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Neuropathic Pain - Diagnosis Mechanism and Management . Dr Amit Verma M.D, D.N.B, P.D.C.C, F.I.P.P CONSULTANT ANAESTHESIOLOGIST DR BALWANT SINGH’S HOSPITAL. 1. CASE 1. 55 yr. , Female Presented with pain in back of chest for 5 yrs No h/o HZ, DM, Trauma, Loss of weight
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Neuropathic Pain - Diagnosis Mechanism and Management Dr AmitVerma M.D, D.N.B, P.D.C.C, F.I.P.P CONSULTANT ANAESTHESIOLOGIST DR BALWANT SINGH’S HOSPITAL 1
CASE 1 • 55 yr. , Female • Presented with pain in back of chest for 5 yrs • No h/o HZ, DM, Trauma, Loss of weight • Quality - burning • Intensity 5 - 6 / 10 • Tried NSAIDs multiple times
CASE 2 • 75 yrs, Female • Feels Depressed due to Pain in chest • Severe lancinating pain with increased sensitivity • H/O very painful rash in the same distribution 5 months back • Rash subsided but pain didnt
CASE 3 • 35 yr., female patient with severe headache. • Diagnosed as a case of migraine • Wincing in pain , ℅ jolts of pain while combing her hair • On Migraine prophylaxis
CASE 4 • 45 yr. Old Male on a hot summer day with a wool shawl draped around his shoulder and right arm • ℅ Pain in the right hand following closed reduction of wrist fracture • Right arm was cold and sometimes sweaty • Severe pain on cutting nail • Visited three physician who referred her to a psychiatrist with the diagnosis of Conversion disorder
Pain • Poena - penalty / punishment • Start of Pain Clinics • Insight into the Etiopathogenesis • Fifth vital Sign 2
Classification ( IASP) • Region • System • Acute Vs Chronic • Mild / Moderate / Severe • Nociceptive / Inflammatory/ Neuropathic ( Clifford J Woolf ) 3
Definition • IASP defines Pain as • an unpleasant sensory or emotional experience which we primarily associate with tissue damage or describe in terms of such damage , or both • Neuropathic Pain as - • Pain initiated or caused by a primary lesion or dysfunction of the peripheral or central nervous system 4
Neuropathic Pain - Difficulties • No Consensus on Definition • Pain Perception is subjective • Rarely One Diagnostic Test • Lack Of Specificity in Diagnosis • Signs & Symptoms Change Over Time • Patients not believed 5
Components of Neuropathic Pain • Pain • Lancinating/burning/pricking/stabbing • No ongoing tissue damage • Delay in onset after nerve injury • Spontaneous paroxysmal electric shock sensation 13
ALLODYNIA HYPERALGESIA PAIN INCREASED PAIN PAINFUL STIMULUS Low Intensity Stimulation Innocuous sensation Abnormal Sensations
Negative sensory signs • Pain with numbness • Presence of neurologic deficit 14
Descriptions of Neuropathic Pain • “I feel as though someone has pulled the skin off my left arm and is then constantly rubbing salt into the wound.” • “I feel as though my leg is on fire. My skin feels burnt, and it is as though someone is taking a claw and tearing into my skin 24 hours a day.” • “I feel as though someone has taken a hot poker knife and is jabbing it deep into my right eye. If I could pull my eye out, only to remove the sensation, I would gladly do so.” 15
Neuropathic Pain Syndromes • Peripheral Nervous System ( focal and multifocal lesions ) • Peripheral Nervous System ( Generalized polyneuropathies ) • Central Nervous System Lesions • Complex Neuropathic Disorders
Peripheral Nervous System (focal and multifocal lesions) • Trigeminal neuralgia • Post herpetic neuralgia • Diabetic Mono neuropathy • Entrapment Syndrome • Ischemic Neuropathy • Phantom Limb • Post Traumatic Neuralgia 7
Peripheral Nervous System Generalized Polyneuropathies • Metabolic - DM, Amyloid • Toxic - Alcohol, taxanes • Infective - HIV • Autoimmune - GBS • Hereditary - Fabry’s Disease • Malignancy 8
Central Nervous System Lesions • Spinal Cord Injury • Prolapsed Disc • Stroke • Multiple Sclerosis • Parkinson’s Disease • Surgical Lesions 9
Complex Neuropathic Disorders • Complex Regional Pain Syndrome I • Complex Regional Pain Syndrome II 10
Ascending Pain Pathway 17 17
Descending Pain Pathway 18 18
Peripheral nerve fibers Sympathetic Fibers • Spinal Cord anatomical reorganization • Dorsal Horn Denervation Sensitivity • Molecular Changes Spinal Cord Cerebral Reorganization Molecular Changes Brain • Ectopic Discharge • Collateral Sprouting • Nociceptive sensitization Ephaptic Crosstalk 19
Ectopic Discharges • Increase in the level of spontaneous firing in the injured neurons as well as their uninjured neighbor neuron • Result of alteration in the expression of Sodium channels
Ephaptic Conduction • Cross excitation among the neurons having spontaneous firing capacity leading to amplification of depolarization • Important in association of Sympathetic system
Collateral Sprouting • Primary afferent neuron injury leads to sprouting of collateral fibers from sensory axon in their attempt to regenerate • These sprouts are sensitive to low threshold stimulus
SNS AND PNS COUPLING • DUE TO ENHANCED SENSITIVITY TO CATECHOLAMINES LEADING TO PAIN PERCEPTION
Nociceptive Sensitization • Increase in Bradykinin binding sites within DRG following axotomy leading hyperalgesia
CENTRAL MECHANIMS • Spinal Cord reorganization • Spinal Cord hyper excitability ( central sensitization ) • Cerebral Reorganization
Healing begins with the History • Clinical description and history taking are the best mechanism to diagnose Neuropathic Pain • Identify • Painful symptom • Altered sensation • History } All matching neuroanatomical or dermatomal pattern 22
Screening Methods • Leeds Assessment of Neuropathic Symptoms and Signs ( LANSS ) scale • Sens / Spec - 83 / 87 % • Pain DETECT questionnaire • Neuropathic Pain Questionaire • Neuropathic Pain Scale 23
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Bedside Examination • Identify the altered sensation in painful area ( compare with non painful area ) • Dysesthesia (Allodynia, Hypoalgesia, Hyperalgesia ) • Inability to distinguish warm and cold objects 25
Pain & Functional Brain Imaging( F.B.I ) • Positron Emission Tomography • Functional MRI • Both Measure energy consumption in activated brain regions • FBI has mapped the brain neuromatrix ( area of brain that processes pain response ) 26
Functional Brain Imaging • Neuromatrix - • 1o & 20 somatosensory cortex ( mediate sensory discriminative features of pain ) • Anterior cingulate gyrus cortex and insula ( mediate affective motivational component of pain • Pre frontal cortex - mediate cognitive aspects of pain • Thalamus - gateway between cortex and brainstem • Increased regional blood flow of neuromatrix in Neuropathic Pain
REDUCE PAIN Approach To Treatment DIAGNOSIS TREAT UNDERLYING CONDITION PREVENTION IMPROVE PHYSICAL FUNCTION IMPROVE QUALITY OF LIFE REDUCE PSYCHOLOGICAL DISTRESS
Management • Mx of ectopic activity / Ephaptic Conduction • Na+ Channel Blockers - • Phenytoin • Lignocaine • Oxcarbazepine • Gabapentin 33
Reducing Central Sensitization • NMDA receptor antagonist • Ketamine • Amitryptyline • Methadone • Gabapentin, Pregabalin 34
Improving Descending Control • Local Inhibitory controls • GABA - B agonist - Baclofen • Opioids - Oxycodone, tramadol • Descending inhibition form brain • Clonidine • TCA 35
Sympathetically Mediated Pain • Sympathetic Plexus Block • Stellate ganglion • Lumbar Sympathetic chain block • Central Neuraxial Block • Epidural infusions of adjuvants and local anesthetics • Intrathecal infusions - opioids / baclofen 36
Somatic / Sensory Nerve Block • Brachial Plexus Block • Para - vertebral Block • Lateral Cutaneous Nerve of Thigh Block • Intercostal Nerve Block 37
Interventional Strategies • Diagnostic • Break in cycle of Pain • Should be Imm. Followed by active physiotherapy • Epidural, Trans Foraminal , Facet Blocks • Spinal Cord Stimulation 38
Complementary Therapies • Acupuncture • Nutritional Counseling • Massage Therapy • Mirror Therapy 39
Pharmacotherapy • Carbamazepine • Dose – 100 mg BD - 1000 mg / day • S/I – Dizziness, Ataxia, N/V, S.J Syndrome, TCP • C/I – Liver Dysfunction, B.M suppresion 40