Presenting signs and symptoms

Clearly, the most consistent predictor of poor functional recovery is the intensity of neck pain at the initial or baseline assessment point.^2–6 Walton et al.⁵ synthesised the data from eight cohorts and established a cut-off point of 55 out of 100 or 5 out of 10 on a visual analogue pain scale. These authors report that a pain intensity of greater than 55 out of 100 demonstrated a nearly sixfold (OR, 5.77; 95% CI: 2.89–11.52) increase in the risk of persistent pain or disability at follow-up. This factor was slightly more robust at predicting an outcome of disability when compared to pain outcomes.⁵ Initially, moderate-to-high levels of pain-related disability have also shown predictive capacity.⁸

Some reviews pointed to other symptoms, such as the presence of headache,⁵ or neurological symptoms, such as arm pain or paraesthesia, as also showing predictive capacity.² The Quebec Task Force classification (see Chapter 1 for description), a predominantly symptom-based system, was evaluated in two reviews, with the authors concluding that increasing grades of whiplash associated disorders (WAD) predicted increasingly higher pain intensities and disability two years later.^{5, 7} Walton et al.⁵ reported that the size of effect was significant when WAD grades II and III were compared against grades I and 0, and this effect was consistent at various follow-up time points.

Other symptoms, such as dizziness, reported sleep disturbances and cognitive difficulties, have not emerged from the systematic reviews as showing any predictive capacity.^2–6

Crash-related factors

Numerous crash-related factors have been investigated for their predictive capacity. Some of these include the vehicle being stationary when hit, a frontal collision, a rear-end collision, side or other collision, being unprepared for the collision, no seat belt use and no head restraint. However, few of these factors have demonstrated significant predictive power. The exceptions to this are not wearing a seat belt, which was reported to nearly double the risk of developing persistent pain or disability.⁵ This is an interesting finding as, in certain jurisdictions where compulsory seat belt use is legislated, the voluntary admission of not wearing a seat belt would not be expected to be common, particularly in jurisdictions operating under a fault-based system. Thus, it is possible that the risk of developing a chronic condition associated with not wearing a seat belt may be even higher than that reported by Walton and colleagues.⁵ Scholten-Peeters et al.⁴ reported some limited prognostic value for accidents that occur on a highway, but also reported that there was strong evidence that rear-end collisions have no predictive value for poor functional recovery.

Thus, the weight of evidence indicates that crash-related factors are of limited value in attempting to predict poor recovery following whiplash injury.

Sociodemographic factors

The predictive capacity of sociodemographic factors has been studied extensively in musculoskeletal pain conditions, and whiplash is no exception. Older age (>50 years), while showing predictive value in some original studies,^{8, 9} when subjected to systematic review seems to not be a strong prognostic factor,⁵ with some reporting that there is strong evidence for no predictive value of this factor.⁴ Similar conclusions have been made for female gender,^{4, 5} with only one review reporting predictive value of either of these factors.² Since this review by Côté et al. was the first to be conducted for WAD, later systematic reviews will have included a greater number of primary studies, which would suggest that at this point in time these factors should not be considered as having predictive capacity.

Lower education level, defined as no post secondary education, has been identified in five cohorts and appears to be a risk factor for poor recovery,⁵ although it is possible that this factor may be mediated by the type of occupation held by those with this risk factor.⁷ The clinical usefulness of this prognostic indicator is questionable as its modification cannot be achieved in the context of the clinical management of WAD.

Potentially modifiable risk factors, such as obesity, have not shown a significant effect on outcomes in three different cohorts.⁵

Health status prior to whiplash injury

It would seem feasible that poorer health status prior to the motor vehicle crash (MVC) may have a detrimental influence on recovery, and this issue has been explored in relation to the onset of more widespread pain conditions.¹⁰ Most studies of whiplash have focused on the existence of previous neck pain or headache and the determination of these prior conditions was usually by patient self-report, which may be associated with recall bias.⁵ While individual studies have reported conflicting findings, the general consensus of most systematic reviews is that these factors do not have predictive value.^{4, 5, 7} The review that performed meta-analysis found only a small, yet significant, risk of developing persistent whiplash pain if the individual reported prior neck pain but no significant effect for prior headache.⁵

Few studies have investigated the predictive capacity of pre-existing neck ‘pathology’ or structural changes, and Carroll et al.⁷ noted that they could find no scientifically admissible studies addressing this factor. One recent study not included in the systematic reviews found that pre-existing degeneration, identified using magnetic resonance imaging (MRI), is not associated with prognosis.¹¹

Physical factors

The physical manifestations of the whiplash condition have been extensively studied and it is clear that a variety of impairments may be present, including: motor/movement dysfunction;^{12, 13} postural control disturbances, including balance loss, head repositioning errors and disturbed eye movement control;^14–16 and sensory disturbances.^{17, 18} These characteristics have been discussed in earlier chapters.

Despite the frequent presence of these factors, few have demonstrated consistent predictive value. Decreased cervical range of movement is the physical factor most commonly investigated for its predictive capacity. An earlier review found only limited evidence for the prognostic capacity of this factor,⁴ and this is supported by more recent reviews where the general consensus is that this factor is not a strong predictor of poor recovery.^{3, 5} However, a recent cohort study conducted in a clinical environment, which measured cervical range of movement with a simple clinical device, showed that the relative risk for a one-year disability increased by 4.6 times with reduced initial movement.¹⁹

Features such as altered muscle activation patterns and greater head repositioning errors have been shown in one cohort to not be predictive of poor functional recovery at six months post accident.⁸ Similarly, disturbed eye movement control measured with the smooth pursuit test demonstrated no predictive capacity for pain or disability at 12 months post injury in a large (n = 262) cohort study,²⁰ despite showing some promise as a predictor in an earlier, much smaller, study.²¹

The exception to the lack of predictive capacity of physical measures is some measures of sensory disturbance. Increased sensitivity to cold stimulation measured via both lowered cold pain thresholds and decreased cold pain tolerance has been shown to be a significant predictor of non-recovery.^{8, 22} Relevant systematic reviews indicated that further research was required before this measure could be considered to have consistent predictive value.^{3, 5} In a later study it has been shown that cold hyperalgesia (cold pain threshold of >13°C) increases the risk of developing a chronic moderate-to-severe pain and disability pathway by 13-fold.²³ Additionally, classifying injured people at three to four weeks post accident based on the presence of cold hyperalgesia and higher levels of pain identified over 80% of those who had persistent moderate-to-severe symptoms at six months post injury.²⁴ This factor will, no doubt, appear in future systematic reviews. The mechanisms underlying the presence of cold hyperalgesia are far from clear but may be a reflection of augmented central processing mechanisms.²⁵

Other sensory measures, such as mechanical hyperalgesia (lowered pressure pain thresholds), have not demonstrated significant predictive value.^{8, 26}