Canine electroencephalographic recording technique: findings in normal and epileptic dogs
Introduction
Although dog electroencephalography (EEG) has been employed for many years (Fox, 1967, Kobayashi, 1992, Pampiglione, 1963, Ruckebusch, 1963, Senba et al., 1984, Susuki et al., 1985a, Susuki et al., 1985b, Takahashi and Inada, 1986, Tourai et al., 1985), its use in research and in veterinary clinical neurology has received, so far, little attention (Redding, 1990, Skerrit, 1984). Despite some excellent reviews (Breitschwerdt et al., 1979, Ettinger, 1989, Herin et al., 1968, Holliday and Williams, 1999, Kersten, 1993, Klemm and Hall, 1968, Klemm and Mallo, 1966, Milic and Keca, 1992, Redding, 1978, Redding and Knecht, 1984), this technique is neither a routine method for complementary diagnosis in veterinary medicine nor a usual tool for experimental research. Technically, difficulties include the lack of an universal standard for the recording technique (number of electrodes, terminology and position) and the absence of a common restraint method. Despite some proposals being made (Herin et al., 1968, Pellegrino and Etchepareborda, 1997), so far there are no universally accepted normal patterns for recordings which can be used in research and in clinical practice (Ettinger, 1989, Ford, 1992, Herin et al., 1968, Sorjonen, 1992, Voit, 1984, Voit, 1989) as happens with the 10–20 system of the International Federation employed in humans. The aim of the present work was to develop a technique able to be employed in different breeds of dogs in normal and pathological conditions.
The development of a universal recording technique in dogs must consider: (a) the number of electrodes that allow covering all brain areas, including the rhinencephalon and prorean gyrus (prefrontal cortex); (b) the anatomical sites of placement of the electrodes that assure the same coverage in dogs with different skull types; and (c) the restraint method to be employed, which should not induce major changes in the ongoing recording.
Section snippets
Population
The anatomic sites for the electrode positions were chosen by using the heads of 80 dead dogs obtained from the Department of Anatomy of the Faculty of Veterinary Sciences at Buenos Aires University; the deaths of these dogs were due to illnesses which did not involve their central nervous systems. Heads were collected, regardless of their breed or age, over the course of 1 year. The heads, which previously were fixed in formaldehyde, were divided into two groups according to the skull type:
Position of the recording electrodes
Based on our anatomical studies (Pellegrino and Etchepareborda, 1997, Pellegrino, 2000b), the best sites for placing the recording electrodes are summarized in Table 2 and illustrated in Fig. 1, Fig. 2. The cortical areas that are projected on each EEG channel are also specified in both.
To position the electrodes, we found it easier to start with the temporalis. We proceeded with the frontalis (first F3 and F4, then Fp1 and Fp2), because these sites were latterly used as references for the
Recording technique
The technique described herein allowed us to obtain EEG recordings from a large population of normal canines and others with epilepsy. The number, terminology and positioning of the electrodes, as well as the restraint method, could be standardized for different breeds. The advantages of this technique are:
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It is simple.
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It provides more extensive coverage of the electrical activity of the canine cerebral cortex, both of the neocortex and the archi- and paleocortices.
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It enables recordings to be
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