Scalp Electrode Placement Accuracy for the Canine Electroencephalography Array

Stephen James Everest^1,2*Myles St-Denis¹Bob Dony³Luis Gaitero¹Alexander Zur Linden¹Miguel Angel Cortez⁴Thomas Parmentier⁵Fiona May Keir James^1*

• ¹Ontario Veterinary College, University of Guelph, Guelph, Canada
• ²ACCESS Specialty Animal Hospital, Royal Palm Beach, FL, United States
• ³School of Engineering, College of Engineering and Physical Sciences, University of Guelph, 5 Guelph, Ontario, Canada, Guelph, Ontario, Canada
• ⁴Division of Neurology, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
• ⁵Département des Sciences Cliniques, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Quebec, Canada

Despite the common occurrence of idiopathic epilepsy amongst neurological conditions in dogs, electroencephalography (EEG), the gold standard for seizure detection, is relatively neglected. The use of EEG in veterinary medicine is rudimentary compared to that in human medicine, particularly with respect to the quantification of EEG electrode placement error, i.e., the accuracy of electrode placement relative to the diverse canine cortical topography. Therefore, we quantified the intraobserver EEG electrode placement error using a single canine EEG electrode placement array, on virtual models of head and brain created from archived computed tomographic scans of Brachycephalic (n=5), Mesocephalic (n=15) and Dolichocephalic (n=5) dogs from breeds with archetypal skull conformation. For the Mesocephalic cohort, a stereotactic brain atlas was incorporated into the brain models to quantify electrode placement error via a universal coordinate system. As this was not possible for the Brachycephalic and Dolichocephalic cohort, instead electrode placement was described in relation to cortical landmarks. Gaps in cortical coverage between cohorts were identified, such as poor coverage of the olfactory and frontal regions in the brachycephalic cohort and the parietal region in the Mesocephalic and Dolichocephalic cohorts. Quantitative analysis of electrode placement in the Mesocephalic cohort showed the minimum variance of electrode localization for the x coordinate of the F8 electrode (0.8 mm) and the greatest variance for the y coordinate of the Cz electrode (35.2 mm). This is the first study to highlight the knowledge gaps regarding the accuracy of canine EEG electrode localization, differences in the array coverage across the diverse canine skull conformations, and the urgent need for a stereotactic brain atlas for specific canine skull conformations.