DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S

1. PAIN PATHOPHYSIOLOGY & MANAGEMENT DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY &CONSULTANT KING KHALID UNIVERSITY HOSPITAL,RIYADH. DR. MANSOOR AQIL B.Sc., M.B.B.S., F.C.P.S ASSOCIATE PROFESSOR, KING SAUD UNIVERSITY &CONSULTANT KING KHALID UNIVERSITY HOSPITAL,RIYADH.

6. PAIN PAIN • Word pain is derived from Latin word “Poena”, meaning penalty, suffering or punishment

7. PAIN • An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. (International association of study of pain)

8. CLASSIFICATION OF PAIN

9. TYPES OF PAINAccording to duration • Acute • Chronic

10. TYPES OF PAINAccording to Etiology • Postoperative OR • Cancer pain

11. TYPES OF PAINAccording to Type of the organ affected • Toothache • Earache • Headache • Low backache

12. TYPES OF PAIN(According to Pathophysiology) • Nociceptive; Due to activation or sensitization of peripheral nociceptors. • Neuropathic: Due to injury or acquired abnormalities of peripheral or CNS.

13. ACUTE PAIN • Caused by noxious stimulation due to injury, a disease process or abnormal function of muscle or viscera • It is nearly always nociceptive • Nociceptive pain serves to detect, localize and limit the tissue damage.

14. PHYSIOLOGICAL PROCESSES IN NOCICEPTION • Transduction • Transmission • Modulation • Perception

15. 400 years ago Reneé Descartes described pain transmission: The flame that burns the hand is transmitted along the nervous system to the brain as a stimulus, where it torments man as a small flame • Noxious stimulus • Activate nociceptors Ouch! • Transmit to Brain • Perception of Pain Mechanisms in Nociception If it were only that simple…..

16. Nociception Transduction Conduction Modulation Perception Modulation Noxious stimulus “Ouch” Pain primary sensory neuron central neuron

17. TYPES OF ACUTE PAIN • Somatic OR • Visceral

18. SOMATIC PAIN • Superficial OR • Deep

19. SUBTYPES OF VISCERAL PAIN • Localized visceral pain • Referred Visceral pain • True Localized parietal pain • Referred parietal pain

20. TRUE VISCERAL PAIN • Dull, diffuse and in Midline • Frequently associated with sympathetic or parasympathetic activity • Nausea • Vomiting • Sweating • Changes in HR and BP.

21. PARIETAL PAIN • Sharp(stabbing sensation) either localized or referred to a distant site. • Phenomenon of visceral pain or parietal pain referred to cutaneous area results from embryologic development and migration.

22. PATTERNS OF REFERRED PAIN

23. REFERRED PAIN

25. PAIN PATHWAY

26. FIRST ORDER NEURON Reach the spinal cord through dorsal spinal root. • Some through ventral root • Trigeminal N Gasserian ganglion • Facial N Geniculate ganglia • Glossopharyngeal N Superior and Petrosal ganglia • Vagus Ganglion Nodosum and Jugular ganglia

27. Spinothalamic tract Dorsal horn of spinal cord • Nociceptive sensory fibres are C-fibres and Ad fibres • C-fibres umyelinated • Ad myelinated • Slow conduction velocity • Signal variety of noxious stimuli - polymodal Dorsal Root Ganglion Peripheral nerve Sympathetic ganglion Viscera Blood vessels Skeletal muscle Tendon bundle C and Ad fibres Nociceptive terminals Muscle and skin receptors Nociceptive pathways: peripheral sensory nerves

28. SPINOTHELAMIC TRACT Axons of the second order neurons cross the midline form spinothalamic tractThalamus, Reticular formation, Nucleus Raphe Magnus and Periaquaductal gray matter. • Medial tractMedial Thalamus • Lateral tract:Ventral Posterolateral Nucleus of Thalamus

29. THALAMIC NUCLEI

30. ALTERNATE PATHWAYS • Spinomesencephalic • Spinoreticular • Spinohypothalamic • Spinotelencephalic • Spinocervical • In the dorsal column

31. THIRD ORDER NEURON Located in Thalamus. Send projections to sensory area 1 &II and Superior wall of Sylvian fissure. Interlaminar and medial nuclei Anterior Cingulate Gyrus.

33. PAIN CENTRE Post Central Gyrus

34. CINGULATE GYRUS

38. Receptors ---Free nerve endings

39. Receptors ---Free nerve endings • Mechanoreceptors:Pinch and Pinprick • Silent Nociceptors:Inflammation • Polymodal mechanoheat nociceptors: Excessive pressure, Extremes of Temperature and Alogens like Bradykinin, Serotonin, Histamine, H, K, Prostaglandins and ATP.

40. Types of Peripheral Fibers Pain Fibers Ad and C A. a, b, d, & g B. C.

41. Classification & Function of Peripheral Nerve Fibers A.Myelinated A- Fibers: • a: Motor , Proprioception (afferent) • b: Motor, Touch (afferent) • g: Muscle spindles (efferent) • d: Pain, Temperature (afferent) B. Myelinated B-Fibers: • Pre-ganglionic Sympathetic Fibers C. Non-Myelinated C- Fibers: Pain, Temperature.

42. PHYSIOLOGY OF NOCICEPTION • Fast pain(First pain) • Slow pain(Second pain)

43. Pain Intensity Time Peripheral Terminal Activation in Acute pain: Phase 1 First pain - sharp, pricking, localising Ad fibres myelinated (12-30 m/s) Second pain - dull, burning, aching, not localised, diffuse C-fibres umyelinated slow conduction (0.5 - 2 m/s

44. MODULATION

45. MODULATION OF PAIN • Peripheral Modulation • Central modulation

46. PERIPHRAL MODULATION • Primary Hyperalgesia • Secondary Hyperalgesia

47. PRIMARY HYPERALGESIA • Decrease threshold •     Increase in frequency of response • Spontaneous discharge

48. State of normosensitivity Low intensity stimulation High intensity (noxious) stimulation Innocuous sensation PAIN

49. State of Normosensitivity Response proportional to stimulus Response Noxious stimulus DRG Pain neuron Central nervous system Peripheral tissue

50. MAST CELLS BASOPHILLS PLATELETS DAMAGED TISSUE MAST CELLS PLEATELETS ACTIVATED FACTOR XII ALOGENS HISTAMINE SEROTONIN BRADY- KIANIN PRIMARY HYPRALGESIA STIMULATION OF C- FIBERS