CASE 2 - pain, sciatica etc

Question 1

antidromic and orthodromic stimulation?

Answer 1

stimulation of nociceptive C fiber results in both orthodromic conduction to the spinal cord and antidromic conduction to other axon branches, i.e., the axon reflex which can stimulate the release of peptides, such as substance P and calcitonin gene-related peptide, resulting in vasodilation and increased permeability

Question 2

what is the most common type of radiculopathy?

Answer 2

lumbar radiculopathy

Question 3

what are the most common causes of radiculopathy?

Answer 3

• herniated disc (compression by displayed iv disc)
• degenerative disc disease
• spondylosis

Question 4

what are the most common sites of herniated disc?

Answer 4

C5/C6 in neck and L5/S1 in lower back

Question 5

what is an acute disc herniation?

Answer 5

herniation of the nucleus pulposus through a rupture in the annulus fibrosis

Question 6

what is a pure hernia?

Answer 6

the nucleus pulposis protrudes from the iv disc

Question 7

what is degenerative disc disease?

Answer 7

vertebra becomes deformed as a result of the ageing process, causing a narrowing in or around the spinal canal

Question 8

what is spondylosis?

Answer 8

discs initially dehydrate, thus losing height and the disc annulus prolapses

Question 9

what is sciatica?

Answer 9

refers to the nerve pain in the back when the sciatic nerve is affected — results in radiating pain to the leg. this nerve pain is often caused by a back hernia

Question 10

what does radiculopathy present with?

Answer 10

pain, weakness, reflex changes and sensory loss

Question 11

what are some signs and symptoms of radiculopathy?

Answer 11

• in disc prolapse, pain may be acute and related to physical exertion
• pain in lower back
• pain radiates to the leg over the course of the nerve (sciatica)
• sensory loss or altered sensation in the distribution of the affected nerve root
• irritation, loss of sensation or a numb or cold sensation in the leg
• loss of strength or disrupted reflexes
• the radiating pain can be sharp and run down to below the knee, over the lower leg and even to the foot
• stretching the nerve makes symptoms worse (straight leg raise test) = sciatic stretch (implies L5 or S1 lesion)

Question 12

how is radiculopathy diagnosed?

Answer 12

• review of medical history and symptoms
• straight leg raise test if lumbar radiculopathy assumed
• MRI or CT scan — identify the cause and location of radiculopathy
• electromyography — can be used to rule out other diseases that cause nerve damage

Question 13

what can MRI be useful to rule out?

Answer 13

cauda equina syndrome

Question 14

what is cauda equina syndrome?

Answer 14

= caused by a compression of the nerve roots forming the cauda equina
- it is a surgical emergency to prevent permanent neurological defects
- can be caused by lumbar disc herniation (may be secondary to degenerative disc disease, trauma or infection), spinal vertebral fractures, infection, malignancy

Question 15

how is radiculopathy treated?

Answer 15

• NSAIDs eg. aspirin, ibuprofen, naproxen
• physical therapy to reduce pain, improve posture, and strengthen muscles
• steroid injections if pain persists, to reduce inflammation specifically in the area affected
• other medications, such as oral steroids, stronger pain medications, or the anti-seizure medications gabapentin, may also be prescribed
• spinal nerve decompression surgeries are sometimes needed

Question 16

what spinal decompression surgeries are available?

Answer 16

• microdisectomy : most common surgery for herniated discs. herniation is found and the herniated piece is removed
• laminectomy : aim is to relieve pressure on the spinal nerve
• spinal fusion surgery : rare treatment. used to treat spinal segments that are unstable or collapsed. a vertebral bone is attached or “fused” to an adjacent vertebral bone so that they
  grow together into one long bone. the immobility caused stops the spinal instability that was causing the pain

Question 17

what are dermatomes?

Answer 17

• sensory nerve fibres that innervate a segment of skin
• an area of skin that is mainly supplied by a single spinal nerve

Question 18

each dermatome is associated with what?

Answer 18

a single spinal nerve

Question 19

how many dermatomes are there and why?

Answer 19

30 = 1 less than the number of spinal nerves — start at C2 because C1 typically doesn’t have a sensory root

Question 20

why are dermatomes important?

Answer 20

• because they can help to assess and diagnose a variety of conditions
• symptoms that occur along a specific dermatome may indicate a problem with a specific nerve root in the spine

eg. radiculopathies — refers to conditions in which a nerve root in the spine is compressed or pinched. symptoms can include pain, weakness and tingling sensations. pain from radiculopathies can follow one or more dermatomes. one form of radiculopathy is sciatica.

Question 21

origin of sciatic nerve?

Answer 21

L4-S3

Question 22

describe the course of the sciatic nerve

Answer 22

• enters the gluteal region through the greater sciatic foramen, beneath the piriformis muscle
• descends over the lateral hip rotators
• passes through the posterior compartment of the thigh to reach the superior border of the popliteal fossa

Question 23

what does the sciatic nerve branch into?

Answer 23

muscular branches and the tibial and common fibular nerve

Question 24

what does the sciatic nerve supply?

Answer 24

• motor innervation to the posterior compartment of the thigh via muscular branches
• motor innervation to the posterior compartment of the leg via the tibial nerve
• motor innervation to the muscles of the anterior and lateral compartments of the leg via the common fibular nerve
• sensory innervation to the skin of the leg and root via the common fibular and tibial nerves

Question 25

label

Answer 25

Question 26

what can acute overdose of paracetamol lead to?

Answer 26

fatal liver damage

Question 27

inhibition of ____ causes the unwanted side effects of ibuprofen

Answer 27

COX1

Question 28

ibuprofen reduces prostaglandin synthesis via what pathway?

Answer 28

arachidonic acid pathway

Question 29

describe gabapentin

Answer 29

- gabapentinoid - anticonvulsant - binds to a2d part of Ca channel — decreases subsequent release of excitatory neurotransmitters - dizziness, sleepiness, water retention difficulty walking, upset stomach

Question 30

describe pregabalin

Answer 30

- gabapentinoid - anticonvulsant - binds to a2d subunit of voltage-gated Ca channels, modulating the release of several excitatory neurotransmitters such as glutamate, substance P, NE and CGRP

Question 31

describe amitriptyline

Answer 31

- tricyclic antidepressant - inhibits the membrane pump mechanism responsible for the reuptake of transmitter amines such as NE and serotonin, thereby increasing their conc at the synaptic clefts of the brain - dry mouth, constipation, dizziness, sleepiness, headache, difficulty peeing

Question 32

describe co-codamol

Answer 32

- compound analgesic —> paracetamol + codeine phosphate - codeine is an opioid analgesic used to treat moderate to severe pain - selective for the mu opioid receptor - opioids reduce pain signal transmission by activating pre-synaptic opioid receptors — leads to reduced intracellular cAMP conc, decreased Ca++ influx and thus inhibits the release of several neurotransmitters such as glutamate and substance P

Question 33

why is chronic pain hard for GPs?

Answer 33

- professional uncertainty - reluctant to up doses — addiciton - emotional burden - unable to help

Question 34

what is a spinal cord stimulator and what is spinal cord stimulation?

Answer 34

= an implanted device that sends low levels of electricity directly into the spinal cord to relieve pain - electrodes placed between the spinal cord and vertebrae (epidural space), and the generator is placed under the skin, usually near the buttocks or abdomen - the stimulators allow patients to send the electrical impulses using a remote control when they feel pain

Question 35

how does transcutaneous electrical nerve stimulation (TENS) work?

Answer 35

- electrodes are used to activate large-diameter afferent fibres that overlap the area of injury and pain - stimulation of the dorsal columns via surface electrodes presumably relieves pain because it activates large numbers of AB fibres synchronously - TENS machines are thought to work in 2 ways: 1. a high pulse rate triggers the ‘pain gate’ to close 2. a low pulse rate stimulates the body to make its own endorphins

Question 36

withdrawal is only in patients who have developed what?

Answer 36

a drug tolerance

Question 37

how is scanning used in pain management?

Answer 37

used to confirm diagnosis

Question 38

MRI vs CT in pain management

Answer 38

MRI - normally used - not used in an emergency - slow, expensive, bit more effort, no radiation, high quality CT - used in emergency - quick, cheap, convenient, involves radiation, poor quality

Question 39

what is biographical distribution? chronic illness?

Answer 39

used to describe the experience of chronic illness and the way in which a life-threatening illness breaks an individual’s social and cultural experience by threatening his pr her self-identity - chronic illness can affect the patient’s role in the family and his or her relationship with family members - also impacts their daily life and relationship with their friends, colleagues and the community

Question 40

what are the 4 phases of pain pathways?

Answer 40

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

Question 41

what are the mechanisms of endogenous opioid peptides in the descending inhibitory pathways?

Answer 41

- activation of mu, kappa, and delta opioid receptors — decreased presynaptic Ca++ influx — decreased release of glutamate and SP - increased K+ conductance in dorsal horn neurons

Question 42

what type of fibre is the afferent axon with the largest diameter?

Answer 42

Ab fibres

Question 43

what are A gamma fibres?

Answer 43

motor neurons that control the intrinsic activation of the muscle spindle

Question 44

what are the 3 main neurotransmitters released by primary afferents?

Answer 44

glutamate, SP and CGRP

Question 45

where do 2nd order neurons cross the midline?

Answer 45

at the white anterior commissure

Question 46

where do 2nd order neurons go after crossing the midline?

Answer 46

ascend to the thalamus via the contralateral spinothalamic tract, carrying both pain and temperature sensations

Question 47

from the thalamus, where is the stimulus sent?

Answer 47

- to the somatosensory cerebral cortex via fibres in the posterior limb of the internal capsule - other thalamic neurons project to areas of the cortex associated with emotional responses (eg. cingulate gyrus, insular cortex)

Question 48

what type of neurons are the 1st order neurons in pain pathways?

Answer 48

pseudounipolar

Question 49

what type of fibres are responsible for dull, deep and throbbing type pain?

Answer 49

C fibres — unmyelinated and slow conducting speed, have large receptive fields (therefore poor localisation of pain)

Question 50

where do C fibres mainly terminate and what do they release?

Answer 50

- Rexed laminae II (AKA substantia gelatinosa) - release substance P

Question 51

what fibres are mainly responsible for localised sharp pain?

Answer 51

alpha delta (Ad) fibres

Question 52

central sensitisation

Answer 52

thought to arise from an increase in the number of NMDA receptors, as well as increased sensitivity of NMDA receptors to glutamate. These changes occur on the dendrites of second-order neurones and are a result of prolonged glutamate release from first-order neurones ( due to persistent nociceptor activation).

Question 53

what are the 3 types of endogenous opioids and what do they bind to?

Answer 53

- B-endorphins — predominantly bind to mu opioid receptors - Dynorphins — predominantly bind to opioid kappa receptors - enkephalins — predominantly bind to delta opioid receptors

Question 54

what are silent nociceptors?

Answer 54

receptors that are normally unresponsive to noxious mechanical stimulation, but become stimulated during inflammation

Question 55

which of the following is a substance that would NOT stimulate a receptor? - substance P - ACh - peptide T - serotonin - K+

Answer 55

peptide T

Question 56

what type of nerve fibre is responsible for deep, unspecific pain?

Answer 56

C fibres

Question 57

chillies taste hot because capcaisin activates whicg type of nerve fibre?

Answer 57

A beta

Question 58

what is the spinocerebellar tract responsible for?

Answer 58

proprioception

Question 59

what is the spinoreticular tract responsible for?

Answer 59

emotional and arousal aspects of pain

Question 60

according to the gate control theory, unwanted pain can be reduced by stimulating whcih type of nerve fibre?

Answer 60

A alpha

Question 61

herniation of a spinal disc is most likely to occur on what side?

Answer 61

posterior

Question 62

which age group is at greatest risk for spinal disc herniation?

Answer 62

30-50