EDITORIAL - Identifying those at risk of developing persistent pain following a motor vehicle collision

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Editorial

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Identifying Those at Risk of Developing Persistent Pain Following a Motor

Vehicle Collision

MICHELE STERLING, PhD, MPhty, BPhty,

Senior Lecturer,

Division of Physiotherapy,

School of Health and Rehabilitation Sciences,

The University of Queensland,

St Lucia, Australia, 4072.

Address reprint requests to Dr. Sterling. E-mail: m.sterling@...

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The development of musculoskeletal pain following trauma, particularly a

motor vehicle collision (MVC), is common, with many people showing poor

recovery1 and incurring substantial personal and economic costs. There is

evidence to suggest that musculoskeletal pain conditions from a MVC

demonstrate a more complex clinical presentation than pain of idiopathic or

insidious onset. Individuals with neck pain (whiplash) from a MVC not only

report higher levels of pain and disability but also widespread sensory

hypersensitivity (a manifestation of central hyperexcitability) when

compared to idiopathic neck pain2.

Interestingly similar sensory disturbances are a feature of conditions with

more widespread pain such as fibromyalgia (FM)3, a condition that occurs

more frequently in those with neck pain following a MVC compared to non-MVC

injuries4. It appears that patients presenting with musculoskeletal symptoms

following a MVC may be both clinically more complex and at greater risk of

chronicity than those with a non-traumatic history.

Of course, it is important to identify factors that are predictive of poor

outcome, in this case the development of persistent pain and disability.

Much of the research in this area has focused on whiplash injury, but

whiplash shares overlapping clinical and epidemiological characteristics

with conditions of more widespread pain, such as FM4. With regard to

whiplash, despite investigation of numerous factors, a recent systematic

review found that high initial pain intensity was the only consistent

prognostic indicator of poor functional recovery5.

In this issue of The Journal, Wynn-, et al showed similar factors to be

important in the development of widespread pain following a MVC6. The

authors prospectively followed (to 12 months post accident) 695 participants

who had lodged a claim with a UK-based insurance company and who reported no

widespread pain prior to their accident. They found that a greater number of

physical symptoms and perceived injury severity following the collision were

predictive of later widespread pain, although it is not completely clear

whether these measures correlate with pain intensity. Nevertheless it does

send a strong message regarding the early clinical assessment of patients

injured in a MVC - that valid measures of perceived pain/symptom intensity

and severity should be included as useful early indicators of potential

non-recovery.

One drawback of most if not all prospective studies of pain development

following a MVC is that the prognostic factors investigated were measured

from either around the time of, or soon after injury. It is possible that

some of these factors (and even additional ones) were present prior to the

occurrence of the collision, thus increasing the vulnerability of some

people to the effects of injury. Research investigating relationships

between pre-existing factors and outcome following MVC is sparse, most

likely due to logistical issues of recruiting the large sample sizes

required. For probably the first time, Wynne-, et al have attempted to

identify pre-collision factors, in addition to collision-specific and

post-collision factors, that may contribute to the occurrence of a new

episode of widespread pain. The authors are to be congratulated in their

attempt of this difficult endeavor.

In multivariate analysis, pre-collision factors of health seeking behavior

(frequent health consultations), somatization (number of somatic symptoms),

and age predicted the onset of widespread pain. One criticism is that

participants were asked to retrospectively recall the required data,

although the authors attempted to account for this by providing the

participants with a precise time frame for recall. The authors suggest that

participants may be more likely to overestimate their health status prior to

the collision, and this could be true particularly in the compensation

environment of the study. It would have been interesting to have information

on the nature of the participants' health visits - were they for previous

musculoskeletal pain (back or neck pain) or perhaps for more systemic type

illnesses? Some may (unjustifiably) draw from the terminology " health

seeking behavior " representation about the participants' psychological

state - for example catastrophizing behaviors.

Leading from this, it may be tempting to extrapolate from the findings of

Wynn-, et al that mainly pre-existing psychological factors (health

seeking behaviors and somatization) predict the onset of widespread pain

following MVC. It should be made clear that insufficient information is

provided to support this conclusion. In particular, the term " somatization "

is controversial, variously defined and often perceived as implying that the

patient has " medically unexplained symptoms7. " Again, using the literature

on whiplash prognosis, it has been shown that a history of neck pain or

headache prior to the accident is associated with a worse functional

outcome8. Further, motor control deficits persist even in those who report

full recovery from both whiplash injury and acute low back pain, a factor

that may be associated with symptom recurrence9,10. Thus it cannot be ruled

out that previous musculoskeletal pain may provide physical reasons for the

individual to be more vulnerable to further insult or injury. Genetic

factors may also play a role. An association between genetic polymorphisms,

pain sensitivity, and chronic pain development has been demonstrated11. This

may prove to be important considering the findings of increased pain

sensitivity in subgroups of patients with whiplash and FM3,12. Early (within

weeks of injury) sensory hypersensitivity to both mechanical and thermal

stimuli has been shown to predict poor recovery, at least following whiplash

injury10,13. It is possible that a prior disposition to increased pain

sensitivity may mean a greater tendency toward central hyperexcitability

following injury and ensuing non-recovery.

This is not a criticism of the work of Wynn-, et al but a suggestion

for future research in this area, where more detailed information (including

both physical and psychological factors) may be gleaned such that firmer

conclusions can be drawn.

Wynn-, et al found few collision-specific factors to be associated with

the onset of widespread pain, findings similar to those in whiplash, where

such factors are not strong predictors of outcome5. Interestingly, while not

an independent predictor in multivariate analysis, perceived collision

severity was associated with pain development in univariate analysis. The

authors did not measure posttraumatic stress symptomatology, but the case

for the inclusion of this factor is strong based on findings of concurrent

chronic pain, including widespread pain and posttraumatic stress disorder

following MVC4. Moreover early posttraumatic stress symptoms also predict

chronicity following whiplash injury10. An interesting model for the

development of chronic pain following MVC, as proposed by McLean, et al4,

incorporates interrelationships between stress responses, central pathways,

and psychological factors. Preliminary support for such a model is provided

by longitudinal whiplash data, where relationships exist between early

sensory disturbances and persistent posttraumatic stress14.

In conclusion, motor vehicle collisions cost the community dearly both in

personal and economic losses associated with the development of persistent

musculoskeletal pain. There is accumulating evidence that both physical and

psychological factors present around the time of injury are associated with

non-recovery. The crucial " window of opportunity " to identify those at risk

and to institute appropriate and effective intervention is likely to be

within this early time frame. Wynn- and colleagues have provided

additional pre-collision factors also involved in the development of

persistent pain. The next challenge will be to further explore all these

factors in order to illuminate underlying mechanisms and develop improved

management strategies.

http://www.jrheum.com/subscribers/06/05/838.html

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