Pain facts – 3 Dr. S. Parthasarathy

MD., DA., DNB, MD (Acu), Dip. Diab. DCA, Dip. Software statisticsPhD (physio)

Mahatma Gandhi medical college and research institute – puducherry, India

Referred pain

• Pain perceived at a location other than the site of the painful stimulus

• What is radiating pain ?? • What is referred pain ??

Radiation or referral • Pain of myocardial infarction is located in the mid or

left side of the chest where the heart is actually

located. The pain can radiate to the left side of the

jaw and into the left arm.

• Referred pain is when the pain is located away from

or adjacent to the organ involved. Referred pain

would be when a person has pain only in their jaw or

left arm, but not in the chest

• Confusion still • ISSP does not clarify ??

Visceral pain

• Does it respond to clamp??• No

• Ischemia • Distension • Active contractions

• Diffuse, referred, autonomic

Organs and site of referred pain

Characteristics

1. segmental Renal colic – loin and scrotum 2. area of referral – tender hyperalgesic, 3. develops after sometime.

Mechanisms

• Morley ‘ s theory • Axon reflex -= Sinclair • Convergent-projection- Ruch • Convergence-facilitation• Hyperexcitability• Thalamic-convergence

Morley ‘ s theory

• It states that the involvement of adjacent somatic structures caused pain !!

• Simultaneous ?• Can be the only symptom ?

• Put to disuse

Axon reflex theory • primary sensory

neurones have widely bifurcating axons and innervate both somatic and visceral targets, thus obscuring the source of afferent activity, and explaining the segmental nature of referred sensations.

Questions about axon theory

• No such axons • No explanation to time delay

No explanation to referred hyperalgesia

Convergent-projection- Ruch

• visceral and somatic primary sensory neurones converge onto common spinal neurones

• This theory proposes that the activity in ascending spinal pathways is misconstrued as

originating from somatic structures ready explanation for the segmental nature

but issue of referred hyperalgesia.??

convergence-facilitation theory

• viscera were wholly insensitive and therefore that visceral

afferent activity never of itself gave rise to pain.

• He proposed instead that this activity was capable of creating

an “irritable focus” within the spinal cord, so that other,

segmentally appropriate, somatic inputs could now produce

abnormal and, of course, referred pain sensations.

• MacKenzie

convergence-facilitation theory

• NO general acceptance, in part because it implicitly denied the existence of “true” visceral palm. However, the theory offers an explanation for referred hyperalgesia and, perhaps, the delay of referred sensations.

• The concept of an irritable focus has more recently been resurrected with another label—central sensitization, which appears to be of major importance in hyperalgesia from somatic and visceral structures.

Supraspinal – theobald

• interactions at supra spinal levels lead to the phenomenon.

• But are there separate systems ??

What happens if we block area referredhyperalgesia lost tenderness lost ,

pain- loss – controversial

Summary

• Referred pain • Features • Theories

Phantom pain• A phantom limb is the sensation that an amputated

or missing limb (even an organ, like the breast) is still

attached to the body and is moving appropriately

with other body parts

• Approximately 60 to 80% of individuals with an

amputation experience phantom sensations in their

amputated limb, and the majority of the sensations

are painful

Phantom pain

Or simply!!

• Painful sensations experienced in a missing limb .

• Tooth and eye also possible

• Stump pain is different.

• phantom pains can also occur in people who are born without limbs and people who are paralyzed.

• So phantom limb, phantom pain, stump pain

History

• Ambrose Paire (1510)

• Military surgeon • First explained

• Mitchell (1979) coined the term – phantom pain

How frequent is it ??

• 4 – 90 %

• Innumerable studies

• Onset • Usually first week after amputation• Rarely months to years

Where is it ??

• Entire – 6%

• Proximal – 10%

• Distal – around 80 %

• Approx figures changes with duration !!

Quality - No proper studies• Varied –Squeeze ,Clenching toes ,Nails digging • The missing limb often feels shorter • feel as distorted • can be made worse by stress, anxiety, and

weather changes. • usually intermittent. • The frequency and intensity of attacks usually

declines with time 70 % ----35 % in 2 years

Preamputation pain

• Striking case reports• Location and character similar – • Vascular and traumatic amputees • Pain memory ? • Melzack (1990) – questioned the fact ??

• CNS lesions made pain disappear

Possible no relation

• Military Vs civilian • Age, side, • Sex• Level of amputation

Etiology

• Peripheral • Spinal • Supraspinal

Peripheral

• Irritation in the severed nerve endings (called

"neuromas").

• Gallamine and Local injection

• Percussion of stump – increases pain

• Stump end pathology ends pain ends

Spinal and thereon

• Disinhibition of neurons at spinal level• Nerve injury – sensitization – spinal plasticity

• In his 1989 paper,"Phantom Limbs, The Self And The Brain“ Melzack proposed the theory of the "neuromatrix.“

Mechanisms

• the experience of the body is created by a wide network of interconnecting neural structures

• the primary somatosensory cortex undergoes substantial reorganization after the loss of sensory input.

• due to this reorganization in the somatosensory cortex, which is located in the postcentral gyrus, and which receives input from the limbs and body.

• Stroke the Face – phantom pain

Etiology

• Peripheral

• Spinal

• Supraspinal

Treatment

• Yes it a form of chronic pain

• Difficult to treat

• 68 treatment , 50 still in use !!• TENS, massage, acupuncture,capsaicin ECT • 75% Vs 44 % placebo• mirror box visual feedback

Drugs

• Carbamazepine and newer anticonvulsants • Antidepressants • IV calcitonin • Beta blockers • Depression or original which is treated ??

Invasive techniques

• Stump revisions• Neuroma excision • Sympathectomy • Dorsal root entry – zone lesions • Spinal stimulation • Brain stimulation • Preemptive – role ??

What I do

• A very low dose IV ketamine as premed

• Always regional

• Add opioids

Villiyanur Ramachandran !!

Statement by an international phantom pain authority

The fingers were illusory, but the pain was real

If we give pain relief then

Is this phantom or real ?

• Thank you all