Psychologic factors are related to some sensory pain thresholds but not nociceptive flexion reflex threshold in chronic whiplash.
OBJECTIVE
Sensory hypersensitivity, central hyperexcitability [lowered nociceptive flexion reflex (NFR) thresholds], and psychologic distress are features of chronic whiplash. However, relationships between these substrates are not clear. This study tested the hypothesis that psychologic distress and catastrophization are correlated with sensory hypersensitivity and NFR responses in chronic whiplash.


METHODS
Pressure and thermal pain thresholds (mean values across 3 body sites), NFR threshold, and pain at threshold Visual Analog Scale were measured in 30 participants with chronic whiplash and 30 asymptomatic controls. Pain and disability levels Neck Disability Index, psychologic distress (GHQ-28), and catastrophization (PCS) were also measured in the whiplash group.


RESULTS
Whiplash injured participants demonstrated lowered pain thresholds to pressure and cold (P<0.05); lowered NFR thresholds (P=0.003), and demonstrated above threshold levels of psychologic distress (GHQ-28) and levels of catastrophization comparable with other musculoskeletal conditions. There were no group differences for heat pain thresholds or pain at NFR threshold. In the whiplash group, PCS scores correlated moderately with cold pain threshold (r=0.51, P=0.01). In contrast, there were no significant correlations between GHQ-28 scores and pain threshold measures or between psychologic factors and NFR responses in whiplash participants. There were no significant correlations between psychologic factors and pain thresholds or NFR responses in controls.


CONCLUSIONS
We have demonstrated that psychologic factors have some association with sensory hypersensitivity (cold pain threshold measures) in chronic whiplash but do not seem to influence spinal cord excitability. This suggests that psychologic disorders are important, but not the only, determinants of central hypersensitivity in whiplash patients.
Sterling
Michele
M
Centre for National Research on Disability and Rehabilitation Medicine, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. m.sterling@uq.edu.au
Hodkinson
Emily
E
Pettiford
Catherine
C
Souvlis
Tina
T
Curatolo
Michele
M
D000328:Adult; D002908:Chronic Disease; D003080:Cold Temperature / Q000009:adverse effects; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D008875:Middle Aged; D009483:Neuropsychological Tests; D009619:Nociceptors / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology*; D010148:Intractable Pain / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology*; D010812:Physical Stimulation; D011312:Pressure / Q000009:adverse effects; D011602:Psychophysiologic Disorders / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D012021:Reflex, Abnormal / Q000502:physiology; D013315:Stress, Psychological / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D014911:Whiplash Injuries / Q000150:complications / Q000503:physiopathology* / Q000523:psychology*