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
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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
3
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
4
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
5
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
6
Pain
Poena - penalty / punishment
Start of Pain Clinics
Insight into the Etiopathogenesis
Fifth vital Sign
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Classification ( IASP)
Region
System
Acute Vs Chronic
Mild / Moderate / Severe
Nociceptive / Inflammatory/ Neuropathic
( Clifford J Woolf )
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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
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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
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Abnormal Sensations
PAINFUL STIMULUS
Low Intensity
Stimulation
Innocuous sensation
INCREASED
PAIN
PAIN
ALLODYNIA
HYPERALGESIA
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Negative sensory signs
Pain with numbness
Presence of neurologic deficit
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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.”
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Neuropathic Pain Syndromes
1. Peripheral Nervous System ( focal and
multifocal lesions )
2. Peripheral Nervous System ( Generalized
polyneuropathies )
3. Central Nervous System Lesions
4. Complex Neuropathic Disorders
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Peripheral Nervous System
(focal and multifocal lesions)
Trigeminal neuralgia
Post herpetic neuralgia
Diabetic Mono neuropathy
Entrapment Syndrome
Ischemic Neuropathy
Phantom Limb
Post Traumatic Neuralgia
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Peripheral Nervous System
Generalized Polyneuropathies
Metabolic - DM, Amyloid
Toxic - Alcohol, taxanes
Infective - HIV
Autoimmune - GBS
Hereditary - Fabry’s Disease
Malignancy
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Central Nervous System Lesions
Spinal Cord Injury
Prolapsed Disc
Stroke
Multiple Sclerosis
Parkinson’s Disease
Surgical Lesions
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Complex Neuropathic Disorders
Complex Regional Pain Syndrome I
Complex Regional Pain Syndrome II
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MECHANISM OF
NEUROPATHIC PAIN
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Ascending Pain Pathway
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Descending Pain Pathway
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Cerebral Reorganization
Molecular Changes
Brain
Spinal Cord
Spinal Cord anatomical reorganization
Dorsal Horn Denervation Sensitivity
Molecular Changes
Peripheral
nerve fibers
Sympathetic
Fibers
•Ectopic Discharge
•Collateral Sprouting
•Nociceptive sensitization
Ephaptic Crosstalk
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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
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Ephaptic Conduction
•
Cross excitation among the neurons having
spontaneous firing capacity leading to
amplification of depolarization
•
Important in association of Sympathetic
system
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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
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SNS AND PNS COUPLING
•
DUE TO ENHANCED SENSITIVITY TO
CATECHOLAMINES LEADING TO PAIN
PERCEPTION
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Nociceptive Sensitization
•
Increase in Bradykinin binding sites within
DRG following axotomy leading hyperalgesia
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Central & Spinal Cord
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CENTRAL MECHANIMS
•
Spinal Cord reorganization
•
Spinal Cord hyper excitability ( central
sensitization )
•
Cerebral Reorganization
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DIAGNOSIS OF
NEUROPATHIC PAIN
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Healing begins with the History
Clinical description and history taking are
the best mechanism to diagnose
Neuropathic Pain
Identify
All matching
neuroanatomical or
dermatomal pattern
Painful symptom
Altered sensation
History
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Screening Methods
Leeds Assessment of Neuropathic
Symptoms and Signs ( LANSS ) scale
Sens / Spec - 83 / 87 %
Pain DETECT questionnaire
Neuropathic Pain Questionaire
Neuropathic Pain Scale
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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
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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 )
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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
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Pain
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Approach To Treatment
DIAGNOSIS
TREAT UNDERLYING CONDITION
REDUCE
PAIN
IMPROVE
PHYSICAL
FUNCTION
PREVENTION
REDUCE
PSYCHOLOGICAL
DISTRESS
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IMPROVE QUALITY OF LIFE
Management
Mx of ectopic activity / Ephaptic Conduction
Na+ Channel Blockers -
Phenytoin
Lignocaine
Oxcarbazepine
Gabapentin
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Reducing Central Sensitization
NMDA receptor antagonist
Ketamine
Amitryptyline
Methadone
Gabapentin, Pregabalin
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Improving Descending Control
Local Inhibitory controls
GABA - B agonist - Baclofen
Opioids - Oxycodone, tramadol
Descending inhibition form brain
Clonidine
TCA
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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
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Somatic / Sensory Nerve Block
Brachial Plexus Block
Para - vertebral Block
Lateral Cutaneous Nerve of Thigh Block
Intercostal Nerve Block
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Interventional Strategies
Diagnostic
Break in cycle of Pain
Should be Imm. Followed by active
physiotherapy
Epidural, Trans Foraminal , Facet Blocks
Spinal Cord Stimulation
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Complementary Therapies
Acupuncture
Nutritional Counseling
Massage Therapy
Mirror Therapy
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Pharmacotherapy
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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
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Gabapentin
•
Multi modal action - Reduces ectopic activity,
dampens central sensitization and decreases
glutamate activity
•
Dose – 300 – 3000 mg / day
•
S/I – dizziness, sedation, weight gain
•
C/I - Hypersensitivity
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Pregabalin
•
•
•
Dose – 75 – 600 mg / day in divided doses
S/E – Dizziness, sedation, confusion,
peripheral edema
C/I - Hypersensitivity
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TCA - Amitriptyline
•
•
•
Dose – 10 – 75 mg / day in EDD
S/E – anticholinergic, constipation,
confusion
C/I – narrow angle glaucoma, urinary
retention, 2nd or 3rd degree heart block
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Ketamine
•
•
•
Dose – 0.25 mg / kg – 1000mg/day
S/I - delirium, hallucinations, confusion,
night mares
C/I – hypersensitivity, psychiatiric disorders
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Lignocaine
•
Dose – 5 mg/kg over 1 hour
•
S/E- hypotension, Neurotoxicity, sedation
•
Effective diagnostic tool to identify
responsiveness to Na channel blockers
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Tramadol
•
Dose – 50mg bd – 400 mg /day
•
S/I – sedation , Nausea
•
C/I- hypersensitivity, drowsy , elderly
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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
59
CASE 2
•
75 yrs, Female
•
Feels Depressed due to
Pain in chest
•
H/O very painful rash in
the same distribution 5
months back
•
Rash subsided but pain
didnt
60
CASE 3
•
35 yr., female patient with severe headache.
•
Diagnosed as a case of migraine
•
•
Wincing in pain , ℅ jolts of pain while
talking, combing her hair
On Migraine prophylaxis
61
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
62
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Conclusion
Neuropathic pain is a neuropsychiatric condition in
which pain is initiated or caused by a primary lesion or
dysfunction in the nervous system. Understanding the
complexity of neuropathic pain becomes the cornerstone
for appropriate diagnosis and management. Successful
management depends on realistic patient-physician
expectations and an individualized, multidisciplinary
approach that takes advantage of the ever-evolving
armamentarium of evidenced- based treatments.
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Thank You
•
We must all die. But that I can save him
from days of torture, that is what I feel as
my great and ever new privilege. Pain is a
more terrible lord of mankind than even
death itself
•
Albert Schweitzer
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