Whiplash associated disorders (WAD) occur frequently, with one of their most common causes being motor vehicle accidents [1]. They are typically associated with psychological distress, sensory and motor dysfunction, and, most notably, pain [1]. Approximately 50% of people with WADs experience persistent pain [1]. Increasing evidence suggests that, in many of these cases, pain following whiplash injury is neuropathic [1].
Neuropathic pain is defined as maladaptive plasticity that alters nociceptive signal processing [2]. Among patients with whiplash associated disorders, neuropathic pain occurs at variable rates, with studies reporting anywhere from 34% to 75% prevalence [1]. Because neuropathic pain patients report greater impairments to their emotional well-being and quality of life than sufferers of other chronic pain conditions, this observation is particularly concerning [1].
Despite the high prevalence of neuropathic pain following a whiplash injury, the pathophysiology behind the condition is still not fully understood, making it difficult to treat [1]. However, studies have uncovered some basic trends between neuropathic pain and whiplash injury that may help healthcare providers better understand the condition.
For instance, an experiment conducted by Sterling and Pedler followed 85 people with acute whiplash to identify medical conditions that occurred concurrently with neuropathic pain [3]. The researchers found that the 35 patients who demonstrated a predominantly neuropathic pain component also reported higher pain/disability and sensory hypersensitivity than the patients without predominantly neuropathic pain [3]. As such, the researchers concluded that neuropathic pain after whiplash injury “is related to a complex presentation of higher pain/disability and sensory hypersensitivity” [3]. While this is only one of many possible relationships that may be uncovered with future research, it could help guide treatment regimens in the future.
The mechanisms undergirding neuropathic pain are also complex, but major strides have been made in identifying them. Whiplash injury can alter the plasticity of multiple neuronal structures [4]. Some of these structures are “responsible for amplification of nociception and exaggerated pain responses,” and it follows that whiplash patients may experience neuropathic pain [4]. Furthermore, tissue damage is likely a major factor in central nervous system hypersensitivity, which could explain how neuropathic pain after a whiplash injury occurs in the absence of an identifiable lesion [4]. Spinal cord hyperexcitability could also be a source [4].
Neuropathic pain often has to be treated differently from other chronic pain conditions, so identifying that a patient is suffering from this type of pain is crucial. However, diagnosis is complicated by the fact that there is no single definition of neuropathic pain; it is a complex condition that may occur by way of several pathological mechanisms [5]. Sterling and Pedler recommended using the Brachial Plexus Provocation Test (BPPT) as a clinical test and the Self-Reported Leeds Assessment of Neuropathic Signs and Symptoms (S-LANSS) as a clinical tool for determining whether a WAD patient is experiencing neuropathic pain [3].
Once a physician has determined that a patient suffers from neuropathic pain, there are multiple treatment options. Medications specifically targeted towards treating neuropathic pain are commonly prescribed [1]. Drug options include topiramate, a compound first licensed for use in patients with intractable partial epilepsy, and pregabalin, a medication currently being tested but demonstrating promising short-term effects on neuropathic pain [1, 6]. Additionally, specific physiotherapy methods may be an effective strategy to reduce patients’ pain levels [1].
Although neuropathic pain is a complex condition, WAD patients who receive early, appropriate treatment for their conditions may avoid the transition to chronicity and enjoy a higher quality of life [3].
References
[1] J. Fundaun et al., “Nerve pathology and neuropathic pain after whiplash injury: a systematic review and meta-analysis,” International Association for the Study of Pain, vol. 35, no. 4, p. 410-417, October 2021. [Online]. Available: https://doi.org/10.1097/j.pain.0000000000002509.
[2] M. Costigan, J. Scholz, and C. J. Woolf, “Neuropathic pain: a maladaptive response of the nervous system to damage,” Annual Review of Neuroscience, vol. 32, p. 1-32, 2009. [Online]. Available: https://doi.org/10.1146/annurev.neuro.051508.135531.
[3] M. Sterling and A. Pedler, “A neuropathic pain component is common in acute whiplash and associated with a more complex clinical presentation,” Manual Therapy, vol. 14, no. 2, p. 173-179, April 2009. [Online]. Available: https://doi.org/10.1016/j.math.2008.01.009.
[4] C. G. Davis, “Mechanisms of chronic pain from whiplash injury,” Journal of Forensic and Legal Medicine, vol. 20, no. 2, p. 74-85, February 2013. [Online]. Available: https://doi.org/10.1016/j.jflm.2012.05.004.
[5] P. V. Rasmussen et al., “Symptoms and signs in patients with suspected neuropathicpain,” Pain, vol. 110, no. 1-2, p. 461-469, July 2004. [Online]. Available: https://doi.org/10.1016/j.pain.2004.04.034.
[6] M. S. Chong and S. E. Libretto, “Management of chronic pain in whiplash injury,” The Clinical Journal of Pain, vol. 19, no. 1, p. 59-68, January 2003. [Online]. Available: https://bit.ly/3KkNK8Q.