Hypoaesthesia occurs with sensory hypersensitivity in chronic whiplash – Further evidence of a neuropathic condition

An investigation of somatosensory profiles in work related upper limb disorders: a case-control observational study protocol

Background

Work related upper limb disorders constitute 45% of all occupational diseases and are a significant public health problem. A subgroup, non specific arm pain (NSAP), remains elusive in terms of understanding its pathophysiological mechanisms with its diagnosis based on the absence of specific clinical findings. One commonly proposed theory is that a neural tissue disorder is the primary dysfunction in NSAP and findings from previous studies lend some support to this theory. However, it is not clear if changes identified are simply a consequence of ongoing pain rather than due to specific neural changes. The presence of neuropathic pain has been investigated in several other musculoskeletal conditions but currently, there is no specific diagnostic tool or gold standard which permits an unequivocal diagnosis of neuropathic pain. The purpose of this study is to further describe the somatosensory profiles in patients with NSAP and to compare these profiles to a group of patients with MRI confirmed cervical radiculopathy who have been previously classified as having neuropathic pain.

Methods/Design

Three groups of participants will be investigated: Groups 1 and 2 will be office workers with either NSAP or cervical radiculopathy and Group 3 will be a control group of non office workers without upper limb pain. Participants will undergo a clinical assessment, pain questionnaires (LANSS, Short Form McGill, DASH and TSK) and quantitative sensory testing comprising thermal detection and pain thresholds, vibration thresholds and pressure pain thresholds.

Discussion

The spectrum of clinically suspected neuropathic pain ranges from more obvious conditions such as trigeminal neuralgia to those with vague signs of nerve disorder such as NSAP. A thorough description of the somatosensory profiles of NSAP patients and a comparison with a more defined group of patients with evidence of neuropathic pain will help in the understanding of underlying neurophysiology in NSAP and may influence future classification and intervention studies relating to this condition.

Bilateral thermal hyperalgesia in trigeminal and extra-trigeminal regions in patients with myofascial temporomandibular disorders

Our aim was to assess thermal sensitivity in both trigeminal and extra-trigeminal regions in patients with myofascial temporomandibular disorder (TMD) but without comorbid conditions as compared to age-matched controls. Twenty women (age 24 +/- 3 years) diagnosed with myofascial TMD according to the research diagnostic criteria for TMD and 20 healthy women (age 24 +/- 4 years) were included. Warm and cold detection thresholds (WDT and CDT, respectively) and heat and cold pain thresholds (HPT and CPT, respectively) were bilaterally assessed over the masseter and frontalis muscles (trigeminal regions) and the wrist (extra-trigeminal region). The mean of three determinations at each site was calculated and used for analysis. The order of the test sites was randomized. A two-way ANOVA was used to test for differences between groups and sides (most painful/contra-lateral side; dominant/non-dominant). No significant differences between groups for WDT or CDT in trigeminal and extra-trigeminal regions (ANOVA, P > 0.389) were found. There were significant differences between groups, but not between sides, for HPT and CPT in both trigeminal and extra-trigeminal areas (ANOVA, P < 0.001). CPT (P < 0.001) over the trigeminal area was positively correlated with both pain intensity and duration of pain symptoms: the longer the history of pain or the greater the pain intensity, the higher the CPT (i.e., the greater cold hyperalgesia) over the trigeminal region. Our findings revealed bilateral thermal hyperalgesia (lower HPT and higher CPT) but normal WDT and CDT in trigeminal and extra-trigeminal regions in women with myofascial TMD as compared to healthy controls. Bilateral heat/cold hyperalgesia in trigeminal and extra-trigeminal areas may reflect a dysfunction of thermal channels in myofascial TMD patients as result of some combination of peripheral sensitization, facilitation of central nociceptive processing and/or decreased descending inhibition.

Relationships between pain thresholds, catastrophizing and gender in acute whiplash injury

The mechanisms underlying sensory hypersensitivity (SH) in acute whiplash associated disorders (WAD) are not well understood. We examined the extent of the relationships between the sensory measures of pressure pain threshold (PPT) and cold pain threshold (CPT), catastrophizing, pain and disability levels and gender in acute WAD. Thirty-seven subjects reporting neck pain following a motor vehicle accident were examined within five weeks post-injury. Measures of neck pain and disability (Neck Disability Index, NDI) and catastrophizing (Pain Catastrophizing Scale, PCS) were taken. CPT was assessed in the cervical spine and PPTs were assessed in the cervical spine (PPTcx) and at a remote site (PPTdistal). CPT and PCS were moderately correlated (r=0.46; p < 0.01); however there were no significant relationships between PPT (cervical and distal) and PCS. Both CPT (r=0.55, p < 0.01) and PPTcx (r=-0.42, p < 0.01) were significantly correlated with NDI but PPTdistal was not (r=-0.08, p=0.65). Finally, gender modulated the relationships between sensory measures, catastrophizing, and pain and disability levels. In conclusion, subjects with higher levels of catastrophizing presented with sensory hypersensitivity to cold stimuli in the acute phase of whiplash. Differences between genders are in accordance with the growing body of evidence suggesting that the relationships between some psychological factors and injury-related symptoms are modulated by gender.

Developing biologically-based assessment tools for physical therapy management of neck pain

SYNOPSIS

Neck pain is a common and episodic condition that is treated using a spectrum of interventions known to be moderately effective but is associated with a significant incidence of chronic pain. Recently, there has been increased focus on defining biological aspects of neck pain. Studies have indicated that neurophysiological, biomechanical, and motor control abnormalities are present and may be useful either in prognosis or classification. We review some of these findings in the context of our own work defining biological markers that may form the basis for clinical tests that can be used for prognosis, classification, or outcome evaluation in patients with neck pain. We have identified abnormalities in neurophysiology using quantitative sensory testing (vibration, touch, and current perception) and response to cold provocation that are related to neck disability. We have identified altered muscle biochemistry by measuring circulating muscle proteins in a lumbar surgery model and are now applying those methods to whiplash injury. We have incorporated capnography into treatment to address central physiological changes present in some patients by monitoring and training CO2 levels. We have developed an innovative new test, the Neck Walk Index, that captures abnormal control of head movement during slow gait as a means of differentiating patients with neck pain from either unaffected controls or individuals with other pathologies. We have used time-varying 3-dimensional joint orientation kinematics to assess deficits in motor control during an upper extremity reach task, the results showing that poor coordination and control of the shoulder girdle leads to shoulder guarding and inconsistencies in elbow joint movement. Despite some promising early results, future research is needed to determine how these measures help clinicians to diagnose, evaluate, and forecast future outcome for patients who present with neck pain.

LEVEL OF EVIDENCE

Diagnosis, level 5.

A neuropathic pain component is common in acute whiplash and associated with a more complex clinical presentation

Whiplash is a heterogeneous condition with some individuals showing features suggestive of neuropathic pain. This study investigated the presence of a neuropathic pain component in acute whiplash using the Self-reported Leeds Assessment of Neuropathic Signs and Symptoms' scale (S-LANSS) and evaluated relationships among S-LANSS responses, pain/disability, sensory characteristics (mechanical, thermal pain thresholds, and Brachial plexus provocation test (BPPT) responses) and psychological distress (General Health Questionnaire-28 (GHQ-28)). Participants were 85 people with acute whiplash (<4 weeks) (54 females, age 36.27+/-12.69 years). Thirty-four percent demonstrated a predominantly neuropathic pain component (S-LANSS>or=12). This group showed higher pain/disability, cold hyperalgesia, cervical mechanical hyperalgesia, and less elbow extension with the BPPT (p<0.03) when compared to the group with non-neuropathic pain (S-LANSS<or=12). Pressure pain thresholds (PPTs) at distant sites and psychological distress (GHQ-28) were not different between the groups (p>0.09). None of the S-LANSS items could discriminate those with cold hyperalgesia (p=0.06). A predominantly neuropathic pain component is related to a complex presentation of higher pain/disability and sensory hypersensitivity. The S-LANSS may be a useful tool and the BPPT a useful clinical test in the early assessment of whiplash.