Y_Spinal cord stimulation

Question 1

When was the gate control theory of pain described?

Answer 1

Melzack and wall 1965

Question 2

Who developed spinal cord stimulation?

Answer 2

Shealy 1967

Question 3

How is SCS postulated to work?

Answer 3

Spinal inputs are a balance between large and small sensory fibres. Large fibres close gates, whilst small fibres open them. Large fibres are depolarised at lower thresholds. SCS therefore depolarises the large fibres and therefore closes the gates for other painful inputs.

Question 4

Does SCS mediate its effect by endogenous opioid release?

Answer 4

No, the administration of naloxone does not change SCS effectiveness.

Question 5

What neurotransmitter changes are found to occur with SCS?

Answer 5

Less excitatory transmitters such as glutamate and aspartate, more GABA and substance P.

Question 6

What drug increases SCS effectiveness?

Answer 6

Baclofen (GABA agonist)

Question 7

What type of pain is best treated with SCS?

Answer 7

Neuropathic pain

Question 8

Why does SCS lead to paraesthesia?

Answer 8

Orthodromic activity depolarises the dorsal column and therefore other sensory inputs are not propogated

Question 9

What proportion of patients that undergo lumbar spine surgery develop failed back syndrome?

Answer 9

10-40%

Question 10

What are the indications for SCS in failed back syndrome?

Answer 10

When radicular leg pain is worse than the axial low back pain following previously successful surgery i.e. no on-going reversible compression

Question 11

What is the PROCESS trial?

Answer 11

Prospective randomised controlled multicenter study of patients with failed back surgery syndrome showed SCS provided improved pain relief and cost-effectiveness compared to medical management

Question 12

Is SCS better than redo surgery?

Answer 12

North et al 1995: An RCT of 42 patients showed that SCS had better outcomes than redo surgery with lower cost

Question 13

What is the other name for complex regional pain syndrome?

Answer 13

Reflex sympathetic dystrophy

Question 14

What is complex regional pain syndrome?

Answer 14

Pain, dysfunction and trophic changes within a limb following trauma or surgery

Question 15

What is the evidence for SCS in CRPS?

Answer 15

Kemler et al showed SCS for CRPS type 1 in addition to physical therapy was better than physical therapy alone up to 3 years, although this was no longer significant at 5 years

Question 16

What is the effect of SCS on vasculature?

Answer 16

Vasodilation due to sympathetic outflow

Question 17

What is the effect of SCS on angina?

Answer 17

Improved exercise tolerance and reduces ST changes

Question 18

What is the difference between CRPS type 1 and 2?

Answer 18

Type 1 is where there no direct injury to a particular nerve whilst type 2 is where a specific nerve is implicated

Question 19

What type of SCS electrodes are used?

Answer 19

Linear arrays (which can be placed percutaneously thorough a Touhy needle) or paddle electrodes that need open surgery

Question 20

What are the contacts made from?

Answer 20

Platinum iridium alloy

Question 21

What electrode contact arrangement minimizes radicular pain whilst improving dorsal column stimulation?

Answer 21

Transverse orientation of the anode and cathode

Question 22

What is the transverse tripole?

Answer 22

Where an cathode (-) is flanked by an anode (+) on each side. i.e. this needs a paddle electrode

Question 23

What is better, laminotomy vs percutaneous SCS electrode placement?

Answer 23

Evidence is not definitive. Open gives better paraesthesia coverage. The difference in pain relief is no significant by 3 years. North et al 2005.

Question 24

How are the SCS electrodes placed?

Answer 24

Percutaneously through a Touhy needle into the epidural space;
Lateral fluoroscopy shows ventral migration of the lead;

Question 25

What is the difference in level of insertion between percutaneous and paddle methods?

Answer 25

Paddle electrode laminotomy is 1-2 levels below the site of stimulation

Question 26

Why are patients awake during SCS lead placement?

Answer 26

To ensure coverage of the paraesthesia / pain

Question 27

Where are SCS batteries implanted?

Answer 27

Into the lower quadrant of the abdomen or into the buttock; Not near a bony prominence of waist band

Question 28

What are the two stages of SCS?

Answer 28

Stage 1 is temporary stimulation with an external power source;
Stage 2 is permanent implantation with a battery