Multi model Intra operative neuromonitoring

Intra operative neuromonitoring

1. Intra Operative Neurophysiological Neuro-Monitoring IOM - MEP Dr DMW Dharmakeerthi Association of Srilankan Neurologists 19.09.2022

2. Corticospinal tract

3. Homunculus / Map of the Brain

4. Why doing IOM Prevent damage during surgery Warn the surgeon if touching important structures Harvesting maximum amount of the tumor Predict the prognosis Retrospective analysis and plan future operations Litigation purposes (both the Surgeon and Neurophysiologist)

5. MEP stimulation (TC and Direct cortical)

6. MEP – Spinal / Epidural recording

7. D wave and I waves

8. MEP – Spinal / Epidural recording

9. For obtaining D waves, single pulse trains at 1 or 2 Hz (i.e. repetitive pluses at 1–2 Hz) are applied, while maintaining constant the other parameters (basically 1 pulse per train). This is due to the fact that each pulse of stimulation (or single-pulse train) triggers a D wave.

10. The amplitude of TCE-evoked SCPs was much larger than that of SCPs by direct electric stimulation of the motor cortex. The latency of the peak of N1 was faster in TCE-evoked SCPs than in SCPs by direct electric stimulation of the motor cortex.

11. The D wave reflects impulses arising from direct activation of the axons of corticospinal tract (CST) neurons. The I waves reflect impulses arising from indirect activation of the CST neurons via synaptic activity. The D wave is considered as the gold slandered test for CST integrity.

12. D wave More reliable and consistent Less liable to anesthetic agents

13. I wave Stimulation of cortico -cortical pathways (mostly dendrites) Les reliable and not consistent Do not use for IOM

14. D wave Proximal and distal to surgical site

15. We use the multipulse train technique for stimulation for muscle MEP. This technique consists of delivering repetitive trains of several pulses. Each train consists of 3 to 8 pulses (we usually use 6 pulses). Each rectangular pulse has a width of 0.5 msec. The interstimulus interval (ISI) can also vary; in general we use ~3.5 msec ISI.

16. Muscle recording APB / ADM (C 8/ T1) Brachioradialis (C6) Triceps (C 7) Deltoid (C 5)

17. H) Rectus Femoris (L3-4) I) Hamstring - S1

18. E) Abductor Halusis (S1) F) Tibialis Anterior (L 5) G) Gastrocnemius (S1)

19. During the tumor resection, responses from bilateral tibialis anterior muscles were significantly decreased. However, these changes recovered immediately after temporal interpretation of the surgical manipulation. TA, tibialis anterior.

20. TCES of a spinal cord tumor removal predicted a severe motor deficit in the right upper and bilateral lower extremities

21. Scoliosis correction

22. D wave amplitude up to 50% from the baseline recordings Transient paraplegia has been reported after surgery, such as patients waking up paraplegic but recovering in a couple of hours or days Gives the neurosurgeon more leeway to continue with the surgery even when the muscle MEP has disappeared

23. If the D wave amplitude declines by more than 50%, the patient has suffered a permanent motor disability D wave and the neurological outcome has been reported in supratentorial surgeries, where uni-hemispherically generated D wave amplitude should not decline by more than 30% Otherwise the patient would be hemiplegic after surgery

24. Electrode positioning for stimulation, recording and more importantly minimizing artefacts and ensuring safety measures has to be done in practical sessions.

25. Thank you