Unpleasant subjective emotional experiencing of pain.

The field of pain medicine that once began as a supportive and compassionate care, adding value to the management of acute and chronic ailments, has now transformed into a vital and essential specialty with structured training programs and service units with professionals dedicating their careers to it. The expansion of understanding of the direct relationship of pain relief to the quality of life, uncovering of neuronal pathways, and technological advances in imaging as well as in interventional techniques have all contributed to this phenomenal growth. However, there is a growing concern whether the training programs and the specialized practitioners are gradually limiting their skilled inputs primarily within the sensory realm of the pain experience with sophisticated interventional techniques and relegating its subjective and emotional dimensions to perfunctory realms within the schema of service provision. While the specialty is still young, if we can understand the inherent aspect of these dimensions within the pain experience and acknowledge the gaps in service provision, it may be possible to champion development of truly comprehensive pain relief programs that responds effectively and ethically to a patient's felt needs. This article attempts to position the subjectivity of pain experience in context and surface the need to design complete systems of pain relief services inclusive of this dimension. It presents authors' review of literature on perspectives of 'unpleasant subjective emotional experiencing of the pain" to elucidate possible clinical implications based on the evidences presented on neuro-biology and neuro-psychology of the pain experience; the aim being to inspire systems of care where this dimension is sufficiently evaluated and managed.

INTRODUCTION

Pain is an experience that is expected in life.

Pain is an in-built multi-dimensional awareness that contributes to adaptation and survival. The pathways for its perception, interpretation, and responses are developed from embryonic stages, and there is a well-established system at maturity of an organism, with networks of interconnections, some known and some yet unknown.

Before the Gate control theory challenged the concept, pain was viewed as a sensory phenomenon with emotions described as reactions.[1] By 1968, the experience was more fully conceptualized, with three systems of concurrent nociceptive processing – “sensory-discriminative,” “motivational-affective,” and “cognitive-evaluative.”[23] This placed the non-sensory component as an integral facet of a pain experience, as articulated in its definition by the International Association for the Study of Pain as “an unpleasant subjective sensory and emotional experience with actual or potential tissue damage, or described in terms of such damage”.i

Although the harmony of experiencing makes it difficult to delineate an emotional arm of the pain pathway distinctly, it may be appreciated through deliberation from few angles; one, unravel those components that connect the pain pathways with the centers known to process emotions in the central nervous system (CNS), i.e., the functional neuro-anatomy and, second, understand impact of personality, context, and mood states on the excitatory and inhibitory modifiers during a pain experience, i.e., cognition and psychology of pain. There is also the emotional impact of uncontrolled/poorly controlled pain and its impact on the ongoing experience, and the influence of severe persistent pain on aggravation/precipitation of psychological disturbances – the realm of psychiatry of pain.

We have focused on the first two aspects, viz., the functional neuro-anatomy and the cognition/psychology of pain.

FUNCTIONAL NEURO-ANATOMY

The neurobiological networks of cognition, negative emotional states, and pain experiences are meshed together with parallel processing at cognitive, affective, and sensory levels. These are synchronized with sensory perception, an immediate vigilance, and a heightened awareness of self and environment, eventually leading to disruption of the ongoing activity.

Although spread across the entire pain pathway, the laminae in the Dorsal Horn (DH) of the spinal cord could be taken as primary units of concurrent processingii. Here, the dense network of dendrites and interneurons integrate signals from the periphery and those from higher centres and modify the net pain inputs sent forward through the spinal tracts.[4] While the pathway for sensory processing follows spino-thalamic pathway, those destined for affective processing follows spino-reticular, spino-hypothalamic, spino-mesenchephalic, and limbic pathways before projecting to neocortexiii [See Tables 1 and 2 and Figure 1].

Table 1

Pain pathways

Table 2

Predominant neurochemicals at different levels of pain pathway

Figure 1

The centers of central nervous system involved in experiencing pain

The visceral noxious afferents along the sympathetic nerves synapse with somatic motor neurons and pre-ganglionic neuronsiv at DH, before proceeding forward.[5] Visceral pain has poor representation in the primary somatosensory cortex, but it has significant projections to the limbic system.[6] Also, the nervous system functioning to avert external threat and the immune system functioning to avert internal threat, seem to work closely and modulate each other's functions.[7] In pain originating from viscera, these interconnections may be expressed as a cascade of activity-limiting symptoms, viz., “sickness response.”[8] Pro-inflammatory agents, e.g., INF-α and IL 2, are implicated.[9] The symptoms of the inflammatory sickness response, commonly accompanying complex visceral cancer pains, can contribute significantly to the unpleasant subjective experience.

Awareness and perception

Checks and modulations exist at various levels of the pathway for assessing and making meaning of a pain situation.[10] The fundamental role of endogenous pain modulatory mechanisms are probably to shape the processing of nociceptive signals dynamically to best fit the ever-changing demands of the environment.[11] It is noteworthy that centres concerned with emotions are involved in its initiation and drive. Although described separately in Table 3, their interlinked nature has to be appreciated to fully comprehend the harmony of experiencing it [See Table 3 and Figure 2].

Table 3

The modulatory systems

Figure 2

The harmony of the pain experience

It may be noted that Limbic system, frontal brain, and pre-frontal cortex, insular cortex, locus ceruleus (LC), hypothalamus, HPA axis, the dorsal raphe nuclei, and peri-aqueductal-grey matter (PAG) are all involved in processing of the content, context, and motivational aspects of noxious signals. There are studies highlighting the active role of cognition and prefrontal lobes in the therapeutic outcome of pain relief measures.[12]

In health, the function of the modulatory system could be modifying perceptions through cognitive barring and prioritisation with suppression of non-significant discomforts. The diminished noxious signal transmission then allows coping with the immediate threat without the distraction of pain. The study on “stress analgesia” in wounded World War II soldiers requiring very little analgesia until an environment of safety is exemplary in this regard.[13]

Sleep, arousal, and pain

Sensory afferents relaying to the arousal system modify sleep and circadian rhythms, providing basis for the necessary behavioural adaptation and survival.[14]

The hypothalamic para-ventricular nucleus (PVN) that is central to the arousal system and is strongly wired to rostral and caudal areasv is involved in sleep mechanisms and also to the descending pain modulatory systems. This network is active during wakefulness and becomes silent, especially during REM sleep, resulting in a relatively lower arousal and pain threshold during this stage than during deep sleepvi[15] The reciprocal interplay between REM sleep and pain modulation systems could explain the disturbed sleep rhythms observed commonly in chronic pain states and the common occurrence of the breakthrough pain during REM sleep stages.[1416]

COGNITION, PSYCHOLOGY, AND BEHAVIOR

Pain is outside, the senses…and within, the passions of the soul.

Aristotle

The interconnections of cognitive and emotional centres are intense and complex. We are capable of creating images of experiences, real or imaginary, which play a significant role in experiencing symptoms. Emotional reactions can be elicited to construed mental images, e.g., needle puncture or on seeing another person's injury. In life, we are constantly construing images of reality based on patterns of perceptions and memory and their emotional magnitude has been found to be proportionate to the internal representation of threat. Research exist to support both emotions determining cognition as well as for cognition driving the emotions.[171819]

Meaning of the pain – Personality, mood, and the pain appraisal

Pain is a bio-psycho-social experience, and its perceived intensity depends on the extent of tissue damage, the perceiver's psychological statevii and the adaptive significance of that experience.viii[2021]

Pain appraisal forms the basis for the meaning ascribed. Primary appraisal evaluates the context of the stimulus, whether threatening, neutral, or benign, and the secondary appraisal evaluates the context of self-controllability and coping resources.[3] If a pain signal is interpreted as harmful and without hope of control, the intensity of perception would be all the more intense.[22]

Two major personality factors that influence appraisal are “negative affectivity” – a tendency to experience the world negatively and viewing it as threatening and distressful, leading to a general heightened vigilance to perceptions[23] and “anxiety sensitivity” – a fear of anxiety related sensations that leads to negative interpretation of body sensations, enhanced pain experiences, catastrophizing, higher analgesic use, and lowered physical and social functioning.[24] Mood disturbances or depression may allow regular sensations from viscera to be perceived as painful.[25]

Prior mastery experiences influence the perceived controllability of pain. The positive resilience traits in the personality that have been studied for its influence on pain experience are “dispositional optimism”ix and “hope and benefit finding.”[2627] The main qualities noted in optimistic persons that seems to reduce catastrophizing and to lower pain readings are problem focused action and/or positive reframing of the situation.[28]

DISCUSSIONS AND CLINICAL APPLICATION

The affective component rather than the sensory component apparently makes sense of the context of an experience and determines a most suitable behaviour/response. The bio-psycho-social conceptualisation of chronic pain can have significant practical and ethical worth.

Pain rating scales were evolved to include the subjective, unique, and individual perception to improve assessment of pain to encompass the influence of disease stage, mental status, personality, memories of prior pain experiences, and the perceived etiology and context of the present pain.[20] [See Figure 3]

Figure 3

Numerical rating scale for pain

The pain score thus is intended to reflect the overall summated primary and secondary appraisals mentioned above. It is especially useful when measured serially and compared. Here, one may also acknowledge the subjective contribution of the assessing professional to the overall rating, which would be influenced by medical knowledge, experiences, and appraisal of the situational context.

We may come across patients who acknowledge having pain, yet based on their appraisal of the situation, they do not feel a need to have regular analgesics and are comfortable with the knowledge that they have access to pain relief if they feel the need of it later. The observation of tolerance and, occasionally, of an exultation in pain during certain religious ritualsx may possibly be related to modifications in the appraisal based on the religious/spiritual connotation of the noxious perception.

Studies note significant neuroplasticity of modulatory processing units. Learned helplessness behaviour and response sensitivity after previous traumatising experiences of pain has been connected to significant neuroplastic changes at Locus Ceruleus.[29] There is evidence to support modification of these to tolerance and adaptability, through empowering psychotherapeutic inputs that couple them with positive experiences.[30] Analgesia has been noted to be initiated and maintained by supported expectations of symptom change and changes in motivation/emotions.[31]

Communications are adaptive functions of emotional expression.[32] Besides the defence responses of fight/flight that pain elicits, the negative feelings associated with pain expresses through vocalisation, startle responses, postures, facial expressions, or alterations of activity aimed to communicate the threat and elicit social support and hence support survival.

The socio-biologic imperative of communicating threat and summoning help during pain experiences, explains the powerful role of sharing and emotional catharsis within a supportive environment as a valuable therapeutic intervention. Communication skills thus become fundamental for effectiveness of any therapeutic intervention. Adequate communications reflect as reduced intensity, improved pain tolerance, modification of meaning, and positive impact on appraisal.[33]

Based on these observations, we may be able to better understand the role of psychotherapeutic interventions in managing pain. Cognitive behavioural therapy (CBT) addresses learned attitudes, beliefs, and expectations and, thus, help modify the appraisal component. It de-emphasises the role of pain as a regulator of the person's functioning. It supports adaptation of responses, improvement in self-efficacy, which reflect as positive pain outcomes and functionality.[34] Cognitive techniques involve self-monitoring (of thoughts, moods, and behaviour), development of coping strategies, and problem solving. There is an enhanced relief regardless of the type of coping strategy employed. Current recommendations emphasize the value of combining CBT with other treatment strategies.[3536]

Pain experience happens within a social context. Although pertinent, we have not featured the specific influence of culture and socially learned behaviors in this context. Yet, evaluation and management of dysfunctional behaviours that are contributory to maintaining chronic pain within the social/family structure would be an important responsibility for the caring team.

Role of multidisciplinary team (MDT): Evidence for adaptability of subjective responses to learning and experience, provides encouragement for evolving systems with MDT inputs for emotional and social support throughout the management plan.[37] An ideal system would integrate appropriate and timely inputs from the nurse, physiotherapist, psychotherapist, occupational therapist, yoga therapist, social worker, and family/community carer[3839] along with the pain physician.

The primary purpose and emphasis of team inputs would be to elicit the details of the pain, possible contributory etiologies for the pain, allow adequate sharing of related thoughts and feelings, understand the person in pain and the meaning of pain to that person, how she/he functions and then design therapies that modify appraisal of the pain and facilitate self-management along with the appropriate pharmacological and non-pharmacological inputs. Valuable inputs for patients at different settings would require multifaceted understanding, prudent planning, coordination, and channelization of funding to ensure adequate availability of not just technical but also skilled human resources within the care setting.

CONCLUSION

Pain does not occur solely in people's bodies, nor does it occur solely in their minds…. it occurs in their lives.

Clarifications on the interplay of emotions, cognition, behaviour, clinical presentations, and better understanding of neuroplasticity and the neurochemicals involved in causing and modulating chronic pain states have helped develop fresh therapeutic approaches for enhanced relief from suffering.

The threat to the individual's bio-psycho-social integrity during a noxious event is a powerful negative experience, much more than mere information appraisal. Emotions alter awareness by imparting subjective information that allows choice of one behaviour over many alternatives within the larger context of self-preservation and preservation of the species.[40]

The perspectives on “unpleasant subjective emotional experiencing” of pain as discussed briefly above has attempted to review the scientific basis for subjectivity of the experience, rationale for psychological/behavioural therapies, and for interventions that modify cognitive processes involved in the experience. It implies that experiencing pain is influenced by psychological processes that are inherent aspects of the signal processing.

Recognition of the above facets demand more than a cursory mention of “psycho-social support” or “communication skills” within the training programs for pain specialists. A comprehensive program ought to familiarise the practitioner with evidence supported guidelines for acknowledging, evaluating, and addressing this dimension of care, help with utilising multidisciplinary skill base, and empower evolution of suitable systems for adequate communications and structured psychotherapeutic interventions within their service setting. These should be integrated within the spectrum of care with equal importance along with the technical and medical know-how.

The acknowledgement of suffering endured during pain and its relationship to quality of life has given it the status of the 5th vital parameter for a patient's wellbeing. As specialists dealing with this condition regularly, let us appreciate these dimensions in their entirety, integrate suitable interventions, and enhance the care provided and perceived.