Chronic Pain After Whiplash Injury—Evidence for Altered Central Sensory Processing

Abstract

Introduction. One of the puzzling problems in chronic pain after a whiplash injury is the discrepancy between the patient's symptoms and the clinical findings. The patients may be incapacitated by their symptoms, but clinical, laboratory or imaging investigations often reveal no or only minor pathology. We have reviewed the present evidence of altered sensory processing in chronic pain after whiplash injury, discuss this mechanism as one of the determinants of the pain complaints and outline possible treatment strategies.Methods. A review of human studies on sensory processing in patients with chronic pain after a whiplash injury, and a review of animal and human studies of mechanisms of altered sensory processing after injury.Results. There is evidence that patients with chronic pain after a whiplash injury have an altered sensory processing indicating a generalized hyperexcitability of the nociceptive system. This could be explained by ongoing nociceptive activity from an unidentified focus, irreversible changes in the nociceptive system, pre-injury altered sensory processing, and contributing psychological factors. Therapeutic options are limited but have not been formally evaluated by clinical studies.Conclusions. Altered sensory processing is probably involved in the determination of pain and disability in patients with chronic pain after whiplash injury. This mechanism can explain symptoms in the absence of evident tissue damage.