Resources
The Breakdown
Important
- Types of chronic pain – There are three types of chronic pain: chronic benign pain, which persists longer than six months and is intractable to treatment (e.g., low back pain); recurrent acute pain, which involves a series of intermittent episodes (e.g., migraine headaches); and chronic progressive pain, which persists longer than six months with increasing severity over time, often associated with malignancies or degenerative disorders like cancer or rheumatoid arthritis.
- Peripheral nerve fibres involved in nociception – Three main types of peripheral nerve fibres are involved: A-delta fibres are fast, small, myelinated, transmit first, sharp pain, and open the pain gate; C-fibres are slower, unmyelinated, transmit the second, dull, achy pain, and also open the pain gate; A-beta fibres are large-diameter, myelinated fibres that transmit information about position and vibration and close the pain gate. The balance between open and closed gates dictates the experience of pain.
- Neurotic triad – Chronic pain patients frequently exhibit elevated scores in three personality areas: hypochondrias, hysteria, and depression.
Core concepts
- Pain Classification: Pain is categorised primarily by duration into two classifications: acute pain, which is shorter (six months or less) and typically results from soft tissue damage, infection, or inflammation, generally resolving over time; and chronic pain, which is longer-lasting and has more complex effects, often linked to long-term illness or disease, sometimes without an apparent cause. Chronic pain is challenging to assess and treat due to its multifaceted nature.
- Factors Influencing Pain: The experience of pain is modulated by various individual factors. Cultural differences influence how pain is reported, with some cultures expressing it more intensely than others. Gender plays a role, as women may be more sensitive to certain types of pain due to hormonal fluctuations and differences in emotional processing, yet they often demonstrate a higher tolerance for intense pain (e.g., labour). Social pain, such as trauma or isolation, can increase susceptibility to and worsen physical pain. Coping styles significantly affect pain perception; for instance, catastrophizing exacerbates pain, whereas resilience and positive emotions can reduce its intensity.
- Measuring Pain: Pain assessment is highly subjective, and there is currently no universal “gold standard” for measuring pain outcomes. Common tools include verbal reports, where patients describe their pain using their own vocabulary (e.g., throbbing, shooting, dull ache), and observing pain behaviour, which encompasses visible expressions of distress, alterations in posture and gait, negative emotional states, and avoidance of activity.
- Physiology of Pain (Nociception): This biological system is responsible for carrying signals of damage and pain to the brain. Nociceptive neurons, found in the dorsal root ganglia, are capable of detecting mechanical, thermal, and chemical stimuli, leading to polymodal nociception. These signals are transmitted through bidirectional axons that connect in the dorsal horn of the spinal cord and then proceed to the brain (e.g., somatosensory cortex and thalamus) for processing. This transmission is exceptionally rapid, facilitating self-preservation.
- Endogenous Opioids: The human body possesses a natural pain suppression system that produces internal pain-relieving compounds known as endogenous opioids, including beta-endorphins, proenkephalin, and prodynorphins. These peptides not only help reduce pain perception but also contribute to feelings of well-being. Additionally, acute stress and physical activity can temporarily decrease sensitivity to pain.
- Pain Management: Strategies for managing pain fall into several categories: Traditional methods include pharmacological treatments (pain medications), surgical interventions (lesions of pain fibres), and sensory techniques (e.g., counterirritation, exercise). Psychological techniques, often employed by psychologists, aim to shift attention away from pain and encompass biofeedback, relaxation, hypnosis, acupuncture, and distraction.
- Chronic Pain’s Distinct Nature: Unlike acute pain, chronic pain often leads patients to develop maladaptive coping strategies. Its management requires a more holistic, biopsychosocial approach, addressing physiological, psychological, social, and behavioural components. Chronic pain can profoundly impact an individual’s life, leading to significant personal, familial, and societal challenges.
- Pain and Personality: An individual’s personality traits can influence their experience of pain. Chronic pain is frequently associated with psychological issues such as depression, anxiety, and even substance abuse, often leading to noticeable changes in personality.
- The Opioid Crisis: This is a severe and ongoing public health issue, particularly prominent in Canada, involving the widespread misuse, addiction, and overdose deaths linked to opioid painkillers.
- OxyContin: Initially introduced as a time-release formulation of oxycodone for moderate to severe pain, it demonstrated high abuse-liability and addiction potential, significantly contributing to the crisis before being withdrawn from the Canadian market in 2012 and replaced by a “tamper-resistant” version, OxyNeo.
- Fentanyl: A potent opioid, up to 100 times more toxic than morphine. While initially available via patches, oral forms emerged, and illicit producers began “tweaking” the molecule, creating adulterated forms with a very narrow therapeutic index, increasing the risk of overdose. China is identified as the primary source of concentrated fentanyl, which is then diluted and mixed in Canada. British Columbia is noted as a significant hotspot for fentanyl-related overdose deaths, with rates increasing considerably since COVID-19.
Theories and Frameworks
- Traditional Model of Pain: An earlier view that suggested pain was solely a direct result of tissue damage, with the degree of pain being dictated by the extent of the injury.
- Gate Control Theory: A more comprehensive theory proposing a “neural pain gate” within the spinal cord that can either open or close to modulate pain signals travelling to the brain. This theory integrates psychological factors (e.g., emotions, attention) as influences on the gate’s activity, explaining why pain perception can vary independently of tissue damage.
- Neuromatrix Theory: Developed to address weaknesses in the Gate Control Theory, particularly regarding phantom limb pain. It suggests that the brain generates a “felt representation of a unified physical self” (the neuromatrix) that is inherently determined but dynamically shaped by sensory input and experience. Pain is seen as a neurosignature, a deviation from this established body-self representation.
- Biopsychosocial (BPS) Model: This overarching framework posits that pain is a complex phenomenon influenced by the interaction of physiological (biological), psychological (thoughts, emotions, coping styles), and social (cultural, environmental, relational) factors. It advocates for a holistic approach to understanding and managing pain, especially chronic pain.
Notable Individuals
- No specific individuals related to pain research or theory are explicitly named as “notable” within the provided lecture slides or transcript.