The Effect of Increasing Current or Pulse Duration on Patient Movement and Intraoperative Transcranial Electric Stimulation Motor Evoked Potential Amplitude (CCCV)

Transcranial electric stimulation (TES) motor evoked potential (MEP) monitoring is standard during surgery risking motor system injury. The stimuli are typically 5-pulse trains with a 4 ms interstimulus interval (ISI). The pulse duration (D) is often set to 50 or 500 µs. Both are effective, but setting D to the chronaxie would be physiologically optimal and limited data suggest that mean MEP chronaxie may be near 200 µs.

When necessary, one can obtain larger MEPs by increasing current (I) or D to increase stimulus charge (Q = I × D). However, this also increases patient movement that can interfere with surgery and reduce MEP acquisition frequency.

The main research question is whether increasing current or pulse duration when applying intraoperative neuromonitoring produces less patient movement during surgery. As such, the IOM ISIS System will be employed for neuromonitoring and an accelerometer will be used to quantify patient movement.

The constant-current TES stimulators will be used in this study with a high-precision oscilloscope. Total intravenous anesthesia (TIVA), surgery and TES MEP monitoring will proceed routinely without modification and normally involves acquiring many MEPs over several hours. The only departure from standard care will be the placement of two small accelerometers and a brief MEP sequence before skin incision to determine chronaxie and compare the effect of an equivalent increase of I or D on MEP amplitude and movement.

Study Overview

• Status: Recruiting
• Conditions: Surgery
• Intervention / Treatment: Device: ISIS IOM System

Detailed Description

Transcranial electric stimulation (TES) motor evoked potential (MEP) monitoring is standard during surgery risking motor system injury. The stimuli are typically 5-pulse trains with a 4 ms interstimulus interval (ISI). The pulse duration (D) is often set to 50 or 500 µs. Both are effective, but setting D to the chronaxie would be physiologically optimal and limited data suggest that mean MEP chronaxie may be near 200 µs.

When necessary, one can obtain larger MEPs by increasing current (I) or D to increase stimulus charge (Q = I × D). However, this also increases patient movement that can interfere with surgery and reduce MEP acquisition frequency. Anecdotal observations suggest that increasing D may produce larger MEPs with less movement than increasing I, but there is no published support. If true, then the optimal D for monitoring may be above the chronaxie because less movement could facilitate more frequent MEP acquisition.

Finally, there is ongoing controversy about constant-current or constant-voltage TES. However, with stable resistance (R) there is no fundamental reason to prefer one or the other since they are related by Ohm's law I = V/R. Also, since threshold current and voltage vary with D their maximum levels should also vary with selected D, which could be confusing. Instead, because the International Electrotechnical Commission 50 mJ safety limit is based on energy (E = I2 × D × R = V2 × D/R), it may be more logical to apply constant-energy TES that would provide a consistent 0-50 mJ selection range at any selected D.

The primary objective is to assess whether intraoperative neuromonitoring with constant current or constant voltage produces less patient movement during surgery. The secondary objectives are to compare MEP amplitudes with the different setups, to estimate the true mean or median chronaxie and to develop the concept of constant-energy TES.

The main research question is whether increasing current or pulse duration when applying intraoperative neuromonitoring produces less patient movement during surgery. As such, the IOM ISIS System will be employed for neuromonitoring and an accelerometer will be used to quantify patient movement.

The constant-current TES stimulators will be used in this study with a high-precision oscilloscope. The calibration will assess 5-pulse trains with a 4 ms ISI and 100 mA output across a 1000 Ω resistor at 250, 500, and 1000 µs D. Measurements will include actual I and D of each pulse, and actual ISI.

Total intravenous anesthesia (TIVA), surgery and TES MEP monitoring will proceed routinely without modification and normally involves acquiring many MEPs over several hours. The only departure from standard care will be the placement of two small accelerometers and a brief MEP sequence before skin incision to determine chronaxie and compare the effect of an equivalent increase of I or D on MEP amplitude and movement.

• Study Type: Interventional
• Enrollment (Estimated): 31
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Kathleen Seidel, MD; Phone Number: +41 31 6320014; Email: kathleen.seidel@insel.ch
• Study Contact Backup: Name: Jonathan Wermelinger, PhD; Phone Number: +316328354; Email: jonathan.wermelinger@insel.ch

Study Locations

• Switzerland
  • Bern, Switzerland, 3010
    • Recruiting
    • Dep. of Neurosurgery, Bern University Hospital
    • Contact: Kathleen Seidel, MD; Phone Number: +41316322409; Email: kathleen.seidel@insel.ch
    • Contact: Jonathan Wermelinger, PhD; Phone Number: +41316328354; Email: jonathan.wermelinger@insel.ch
    • Principal Investigator: Kathleen Seidel, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Informed Consent signed by the subject
• The patient has a supra- or infra-tentorial lesion requiring surgery
• The patient is undergoing neurosurgery with the use of Intraoperative Monitoring (IOM) during surgery to protect functional tissue
• The patient is older than 18 years

Exclusion Criteria:

• No need for Intraoperative Monitoring (IOM)
• Vulnerable subjects (pregnant women, pregnant, impaired consciousness)
• People who do not want to participate in the study
• Emergency procedures in which no consent was obtained before the operation
• Multiple surgeries on the same patient
• Preoperative non-affected arm motor deficit (MRC <5), that is to say, no motor deficit of the arm ipsilateral to the surgery
• Inhalational anesthesia
• Persisting neuromuscular blockade

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: ISIS IOM System; Total intravenous anesthesia (TIVA), surgery and TES MEP monitoring will proceed routinely without modification and normally involves acquiring many MEPs over several hours. The only departure from standard care will be the placement of two small accelerometers and a brief MEP sequence before skin incision to determine chronaxie and compare the effect of an equivalent increase of I or D on MEP amplitude and movement.

Device: ISIS IOM System; The constant-current TES stimulators will be used in this study with a high-precision oscilloscope. The calibration will assess 5-pulse trains with a 4 ms ISI and 100 mA output across a 1000 Ω resistor at 250, 500, and 1000 µs D. Measurements will include actual I and D of each pulse, and actual ISI. Total intravenous anesthesia (TIVA), surgery and TES MEP monitoring will proceed routinely without modification and normally involves acquiring many MEPs over several hours. The only departure from standard care will be the placement of two small accelerometers and a brief MEP sequence before skin incision to determine chronaxie and compare the effect of an equivalent increase of I or D on MEP amplitude and movement.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparison of the effect of a 2-fold increase of I or of D from threshold on patient movement	Comparison of the effect of a 2-fold increase of I or of D from threshold on patient movement quantified by accelerometers on the patient's forehead and contralateral (non-affected) shoulder.	During surgery, estimated on average to be about 4 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Comparing the effect of a 2-fold increase of I or of D from threshold on MEP amplitude	Compare the effect of a 2-fold increase of I or of D from threshold on MEP amplitude as measured by the ISIS IOM System	During surgery, estimated on average to be about 4 hours
Chronaxie	The stimulation strength (in mA) necessary to elicit an MEP are measured with the different pulse durations (in μs)	During surgery, estimated on average to be about 4 hours

Collaborators and Investigators

• Sponsor: Insel Gruppe AG, University Hospital Bern
• Investigators: Principal Investigator: Kathleen Seidel, MMD, Inselspital Bern, Department of Neurosurgery

Publications and helpful links

General Publications

• Szelenyi A, Kothbauer KF, Deletis V. Transcranial electric stimulation for intraoperative motor evoked potential monitoring: Stimulation parameters and electrode montages. Clin Neurophysiol. 2007 Jul;118(7):1586-95. doi: 10.1016/j.clinph.2007.04.008. Epub 2007 May 15.
• Abalkhail TM, MacDonald DB, AlThubaiti I, AlOtaibi FA, Stigsby B, Mokeem AA, AlHamoud IA, Hassounah MI, Baz SM, AlSemari A, AlDhalaan HM, Khan S. Intraoperative direct cortical stimulation motor evoked potentials: Stimulus parameter recommendations based on rheobase and chronaxie. Clin Neurophysiol. 2017 Nov;128(11):2300-2308. doi: 10.1016/j.clinph.2017.09.005. Epub 2017 Sep 28.
• Macdonald DB, Skinner S, Shils J, Yingling C; American Society of Neurophysiological Monitoring. Intraoperative motor evoked potential monitoring - a position statement by the American Society of Neurophysiological Monitoring. Clin Neurophysiol. 2013 Dec;124(12):2291-316. doi: 10.1016/j.clinph.2013.07.025. Epub 2013 Sep 18.
• MacDonald DB. Safety of intraoperative transcranial electrical stimulation motor evoked potential monitoring. J Clin Neurophysiol. 2002 Oct;19(5):416-29. doi: 10.1097/00004691-200210000-00005.
• Eng J. Sample size estimation: how many individuals should be studied? Radiology. 2003 May;227(2):309-13. doi: 10.1148/radiol.2272012051.

Study record dates

Study Major Dates

• Study Start (Actual): August 10, 2022
• Primary Completion (Estimated): December 31, 2025
• Study Completion (Estimated): March 31, 2026

Study Registration Dates

• First Submitted: April 21, 2022
• First Submitted That Met QC Criteria: May 10, 2022
• First Posted (Actual): May 17, 2022

Study Record Updates

• Last Update Posted (Actual): January 30, 2024
• Last Update Submitted That Met QC Criteria: January 29, 2024
• Last Verified: January 1, 2024

More Information

Terms related to this study

• Other Study ID Numbers: CCCV

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No