Electroencephalographic findings of encephalitis in beagle dogs experimentally infected with canine distemper virus (CDV)

Artifacts During Short-Term Interictal Electroencephalographic Recording in Dogs

The electroencephalogram (EEG) is an electrodiagnostic technique widely used in both scientific research and clinical medicine. It makes it possible to study the neurophysiology of brain activity by recording real-time changes in electrical potential produced by cortical activation. The importance of EEG in diagnosing canine epilepsy demonstrates its usefulness when the owner's description of crises is not clear or when the episodes cannot be differentiated from behavioral or cardiac disorders. However, EEG recordings also often record electrical activity from sources other than the brain, which may interfere with the clinical event-related signal. This activity is known as artifactual electrical activity, and the signal changes recorded in these cases corrupt the trace when they are superimposed on brain activity or even, in some cases, mimic pathologic abnormalities. The first step in analyzing and interpreting EEG traces is to recognize artifacts and other specific transient events. This retrospective study set out to ascertain whether artifacts comparable to those described in humans are observed in protocols used to perform short-term interictal EEG for canine epilepsy and how these can be classified.

Quantitative electroencephalographic findings in beagles anaesthetized with propofol

The purpose of this study was to assess quantitative electroencephalography (q-EEG) in 10 healthy beagle dogs under propofol anaesthesia in order to determine objective guidelines for diagnostic electroencephalographic (EEG) recordings and interpretation. The basic pattern after preliminary visual examination of EEG recordings was characterized by spindles, k-complexes, vertex sharp transients, and positive occipital transients that were superimposed on the slow background activity. The results of the q-EEG were characterized by the prevalence of slow rhythms delta and theta, both in absolute and relative power spectrum analysis, while fast rhythms (alpha and beta) were poorly represented. The distribution of single frequency bands was widespread for delta, focal for frontal and central for theta, as well as for most alpha and beta patterns. The present study has shown that the use of quantitative EEG gives information on the frequency content of the bio-electrical activity and defines the distribution of the single frequency bands under a standardized anaesthetic protocol.

Idiopathic epilepsy in 125 dogs: a long-term study. Clinical and electroencephalographic findings

Well-documented cases of confirmed idiopathic epilepsy in 125 dogs were evaluated retrospectively. Forty-six breeds (each with no sex predisposition) were examined. Although dogs of all ages were affected, the peak value for the onset of first seizure was between one and five years. Approximately 75 per cent of animals had generalised grand mal type seizures with loss of consciousness. Preictal and postictal phases were present in the majority of dogs. Interictal electroencephalographic recordings of 37 anaesthetised dogs were statistically analysed. High frequency and low amplitude paroxysmal discharges with either a focal or generalised distribution were found in the majority of these dogs. Possible causes for this variation from dog to dog were analysed. It was concluded that, despite anaesthesia, electroencephalographic features were consistent and unique in dogs with idiopathic epilepsy.

Clinical and electroencephalographic findings of inflammatory and infectious diseases of the central nervous system in dogs: a retrospective study

In the present study medical records of 97 dogs with inflammatory/infectious diseases of the central nervous system (CNS), including 26 dogs with a history of seizures, were retrospectively examined. The aims of the study were to analyse the incidence rate of seizures, to search for criteria to recognize specific inflammatory diseases and to determine how far electroencephalography may be useful in the early confirmation of encephalitis and encephalitis-associated seizures. The incidence rate of seizures in this dog population was 26.8%, and dogs with protozoal encephalitis had the highest rate. Signalment, history, extraneural and neurological signs including localization contributed only a little to a specific diagnosis. Surprisingly focal clinical signs were observed in two-thirds of the dogs. Either focal or multifocal clinical signs were related mainly to the forebrain in dogs with a history of seizures and to the brainstem in dogs without seizures. Cerebrospinal fluid (CSF) analyses were useful to separate encephalitis from other CNS diseases and to distinguish certain conditions from others in approximately half the cases. Electroencephalography (EEG) revealed two distinct patterns in 25 examined dogs with histopathologically confirmed disease entities, which were characterized by high voltage, slow activity (HVSA) with superimposed low voltage, fast activity (LVFA). These changes were consistent and no significant differences (P > 0.05) between dogs with and without seizures, nor between different disease entities, were noted. However, all the dogs with seizures had in addition a uniform paroxysmal EEG activity with a high voltage (mean = 106.3 microV), fast activity (mean = 8.5 Hz) pattern. Moreover in several dogs from the present study this pattern had a focal distribution despite the fact that clinically seizures appear generalized. Therefore it was concluded that EEG may be a very helpful diagnostic tool to confirm an early diagnosis of encephalitis and to separate potential seizure cases from those without seizures.