Decreased Regional Grey Matter Volume in Women with Chronic Whiplash-Associated Disorders: Relationships with Cognitive Deficits and Disturbed Pain Processing.

BACKGROUND

Patients with chronic whiplash-associated disorders (CWAD) are characterized by pain of traumatic origin, cognitive deficits, and central sensitization (CS). Previous neuroimaging studies revealed altered grey matter volume (GMV) in mild traumatic brain injury patients and chronic pain conditions also characterized by CS. It can therefore be hypothesized that GMV alterations also play a role in the persistent complaints of CWAD. However, brain alterations remain poorly investigated in these patients.

OBJECTIVES

This study examined regional GMV alterations in patients with CWAD compared to patients with non-traumatic chronic idiopathic neck pain (CINP), who normally do not show CS at a group level, and healthy controls. Additionally, in both patient groups, relationships between regional GMV and measures of cognition as well as pain processing were assessed.

STUDY DESIGN

A cross-sectional case-control study.

SETTING

This study was performed at the Department of Rehabilitation Sciences and Physiotherapy of Ghent University in cooperation with the Ghent Institute for Functional and Metabolic Imaging.

METHODS

Ninety-three women (28 healthy controls, 34 CINP patients, and 31 CWAD patients) were enrolled. First, T1-weighted magnetic resonance images (MRIs) were acquired to examine GMV alterations in the brain regions involved in processing cognition and pain. Next, cognitive performance, pain cognitions, and CS symptoms were assessed. Finally, hyperalgesia and conditioned pain modulation efficacy were examined.

RESULTS

Regional GMV of the right lateral orbitofrontal cortex, left supramarginal cortex, and left posterior cingulate cortex was decreased in CWAD patients compared to healthy controls (P = 0.023; P = 0.012; P = 0.047, respectively). Additionally, GMV of the right superior parietal cortex and left posterior cingulate cortex was decreased in CWAD patients compared to CINP patients (P = 0.008; P = 0.035, respectively). Decreased regional GMV correlated with worse cognitive performance, higher maladapted pain cognitions, CS symptoms, and hyperalgesia in CWAD patients (rs = -0.515 to -0.657; P < 0.01). In CINP patients, decreased regional GMV correlated only with worse cognitive performance (rs = -0.499 to -0.619; P < 0.01), and no GMV differences compared with the controls could be revealed.

LIMITATIONS

No conclusions about the causality of the observed relationships can be drawn.

CONCLUSIONS

These results provide the first evidence for reduced GMV in cortical regions involved in processing cognition and pain in patients with CWAD. Accordingly, it is recommended that therapy approaches for CWAD patients should address the brain and take into account neuroplasticity of the central nervous system (CNS).

KEY WORDS

Whiplash injuries, neck pain, magnetic resonance imaging, grey matter, cognitive dysfunction, pain catastrophizing, central sensitization.