Anaes · Neuroanaesthesia
Neuromonitoring: EEG, SSEP, MEP and anaesthetic constraints
Also known as SSEP MEP anaesthesia · Intraoperative neurophysiology · Evoked potential TIVA
Anaesthetic effects on EEG and evoked potentials, TIVA vs volatile strategies for SSEP/MEP, neuromuscular blockade rules, warning criteria, and crisis response when signals degrade.
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Red flags
- MEPs usually require minimal or no ongoing neuromuscular blockade.
- High-dose volatiles and N2O depress cortical EPs — prefer TIVA for critical MEP windows.
- Signal loss is ischaemia until proven otherwise — communicate MAP, Hb, PaCO2, depth.
- Hypothermia, hypoxia, and severe hypotension confound interpretation.
- Bite block needed for MEP jaw stimulation risk.
Meet the patient
A 14-year-old with adolescent idiopathic scoliosis is undergoing posterior spinal fusion with pedicle screw instrumentation. Motor evoked potentials are the modality that tells the surgeon whether a screw is pressing on the cord. After rod distraction, the MEP amplitude falls by 60 percent. The surgeon looks at you — and what you do in the next thirty seconds determines whether this child walks.[4]
Fellowship exams test whether you understand how anaesthetic drugs and physiology distort EEG and evoked potentials, not merely the names of waveforms. Scoliosis, complex spine, thoracic aortic, and posterior fossa lists all pivot on SSEP and MEP strategy. Signal loss without a structured intraoperative protocol fails the hot case.[5]
References5ShowHide
- [1]Goettel N, Bharadwaj S, Venkatraghavan L, et al. Dexmedetomidine vs propofol-remifentanil conscious sedation for awake craniotomy: a prospective randomized controlled trial. Br J Anaesth, 2016.PMID 27099154
- [2]Lewis SC et al. General anaesthesia versus local anaesthesia for carotid surgery (GALA): a multicentre, randomised controlled trial Lancet, 2008.PMID 19041130
- [3]Davidson AJ et al. Neurodevelopmental outcome at 2 years of age after general anaesthesia and awake-regional anaesthesia in infancy (GAS): an international multicentre, randomised controlled trial Lancet, 2016.PMID 26507180
- [4]Walker CT, Kim HJ, Park P, et al. Neuroanesthesia Guidelines for Optimizing Transcranial Motor Evoked Potential Neuromonitoring During Deformity and Complex Spinal Surgery: A Delphi Consensus Study. Spine, 2020.PMID 32539292
- [5]Fehlings MG, Alvi MA, Evaniew N, et al. A Clinical Practice Guideline for Prevention, Diagnosis and Management of Intraoperative Spinal Cord Injury: Recommendations for Use of Intraoperative Neuromonitoring and for the Use of Preoperative and Intraoperative Protocols for Patients Undergoing Spine Surgery. Global Spine J, 2024.PMID 38526921