FROM: Physical Therapy 2021 (Mar 26); pzab104 ~ FULL TEXT
É P Rampazo, V R da Silva, A L M de Andrade, C G N Back, P M Madeleine, L Arendt–Nielsen, Richard Eloin Liebano
Physiotherapeutic Resources Laboratory,
Department of Physical Therapy,
Federal University of São Carlos (UFSCar),
São Carlos/SP, Brazil.
Objective: Given the complex and unclear etiology of neck pain, it is important to understand the differences in central sensitization as well as psychosocial factors in individuals with chronic neck pain and healthy controls. The purpose of this study was to benchmark differences in central sensitization, psychosocial factors, and range of motion between people with nonspecific chronic neck pain and healthy controls and to analyze the correlation between pain intensity, neck disability, and psychosocial factors in people with chronic neck pain.
Methods: Thirty individuals with chronic neck pain and 30 healthy controls were included in this case–control study. Outcome measures were as follows: central sensitization (pressure pain threshold, temporal summation, and conditioned pain modulation), psychosocial factors (depressive symptoms, pain catastrophizing, and quality of life), and active cervical range of motion.
Results: People with neck pain had lower local pressure pain threshold, a decrease in conditioned pain modulation, more depressive symptoms, greater pain catastrophizing, lower quality of life, and reduced range of motion for neck rotation when compared with healthy controls. In people with neck pain, moderate correlations were observed between pain intensity and quality of life (p = –0.479), disability and pain catastrophizing (p = 0.379), and disability and quality of life (p = –0.456).
Conclusions: People with neck pain have local hyperalgesia, impaired conditioning pain modulation, depressive symptoms, pain catastrophizing, low quality of life, and reduced active range of motion during neck rotation, which should be taken into account during assessment and treatment.
Impact: This study shows that important outcomes, such as central sensitization and psychosocial factors, should be considered during assessment and treatment of individuals with nonspecific chronic neck pain. In addition, pain intensity and neck disability are correlated with psychosocial factors.
Keywords: Chronic Pain; Neck Disability; Neck Pain; Pain Modulation; Pain Threshold; Pressure Pain Threshold.
From the FULL TEXT Article:
The incidence and prevalence of neck pain has risen in recent years, the latter increasing with age. [1, 2] This musculoskeletal disorder may be associated with whiplash injuries, myofascial pain syndrome or degenerative abnormalities such as osteoarthritis and cervical spondylolysis. [3–5] Chronic neck pain is generally persistent and can cause functional disability,  limiting activity  and lowering quality of life. [6, 8]
Central sensitization (CS) is defined as “increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input.”  Many individuals with chronic pain, such as fibromyalgia, [10, 11] rheumatoid arthritis,  osteoarthritis,  low back pain,  and whiplash [11, 15] have presented an involvement of central sensitization and impaired endogenous pain modulation. Nevertheless, in individuals with nonspecific chronic neck pain, the presence of CS is not clear, the available literature provides an inconclusive message and more studies are required.  Then, to investigate the presence of central sensitization in nonspecific chronic neck pain compared to healthy controls may lead to more effective therapeutic approaches.
Previous studies have investigated deep tissue hyperalgesia in patients with chronic neck pain compared to healthy controls and evaluated the pressure pain threshold (PPT) in only one or two points on the neck. [17–20] Further, these studies have considered populations consisting of women,  adolescents,  elderly women,  female office workers  or patients with chronic whiplash.  We found only one study that has investigated the hyperalgesia considering more points on the neck and shoulder girdle area, however, only computers users were recruited.  Consequently, there is a lack of studies investigating local hyperalgesia in a larger area of the neck and upper back region in patients with nonspecific chronic neck pain compared to healthy controls.
We have found few studies that have investigated the central sensitization or psychosocial factors and in some cases the sample was composed only by women  or adolescents  or computers users26 with neck pain or it was considered only in patients with chronic whiplash.  Psychosocial factors play an important role in the chronification of neck pain.  Then, the correlation between psychosocial factors and pain intensity or neck disability is also important to promote a better therapeutic approach for patients with neck pain. Some studies have observed that greater pain catastrophizing was associated with greater neck disability [17, 22, 28] or greater pain intensity.  However, until this moment we have found no studies that have investigated the correlation between neck disability, pain intensity and depression symptoms or quality of life.
Individuals with neck pain seem to exhibit reduced active ROM. [29–31] A recent study showed that reduced neck mobility was associated with pain intensity, neck disability, fear of movement and central sensitization, however this study was performed only in females.  Therefore, more wide studies are needed to confirm this information. The active neck ROM is important variable that should be investigated in individuals with nonspecific chronic neck pain compared healthy controls in order to promote a more effective treatment.
As such, it is important to highlight that investigating central sensitization and psychosocial factors could contribute to more effective assessments and treatment choices for this population in the future. As such, the first aim of this study was to evaluate the possible differences in central sensitization (PPT, temporal summation (TS) of pain, conditioned pain modulation (CPM)), psychosocial factors (ie, depressive symptoms, pain catastrophizing and quality of life) and active neck range of motion (ROM) between individuals with nonspecific chronic neck pain and healthy controls. The second aim was to analyze the correlation between pain intensity, neck disability and psychosocial factors in individuals with nonspecific chronic neck pain. We hypothesized that individuals with nonspecific chronic neck pain would present central sensitization, presence of psychosocial factors, and reduced active neck ROM. In addition, we also hypothesized that psychosocial factors would be correlated with their pain intensity and/or neck disability.
The results of this study revealed lower PPT in the neck and shoulder girdle areas, a decrease in CPM, the presence of depressive symptoms, greater pain catastrophizing, lower quality of life, and reduced active ROM for rotation in individuals with chronic neck pain compared to healthy controls. In addition, as hypothesized, greater pain intensity and neck disability were moderately correlated with psychosocial factors.
Similarly to our findings in relation to PPT of the neck, other studies reported a decline in PPT in individuals with chronic NP when compared to controls. [17, 22, 23, 56–58] However, these studies investigated only one or two points on the neck and in our study PPT was measured in twelve points on neck and shoulder girdle areas.
With respect to PPT in TA muscle, our findings are in line with those of other studies that also reported no distant hyperalgesia in individuals with neck pain compared to healthy controls/ [17, 19, 21, 23, 24, 26, 59] By contrast, other studies have observed lower PPT values of the anterior tibialis muscle in individuals with neck pain when compared to healthy individuals. [22, 24, 57, 60] Given the controversial results regarding secondary hyperalgesia in individuals with neck pain, further research is needed to assess the presence of this variable.
In this study, topographical mapping confirmed that individuals with chronic neck pain showed greater pressure pain sensitivity. Additionally, the neck region was more sensitive than the shoulder girdle area in both groups, in agreement with Binderup at al.  In contrast with our findings, Ge et al, 2014 reported no significant differences in topographical pressure pain sensitivity maps between computer users with and without chronic pain in the neck.  However, it should be noted that the authors analyzed individuals who reported pain on the day of the experiment or in the last 24 hours, whereas individuals in the present study had experienced pain for more than 3 months.
Our findings are in line with other studies that also found no increase in TS in individuals with whiplash–associated disorders25 and musculoskeletal shoulder pain  compared to healthy controls. In this study, the effectiveness of CPM decreased in individuals with nonspecific chronic neck pain in relation to healthy controls. These findings indicate changes in the endogenous pain inhibition mechanism also observed in individuals with chronic low back pain.  However, in those with chronic neck pain, other studies found no decrease in the effectiveness of CPM in individuals with nonspecific chronic neck pain when compared to healthy controls. [21, 63]
The PPTs, TS of pain and CPM tests were used to investigate the presence of central sensitization in individuals with nonspecific chronic neck pain. As previously mentioned, the results obtained for these outcomes are controversial, however, central sensitization may be present in some individuals with neck pain  even though it is not characteristic in this population. 
As in our study, other studies displayed the presence of depressive symptoms, [64, 65] pain catastrophizing [17, 22, 64] and lower quality of life [18, 21] in individuals with chronic neck pain compared to controls. Assessing and treating these psychological factors are important in order to optimize the effectiveness of pain therapy for these individuals.
Individuals with neck pain exhibited reduced ROM for neck rotation when compared to healthy controls. Recent reviews concluded that individuals with neck pain seem to exhibit reduced active ROM for flexion, extension and rotation in relation to healthy individuals. [29, 30] It is important to highlight that these differences in findings may be related to the different measuring instruments used. In our investigation, active ROM of the cervical spine was measured with a fleximeter, whereas previous studies used other devices. [29, 30] In addition, some limitations are mentioned by aforementioned reviews [29, 30]: studies with no difference between patients and healthy controls are more likely to keep unpublished than those reporting positive results, inadequate blinding of evaluators may have enlarged the difference in measurements and there is a poor reporting in relation to test methods and evaluator background and training. Then, additional research with better quality and more detailed descriptions of the individuals and methods to obtain more consistent findings are needed.
Correlation between pain intensity, neck disability and psychosocial factors in individuals with neck pain.
The present study demonstrated that higher pain intensity is correlated with greater neck disability and low quality of life. In contrast with our results, MuñozGarcía et al, 2017 found no correlation between pain intensity and neck disability.  Our study also showed that neck disability is correlated with poor quality of life. In addition, the neck disability also is moderately correlated with pain catastrophizing, as reported in other studies with patients with neck pain. [17, 22, 28] Therefore, pain intensity and disability can affect quality of life, while neck disability may influence pain catastrophizing or vice versa, since a causal relation cannot be established. Based on these findings, these aspects should be evaluated, and the therapeutic approach requires more than analgesics and physical treatment modalities (electrophysical agents, manual therapy or exercises) to improve ROM. The presence of central sensitization and psychosocial factors makes it important to adopt a multidisciplinary approach as well as neurophysiological pain education to effectively rehabilitate these individuals.
The PPT at distant sites was only assessed in the middle third of the TA muscle and additional points should be evaluated to analyze the distant hyperalgesia mechanism in this group. Anxiety was not evaluated, and we think it is important to investigate it, and to verify if it is correlated with pain intensity or neck disability. It will provide more information that can be used for a better approach in the assessment and treatment of individuals with nonspecific chronic neck pain.
Local hyperalgesia, impaired conditioning pain modulation, depressive symptoms, pain catastrophizing, poor quality of life and reduced active ROM for neck rotation were observed in individuals with nonspecific chronic neck pain. Additionally, there is a significant correlation between intensity pain, neck disability and psychosocial factors. As such, pain management, neck mobility and psychosocial components should be assessed and taken into account in the therapeutic approach adopted for this population.
The authors gratefully acknowledge the individuals of this study
This study was supported by a grant (É.P.R.) from Fundação de Amparo à Pesquisa do Estado de São Paulo (2017/26447–2).
The authors completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest.
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