WHY DOES ENDOMETRIOSIS
CAUSE SO MUCH PAIN?
Dr Michael W Platt MA MB BS FRCA
Lead Clinician in Pain Medicine, Consultant in Anaesthetics,
Honorary Senior Lecturer, Faculty of Medicine, Imperial
College London,
Department of Anaesthetics
St Mary's Hospital, Imperial College Healthcare NHS Trust
Praed Street, London W2 1NY
• The pain associated with Endometriosis
is the most difficult symptom to cope with
for most women. For many, the pain they
suffer severely interferes with every day
life. It can be constant or it can be
cyclical and coincide with a woman’s
period.
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
What is pain?
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Emotional
Sensory
Acute or Chronic
Totally subjective
Can be described qualitatively
Can be graded quantitatively
2007
Dr Michael W Platt
Imperial College
What is pain?
2007
Dr Michael W Platt
Imperial College
What is pain?
• Can be graded quantitatively:
2007
Dr Michael W Platt
Imperial College
Why do we have pain?
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Recognition of self
Protection from trauma
Reduction of trauma
Warning sign of illness
Warning sign of infection
2007
Dr Michael W Platt
Imperial College
What happens when pain is
absent?
• Congenital insensitivity to pain
• Sensory nerve damage secondary to disease
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2007
Diabetes
Stroke
Trauma
Syphilis
Leprosy
Dr Michael W Platt
Imperial College
Pain
• Acute (physiological) Pain:
– An unpleasant sensory and emotional
experience associated with actual or potential
tissue damage.
• Chronic (pathological, intractible) Pain:
– Pain in the absence of, or persisting following
the removal of, a noxious stimulus.
2007
Dr Michael W Platt
Imperial College
PAIN
• Acute: Post-trauma, surgery etc.
• Chronic:
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Neuropathic pain
Mechanical pain
Chronic inflammation
Complex regional pain syndrome
• Cancer pain
2007
Dr Michael W Platt
Imperial College
Complicated neurobiology of
pain
• Not a simple ‘hard-wired’ system.
• Long-term changes occur in the PNS and
CNS following a noxious stimulus.
• This ‘plasticity’ changes the body’s
response to further stimuli
2007
Dr Michael W Platt
Imperial College
Pain Pathways
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Nociceptor
Axon
Dorsal Root Ganglion
Dorsal Root
Internuncial neurones
Cross-over to opposite side
Thalamus and Cortex
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
Peripheral sensitisation
• Inflammatory response:
Release of mediators from mast cells etc:
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Substance P
neurokinin A
calcitonin gene-related peptide
lead to further release of ‘inflammatory soup’:
• K, 5-HT, bradykinin, histamine etc
• Act to sensitise high-threshold receptors
2007
Dr Michael W Platt
Imperial College
‘Neuropathic pain’
• Burning, sharp, stabbing sensations
• eg diabetic neuropathy, post-amputation
pain etc.
• Treatment of peripheral neuropathic pain
include tricyclic antidepressants, anticonvulsants, clonidine, opioids, local
anaesthetics and anti-arrhythmic agents.
2007
Dr Michael W Platt
Imperial College
Sympathetic nervous system
• Important role in generation and
maintenance of chronic pain states.
• ‘Complex regional pain syndromes:
– Sympathetic dysfunction:
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2007
vasomotor & sudomotor changes
abnormal hair & nail growth
osteoporosis
sensory symptoms: burning, hyperalgesis, allodynia
Dr Michael W Platt
Imperial College
Gate Theory of Pain
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
Central sensitisation
• Changes that occur in the dorsal horn in
response to an injury, following barrage of
stimuli into the horn.
• Phenomenon of ‘wind-up’ involving the
NMDA receptor, making neurons more
sensitive - ie sensitising them.
• Expansion in receptive field size.
2007
Dr Michael W Platt
Imperial College
Ascending tracts
• 2nd order neurons ascend in spinothalamic,
spinoreticular and spinomesencephalic
tracts.
• Terminate in structures throughout the brain
stem, thalamus, and cortex.
• Thalamus has 2 main groups of relays:
– sensory discriminative aspects
– affective-motivational aspects
2007
Dr Michael W Platt
Imperial College
Descending modulation
• descending inhibitory modulation from:
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hypothalamus
PAG
locus coeruleus
nucleus raphe magnus
etc
• Involves opioids, 5-HT, n-adr, GABA
2007
Dr Michael W Platt
Imperial College
Visceral Pain
• There are specific nociceptors originating in
viscera.
• They respond to:
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2007
tension (contraction)
chemical nociception
sensitisation of nociceptors
effects of ischaemia
Dr Michael W Platt
Imperial College
Concept of referred pain
• Visceral nociceptors rarely activated
• Much more common to activate somatic
nociceptors
• Spinal cord and brain interpret visceral
signals as emanating from somatic source
• Convergence of visceral and somatic
afferents may account for this
2007
Dr Michael W Platt
Imperial College
Diagnosis of Pain in Endometriosis
• Acute, cyclical pain – due to pressure,
chemical irritation, nerve compression
• Chronic, non-cyclical pain – due to
neuropathic pain, sources outside the pelvis
(back, groin, etc.)
• Other visceral pain – especially bladder
pain.
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
2007
Dr Michael W Platt
Imperial College
Measurement of Pain
• Visual Analogue Score
– make as objective as possible
– Straight line 10 cm long
– No other markings
• Personality inventories
– Help to score chronic pain in terms of
personality type and stress markers.
2007
Dr Michael W Platt
Imperial College
Treatment of Pain in Endometriosis
• Acute Pain:
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NSAIDS
Hormonal
Oral Contraceptive
Systemic analgesia, opioids
Other techniques (TENS, Acupuncture)
Dr Michael W Platt
Imperial College
Pain Ladder
• Minor pain: paracetamol, aspirin
• Moderate pain:
– combination with minor opioids
• Co-proxamol (propoxifine), Co-dydramol (codeine)
– Minor opioids alone - eg Pethidine, Tramadol
• Severe pain:
– Opioids:
2007
Morphine etc.
Dr Michael W Platt
Imperial College
Endometriosis and Inflammatory
Pain: Use of NSAIDS
• Cyclo-oxygenase pathway blocked
– 2 forms:
• COX1 & COX2
• COX1 always present
• COX2 only induced by inflammation
• Also have central role, where both COX1 &
COX2 are found as neuro-transmitters
2007
Dr Michael W Platt
Imperial College
NSAIDS
• COX 2 antagonists preferable where there is
high-risk of peptic ulceration / bleeding
• Still not 100% guarantee.
2007
Dr Michael W Platt
Imperial College
Treatment of Pain in Endometriosis
• Chronic / Intractable Pain:
– Multiple modality pain clinic - holistic
approach
– Drugs
– Nerve blocks
– TENS, Acupuncture
– Physio, occupational Ther., Psychology
2007
Dr Michael W Platt
Imperial College
Neuropathic Pain in Endometriosis
• Not responsive to opioids
• Two main classes of drugs used:
– Tricyclic antidepressants (esp Amitriptyline)
– Anti-epileptics:
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Carbamazepine
Sodium valproate
Clonazepam
Gabapentin (Pregaballin)
Dr Michael W Platt
Imperial College
Gracilis
Adductor longus
Adductor
brevis
Adductor
magnus
Obturator
externus
Obturator
internus
2007
Dr Michael W Platt
Imperial College
Other complicating factors
• Psychosocial & spiritual processes strongly
influence the impact and expression of pain.
• (Saunders 1985, Portenoy 1992; Breitbart 1994)
2007
Dr Michael W Platt
Imperial College
Some factors:
• Pain interrelated with:
– depression (r = 0.33 with pain)
– lack of family support (r = -0.15 with pain)
– desire for death (r = 0.47 with depression)
2007
Dr Michael W Platt
Imperial College
Some correlates with severe pain:
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2007
Patient anxiety: r = 0.30
Communication problems: r = 0.29
Constipation: r = 0.24
Poor co-ordination: r = 0.21
Family anxiety: r = 0.19
Nausea: r = 0.19
Vomiting: r = 0.13
Other symptoms: r = 0.11
Dr Michael W Platt
Imperial College
Factors that diminish
quality of life:
Pain
Other symptoms
Psychological
distress
Spiritual/existential
distress
Family distress
Social distress
Financial needs
Health care concerns
(eg poor
communication)
Perception &
appraisal of
pain
Expression
of suffering
A MODEL OF SUFFERING
Summary
• The pain system is a very complex one.
• Endometrial Pain may be difficult to treat
due to a variety of causes, and these should
be addressed in the management of the
patient:
• Adequate pain assessment, including those
factors which are inter-related is essential.
2007
Dr Michael W Platt
Imperial College