Greetings from the United Kingdom and I thank the Scientific Program Committee of the AANS for the invitation to present at this meeting. I'm going to tell you why we feel preoperative evoke potential testing should be a key component in the workup for complex pediatric neurosurgical patients. Intraoperative SSCP and MEP monitoring evaluates the functional integrity of the central and peripheral nervous system in many surgical disciplines. They are performed semi-continuously and changes in the evoked response can inform us to potential neurological sequelae. By following evidence-based alarm criteria and taking specific steps when these are breached, intraoperative neuromonitoring of evoked potentials can detect and prevent postoperative deficit. However, many factors can distort the morphology, amplitude, and latency of waveforms monitored intraoperatively. A poor intraoperative baseline may result in procedures being abandoned or monitored with modified IONM criteria that reduce the window for therapeutic intervention. A baseline EP study performed in the outpatient setting could identify pre-existing abnormalities, inform the likely utility of IONM, and may help plan the surgical strategy. In our hospital, we have been doing this for several years. Our aim was to identify the utility of preoperative EPs and clinical factors associated with intraoperative EP baselines and alert criteria. We did this via a retrospective review of data that we felt may be associated with intraoperative EP baseline and the alert criteria used. This included the type of neurosurgery performed and the level of the lesion operated on, preoperative sensory motor function assessed via modified MACOMIC rate, and abnormalities in preoperative EP tests. This is the categorization of the preoperative EPs, and IONM EPs were categorized in a similar fashion. Our primary outcome was IONM alert criteria category, and we hypothesized that preoperative EP category would be associated with intraoperative EP category and IONM alert criteria used. We used a categorization to identify the type of alert criteria used, as in this table. The neurophysiologist prefers to monitor cases which fall into category 1. An amplitude reduction in the evoked potential acts as an early warning to neurological deterioration which, if acted on quickly, can prevent injury. Intraoperative baselines that fall within category 2 are less than ideal because the opportunity is reduced for regaining neurological function. Prior knowledge of which category a patient will fall into reassures the neurophysiologist, helps to plan an intervention strategy during MDT, and can be used to counsel patients' families during the informed consent process for surgical intervention. With that in mind, this is what we found. About half of our cohort between 2015 and 2020 had a full set of both pre- and intraoperative baseline studies. Clinical and neurophysiological abnormalities were common in this cohort, and almost half had at least one modality monitored with modified alert criteria. Statistical analysis showed that there was an association between sensory motor deficit and preoperative evoked potential test. Patients were more likely to have normal preoperative EPs with no or mild deficit, and more likely to have abnormal EPs if a moderate to severe deficit was reported. Interestingly, preoperative sensory motor function was not associated with intraoperative EP abnormality, or the type of alert criteria used. The only variable that was associated with IONM was preoperative EP test result, as can be seen with significant odds ratio. In other words, more abnormal preoperative test results were seen in cases where modified alert criteria were used to monitor, and more normal preoperative EPs were seen in the group of patients monitored with standard criteria. In conclusion, preoperative evoked potential abnormality and sensory motor deficits are common in complex pediatric neurosurgical patients. Preoperative evoked potentials are the only variables associated with baseline IONM abnormalities and alert criteria employed. Preoperative evoked potentials aid the clinical team in surgical decision making, as well as risk counseling children and their families. We recommend preoperative evoked potentials for complex neurosurgical patients who require intraoperative neuromonitoring. We will be very happy to take questions or comments, so please forward them to us, and thank you.

preoperative evoke potential testing

pediatric neurosurgery

intraoperative monitoring

central and peripheral nervous system function

baseline evoke potential study