Canine electroencephalographic recording technique: findings in normal and epileptic dogs

Objective: The absence of a standardized recording technique and of normal reference patterns may have hindered the use of experimental electroencephalography (EEG) in dogs and in veterinary medicine as well. Therefore, the aim of the present work was to develop a recording technique for brachycephalic, mesocephalic and dolichocephalic breeds of dogs that would standardize the recording parameters, including the electrical activity of the rhinencephalon and prorean gyrus, and to prove its feasibility for detecting abnormal activity. Methods: We accomplished this task by employing 12 recording electrodes. Three different doses of xylazine (0.5, 1 and 1.5 mg/kg) were used to determine which gave enough sedation to obtain a recording free of artifact. Fifty normal dogs were studied; for comparison 9 epileptic dogs were also explored. Results: We found specific anatomical skull sites where the EEG recording electrodes should be attached; the location of these sites is, in practical terms, the same for every dog, regardless of their skull type. A dose of 1 mg/kg xylazine was chosen for restraining. Normal dogs displayed predominant 6–12 Hz waves which could be recognized all over the cortex. Epileptic dogs were individualized because of the appearance of paroxysmal discharges, composed of spikes, sharp and anomalous sinusoidal waves which usually started in one area, spreading to the whole cortex later on, in the clinical interictal periods. Conclusions: It was possible to obtain more extensive electrophysiological coverage of the canine cerebral cortex, including the rhinencephalon and prorean gyrus, than previously described in the literature. Intramuscular or subcutaneous xylazine, at a dose of 1 mg/kg, proved to produce the best restraint for recordings. The technique allowed to distinguish abnormal activity in epileptic dogs.