Regardless of culture, age, or life experience, pain is a feeling in which all people can relate. Scientific advances have shaped our understanding of pain, but its manifestations are not always predictable. Pain assessments are oversimplified with numerical scores, but in reality, the experience varies between each person, medical problem, and situation. In 1979, the International Association for the Study of Pain defined pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”¹ As our understanding of pain grows, many have questioned if this definition is still sufficient. Pain is now thought of as a subjective, multidimensional experience. An individual’s perceptions mold their processing of experiences. This incorporates factors beyond sensory and emotional experiences as previously defined (Fig. 9.1).

With advancements in technology, our understanding of pain has evolved. Previously, the brain and sensory processing of pain was believed to be a part of thalamic processing or solely sensory processing. However, anatomical studies including imaging studies such as functional magnetic resonance imaging and positron emission tomography have revealed several cortical areas involved in pain. Several studies agree the parietal, insular, and anterior cingulate cortices play major roles in acute pain perception and each likely process different aspects of pain.²,³,⁴ This leads us to believe that pain should not be thought of as two distinct branches of physical sensory vs emotional behavior components. Rather, these elements interact with one another within neural networks resulting in multidimensional pain. These studies reveal multiple physiologic changes that occur in response to painful stimuli. For example, cerebral brain flow increases in specific regions in response to painful stimuli in humans and animals. Functional image studies reflect different responses when acute pain is introduced to a site of chronic pain vs acute pain to a pain-naive site.⁵ These findings point to a complex physiologic processing of pain that is beyond the traditionally taught neurologic pain tracts (Fig. 9.2).

The experience of pain, like many other medical conditions, varies between each patient. Looking at objective data from functional imaging studies, findings continue to support individual differences in pain perception.⁶ Beyond physiologic differences, several factors alter the experience of pain including family history, cultures, gender, and psychology.
Studies have found that family history can shape an individual’s experience of pain. Parental models affect an individual’s response including reaction to pain and affect the frequency in which a patient may report pain. This is a reflection of coping mechanisms learned throughout childhood to stressors. Family history of pain may serve as a predictor to a patient’s experience of pain and is an important area of focus when considering management especially in pediatric populations.⁷,⁸ It may suggest a future direction of managing a family’s pain and coping techniques rather than fixating on the individual level.

When looking at gender differences in the experience of pain, several studies have found women experience more chronic pain with higher incidences of migraines, fibromyalgia, and lower back pain. However, when looking at acute pain, such as the postoperative setting, there is minimal clinical difference between males and females.⁹ In studies investigating the sex differences in pain perception, women tend to have stronger modulation to pain with increased inhibitory responses to repeated, painful stimuli. Women tend to have greater awareness of their pain, but this does not translate to a higher frequency of reported pain.¹⁰ Many theories have been offered to explain the different pain thresholds and responses between men and women, but it is not yet fully understood.⁹ Many argue that the socioeconomic and cultural factors may skew the data around genders differences to pain, given that most studies are focused on homogenous culture sample groups. This remains an important area of study, as women and men both respond to pain interventions differently. In order to optimize pain management in both the acute and chronic setting, additional research must be done to better understand the contribution of gender to multidimensional pain.