The Neurophysiology of Peripheral Neurogenic Pain - Essay Example

The Neurophysiology of Peripheral Neurogenic Pain Introduction A simpler and basic definition of pain can betaken to imply the unpleasant feeling that is usually caused by the intense stimuli thus resulting into illness and injury. It may be physical or mental depending on the form and nature that is applied towards an individual. According to Sofaer, pain refers to an unpleasant sensory and emotional experience that is usually concomitant to actual or potential damage to the tissues or described in terms of such damage. In medicine, pain can be referred to as a sensation that hurts thus, causing discomfort, agony or distress depending on the level of severity (15-21). This study focused on the aspects of peripheral neurogenic pain with regard to its neurophysiology. Epidemiology of pain According to Hecke et al., epidemiology of pain involves the investigation of the distribution, as well as, the causes of pain and ill health and also how this information can be integrated into managing these predicaments. The epidemiology of pain can be addressed through paying much attention onto the widespread and intermittent pain disorders that are commonly experienced by persons in their daily lives. In focusing on the epidemiology of pain, the core question that might arise would be in relation whether the persistence of pain is a result of unremitting or never-ending ailment. The term scale in this aspect denotes that pain may either be bodily, emotional, or mental. Subsequently, individual views or opinions regarding pain also differs (Simpson et al. 90-95). Differences of pain levels and occurrence a. Differences of pain levels according to gender and age Stewart, in a study to determine the difference in the pain levels between the two genders and based on their ages, conducted a study that recorded a higher frequency of felt pain among women who rated higher levels of painful feelings as compared to men. This factor is attributed to genetic differences between male and female, as well as, the variations in responsibilities that are bestowed upon each gender by the society. The following graph illustrates the differences on frequency or commonness of pain between men and women Seattle Washington. The results as shown are in percentages. Figure 1: Age-Sex frequency of painful situations in Seattle, WA Source: Stewart In the graph above, the values on the y-axis represent the percentages of age-sex frequency as was conducted between males and females, while the x-axis represents the ages in groups spanning from 18 to over 65 years of age of the respondents. According to Hecke et al., the medical records in that are found in health institutions have shown a higher proportion of women seeking treatment for pain related problems more than males do. The difference in the perception of pain levels is based on the gender with females largely responding to pain stimuli. The graph as shown in figure 1 indicates that the pain levels were higher for women who were between the age of eighteen to forty-four years of age. This is due to hormonal variations existing in women especially when a person nears their old age. After attaining the age of forty four, pain reception levels drop significantly given that it is at around this level age that women averagely begin to undergo a period of menopause. Psychologically, the significant decline in the reception of pain among the females could be attributed to having experienced various intensities of pain in one’s life to the extent in which the same does not cause an alarm or worry not unless it is to an intense level. b. Differences of pain according to levels of income There are also other factors associated with pain such as the place of origin. Pain is more prevalent in third world countries as compared to developed nations based on the fact that developed nations have more advanced health care systems (Hecke et al., 145-156). In most cases, conditions that may elevate the intensity of pain in developing countries may go unattended; hence, lead to an increase in the severity of painful conditions. Haneline and Meeker have noted that the commonness of pain, and its greatness is largely dependent on the socio-economic status of individuals (242-249).6 In developed countries, the systems that are geared towards the management of a person’s health are of a higher standard as compared to those that are used in the developing or less developed countries globally. These countries also have better political systems as compared to developing nations, in that a good political system aids in the restructuring of a better health system that caters for the needs of individuals thus, alleviating the instances of painful experiences even if one is involved in one of such kind. This basically implies that the health care system is dependent on the political situations of the country hence, the differences in pain occurrences between countries. Haneline and Meeker, comparing the commonness of migraines, centered on the economic state of persons between the ages of 12 to 80 years. The obtained results are as presented in the figure below, whose y-axis indicates the percentages and the x-axis indicates the gender, are revealed (256-267).6 Figure 2: Commonness of migraines according to economic status in the US for people aged between 12-80 years Source: Stewart This graph indicates that the lower the level of income, the higher the incidence or commonness of migraines that an individual suffers. As a result, the prevalence of pain is based on the level of income, which can also be illustrated through elucidating how pain can limit an individual’s activity levels as shown in the table below: Table 1: Limitations in activity contributed by chronic back pain according to level of income in 1997. Adults age 18 years and above Activity limitations due to Chronic back conditions (per 1000 people) Poor people 77 people Near poor people 53 people Middle/High income people 24 eople c. Occupation. The prevalence of pain is also determined by an individual’s occupational activities or work levels. This is because pain may also result from the nature of work that a person engages in or the work related factors such as the market dynamics. For instance, workers are more likely to suffer from migraines when market conditions are dire. Therefore, employees are more likely to fail to report to the office depending on the severity of the pain. According to Schultz and Gatchel, the type of work is determined by the individuals level of education (145-159). However, it doesn’t scientifically prove to be true given that back pains are mostly as a result of the daily work experiences and exposures that individuals engage in and not with their level of education. More learned individuals work mostly at the supervisory roles in the workplace while those who have attained high school level education are involved in physical and more challenging roles in the workplace. The results of this can be represented in the figure 3 below, given that all those who were sampled averaged 25 years of age and above. The selection of this age limit was based on the fact that most are the ones engaged in the job market. The y-axis indicates the percentages of pain recorded by participants of the study while the x-axis indicates the level of education obtained by an individual. Figure 3: Commonness of lower back pains according to the level of education in the US among individuals above the age of 25. Source: Stewart From the graph above, the indication is that those who only have elementary education undergo an intense amount of pain as compared to those who had college education minimally due to the fewer instances of pain recorded. In delineating the epidemiology of pain, it would also be important to illustrate locations in the human body prone to pain, its persistency, as well as it effect. Yang & Tsui in a guide they offer as medicine for pain indicate that more people have complained of headaches globally as compared to other locations in the body (145-149).9 Pain in the ankles and foot are the least common sources of pain as shown in the table 2 below. Table 2: Pain location prevalence, persistency, and effects. LOCATION PRVLENCE DURATION >3 MONTHS OCCURS ON HALF DAYS+ HIGH IMPACT ON ACTIVITIES Headache 40% 66% 16% 11% Abdominal 23% 67% 30% 18% Back 39% 81% 45% 32% Neck 31% 81% 47% 32% Shoulder 29% 79% 51% 33% Hand/wrist 23% 77% 52% 37% Hip/knee 28% 83% 55% 40% Ankle/foot 17% 80% 61% 42% d. Differences of pain levels according to Race. Ethnicity contributes significantly on the increased incidences of pain. In the US, for example, the African-American race and other minority groups have been known to report increased cases of pain, especially during the slavery times. Several reasons can be fronted for this scenario. First, the infliction of pain may be due to the prejudice and cultural obstacles that limits the ease of access to health care facility for the less privileged individuals or races. Individual views and opinions towards health also differ depending on the cultural beliefs of each ethnic group. For instance, individuals with Asian backgrounds tend to fear the consequences of using pain relieving medicines more than the pain itself. On the contrary, other ethnic groups such as the whites would prefer to use medication to alleviate the pain instead of worrying about the consequences. The following table shows pain levels and occurrences according to race as were recorded by the US National Centre for Health Statistics. Table 3: Prevalence of headache, low back pain, and neck pain in the US in 2011. Race Severe Headaches or Migraines Low back pain Neck pain Whites only 16.9% 29.0% 15.6% Black/African American 17.2% 27.6% 13.0% Hispanic or Latino 16.1% 27.4% 14.7% American Indian or Alaska Native Only 21.5% 31.0% 16.6% Asian only 11.4% 19.8% 10.6% Two or more races 19.5% 37.6% 20.2% Adjustable aspects associated with pain. Some causes of pain are adaptable, meaning they can be prevented such as the psychological causes of pain as depression and stress. Pain is also associated with other underlying medical conditions. For instance, pain may be as a result of heart related ailments. According to Hecke et al., several chronic conditions may increase the risk of chronic pain through increased nociception from the periphery, resulting in central and peripheral pathophysiological changes associated with chronic pain (180-189). Other factors that elevate the incidences of pain include lifestyle diseases such as obesity, erroneous physical activity and exercises lack of enough sleep, and poor nutrition. Types of pain According to Hardy and Hardy, there are two main types of pain, actual and chronic pain. Chronic pain in itself may be intense or mild depending on the magnitude felt by a person.16 Each of these two types of pains is also divided into four other sub-types of pain. These types of pains are clustered based on their reaction to the various modes of management. In outlining the types of pain, Hardy and Hardy assert that the pain level experienced by an individual does not depend on a measure of its degree.16 A detailed diagrammatical representation of the types and classifications of pain is as shown in the figure below. Figure 4: The types of pain. Source: Nature reviews 1. Acute pain: Acute pain is defined as the pain that takes place instantaneously when there is damage to body tissue or when a medical condition arises. This pain is usually short-lived and intense hence, is a likely indication of injury caused to the individual. For instance, pain felt on the leg or hand after a bone fracture is considered an acute pain. This type of pain is one in which as soon as the injury heals, it ceases to exist. This implies that it is not continuous and may be felt only when the injured part of the body is distressed or subjected to any form of pain. This type of pain is closely linked with the discharge of specific chemical elements that functions to hearten and persuade immobility or apathy geared towards permitting and fastening recuperation (Kaye and Urman 23-28). Chronic pain Bono defines chronic pain as a type of pain that continues even after recuperation and may exceed by up-to one month.18 Given that this pain takes place after acute pain, it is linked with an individuals attempt to move the part of the body that was motionless or static during an acute pain period. Therefore, an individual may not be prepared both physically and mentally to provoke movement; hence, an individual may be rendered motionless. In fact, this type of pain is believed to be as a result of misery due to changes in normal functioning of the body.19 Nocigenic and behavioral pain These types of pain are usually linked to the arousal or activation of the typical and well established conduit or course of pain starting from the tangential protein molecules located within or on the outer surface of a cell that obtains signals from the cell. It is important to expound on the verity that this type of pain is felt at the preliminary phase of tissue damage or when a sickness arises. Behavioral pain is a type of pain that commences as a Nocigenic pain that later cause a transformation in terms of behavior. Neurogenic pain: Neurogenic pain, on the other hand, is a kind of pain felt as a result of injury to the nervous system tangentially or internally. Psychogenic pain: Hardy and Hardy posit that psychogenic pain is a type of pain that arises as a result of psychological infirmity.16 The following diagram shows the difference between Nocigenic (Nociceptive) and Neuropathic (Neurogenic) pains.21 Table 1: Difference between Nociceptive and Neurogenic pain.21 Source: www.vemcomeded.com/pain/pain7 Classification of pain a. Classification in terms of length/duration. This is considered one of the universal methods or technique of classifying pain.22 At this level, pain is either acute, or chronic. General examples of acute pain may include injury to the body tissues, irritation as a result of soreness, and ailments with short intervals.23, 24 Chronic pains on the other hand goes on for a long time and it supersedes acute pain.25 b. Classification in terms of the medical perspective. This mode of classification focuses on the part of the body affected by the pain. Practically every part of the body can experience pain. Some of the most common ones include migraines and back pains. In categorising pain in this perspective, the part of the body where pain is felt sends warning signs that become prevalent and are identified.24 c. Classification according to the severity. In this, pain is considered based on its roughness taken in a range of values from zero to ten. A range of zero denotes the absence of pain while a range of ten denotes the most severe pain. However, this mode of classification may produce skewed results due to the fact that personal or individual accounts, details, and descriptions used to classify the pain may vary over time.24 Pathways and mechanisms in pain One of the roles of pain in the body is that it helps prevent injury through firing warning signals by involving the body senses, as well as, the mental conditions.26 The detailed explanation of this aspect will be categorised in subsections as below. a. Nociceptors. These are specific sensory nerve endings with the capacity to retort to either peripheral stimuli or from stimuli originating from the inside of the body.26 These nerve endings are used to sense and identify repulsive occurrences that induce precise responses within an organ or body tissue. These repulsive occurrences are then transmitted into either the brain or the spinal cord for as electrical currents for processing. When the skin or any other part of the body is injured, the body discharges seditious elements that lead to swelling.26 A good example of these elements includes cytokines and serotonin. b. Primary afferent fibres. These are beta amyloid threads or filaments whose main objective is to transport non-toxic or non-lethal stimulus. Others include delta fibres, and group C nerve fibres.26 These three types of fibres all have different sizes, speeds of transmission, and a sense as shown in the table below. Table 5: Distinguishing features of primary afferent fibres.26 Feature Amyloid-beta Amyloid delta C nerve fibres Width Big tiny least Myelination Very myelinated Lightly myelinated Not myelinated Speed of transmission Less than 40ms-1 5 to 15 ms-1 Less than 2 ms-1 Receptor activation thresholds Short Both short and soaring Soaring Sensation on stimulation Light touch, non-toxic Fast and razor-sharp pain restricted to a small area Sluggish, distributed, and tedious pain c. Dorsal horn of the spinal cord: Lewis et-al., brings forward the fact that the amyloid-delta together with group C nerve fibres allow the transmission of electric signals or currents from the nerves into the cells in the dorsal horn of the spinal cord. At this region, there are composite and intricate communications taking place involving afferent neurons, interneuron, as well as other conduits or courses.26 It is important to suggest that these communications involving these neurons are the decision makers on the actions carried by the secondary afferent neurons.26 d. Ascending tracts in the spinal cord: Ascending tracts are the pathways that transmit or relay Nociceptive signals towards the brain for processing.27 There are two courses involved in this process; first, the signals are transmitted through spinothalamic and spinoreticular strips. In the spinothalamic strip, secondary afferent neurons are involved in the transmission process as they originate from the spinal cord into the brain. This strip only transmits electric signals significant for the containment of the twinge or hurting. In the spinoreticular strip, threads intersect and crisscross each other and then rise parallel to arrive at the posterior part of the brain. From the posterior part of the cerebrum, these strands extend further into the thalamus, hypothalamus, and into the remotest and encrusted structure of neurons in the cerebrum.27 In comparison to the spinothalamic strip, the spinoreticular strip is concerned with expressive or sentimental features of ache or hurting.27 Figure 5: Ascending pathway.28 e. How pain is processed in the brain. Pain is considered a very intricate and multifarious occurrence influenced by various aspects such as individuals disposition, conviction, as well as heredity issues.29 The containment and limitation of the feeling of pain are achieved by the somatosensory cortex. The figure below shows how pain is processed in the cerebrum. Figure 6: How Pain works.30 f. Inhibition of pain transmission. The process of pain is an intricate one as it attributed to the fact that there are additional processes in action with the sole and main function of hindering or slowing down the communication or conduction of pain when it reaches the spinal cord.31 In fact, there are two processes involved in this; gate control theory of pain and the descending inhibition. g. Gate control theory of pain. This theory was coined in by two individuals by the name Melzack and Wall in the year 1965. According to Smeltzer et-al, stimulation of the skin evokes nervous impulses that are then transmitted by three systems located in the spinal cord. The dorsal column fibres, substantia gelatinosa and the central transmission cells act to influence nociceptive impulses.32 This theory postulated that there is a gated system that controls harmful signals.32 This system is controlled by electric signals originating from the cerebrum.32 This theory asserts that there are mental or emotional aspects participating in a critical role, in the pain process. As a result, this theory has directed methodical investigations aimed at recognising and categorising psychosomatic and action based advances to the management of pain.32 h. Descending inhibition. It denotes the dominant hindering pressures or control located on the nociceptors during the relay of signals to the cerebrum.33 According to Bountra et al., there are a certain matters that lead to the stimulation of these pressures such as anxiety, trauma, dissemination and subsequent distribution of harmful signals, and tangential and other internal stimulus in the brain and spinal cord.34 i. Nociceptive pain. These are pains that are controlled by the internal body tissues as opposed to tangential systems.35 This kind of pain is also relayed by the afferent strands characterised by reduced thickness and it passes through the gate mechanism coined in by Melzack and Wall (As elucidated ear. Nociceptive pain is followed by swelling of body tissues, softness of the tissues, and an increase in temperature.35 In assessing this kind of pain, psychotherapist examines and investigates vigorousness in relation to mobility of the affected part of the body. Through this, he is able to identify and classify the kind of injury to the tissues.36 Figure 7: Transmission of Nociceptive pain.36 Source: www.intechopen.com/books/gene-therapy-tools-and-potential-applications/gene-therapy-for-chronic-pain-management Central sensitisation. This refers to the increase and augmentation of the role of neurons in the nociceptive courses or conduits.37 The augmentation is as a result of an elevation of the stimulation of outer surfaces of a cell or tissue, and as a result of minimised stimulation of the brain and spinal cord.37 This increase is what leads to swelling on the injured or damaged tissue.37 Olesen outlines some of the symptoms of central sensitisation as elevated levels of sensitivity from illumination, contact, sound, chemicals, external strain, and temperature fluctuations.38 Treatment include relaxation, employment of electrical stimulants, channeled, psychological, or motor imagery, mirror psychoanalysis, and physical rehabilitation.38 Figure 8: The role of central sensitization.39 Neurogenic pain. Neurogenic pain is an immediate pain resulting from a cut, wound, or ailments.35 According to Kumar and Saha, the main symptom of Neurogenic pain include reproduction of pain in neurodynamic tests and incidence of automated allodynia on nerve trunk palpation.35 Massaging the affected nerves or tissues is one of the treatment techniques used in treating this kind of pain.40 Additional treatment technique includes electrical stimulation of the nerves.40 Neurogenic/Neuropathic pain may occur at different parts of the body ranging from the nerve endings on the tangential sections to the cerebrum. Symptoms of this form of pain present themselves singly or may occur together. The symptoms include absence of feelings or consciousness, degeneration and total weakness of the muscles, pain on the skin as a result of touch, temporary itching or tingling sensation, and increased sensitivity to pain when exposed to heat. In assessing neurogenic pain, the initial phase is acquire the history of the painful occurrence. In taking a history, a physician focuses on the pattern, greatness, and length of the pain. There are various tools used in assessing this kind of pain. According to Bennett, these comprise of "neuropathic pain scale, Leeds Assessment of Neuropathic symptoms and signs (LANSS), neuropathic pain questionnaire, ID-pain and the Douleur neuropathic.41 Figure 9: Neurogenic pain.40 Case study: Trapped nerve at the back John, a 30 years old man went to see his doctor complaining of incessant back pains developed after a lifting a heavy load.. This man had never undergone any surgery prior to the accident. His intention was to receive painkillers to relieve the pain. Physical examination: Height-------------------------5 ft 9 in weight ----------------------------198 lb Blood pressure-----------------132/89 mm Hg Current Medication Diazepam 10 mg 3 times a day Assessment tools Leeds Assessment of Neuropathic symptoms and Signs (LANSS) Questionnaire Pain Detect Questionnaire Tests CT scan (computerised tomography)---------Showed a trapped nerve Clinical representation Lack of sensation degeneration and total weakness of the muscles, pain on the skin as a result of touch, temporary itching or tingling sensation, increased sensitivity to pain when exposed to heat Treatment Bed rest for two weeks Regular massage Apply ice and heat Medication Non-Steroidal anti inflammatory drugs (NSAIDs): Main objective to decrease puffiness or inflammation Summary of the case study In assessing his condition in order to identify the kind what was wrong, the doctor had to conduct physical examinations. After observation, the doctor inquired whether John had ever had any prior surgical procedure conducted on his back, to which he rebuffed. John explained to his doctor that he had difficulties performing his daily chores as the result of the back pain. In addition, John reported of poor coordination of his muscles especially the arms. His other reported signs included numbness, involuntary muscle movements, and a sharp pain on his lower back. The doctor had to conduct a CT scan (computerised tomography) to identify the extent of the damage. The doctor suspended a trapped nerve and his assumption were proven right by the CT scan.42 The diagram below from the Riverside Health Systems shows how a nerve may be trapped at the back. Figure 10: Trapped nerve42 In treating this condition, the doctor allotted John painkillers to reduce the pain. In treating the involuntary muscle movements, tablets known as diazepam whose main work is to relax the muscles, were used. Subsequently, the doctor advised John to take as much rest as possible in a bid to try and avoid additional injury to the back. The doctor also recommended frequent back massages. For long term care, the doctor advised John to undergo physiotherapy.43 Conclusion Pain is a distasteful feeling that takes place immediately the body is injured attacked by an ailment. The prevalence of pain is dependent on factors such as gender, age, income level, occupation, and race. The two main types of pain are chronic and acute pain, which are further divided into Nocigenic, Behavioural, Neurogenic, and psychogenic. Subsequently, pain is classified on the basis of its length, greatness, means, and according to medical perspective and situation. The pain pathway includes Nociceptors, and primary and secondary afferent fibres. Other forms of pain include Nociceptive pain, Central sensitisation, and Neurogenic pain. The Gate Control Theory affirms that there is a gated system that controls harmful signals from being sent into the nervous system for processing. All the types of pain display have divergent characteristic in terms of their signs and symptoms, clinical representation, assessment, and the kind or types of assessment tools used. Works Cited 1. Sofaer B. Pain: Principles, Practice and Patients. Cheltenham: Nelson Thornes, 2003. Print. 2. Stewart W F. The Epidemiology of Chronic Pain. Geisinger Center for Health Research. PowerPoint. n.d. 12 March 2014. 3. Simpson D, McArthur J, Dworkin R. Neuropathic Pain: Mechanisms, Diagnosis and Treatment. New York: Oxford University Press, 2012: 90. Print. 4. Fishman S, Ballantyne J, Rathmell J. Bonicas Management of Pain. New York: Lippincott Wilkins & Wilkins, 2010: 699-790. Print. 5. Hecke O, Torrance N, Smith B. Chronic pain epidemiology-where do lifestyle factors fit in?." British Journal of Pain. 8.1 (2014): A4. JSTOR. Web. 12 Mar. 2014. 6. 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