Differences in the clinical presentation of chronic whiplash-associated disorders and nontraumatic neck pain: a systematic review and meta-analysis

ABSTRACT

Health outcomes may be worse for individuals with whiplash-associated disorders (WAD) compared to nontraumatic neck pain (NTNP), and clinical characteristics may differ. This systematic review examined evidence comparing WAD and NTNP in terms of pain, disability, psychological status, quality of life, measures of nociceptive processing, movement, sensorimotor, and muscle function. Studies were identified through electronic database searches and included after screening against predefined eligibility criteria. Standardized mean differences (SMD) or mean differences (MD) and 95% confidence intervals (CI) were calculated. Associations between MDs with demographics and study characteristics were explored using meta-regression. Certainty of evidence was assessed using Grades of Recommendation, Assessment, Development, and Evaluation. Sixty-one studies were eligible with 45 included in meta-analysis. Individuals with WAD reported clinically relevant higher disability (100-point Neck Disability Index MD [95% CI] 11.15 [8.63, 13.68]), greater remote cold sensitivity (SMD 0.89 [0.57, 1.21]), lower quality of life (SMD -0.96 [-1.77, -0.16]), greater depression (SMD 0.60 [0.27, 0.93]), greater local (SMD -0.56 [-1.00, -0.13]) and remote (SMD -0.50 [-0.81, -0.19]) pressure sensitivity, less cervical flexion (MD -5.30° [-7.44, -3.16]) and extension (MD -5.43° [-9.31, -1.55]), higher pain intensity (100-point numerical rating scale: MD 8.15 [5.80, 10.50]), and greater kinesiophobia (SMD 0.35 [0.11, 0.59]). No between-group differences were found for dizziness symptoms, stress, anxiety, balance, and local cold sensitivity. Meta-regression indicated that disability differences were negatively associated with age (R2 = 29.6%, P = 0.006). Certainty of evidence was mostly moderate. Individuals with chronic WAD have a worse clinical presentation compared to those with chronic NTNP, which has implications for patient assessment and management.

A Randomized, Double-Blind, Controlled Trial Protocol for Therapeutic Neuroscience Education in Chronic Migraine Patients: A Clinical-Neurophysiological Combined Study Design

Chronic migraine (CM) is a highly disabling condition, affecting about 2% of the global population. Non-pharmacological treatments can be optimal for their non-invasive nature. This prospective, randomized, double-blind, controlled trial aimed to test the efficacy of therapeutic neuroscience education (TNE) in CM. Early response biomarkers were also evaluated. A total of 80 CM patients were consecutively enrolled and randomly allocated to TNE or a general education program. Treatment effectiveness was evaluated at baseline (T1) and 2 months after the end of treatment (T4). We collected the responses to disability and comorbidity questionnaires at the start (T1) and end of treatment (T3, 10 weeks after start). Early response biomarkers were evaluated at screening (T0) and mid-way through the process (T2, 5 weeks after start). We expected that TNE would provide a greater benefit than the general education program, which served as the primary outcome of this study. We also expected that a change in clinical and neurophysiological measures could potentially occur, reflecting plasticity-induced reorganization and predicting clinical response. This is the first study selectively exploring the effect of TNE as a standalone treatment for CM. A new, effective treatment regime without interactions with other medication could be of great interest as an addition to migraine therapeutic strategies.

IL-6 from cerebrospinal fluid causes widespread pain via STAT3-mediated astrocytosis in chronic constriction injury of the infraorbital nerve

BACKGROUND

The spinal inflammatory signal often spreads to distant segments, accompanied by widespread pain symptom under neuropathological conditions. Multiple cytokines are released into the cerebrospinal fluid (CSF), potentially inducing the activation of an inflammatory cascade at remote segments through CSF flow. However, the detailed alteration of CSF in neuropathic pain and its specific role in widespread pain remain obscure.

METHODS

A chronic constriction injury of the infraorbital nerve (CCI-ION) model was constructed, and pain-related behavior was observed on the 7th, 14th, 21st, and 28th days post surgery, in both vibrissa pads and hind paws. CSF from CCI-ION rats was transplanted to naïve rats through intracisternal injection, and thermal and mechanical allodynia were measured in hind paws. The alteration of inflammatory cytokines in CCI-ION's CSF was detected using an antibody array and bioinformatic analysis. Pharmacological intervention targeting the changed cytokine in the CSF and downstream signaling was performed to evaluate its role in widespread pain.

RESULTS

CCI-ION induced local pain in vibrissa pads together with widespread pain in hind paws. CCI-ION's CSF transplantation, compared with sham CSF, contributed to vibrissa pad pain and hind paw pain in recipient rats. Among the measured cytokines, interleukin-6 (IL-6) and leptin were increased in CCI-ION's CSF, while interleukin-13 (IL-13) was significantly reduced. Furthermore, the concentration of CSF IL-6 was correlated with nerve injury extent, which gated the occurrence of widespread pain. Both astrocytes and microglia were increased in remote segments of the CCI-ION model, while the inhibition of astrocytes in remote segments, but not microglia, significantly alleviated widespread pain. Mechanically, astroglial signal transducer and activator of transcription 3 (STAT3) in remote segments were activated by CSF IL-6, the inhibition of which significantly mitigated widespread pain in CCI-ION.

CONCLUSION

IL-6 was induced in the CSF of the CCI-ION model, triggering widespread pain via activating astrocyte STAT3 signal in remote segments. Therapies targeting IL-6/STAT3 signaling might serve as a promising strategy for the widespread pain symptom under neuropathological conditions.

Neural correlates of central pain sensitization in chronic low back pain: a resting-state fMRI study

PURPOSE

The objective of this study is to explore the neural correlates of pain sensitization in patients with chronic low back pain (cLBP). While the association between cLBP and pain sensitization has been widely reported, the underlying brain mechanism responsible for this relationship requires further investigation.

METHODS

Our study included 56 cLBP patients and 56 healthy controls (HC). Functional magnetic resonance imaging data were obtained, and the voxel-wise amplitude of low-frequency fluctuation (ALFF) was calculated to identify brain alterations in cLBP patients compared to HC groups. Pearson correlation coefficients were computed to explore the association between clinical data and brain alterations. Furthermore, mediation analyses were performed to investigate the path association between brain alterations and pain-related behaviors.

RESULTS

Our findings revealed that patients with cLBP exhibited higher sensitivity, attention, and catastrophizing tendencies towards pain compared to HC. Furthermore, cLBP patients displayed significantly higher ALFF in various brain regions within the "pain matrix" and the default mode network when compared to HC. The altered precuneus ALFF was positively correlated with pain intensity (R = 0.51, P<0.001) and was negatively correlated with pain sensitivity (R = -0.43, P<0.001) in cLBP patients. Importantly, the effect of altered precuneus ALFF on pain intensity was mediated by pain threshold in these patients.

CONCLUSION

Our study suggests that altered neural activity in the precuneus may contribute to pain hypersensitivity, which further exacerbating pain in cLBP patients.

Deficits in the thalamocortical pathway associated with hypersensitivity to pain in patients with frozen shoulder

Background and purpose

Frozen shoulder (FS) is a chronic pain condition and has been shown to be associated with pain sensitization. However, the underyling brain mechanisms remain unclear. Here, we aimed to explore brain alterations and their association with pain sensitization in patients with FS.

Materials and methods

A total of 54 FS patients and 52 healthy controls (HCs) were included in this study. Here, we applied both structural and functional magnetic resonance imaging (MRI) techniques to investigate brain abnormalities in FS patients. Voxel-wise comparisons were performed to reveal the differences in the gray matter volume (GMV) and amplitude of low-frequency fluctuation (ALFF) between FS patients and HCs. Furthermore, the region of interest (ROI) to whole-brain functional connectivity (FC) was calculated and compared between groups. Finally, Pearson's correlation coefficients were computed to reveal the association between clinical data and brain alterations.

Results

Four main findings were observed: (1) FS patients exhibited decreased thalamus GMV, which correlated with pain intensity and pain threshold; (2) relative to HCs, FS patients exhibited a higher level of ALFF within the anterior cingulate cortex (ACC) and the thalamus; (3) FS patients exhibited a significant increase in Tha-S1 FC compared to HCs; and (4) the effect of thalamus GMV on pain intensity was mediated by pain threshold in FS patients.

Conclusion

The dysfunctional thalamus might induce pain hypersensitivity, which further aggravates the pain in FS patients.

Myofascial Pain Syndrome: A Nociceptive Condition Comorbid with Neuropathic or Nociplastic Pain

Myofascial pain syndrome is featured by the presence of myofascial trigger points (TrPs). Whether TrPs are primary or secondary phenomena or if they relate to central or peripheral nervous system disorders is controversial. Referred pain, a cardinal sign of TrPs, is a central phenomenon driven by peripheral input. In 2021, the International Association for the Study of Pain (IASP) proposed a clinical criteria and grading system for classifying patients with pain on nociceptive, neuropathic, or nociplastic phenotypes. Myofascial TrP pain has been traditionally categorized as a nociceptive phenotype; however, increasing evidence supports that this condition could be present in patients with predominantly nociplastic pain, particularly when it is associated with an underlying medical condition. The clinical response of some therapeutic approaches for managing TrPs remains unclear. Accordingly, the ability to classify myofascial TrP pain into one of these phenotypes would likely be critical for producing more successful clinical treatment outcomes by a precision medicine approach. This consensus paper presents evidence supporting the possibility of subgrouping individuals with myofascial TrP pain into nociceptive, nociplastic, or mixed-type phenotype. It is concluded that myofascial pain caused by TrPs is primarily a nociceptive pain condition, is unlikely to be classified as neuropathic or nociplastic, but can be present in patients with predominantly neuropathic or nociplastic pain. In the latter cases, management of the predominant central pain problem should be a major treatment goal, but the peripheral drive from TrPs should not be ignored, since TrP treatment has been shown to reduce sensitization-associated symptomatology in nociplastic pain conditions, e.g., fibromyalgia.

Pressure Pain Threshold of the Upper Trapezius Trigger Point: A Systematic Review with Meta-Analysis of Baseline Values and Their Modification after Physical Therapy

BACKGROUND

Myofascial trigger points (TrP) are diagnosed upon the presence of clinical signs among which hypersensitivity is considered one of the most important. The detection of the pressure pain threshold (PPT) is used to quantify the degree of hypersensitivity. However, there is a lack of normative data about how hypersensitive a TrP is. Therefore, the objective was to quantify the PPT for myofascial TrP in the upper trapezius muscle and its modification after manual or instrumental physical therapy interventions.

METHODS

A systematic review and meta-analysis were conducted among three databases (MEDLINE, Cochrane Library, and PEDro). Two independent reviewers conducted the electronic search and assessed the methodological quality of the included studies.

RESULTS

Eleven studies with a high-risk bias indicated that the PPT at TrP sites was 105.11 kPa lower (95% CI: -148.93; -61.28) at active TrP sites (Chi-squared = 1.07, df = 1 (p = 0.30), I2 = 7%) compared to the PPT of the upper trapezius muscles of healthy subjects. In addition, the PPT of TrP was also lower than the reference values coming from the pain-free population. Moreover, the PPT increased after both manual and instrumental treatment by 28.36 kPa (95% CI: 10.75; 45.96) and 75.49 kPa (95% CI: 18.02; 132.95), respectively.

CONCLUSIONS

The results of the present study show that TrP has a decreased PPT when compared to healthy muscles and that physical therapy may increase the PPT. However, the clinical relevance of this decreased PPT needs to be further elucidated. Further, the high risk of bias in all the retrieved studies undermines the validity of the results.

Clinical efficacy and learning curve of posterior percutaneous endoscopic cervical laminoforaminotomy for patients with cervical spondylotic radiculopathy

In this study, we aimed to investigate the clinical efficacy and learning curve of posterior percutaneous endoscopic cervical laminoforaminotomy (PPECLF) in patients with cervical spondylotic radiculopathy (CSR). A total of 64 patients with CSR received PPECLF. Clinical outcome scores included the visual analog scale, Japanese Orthopedic Association score, neck disability index, and modified Macnab criteria. Radiological outcomes included the disc height, C2 to C7 Cobb angle, and range of motion. The learning curve was evaluated using cumulative sum analysis. Patients were divided into accumulation phase and mastery phase groups (A and B), and general data and surgical efficacy were compared between the 2 groups. Follow-up ranged from 12 to 24 months. Clinical outcome scores improved significantly at the final follow-up, and there were no differences in radiological outcomes. Surgical efficacy was excellent and good in 82.8% of patients. The operative time showed a decreasing trend with the accumulation of cases. Patients were divided and the 26th case was the cutoff point according to the learning curve. No significant differences were found in the clinical outcomes between the 2 groups. Decompression with PPECLF was safe and effective in the treatment of CSR. With the accumulation of cases, the operative time was gradually shortened, and the clinical efficacy was significant. The PPECLF procedure can be performed efficiently and safely to treat CSR.

Enhanced amygdala-frontal operculum functional connectivity during rest in women with chronic neck pain: Associations with impaired conditioned pain modulation

BACKGROUND

Chronic neck pain is a leading cause of disability worldwide, affecting the lives of millions of people. Research investigating functional brain alterations in relation to somatosensory function is necessary to better understand mechanisms underlying pain development and maintenance in individuals with chronic neck pain, yet remains scarce. This case-control study aimed to examine resting-state functional connectivity alterations and associations with pain outcomes, self-reported central sensitization-related symptoms and quantitative sensory testing (QST) measures in patients with chronic non-traumatic (idiopathic/CINP) neck pain and chronic traumatic (whiplash associated/CWAD) neck pain compared to pain-free controls.

METHODS

Resting-state functional magnetic resonance images were acquired in 107 female participants (38 CINP, 37 CWAD, 32 healthy controls). After data pre-processing, seed-to-seed analyses were conducted focusing on resting-state functional connectivity involving pre-defined regions of interest that have previously been observed to be structurally or functionally altered and/or associated with pain-related measures in this patient population.

RESULTS

Findings demonstrate enhanced left amygdala functional coupling during rest with the left frontal operculum in women with CINP and CWAD compared to controls. This increased resting-state functional connectivity was associated with more self-reported symptoms related to central sensitization and decreased efficacy of conditioned pain modulation. Furthermore, enhanced connectivity between the left amygdala and left frontal orbital cortex, and between the left pallidum and the left frontal operculum was observed only in patients with CWAD compared to healthy controls. In patients, additional associations between local hyperalgesia and enhanced connectivity between the left superior parietal cortex and the left and right precentral gyrus were found.

CONCLUSIONS

In line with our hypotheses, patients with CWAD showed the most pronounced alterations in resting-state functional connectivity, encompassing subcortical limbic (amygdala) and basal ganglia (pallidum), and ventral frontal regions (frontal operculum, orbitofrontal cortex) when compared to CINP and controls. Findings are generally in line with the idea of a continuum, in absence of significant group differences across CINP and CWAD. Enhanced amygdala-frontal operculum functional connectivity was the most robust and only connectivity pair in the cluster that was associated with QST (i.e., dynamic QST; endogenous pain inhibition), and that was observed in both patient groups. In addition, independent of group differences, enhanced resting-state functional connectivity between superior parietal cortex (involved in attention) and primary motor cortex was associated with static QST (i.e., greater local hyperalgesia). Taken together, our findings show a key role for enhanced amygdala-ventral frontal circuitry in chronic neck pain, and its association with diminished endogenous pain inhibition further emphasizes the link between cognitive-affective and sensory modulations of pain in women with chronic non-traumatic and traumatic neck pain.

Local and Widespread Pressure Pain Hyperalgesia Is Not Side Specific in Females with Unilateral Neck Pain that Can Be Reproduced during Passive Neck Rotation

Current evidence for widespread hyperalgesia in non-specific neck pain (NSNP) is unclear. It is currently recommended to group NSNP patients according to pain-provoking movements. The aim of this study was to investigate local and widespread pain sensitivity in females with unilateral NSNP that is reproducible during passive neck rotation compared with matched controls, and to compare the side specific effect of pain location on pressure pain sensitivity among females with unilateral NSNP. Thirty-six females with unilateral NSNP evoked during passive ipsilateral (n = 20) or contralateral (n = 16) rotation toward the painful side were compared with 20 controls. Participants reported their pain intensity at rest and during passive neck rotation and completed the Neck Disability Index. Pressure pain thresholds (PPTs) were assessed bilaterally over the anterior scalene; the sternocleidomastoid; the levator scapulae; lateral to the spinous process of C6; the median, ulnar, and radial nerves; and the tibialis anterior. The ANOVA revealed lower PPTs in females with unilateral NSNP compared with the controls (all at p < 0.001), but no differences were found between the sides, nor was there any Group × side interaction. Among females with NSNP, those with higher pain intensity during ipsilateral rotation toward the painful side showed lower PPTs over the anterior scalene, median nerve, ulnar nerve, and tibialis anterior (all, p < 0.05) than females with higher pain intensity during contralateral rotation toward the painful side. These findings demonstrated bilateral local and widespread pressure pain hyperalgesia in females with unilateral NSNP that was reproducible during passive neck rotation compared with controls. There was no side specific effect of pain location on PPTs among females with unilateral NSNP.