1. Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. 2. Pain is commonly classified based on duration as either acute (less than 1 month) or chronic (more than 3-6 months), or based on underlying mechanisms as either nociceptive or neuropathic. 3. Neuropathic pain specifically refers to pain caused by damage or disease that directly affects the somatosensory nervous system.

1. Understanding Pain
Dr Yeo Sow Nam
Director, The Pain Specialist,
Mount Elizabeth Hospital &
Founder and Past Director,
Pain Management and Acupuncture Services,
Singapore General Hospital
MBBS (Singapore)
MMED (Anesthesiology, S’pore)
FANZCA (Anesthesiology, Aust/NZ)
FFPMANZCA (Pain Medicine, Aust/NZ)
FAMS, Registered Acupuncturist
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2. Sections
1. What Is Pain?
2. Classification Of Pain
3. What Is Neuropathic Pain?
4. Summary
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3. What Is Pain?
“An unpleasant sensory and emotional experience
associated with actual or potential tissue damage, or
described in terms of such damage.”
International Association for the Study of Pain
(IASP), 1994
Merskey H, et al. (Eds) In: Classification of Chronic Pain: 3
Descriptions of Chronic Pain Syndromes and Definitions of Pain Terms. 1994:209-212.

4. Classifications Of Pain
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5. The Continuum Of Pain
Insult Time to resolution
Acute Chronic
Pain Pain
<1 month 3-6 months
• Usually obvious tissue damage • Pain for 3–6 months or more2
• Increased nervous system activity • Pain beyond expected period
• Pain resolves upon healing of healing2
• Serves a protective function • Usually has no protective
function3
• Degrades health and function3
1. Cole BE. Hosp Physician 2002;38:23-30;
2. Turk and Okifuji. Bonica’s Management of Pain. 2001;
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3. Chapman and Stillman. Pain and Touch. 1996.

6. IASP Definitions: Peripheral Neuropathic and
Central Neuropathic Pain
Neuropathic pain
Pain initiated or caused by a primary
lesion or dysfunction in the nervous system
Peripheral neuropathic pain Central neuropathic pain
Pain initiated or caused by a primary Pain initiated or caused by a primary
lesion or dysfunction in the lesion or dysfunction in the
peripheral nervous system central nervous system
Merskey H, et al. (Eds) In: Classification of Chronic Pain: 6
Descriptions of Chronic Pain Syndromes and Definitions of Pain Terms. 1994:209-212.

7. Neuropathic Pain: A Redefinition
Pain arising as a direct consequence
of a lesion or disease affecting the
somatosensory system.
Treede R-D, et al. Neurology 2008;70:1630-1635. 7

8. Presentation Across Pain States Varies
Neuropathic Pain Mixed Pain Nociceptive Pain
Pain initiated or caused by a Pain with Pain caused by injury to
primary lesion or dysfunction neuropathic and body tissues
in the nervous system nociceptive (musculoskeletal,
(either peripheral or components cutaneous or visceral)2
central nervous system)1
Examples Examples Examples
• Postherpetic neuralgia • Low back pain with • Pain due to inflammation
• Trigeminal neuralgia radiculopathy • Limb pain after a fracture
• Painful diabetic neuropathy • Cervical • Joint pain in osteoarthritis
• Postsurgical neuropathic pain radiculopathy • Postoperative visceral pain
• Posttraumatic neuropathy • Cancer pain
• Central poststroke pain • Carpal tunnel Common descriptors2
syndrome • Aching
Common descriptors2 • Sharp
• Burning • Throbbing
• Tingling
• Hypersensitivity to touch or cold
1. International Association for the Study of Pain. IASP Pain Terminology; 8
2. Raja et al. in Wall PD, Melzack R (Eds). Textbook of Pain. 4th Ed. 1999;11-57.

9. Development Of Neuropathic Pain
Syndrome Neuropathic pain
Symptoms Spontaneous pain Stimulus-evoked pain
Pathophysiology Mechanisms
Metabolic Traumatic
Ischemic Toxic
Etiology
Hereditary Infectious
Compression Immune-related
Nerve damage
Woolf CJ, Mannion RJ. Lancet 1999;353:1959-64. 9

10. Signs And Symptoms Of Neuropathic Pain
Spontaneous symptoms
Persistent burning, intermittent shock-like or
• Spontaneous pain1
lancinating pain
Abnormal unpleasant sensations, eg, shooting,
• Dysesthesias2
lancinating, burning
• Paresthesias2 Abnormal, not unpleasant sensations, eg, tingling
Stimulus-evoked symptoms
Painful response to a non-painful stimulus, eg,
• Allodynia2
warmth, pressure, stroking
Heightened response to painful stimulus, eg,
• Hyperalgesia2
pinprick, cold, heat
• Hyperpathia2 Delayed, explosive response to any painful stimulus
1.Baron R. Clin J Pain 2000;16:S12-S20;
2. Merskey H et al. (Eds) In: Classification of Chronic Pain:
Descriptions of Chronic Pain Syndromes and Definitions of Pain Terms. 1994:209-212. 10

11. Summary
• An unpleasant sensory and emotional
experience associated with actual or potential
tissue damage, or described in terms of such
damage
• The two most frequently used approaches for
classifying pain are based on pain duration
(i.e. acute vs chronic pain) and underlying
pathophysiology (i.e. nociceptive vs.
neuropathic pain)
• Acute and chronic pain are often classified
along a pain continuum
• Neuropathic pain is defined as pain arising as
a direct consequence of a lesion or disease
affecting the somatosensory system.
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