The findings from this study are very encouraging for neck pain patients undergoing chiropractic treatment who also suffer from dizziness. A high proportion of neck pain patients with and without dizziness reported clinically relevant improvement at 1 month, 3 months and 6 months, with 80% of patients with dizziness reporting that they were significantly ‘improved’ specifically relating to their dizziness symptoms at 6 months. Only the scores of ‘much better’ or ‘better’ (1 or 2) were counted as clinically relevant improvement. ‘Slightly better’ was not considered to be improved in order to error on the side of caution [16, 17]. Statistically significant decreases in all secondary outcome measures at every data collection time point were also found for both groups, although arm pain was somewhat slower to respond in females. However, the low mean baseline NRS scores both for the patients with and without dizziness shows that compared to other pain, disability and functional measures, arm pain was the least problematic.
It is important to point out that at baseline neck pain patients with dizziness reported significantly higher scores for severity of neck pain, arm pain, all subscales on the BQN as well as the BQN total score compared to the neck pain patients without dizziness. However, over time fewer differences between these two groups were found with no significant differences between the two cohorts at the 6 month data collection time point. Depression and social disability were the two categories that remained significantly different at one and 3 months. However, although significant, the mean scores at 3 months of 1.35 and 0.81 for depression and 0.83 and 0.43 for social disability are very low on the 11 point BQN subscales so it can be suggested that these differences are clinically unimportant. The BQN subscale ‘depression’ stood out as the most dramatic difference between patients with and without dizziness as well as between males and females with and without dizziness. It was nearly 2 points higher in the patients with dizziness at baseline but also demonstrated the most dramatic change score at 6 months of nearly 3.5 points. At that time point the mean score was no longer significantly different compared to patients without dizziness.
It was somewhat surprising to find that nearly 44% of neck pain patients presenting to Swiss chiropractors stated that they had associated dizziness. However, the fact that 75% of neck pain patients with dizziness in this study were female is not surprising. It is well documented that females are more likely to suffer from neck pain in general [10–12] and that a large proportion of chronic whiplash sufferers report symptoms of dizziness and unsteadiness [7, 8]. However, what is unusual in this study is that there was no difference between neck pain patients with and without dizziness in terms of a trauma onset.
Cervicogenic dizziness or dizziness of suspected cervical origin with or without unsteadiness can arise from mechanical, degenerative, inflammatory or traumatic problems affecting various structures of the neck . In particular, altered afferent information from dysfunctional mechanoreceptors in the cervical facet joints and deep cervical tissues and neck muscles, especially in whiplash patients, may lead to cervicogenic dizziness [6–8, 18, 19]. The dizziness and unsteadiness is thought to arise from dysfunction of the cervical somatosensory system [7, 8, 20]. In particular there is a mismatch of sensory information from the dysfunctional deep cervical tissues and proprioceptors compared to the vestibular and oculomotor afferent impulses [19, 20].
Therefore it is hypothesized that manual therapy such as spinal manipulation may be effective in treating cervicogenic dizziness by restoring normal movement of the zygoapophyseal joints, reducing pain and muscle hypertonicity and thereby restoring normal proprioceptive and biomechanical functioning of the cervical spine [18, 21]. Indeed, current evidence, although limited, supports a neuroanatomical and neurophysiological basis for cervicogenic dizziness and that manual therapy particularly in the upper cervical spine may be helpful in reducing cervicogenic dizziness .
Limitations to this study must start by stating that because this was not a randomized clinical trial the favourable results reported here cannot be attributed to the chiropractic treatment. There was also no attempt to compare outcomes based on the specific treatments applied or the frequency of treatment. Additionally, acute vs. chronic patients were not evaluated separately because no difference in duration of complaint was found between those with and without dizziness. It is well known that most acute neck pain patients improve due to natural history. Neck pain is most likely recurrent however, and as such, the improvement noted by these patients may very well be noteworthy. Another limitation to this study may be that there were fewer patients with 6 month data compared to baseline data. This was primarily due to the fact that this is an ongoing study and the time point had not yet been reached for the 6 month telephone call. However, with 121 patients with baseline dizziness and 176 patients without dizziness at baseline for the 6 month data collection time point, additional patients would be unlikely to alter the results .
The fact that only 29% of practicing chiropractors contributed patients to this study may also be a limitation as it is unknown whether or not this sample is representative of the greater chiropractic population. Additionally, some chiropractors contributed several patients and others only a few. It is known however, that chiropractors from the two largest geographic regions of Switzerland submitted patients and that those participating had a wide range of practice experience. Additionally, all Swiss chiropractors must complete a two year full time post-graduate residency programme with a fairly standardized curriculum and pass a rigorous post-graduate examination in order to practice as independent chiropractors in this country. It is known from the Swiss job analysis study published in 2010 that the ‘diversified’ manipulative technique is applied to the majority of patients by the vast majority of chiropractors. Additional commonly applied therapies include trigger point therapy, advice on activities of daily living, therapeutic exercises and mobilization techniques . Thus differences in practices here may be less dramatic than in other countries.
Finally, the use of multiple, uncorrected statistical tests may be another limitation to this study. In particular the large number of statistical tests used in this study may have resulted in a chance-statistically significant finding (one significant finding per 20 tests if p < 0.05). Further exploration of predictors of improvement for neck pain patients with dizziness should use multiple regression analysis.