Y_Spinal cord stimulation Flashcards
When was the gate control theory of pain described?
Melzack and wall 1965
Who developed spinal cord stimulation?
Shealy 1967
How is SCS postulated to work?
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.
Does SCS mediate its effect by endogenous opioid release?
No, the administration of naloxone does not change SCS effectiveness.
What neurotransmitter changes are found to occur with SCS?
Less excitatory transmitters such as glutamate and aspartate, more GABA and substance P.
What drug increases SCS effectiveness?
Baclofen (GABA agonist)
What type of pain is best treated with SCS?
Neuropathic pain
Why does SCS lead to paraesthesia?
Orthodromic activity depolarises the dorsal column and therefore other sensory inputs are not propogated
What proportion of patients that undergo lumbar spine surgery develop failed back syndrome?
10-40%
What are the indications for SCS in failed back syndrome?
When radicular leg pain is worse than the axial low back pain following previously successful surgery i.e. no on-going reversible compression
What is the PROCESS trial?
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
Is SCS better than redo surgery?
North et al 1995: An RCT of 42 patients showed that SCS had better outcomes than redo surgery with lower cost
What is the other name for complex regional pain syndrome?
Reflex sympathetic dystrophy
What is complex regional pain syndrome?
Pain, dysfunction and trophic changes within a limb following trauma or surgery
What is the evidence for SCS in CRPS?
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
What is the effect of SCS on vasculature?
Vasodilation due to sympathetic outflow
What is the effect of SCS on angina?
Improved exercise tolerance and reduces ST changes
What is the difference between CRPS type 1 and 2?
Type 1 is where there no direct injury to a particular nerve whilst type 2 is where a specific nerve is implicated
What type of SCS electrodes are used?
Linear arrays (which can be placed percutaneously thorough a Touhy needle) or paddle electrodes that need open surgery
What are the contacts made from?
Platinum iridium alloy
What electrode contact arrangement minimizes radicular pain whilst improving dorsal column stimulation?
Transverse orientation of the anode and cathode
What is the transverse tripole?
Where an cathode (-) is flanked by an anode (+) on each side. i.e. this needs a paddle electrode
What is better, laminotomy vs percutaneous SCS electrode placement?
Evidence is not definitive. Open gives better paraesthesia coverage. The difference in pain relief is no significant by 3 years. North et al 2005.
How are the SCS electrodes placed?
Percutaneously through a Touhy needle into the epidural space;
Lateral fluoroscopy shows ventral migration of the lead;
