Theories & Measuring Pain

Types of Pain

  • Chronic Pain:

    • Lasts several months or longer

    • Often associated with a disease

    • Can be treatment resistant

    • More common in females and the elderly

    • Most common type is musculoskeletal pain (muscles, bones, ligaments)

  • Acute Pain:

    • Comes on suddenly and resolves quickly

    • Usually diagnosed and treated based on specific location

    • Results from disease, inflammation, or tissue injury

    • Often a symptom of a recent event, such as an injury

Factors Affecting Pain

Several factors can influence the experience of pain:

  • Learning:

    • E.g. Jamner and Turskey (1987) found that exposure to words associated with pain in migraine sufferers increased anxiety and their sense of pain.

  • Anxiety:

    • McGowan et al. (1988) found a correlation between anxiety and the strength of pelvic pain in women.

  • Gender:

    • Morin et al. (2000) showed that women often experience more intense post-surgical pain than men, whereas men are more affected by mild pain lasting several days.

  • Cognition:

    • The perception of control and ability to manage pain affects pain sensation, forming the basis for cognitive therapies.

Phantom Limb Pain (PLP)

  • Common among amputees, causing sensations of pain in missing limbs.

  • Melzack (1992) - Characteristics of PLP:

    • Phantom limb feels real.

    • Can become stuck in awkward positions.

    • Patients perceive artificial limbs as part of their body.

Example Study: MacLachlan et al. (2004)

  • Sample: 32-year-old male, Alan, underwent leg amputation at the hip.

  • Procedure:

    • Experienced PLP two days post-surgery; described pain as "pins and needles" at first, which escalated throughout the day.

    • Used mirror therapy to alleviate pain.

  • Treatment:

    • Mirror treatment began after unsuccessful pain medication and TENS.

    • Engaged in exercises using a mirror to perceive movement without pain.

    • By the end of the three weeks, participation was independent and frequent.

  • Results:

    • Initial phantom pain reported as 5-9 and stump pain as 0-2.

    • End assessment indicated phantom pain rated as 0 and stump pain as 1.

    • Sense of control over PLP increased from 0-3% to 25-30%.

    • The phantom limb felt shorter but could be ‘straightened out’.

  • Conclusion:

    • Demonstrated mirror therapy as an effective treatment for PLP.

Evaluation of the MacLachlan et al. Study:

  • Strengths:

    • Case study method provided detailed, rich qualitative data.

    • First reported case of successful mirror therapy for PLP.

  • Weaknesses:

    • Low generalizability due to one participant.

    • Low reliability in the findings.

Theories of Pain

Specificity Theory (Von Frey, 1895)

  • Proposes a separate sensory system for processing pain.

  • Specialized pain receptors respond to stimuli and send signals to the brain.

  • Provides a straightforward explanation for pain perception.

Evaluation:

  • Strengths:

    • Clarity in explaining pain perception.

  • Weaknesses:

    • Reductionist; overlooks psychological and cognitive factors.

    • New research indicates pain involves more than specific receptors.

Gate Control Theory (Melzack & Wall, 1965)

  • Suggests that non-painful input can affect pain perception by closing gates in the spinal cord, preventing pain signals from reaching the brain.

  • Increased activity in large nerve fibers (for touch and pressure) versus small nerve fibers (for pain) can reduce pain sensation.

Evaluation:

  • Strengths:

    • Supported by animal studies showing brain stimulation leading to numbness.

  • Weaknesses:

    • Lacks physical evidence for the existence of a 'gate'.

    • Treats physical and psychological processes as separate.

Measuring Pain

Subjective Measures: Clinical Interview

  • Consists of gathering medical history and performing clinical interviews using open-ended questions.

  • Uses acronym ‘ACT-UP’ to guide inquiries regarding activities, coping, thoughts, emotions, and reactions from others.

Evaluation:

  • Strengths:

    • Deep understanding of patient experience; qualitative data.

  • Weaknesses:

    • Potential inaccuracies in self-reporting due to downplaying/misinterpreting pain.

McGill Pain Questionnaire (MPQ)

  • Evaluates intensity and quality of pain by categorizing descriptors.

  • Ranges from 0 (no pain) to 78 (severe pain).

Evaluation:

  • Strengths:

    • Detects changes in pain over time; easier statistical analysis.

  • Weaknesses:

    • Closed questions limit full representation; no qualitative data.

Visual Analogue Scale (VAS)

  • Allows patients to indicate pain on a continuum from no pain to extreme pain.

  • Total distance from endpoint represents pain level, converted to numerical value between 0-100.

Evaluation:

  • Strengths:

    • Quick and sensitive to small changes.

  • Weaknesses:

    • Lack of qualitative data limits comprehensiveness.

UAB Pain Behaviour Scale

  • Observer records behaviors associated with pain severity, frequency, and intensity.

Evaluation:

  • Strengths:

    • Provides observable data about pain behaviors.

  • Weaknesses:

    • Observer bias can affect interpretation; may not reflect subjective experience.