Pain PDF

 PAIN Omniya Abdel Aziz Assisstant Professor, Oral and Maxillofacial Surgery department Nervous system is divided into : The peripheral nervous system Autonomic Somatic The central nervous system Made up of brain and spinal cord Neuron Types: Sensory (afferent)...

 PAIN Omniya Abdel Aziz Assisstant Professor, Oral and Maxillofacial Surgery department Nervous system is divided into : The peripheral nervous system Autonomic Somatic The central nervous system Made up of brain and spinal cord Neuron Types: Sensory (afferent) Conducts impulses from the body to the CNS Motor (efferent) Conducts impulses from CNS peripherally  Nociceptors Specialised sensory receptors responsible for the detection of noxious (unpleasant) stimuli, transforming the stimuli into electrical signals, which are then conducted to the central nervous system. Pain nerve fibers Primary afferent fibers Aβ fibers are highly myelinated and of large diameter, therefore allowing rapid signal conduction. They have a low activation threshold and usually respond to light touch and transmit nonnoxious stimuli.  Aδ fibres are lightly myelinated and smaller diameter, and hence conduct more slowly than Aβ fibres. They respond to mechanical and thermal stimuli. They carry rapid, sharp pain and are responsible for the initial reflex response to acute pain.  C fibres are unmyelinated and are also the smallest type of primary afferent fiber. Hence they demonstrate the slowest conduction. C fibers are polymodal, responding to chemical mechanical and thermal stimuli. C fiber activation leads to slow, burning pain. An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage “International Association for the Study of Pain”  Pain is an experience that cannot be shared. It is wholly personal, belonging to the sufferer alone Is pain protective mechanism against injury or not?  Benefits of pain Although its an unpleasant sensation yet it has a protective benefit: Gives warning signal about the existence of a problem. Prevents further damage by causing reflex withdrawal of the body from the source of injury  Forces the patient to rest or to minimize activities thus enabling rapid healing of injured part Urges the person to take the required treatment to prevent major damage  Pain Tolerance and Pain Threshold Pain tolerance refers to how much pain a person can reasonably handle. Some people have a higher pain tolerance than others. Pain threshold is the point at which a stimulus becomes painful. Pain threshold also varies from person to person. Factors affecting pain tolerance Genes Age Stress Expectation Experience of pain Not All Pains Are Alike Dentists must be able to differentiate between pains that stem from dental, oral, and masticatory sources and those that emanate from elsewhere  Types of pain Acute Sudden onset Sharp, localized sensation Usually subsides quickly Chronic Lasting more than 3 to 6 months Persistent or episodic in duration or intensity  Referred pain Pain that is perceived at a site adjacent to or away from the site of origin Historical Note  In ancient times, Homer thought that pain was due to arrows shot by the gods. Aristotle, the first to distinguish the five physical senses, considered pain to be a “passion of the soul” that somehow resulted from the intensification of other sensory experience.  Plato contended that pain arose from within the body, an idea that gave birth to the concept that pain is an emotional experience more than a localized body disturbance In 1664, Descartes first described the concept of pain being carried by fibers to the brain to be perceived as pain. He thought that pain resulted from the overstimulation of these sensory fibers.  During the 19th century, development of the concept that pain was mediated by specific pain pathways and was not simply due to excessive stimulation of the special senses.  Theories of pain Specificity Theory Each modality of sense, touch or pain, is encoded in separate pathways. Thus, its fundamental thought is that each sense of modality has a specific receptor and associated sensory fiber sensitive to only one specific stimulus  Intensity Theory There are no distinct pathways for touch or pain perception. Pain not as a unique sensory experience but as an emotion that occurs when stimulus is too strong.  Pattern Theory Nerves involved in detecting pain also detect other sensations. No specific nerve fibers or endings used just for the sensation of pain. Different sensations, such as cold, pain, heat, and touch, are detected by the same nerves, which then send specific signal patterns to the brain. The brain interprets the pattern, which includes both the sensation and its intensity, and the specific sensation is felt  Gate Control Theory A nerve-based theory that reconciles the specificity and pattern theories. Includes both the central nervous system and peripheral nervous system. Suggests that a metaphorical “gate” either blocks or allows pain to travel through the spinal cord to the brain  Neuromatrix theory  Diagnosis A.Chief complaint (perhaps more than one) Recorded in patient’s own words 1. Location of the pain 2. Onset of the pain a. Association with other factors b. Progression 3. Characteristics of the pain a. Quality of the pain (pricking, itching, stinging, burning, aching, or pulsating) b. Behavior of the pain i. Temporal behavior (intermittent or continuous) ii. Pain duration (seconds, minutes, hours, days) iii. Localization (localized, diffuse, migrating, radiating) c. Intensity of the pain (mild, modearte ,severe) Visual analogue scale (VAS) d. Concomitant symptoms Hyperesthesia : extreme sensitivity to touch. Hypoesthesia: reduced sense of touch or sensation. Anesthesia: loss of sensation Paresthesia: an abnormal sensation, typically tingling or pricking Dysesthesia:an abnormal unpleasant sensation felt when touched e. Flow of the pain (steady or paroxysmal) 4. Aggravating and alleviating factors a. Effect of functional activities (talking,chewing…) b. Effect of physical modalities (hot,cold,massage) c. Medications (doses) d. Emotional stress e. Sleep quality 5. Past consultations and treatments 6. Relationship to other pain complaints B. Past medical history C. Review of systems D. Psychologic assessment  Neural Pathways of Pain The subjective experience of pain arises by way of four distinct processes: Transduction Transmission Modulation Perception  Transduction is the process by which noxious stimuli are converted into electrical activity in the appropriate sensory nerve endings.  Transmission refers to the neural events that carry the nociceptive impulses through synaptic junctions from one neuron to the next Modulation a neural process that acts specifically to reduce the activity in the pain transmission system and reduce the perception of pain in healthy individuals Perception The final process involved in the subjective experience of pain If nociceptive input reaches the cortex, perception occurs, which immediately initiates a complex interaction of neurons between the higher centers of the brain It is at this point that suffering and pain behavior begin.  Pain pathway The pain pathway (spinothalamic pathway) is made up of three neurons that ultimately transmit the sensory information to the appropriate area of the cortex. The first order neuron is the sensory nociceptor neuron The second order neuron is located within the spinal cord Third order neuron is located in the thalamus, that extends out to the primary somatosensory cortex. 1st order neuron: Arise from sensory receptors of the body The fibers enter the white mater and ends at the substantiagelatinosa 2nd order neuron: The fibres synapse with the 2nd order neuron at the substantiagelatinosa Fibres then cross to the opposite side and enters the lateral spinothalamic tract Tracts ascends to brainstem to medulla oblongata, pons and midbrain and reaches the ventral posterolateral nucleus of the thalamus 3rd order neuron: Arise from the thalamus and carries the pain impulses to the cortex  Control of pain Removing of the cause Raising the pain threshold Blocking the pathway of the painful impulses  Local anesthesia Any technique that render part of the body insensitive to pain without affecting consciousness General anesthesia Drug induced loss of consciousness during which patient are not arousable even by painful stimulation Medications Non steroidal anti inflammatory drugs(NSAIDs) Opioids  THANK YOU