Transcript 29 PainModulation 12.10.20112012-10

PAIN MODULATION
Prof. Ashraf Husain
MODULATION
• Pain modulation means pain
perception variability which is
influenced by endogenous and
exogenous mechanism
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Referral of pain from the internal
organs
Organ
Site of reffered pain
• Meninges
• Heart
Back of head and neck
Central chest arms
(usually left), neck,
occasionally abdomen.
Behind sternum
Shoulder tip
Behind sternum
Cont…5
• Trachea
• Diaphragm
• Oesophagus
Organ
Site of reffered pain
• Stomach, duodenum
Upper abdomen,
epigastrium
• Small bowel, pancreas Around umbilicus
• Large bowel, bladder Lower abdomen
above pubic bone
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VISCERAL PAIN
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VISCERAL PAIN PATHWAY
Pain - Aδ and fibers
Travel with autonomic afferent
Spinal cord
(Dorsal Horn)
Lat. spinothalamic tract
Thalamus
Somatosensory Cortex
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CHARACTERSITICS OF VISCERAL PAIN
• Poorly localized
• Associated with nausea and autonomic
disturbance
• Often referred to another part of the body
• Cutting, crushing are not painful when applied
to viscera
• Pain is caused by distension, ischemia and
inflammation
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MODULATION
• Pain modulation means pain
perception variability which is
influenced by endogenous and
exogenous mechanism
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• Pain modulation can be discussed under
following headings
– Spinal modulation of pain input
• Gate theory of pain
– Supra spinal modulation
• Role of periaqueductal grey (PAG) matter
• Role of Nucleus Raphe Magnus (NRM)
– Pain modulation by use of Opioid
neurotransmitters eg: endorphin, enkaphalin
Dynorphin.
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SPINAL MODULATION
A MODAL OF “GATING” OF PAIN
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SPINAL MODULATION
DORSAL HORN GATING MECHANISM
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ASCENDING AND DESCENDING PAIN PATHWAYS
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SUPRASPINAL MODULATION
Descending
Analgesic
Pathway
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SUPRASPINAL MODULATION
OPIOID RECEPTOR MODULATION
Neurotransmitters in
Analgesic
Pathway
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MECHANISM OF OPIOID NEUROTRANSMITTER
ACTION:
•ENDORPHIN:
•Neurons using endorphin or enkaphalin are found in
PAG where they inhibit GABAnergic interneurons
that normally suppress the anti-nociceptor neurons
•ENKAPHALIN:
•It is used by interneurons in lamina II responsible for
inhibiting the lamina – I nocioceptor-specific
spinothalamic neurons
•ENDOGENOUS MORPHIN:
•It has been identified in terminals forming synapses
with neuron having μ-opioid receptors in pain
modulating pathways.
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Chronic Pain
• Chronic pain can be considered as bad
pain because it persist long after injury
and is often refractory to pain killers.
• Chronic pain caused by nerve injury is
called neuropathic pain.
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Neuropathic pain
• Caused by the damage to peripheral nerve
( adrenalin release by sympathetic
discharge)
• The distal cut end develops a scar tissue
forming rounded ball ( neuroma) which is
sensitive to pressure.
• Repeated activation causes continuous
pain.
• Examples are like, post herpetic neuralgia
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and diabetic neuropathy.
Phantom pain
• Pain felt in an amputated part long after
amputation was done.
• Many explanations are given to explain
this phenomenon.
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Stress induced analgesia
• It’s a well known phenomenon seen when
the soldier is wounded in battle field but
feels no pain until the battle is over. The
cause is not known may be it is similar to
Gate control hypothesis.
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TERMS FREQUENTLY USED
• Hyperalgesia: Excessive Pain
• Allodynia: Pain caused by any other sensation
e.g. touch will cause pain.
• Muscular Pain: Less blood flow in the muscles
(ischemia).
• Stress analgesia: Mild degree of pain is not felt if
the other part of the body has excessive pain.
• Causalgia: Burning pain.
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TERMS FREQUENTLY USED
Thalamic Syndrome
.Obstruction of the thalmogeniculate branch of
the posterior cerebral artery Affects posterior
thalamic nuclei.
. Prolonged severe pain.
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TERMS FREQUENTLY USED
TRIGEMINAL NEURALGIA
•It is excruciating intermittent pain by stimulation
of trigger area in the face as for eg. Washing of
face, combing hair, blast of air on face.
•It results from compression of trigeminal nerve
root by blood vessels
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SITES & MECHANISM OF PAIN RELIEF
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Trans Coetaneous
Electrical Nerve Stimulation
(TENS)
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