprioception and muscle coordination. To further develop this type of exercises we have designed a novel device and method for neck coordination training. The aim of the study was to investigate the clinical applicability of the method and to obtain indications of preliminary effects on sensorimotor functions, symptoms and self-rated characteristics in non-specific chronic neck pain

METHODS: The study was designed as an uncontrolled clinical trial including fourteen subjects with chronic non-specific neck pain. A new device was designed to allow for an open skills task with adjustable difficulty. With visual feedback, subjects had to control the movement of a metal ball on a flat surface with a rim strapped on the subjects' head. Eight training sessions were performed over a four week period. Skill acquisition was measured throughout the intervention period. After intervention subjects were interviewed about their experience of the exercise and pain and sensorimotor functions, including the fast and slow components of postural sway and jerkiness-, range-, position sense-, movement time- and velocity of cervical rotation, were measured. At six-month follow up, self-rated pain, health and functioning was collected.

RESULTS: The subjects improved their skill to perform the exercise and were overall positive to the method. No residual negative side-effects due to the exercise were reported. After intervention the fast component of postural sway (p = 0.019) and jerkiness of cervical rotation (p = 0.032) were reduced. The follow up showed decreased disability (one out of three indices) and fear of movement, and increased general health (three out of eight dimensions).

CONCLUSION: The results support the clinical applicability of the method. The improvements in sensorimotor functions may suggest transfer from the exercise to other, non-task specific motor functions and justifies a future randomized controlled trial.

Objective: To evaluate end-point acuity in goal-directed arm movements in subjects with chronic neck pain, while taking the trade-off between speed and accuracy into account, and to evaluate associations between reduced acuity and self-rated characteristics.

Design: Single-blinded, controlled, comparative group study.

Subjects: Forty-five subjects with chronic non-traumatic, non-specific neck pain (n = 24) and whiplash-associated disorders (n = 21). Healthy subjects served as controls (n = 22). The groups were age- and sex-matched.

Methods: Subjects performed fast and accurate pointing movements to a visual target. Group differences in end-point variability, controlled for peak velocity, were evaluated. Associations between end-point variability and self-rated symptoms, functioning, self-efficacy and kinesiophobia were analysed.

Results: End-point acuity, controlled for peak velocity, was reduced for both neck-pain groups. Similar spatial error patterns across all groups indicated no direction-specific reduction. For both neck-pain groups, associations were found between end-point acuity and neck movement deficits, physical functioning and, in whiplash, also balance and pain.

Conclusion: Acuity of goal-directed arm movements can be reduced in chronic neck pain. Associations between acuity and self-rated characteristics support the clinical validity of the results and indicate that impaired neck function contributes to reduced end-point acuity. The results can be of importance for characterization and rehabilitation of neck disorders.