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

Abstract

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.

Introduction

Whiplash injury results in chronic pain and disability in up to 40% of individuals (Barnsley et al., 1994, Sterling et al., 2005) and contributes to substantial personal and societal costs. Whiplash associated disorders (WADs) is characterized by a diversity of clinical manifestations including both physical and psychological symptoms.

Studies have demonstrated the presence of sensory hypersensitivity (SH) in a variety of subjects (Sheater-Reid and Cohen, 1998, Moog et al., 2002, Sterling et al., 2003). While most studies have investigated SH in chronic WAD, sensory disturbances are thought to be present early after the injury (Sterling et al., 2003). It is estimated that approximately 22% of people with WAD present with SH within four weeks post-injury and that symptoms persist to the chronic phase (Sterling et al., 2003). In neck disorders, SH may be confined to the neck but may also be generalized to remote body parts (Curatolo et al., 2001, Sterling et al., 2003). The mechanisms underlying SH in WAD have not been clearly demonstrated yet, but it is generally accepted that SH reflects augmented central pain processing mechanisms (Banic et al., 2004, Curatolo et al., 2004, Herren-Gerber et al., 2004).

Moreover, we cannot rule out the possible influence of psychological factors in the development of SH symptoms. It has been demonstrated that fear and anxiety have an effect on pain tolerance (Rhudy and Meagher, 2000). There is also some support from monkey experiments for the influence of cognitive and behavioural alterations on injury-induced sensitization (Dubner and Ren, 1999).

One emerging variable of interest that has not been well investigated in whiplash injury is catastrophizing - an exaggerated negative orientation toward noxious stimuli (Rosenstiel and Keefe, 1983, Sullivan et al., 1995, Söderlund and Lindberg, 1999). Higher levels of catastrophizing have previously been associated with persistent pain and disability levels in a variety of chronic musculoskeletal conditions including WAD (Sullivan et al., 2002, Carroll et al., 2006). A relationship between catastrophizing and decreased pain thresholds has also demonstrated in fibromyalgia (Geisser et al., 2003) but not in chronic neuropathic pain (Sullivan et al., 2005). Only one study evaluated the relationship between catastrophizing and sensory measures in WAD. Sterling et al. (2008) found a moderate association between catastrophizing and cold pain threshold but not with pressure pain threshold or nociceptive flexion reflex (NFR) in chronic whiplash (mean duration of symptoms post-injury = 18 months). Surprisingly, catastrophizing has never been assessed in the acute phase of a whiplash injury.

Finally, a growing body of literature suggests that men and women differ with respect to their perception and experience of pain (Bernades et al., 2008, Hurley and Adams, 2008). It is acknowledged that these differences reflect both biological and psychological factors, since significant sex differences have previously been reported in expressing psychological and sensory characteristics (Edwards et al., 2004, Sullivan et al., 2005, Rolke et al., 2006).

Since SH is already present in the early stage of WAD and catastrophizing has not been evaluated in acute whiplash, the objective of the study was to investigate the relationship between the sensory measures of pressure pain threshold (PPT) and cold pain threshold (CPT), catastrophizing and pain and disability levels in subjects with acute WAD. We also examined whether these relationships were influenced by gender.