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“Spinal Cord Monitoring”

“Spinal Cord Monitoring”. (intraoperative neurophysiological monitoring). Why do I want to know about this?!!. Scoliosis surgery. Other spinal surgery. Joint replacement. Brachial plexus. History at RNOH.

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“Spinal Cord Monitoring”

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  1. “Spinal Cord Monitoring” (intraoperative neurophysiological monitoring)

  2. Why do I want to know about this?!!

  3. Scoliosis surgery Other spinal surgery Joint replacement Brachial plexus

  4. History at RNOH... Sensory nerve conduction in the human spinal cord: epidural recordings made during scoliosis surgery. Jones SJ. Edgar MA. Ransford AO. Journal of Neurology, Neurosurgery & Psychiatry. 45(5):446-51, 1982 May. Spinal cord monitoring in scoliosis surgery. Experience with 1168 cases. Forbes HJ.Allen PW. Waller CS.Jones SJ.Edgar MA.Webb PJ.Ransford AO. Journal of Bone & Joint Surgery - British Volume. 73(3):487-91, 1991 May. Temporal summation--the key to motor evoked potential spinal cord monitoring in humans. Taylor BA. Fennelly ME. Taylor A. Farrell J. Journal of Neurology, Neurosurgery & Psychiatry. 56(1):104-6, 1993

  5. Concept Basic neurophysiology History Scoliosis monitoring Other applications Medicolegal

  6. Concept of monitoring

  7. Basic Neurophysiology 1 Resting potential Cell membrane + + + + + + - - - - - - - -80mV

  8. action potential resting potential -80mV + + + + + - - - - - - - + +

  9. Extra cellular recording of AP

  10. latency response stimulus Signal triggered averaging “extracts time-locked response from noise”

  11. x1 x10 x50 x300

  12. Gracile & cuneate fasciculi Sensory tracts in the spinal cord

  13. Axon 1 - fast Axon 2 - slow stim. distance Effect of conduction velocity

  14. Spinal Cord Monitoring……. …..How to do it

  15. Open technique for epidural catheter

  16. Other recording “montages”

  17. Nomenclature “EP” = Evoked Potential “SEP” = Somatosensory E P “MEP” = Motor E P “SSEP” = Spinal Somatosensory E P “CMEP” = Cortical Motor E P

  18. Cortical SEP

  19. active reference Cuneate & gracile nuclei C2 montage

  20. Mechanisms of Injury …...1 Direct mechanical... “Whoops!”

  21. Mechanisms of Injury ……2 …….Indirect mechanical

  22. L4 L5 P.L.I.F.

  23. PLIF - Ogival Cages Monitoring Stimulation Post Tib 8 Post Tib / Sural 7 Recording Cortical 2 Epidural 11 Both 2 Results No change / improved 1 Minor changes 1 Temporary worsening 2

  24. Segmental a. Anterior spinal a. Radicular a. Mechanisms of Injury ……3 aorta “PERFUSION” ischaemia

  25. Causes of decreased perfusion…... 1. Hypotension 2. Local arterial injury / spasm 3. Oedaema or venous hypertension

  26. Motor end-plate Motor neuron synapse M.E.P.

  27. action potential threshold e.p.s.p. -80 mV resting Temporal summation

  28. “The Anaesthetic Effect” Nitrous oxide Isoflurane Muscle relaxation Propofol Fentanyl

  29. Q. How do I select a monitoring technique for my surgery? A. What is at risk?

  30. latency response stimulus Q. How do I interpret the results? 1. Latency change

  31. control Q. How do I interpret the results? 2. Amplitude change

  32. From Jones et al 1985

  33. Q. Should I use MOTOR or SENSORY monitoring?

  34. Q. When should I start and finish monitoring my case?

  35. Other uses for intraoperative monitoring Complex THR Brachial plexus surgery Cardiac surgery

  36. Q. Who is responsible for the monitoring? 1. Concept…surgeon & neurophysiologist 2. Technical…technician 3. Reporting changes…technician 4. Interpreting changes…surgeon & np 5. Action…..SURGEON

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