Transforming pain medicine: adapting to science and society

Abstract

The field of chronic pain medicine is currently facing enormous challenges. The incidence of chronic pain is increasing worldwide, particularly in the developed world. As a result, chronic pain is imposing a growing burden on Western societies in terms of cost of medical care and lost productivity. This burden is exacerbated by the fact that despite research efforts and a huge expenditure on treatment for chronic pain, clinicians have no highly effective treatments or definitive diagnostic measures for patients. The lack of an objective measure for pain impedes basic research into the biological and psychological mechanisms of chronic pain and clinical research into treatment efficacy. The development of objective measurements of pain and ability to predict treatment responses in the individual patient is critical to improving pain management. Finally, pain medicine must embrace the development of a new evidence-based therapeutic model that recognizes the highly individual nature of responsiveness to pain treatments, integrates bio-psycho-behavioural approaches, and requires proof of clinical effectiveness for the various treatments we offer our patients. In the long-term these approaches will contribute to providing better diagnoses and more effective treatments to lessen the current challenges in pain medicine.

Figure 1. Current Treatment Approaches in Chronic Pain – Treatment Centered

Current pain treatment is essentially “educated trial and error” where specific treatments are offered, usually within the focus of a clinical domain (e.g., interventional, alternate, behavioral etc.). Even within treatment domains (e.g., pharmacological), medications are tried, response evaluated, and depending on effects and side effects another medication evaluated.

Figure 2. Curating Responders and Non-Responders

Top: Within every treatment, few patients are responders where the treatment offers more than 50% long-lasting pain relief. In this model, significant numbers of patients are exposed to medications that are not very helpful or unhelpful or even produce side effects. Bottom: In an ideal therapeutic approach, individualized methods would allow for selection of patients who respond to medications with high efficacy and low side effect profiles.

Figure 2. Curating Responders and Non-Responders

Top: Within every treatment, few patients are responders where the treatment offers more than 50% long-lasting pain relief. In this model, significant numbers of patients are exposed to medications that are not very helpful or unhelpful or even produce side effects. Bottom: In an ideal therapeutic approach, individualized methods would allow for selection of patients who respond to medications with high efficacy and low side effect profiles.

Figure 3. Brain Dependent Changes in Chronic Pain

Top: A model of stress and allostasis in chronic pain. Under normal conditions, adaptive responses occur to a stressor (e.g., nociceptive pain). However, with stressors that results in ongoing process (e.g., neuropathic pain), responses become abnormal and maladaptive with changes in brain dependent behaviors (e.g., onset of depression or depression induced chronic pain). Bottom: The figure shows containment and normal adaptive processing to various stressors (noted below in the key); these normal responses are balanced and adaptive (adapt to ‘homeostatic set-point’) over time. In chronic pain responses may be exaggerated (out of ‘homeostatic set-point’) or inhibited. In a multidimensional biological process such as chronic pain each of these stressors may affect an individual differently as represented in the ‘bar-code’ noted on the right.

Figure 3. Brain Dependent Changes in Chronic Pain

Top: A model of stress and allostasis in chronic pain. Under normal conditions, adaptive responses occur to a stressor (e.g., nociceptive pain). However, with stressors that results in ongoing process (e.g., neuropathic pain), responses become abnormal and maladaptive with changes in brain dependent behaviors (e.g., onset of depression or depression induced chronic pain). Bottom: The figure shows containment and normal adaptive processing to various stressors (noted below in the key); these normal responses are balanced and adaptive (adapt to ‘homeostatic set-point’) over time. In chronic pain responses may be exaggerated (out of ‘homeostatic set-point’) or inhibited. In a multidimensional biological process such as chronic pain each of these stressors may affect an individual differently as represented in the ‘bar-code’ noted on the right.

Figure 4. Integrative Personalized Medicine for Chronic Pain

For each chronic pain patient the process of Diagnosis, ‘Treatment’ and ‘Follow-up’ need to be integrated in a manner that optimizes specificity of diagnosis (including phenotype, predictors of drug responsiveness etc.) and objective measures of treatment efficacy.