Pinniped electroencephalography: Methodology and findings in California sea lions (Zalophus californianus)

D Colette Williams; Martin Haulena; Sophie Dennison; Lynnette Waugh; Tracey Goldstein; Felicia Nutter; Bill Van Bonn; Vanessa Hoard; Kenneth D Laxer; Paul S Buckmaster; Frances M D Gulland; Barry Tharp

doi:10.3389/fvets.2023.1040125

Pinniped electroencephalography: Methodology and findings in California sea lions (Zalophus californianus)

Front Vet Sci. 2023 Mar 31:10:1040125. doi: 10.3389/fvets.2023.1040125. eCollection 2023.

Authors

Affiliations

¹ Vet EDX, Retired Veterinary Medical Teaching Hospital, University of California, Davis, Davis, CA, United States.
² The Vancouver Aquarium, Vancouver, BC, Canada.
³ Imaging Solutions, PLLC, Oakton, VA, United States.
⁴ UC Davis School of Veterinary Medicine, Davis, CA, United States.
⁵ Zoological Pathology Program, University of Illinois at Urbana-Champaign, Brookfield, IL, United States.
⁶ Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA, United States.
⁷ A. Watson Armour III Center for Animal Health and Welfare, Animal Care and Science Division, John G. Shedd Aquarium, Chicago, IL, United States.
⁸ Department of Neurology, The Pacific Marine Mammal Center, Laguna Beach, CA, United States.
⁹ Sutter Pacific Medical Foundation, San Francisco, CA, United States.
¹⁰ Departments of Comparative Medicine and Neurology and Neurological Sciences, Stanford University, Stanford, CA, United States.
¹¹ The Marine Mammal Center, Sausalito, CA, United States.
¹² Wildlife Health Center, University of California, Davis, Davis, CA, United States.
¹³ Emeritus, Department of Neurology, University of California Davis Medical Center, Sacramento, CA, United States.

Abstract

This study was designed to identify abnormalities in the electroencephalograms (EEGs) recorded from stranded California sea lions (Zalophus californianus) with suspected domoic acid (DA) toxicosis. Recordings from animals presenting for non-neurological issues were also obtained to better understand the normal EEG (background activity and transient events) in this species, as, to date, studies have focused on examining natural sleep in pinnipeds. Most animals were sedated for electrode placement and EEG acquisition with some receiving antiepileptic medications or isoflurane during the procedure. A total of 103 recordings were read and scored from 0 (normal) to 3 (severely abnormal). Epileptiform discharges, consisting of spikes, sharp waves, slow waves, and/or spike waves, were present in all EEGs with scores of 1, 2, or 3. The distribution of these events over the scalp varied. While often generalized, others were lateralized over one hemisphere, bifrontal, bioccipital, and/or bitemporal, while some discharges were multifocal. Findings were different between sea lions and occasionally changed within the EEG on a given sea lion. No clinical seizures were observed during the recording but a few sea lions had findings consistent with electroencephalographic seizures. When available, supporting diagnostic results obtained from magnetic resonance imaging (MRI) and/or necropsy/histopathology were described, as well as the status of those sea lions that recovered and were released with satellite tags.

Keywords: EEG; domoic acid (DA); epilepsy; hippocampus; memory; seizures; spatial ability.

Abstract

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