Pain

Question 1

what is the definition of pain

Answer 1

an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage

Question 2

what are the two types of pain and what are their receptors

Answer 2

• immediate pain which is transmitted through A delta fibres
• Persisting pain which is transmitted through c fibres

Question 3

what is a common consequence for diabetic patients in relation to pain

Answer 3

diabetic patients can get peripheral neuropathy which means they cannot feel their feet so commonly get problematic ulcers which can cause the foot to become gangrenous

Question 4

A-alpha nerve fibre

Answer 4

motor fibres to muscles and proprioception

Question 5

A-beta fibres

Answer 5

touch and pressure

Question 6

A-gamma fibres

Answer 6

motor fibres to muscle spindles

Question 7

A-delta fibres

Answer 7

temperature and pain

• myelinated
• sharp and localised pain
• fast conduction
• polymodal
• not usually visceral

Question 8

B fibres

Answer 8

autonomic nervous system

Question 9

C fibres

Answer 9

temperature and pain

• unmyelinated
• dull throbbing pain
• slow conduction
• polymodal

Question 10

what are the 4 factors which summarise the physiology of pain

Answer 10

1. transduction
2. transmission
3. modulation
4. perception

Question 11

what is transduction

Answer 11

conversion of a noxious stimulus (heat, mechanical, chemical) into an action potential in a nociceptor

• heat more than 45 degrees or less than 15
• chemical = K+, ATP, Bradykinin, histamine, substance P
• mechanical

Question 12

transduction

Answer 12

nociceptors are the free nerve endings of A delta and C fibres

they respond to stimuli that will potentially cause damage to the tissue
- primary hyperalgesia (pressing on a bruise)

Question 13

give examples of substances which activate nociceptors

Answer 13

• potassium
• protons
• serotonin
• bradykinin
• histamine

Question 14

give examples of substances which lower the threshold for nociceptors

Answer 14

• prostanoids
• leukotrienes
• substance p
• CGRP
• Glutamate (MAIN)

Question 15

No single “pain receptor” but glutamate binds to

Answer 15

• AMPA
• NMDA (sleeping but important!)
• G-protein couple receptors

Question 16

The Neospinothalamic tract

Answer 16

which terminates in the ventral posterior lateral nucleus (VPL) is mainly composed of Aδ fibres.

Question 17

The Paliospinothalamic

Answer 17

tract which terminates in the dorsomedial (DM) and intra laminar areas is composed of C fibres.

Question 18

Descending Inhibition (3 mechanisms)

Answer 18

1. GABA & Glycinergic interneurones
2. Descending inhibition PAG-RVM-DH
3. Endogenous opioids

+ DISTRACTION

Question 19

What is the gate control theory

Answer 19

based on the theory of presynaptic inhibition of pain information produced by mechanical stimulation.

basically your nociceptor fibres transmit the pain signals to the dorsal horn but if someone rubs your leg then the mechanoreceptors that deal with this sensation synapse on an inhibitory neurone and therefore cut off this signal before it gets there (presynaptic inhibition which closes the gate to noxious information)

Question 20

Pain perception

Answer 20

• Reticular system elicits an autonomic response

* Limbic system links perception of pain with mood

Question 21

Visceral Pain

Answer 21

• Visceral nociceptors respond to distension or ischaemia
• Visceral primary afferent will activate multiple second order neurones
• Pain more diffuse (less well localised)
• Converge on second order neurones with somatic input
• Referred pain (convergence)

Question 22

Associated features of pain

Answer 22

• Sweating
• Pallor
• Nausea
• Tachycardia
• Hypertension

Question 23

step 1 on pain ladder - mild pain

Answer 23

simple analgesics

Question 24

step 2 on pain ladder - moderate pain

Answer 24

use mild opioid like codeine or tramadol

continue the simple analgesics

Question 25

step 3 on the pain ladder - severe pain

Answer 25

use strong opioid such as morphine continue simple analgesics

Question 26

medications for neuropathic pain

Answer 26

amitriptyline and gabapentin

Question 27

Neuropathic Pain

Answer 27

A pain arising as a direct consequence of a lesion or a disease affecting the somatosensory system

Question 28

• Allodynia

Answer 28

pain response to things that should not elicit pain such as touch

Question 29

causes of neuropathic pain and what can be found on examination

Answer 29

Traumatic (phantom limb pain) Diabetic neuropathy Postherpetic neuralgia Trigeminal neuralgia Post-stroke pain changes in colour of limb to changes in sensation

Question 30

dysaesthesia

Answer 30

unpleasant/abnormal sensation

Question 31

hyperalgesia

Answer 31

over reactive pain to something that would normally be painful but is over dramatic

Question 32

neuroglia

Answer 32

pain in the anatomical distribution of a nerve or nerves

Question 33

Neuroplasticity behind chronic pain

Answer 33

* Prolonged inflammatory response results in decreased pain threshold in primary afferents * Increased production of substance P & CGRP * Recruitment of NMDA receptors • Wakes up WDR * “wind-up” phenomenon

Question 34

spinal cord changes to neuroplasticity in chronic pain

Answer 34

Spinal Cord - changes in gene & receptor expression in DRG & dorsal horn neurons

Question 35

Risk Factors for Chronic Pain

Answer 35

``` female age genetics low socio-economic status occupational history of abuse compensation ``` modifable: - anxiety and depression - surgical approach - attitudes - communication

Question 36

what is the Budapest criteria

Answer 36

1. Patients must report continuing pain disproportionate to the trauma 2. Patients must report at least one symptom in three of the four following categories: (a) Sensory: hyperalgesia (that is, exaggerated pain to a painful stimulus, such as pinprick) and/or allodynia (that is, pain elicited by a normally non-painful stimulus, such as light touch) (b) Vasomotor: skin colour and/or temperature changes/asymmetry (c) Sudomotor/oedema: swelling and/or sweating changes or asymmetry (d) Motor/trophic: weakness, tremor, dystonia, decreased range of motion and/or trophic changes/asymmetry involving nails, skin and/or hair 3. Patients must display one sign in two of the categories above 4. Signs and symptoms must not be better explained by another diagnosis.