Neurosurgical Skill Enhancement Using Transcranial Stimulation

Rationale: Recent changes in medical training environments have resulted in many trainees lacking sufficient opportunity to acquire specific skills necessary for their specialty. New methods to enhance the acquisition and retention of medical and surgical skills are required to ensure the quality of the future physician workforce. Transcranial direct-current stimulation (tDCS) is an emerging method of non-invasive brain stimulation that has been show to safely enhance motor learning in adults and children. Even a modest enhancement of acquisition and retention of medical-surgical skill with tDCS carries the potential to accelerate skill training for health care providers, thereby contributing to greater training efficiency and improved patient outcomes.

Objectives: The objective of this study is to assess whether tDCS can enhance the acquisition and retention of neurosurgical ability.

Ethics:This study has been approval by the University of Calgary Research Ethics Board

Design: Randomized, double blind, sham-controlled trial to evaluate the ability of tDCS to enhance learning and retention of neurosurgical skills.

Transcranial Direct-Current Stimulation: The tDCS methods used are based on best-available evidence and practices, and will be applied in a standardized fashion by experienced investigators. Anodal tDCS will be delivered through saline-soaked sponge electrodes using a NeuroConn Direct-Current Stimulator (NeuroConn, Ilmenau, Germany). The anode will be centered over the left primary motor cortex (localized using the 10-20 EEG System), with the cathode over the contralateral supraorbital area. Both anodal and sham tDCS groups will have the current ramped-up to 1milliamp over 30 seconds. In the anodal tDCS group, the current will be held for 20 minutes. In the sham tDCS condition, the current will be held for only 60 seconds (no changes in cortical excitability) followed by a 30 second ramp-down.

Participants: Medical students (years 1-3) from the Cumming School of Medicine (University of Calgary) will be recruited. To ensure comparable baseline skills, trainees will be excluded if they have undergone formal neurosurgical training in the past 3 months.

Sample size calculations are based on the performance measures for the percentage of virtual tumor resected, determined through pilot studies. Based on 20% more tumor being resected at post-training, power of 90% and type-1 error of 0.05, the investigators estimate a sample size of a minimum of 24 participants (n=12 per stimulation condition).

Study Design: A short questionnaire will be completed to determine demographic characteristics, including: gender, age, level of training, how many times participants have performed on a virtual surgical simulator, how often participants play video games, and how often participants play a musical instrument.

Participants will be recruited at the Project NeuroArm Laboratory (University of Calgary) and be oriented to the workspace. Participants will complete virtual tumor resections on a NeuroTouch (National Research Council of Canada) surgical simulator. Participants will view a standardized training video, created by an expert in neurosurgery, demonstrating a virtual tumor resection using the simulator. Participant will have 3 minutes to resect a virtual tumor, avoiding resection of healthy tissue. Recorded outcome metrics will include: % tumor resected, volume of healthy tissue resected, time of excessive force on tumor and time of excessive force on healthy tissue.

Participants will perform one resection at baseline, establishing baseline skill. Participants will be randomized to receive sham or active tDCS by blinding selecting a code from the envelope, corresponding to a particular stimulation condition. Participants will perform eight training repetitions, taking approximately 30 minutes. Following approximately 30 minutes of training (eight training repetitions) the tDCS electrodes will be removed, and a final resection will be performed. Six weeks following the training the participants will return to assess retention of skill, performing a single resection. Emerging evidence suggests that a significant decay in surgical skill is present six weeks following training.

Data Analysis: Independent samples t-test will evaluate difference in outcome metrics at post-training between stimulation conditions. Two-way repeated-measures ANOVA for factors "stimulation type" and "training block" will explore the interaction between tDCS and training for each outcome metric. Retention of skill will be assessed using a paired t-test for each stimulation group.