Читать книгу Canine and Feline Epilepsy - Luisa De Risio - Страница 55

Apart from identifying genetic backgrounds, which can be associated with poor response to AEDs, much attention has been spent in the last decade to identify clinical risk factors that predict pharmacoresistant epilepsy. In people, it was commonly believed that seizure freedom was more likely to be achieved when a patient received AEDs immediately after the occurrence of the first seizure. Interestingly, epidemiological studies in developing countries, where AEDs are not freely available, revealed remission rates similar to those in industrial countries (Placencia et al., 1993). Most AEDs despite having good seizure suppressing activities have little influence on the natural course of the disease (epilepsy) itself. New AEDs that were thought to also have an anti-epileptogenic effect have failed in chronic epilepsy models and have not prevented the development of epilepsy (Brandt et al., 2007).

Heynold and colleagues have shown in 1997 that Labrador retrievers, which achieved freedom from seizures, received medication a longer period of time after their first seizure than those dogs that continued to seizure (Heynold et al., 1997). This implies that timing in relation to onset of seizure activity does not influence long-term seizure control in the canine patient. However, there is enough evidence in dogs, rodent models and humans that disease severity, such as high seizure frequency, cluster seizures and status epilepticus can influence drug responsiveness (Heynold et al., 1997; Kwan and Brodie, 2000; Hülsmeyer et al., 2010; Löscher and Brandt, 2010; Weissl et al., 2012). Intact male and female dogs have a higher likelihood of having cluster seizures (Monteiro et al., 2012). Seizure severity will ultimately guide clinical reasoning and the more severely affected patient will receive treatment earlier than dogs with a less severe epilepsy phenotype. It was formerly believed that very young dogs starting to have recurrent seizures have a worse outcome. As an example, Labrador retrievers had a better outcome when they developed epilepsy later in life (Heynold et al., 1997). However, a recent study from the UK could not find that the onset of seizures before the age of 1 year had any influence on survival outcome (Arrol et al., 2012). Interestingly, the same group could not find that the presence of focal seizures influenced the overall outcome, which is different to what is seen in human medicine (Kwan et al., 2011).