Temporal changes in pain processing after whiplash injury, based on Quantitative Sensory Testing: A systematic review

BACKGROUND AND OBJECTIVE: After whiplash injury, some patients develop chronic whiplash-associated disorders. The exact pathophysiology of this chronification is still unclear and more knowledge is needed regarding the different post-injury phases. Therefore, studies were searched that examined temporal changes in pain processing, measured by Quantitative Sensory Testing (QST). DATABASES AND DATA TREATMENT: This systematic review searched three electronic databases (Medline, Web of Science and Embase) for articles meeting the eligibility requirements. Risk of bias was assessed according to a modified Newcastle-Ottawa Scale. RESULTS: The 12 included studies presented moderate to good methodological quality. These studies showed altered pain processing within the first month after injury and normalization within 3 months in 59%-78% of the patients. After 3 months, recovery stagnates during the following years. Thermal and widespread mechanical hyperalgesia occur already in the acute phase, but only in eventually non-recovered patients. CONCLUSIONS: Differences in pain processing between recovering and non-recovering patients can be observed already in the acute phase. Early screening for signs of altered pain processing can identify patients with high risk for chronification. These insights in temporal changes show the importance of rehabilitation in the acute phase. Future research should target to develop a standardized (bed-site) QST protocol and collect normative data which could, in relation with self-reported pain parameters, allow clinicians to identify the risk for chronification. SIGNIFICANCE: Altered pain processing is present soon after whiplash injury, but usually recovers within 3 months. Non-recovering patients show little to no improvements in the following years. Differences between recovering and non-recovering patients can be observed by Quantitative Sensory Testing already in the acute phase. Therefore, it is considered a feasible and effective tool that can contribute to the identification of high-risk patients and the prevention of chronification.