Estudio neuropsicológico y de meta-análisis de la epilepsia del lóbulo frontal

Abstract

Epilepsy is one of the most common neurological diseases with 50 million people worldwide who suffer it (Organización Mundial de la Salud, 2001). It is defined as "a brain disorder that has an enduring predisposition to generate epileptic seizures with a neurobiological, psychological and social consequences" (p. 476, Fisher et al., 2014). The International League Against Epilepsy (ILAE) and the International Bureau for Epilepsy define epileptic seizures as a “transient occurrence of signs/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain” (p. 471, Fisher et al., 2005). Incidence data indicate an average of 50.4 new cases per 100,000 inhabitants per year in adults (Ngugi et al., 2011) and between 27-70/100,000 inhabitants/year in children (Palencia, 2000). The point prevalence of active epilepsy in Spanish adults is 5.79/1,000 inhabitants (Serrano-Castro et al., 2006) and 5.72/1,000 inhabitants in children (Durá-Travé et al., 2007). Frontal Lobe Epilepsy (FLE) is a focal epilepsy in which the epileptic focus is located in the frontal lobe. Frontal seizures are less frequent than those in the temporal lobes, with a frequency between 15% and 20% within all focal epilepsies (Álvarez-Carriles, 2007). Functional and structural heterogeneity of the frontal lobes causes that the diagnosis of FLE to be a complex issue. Its tendency to spread to other brain areas, the variability of the behavioural and neuroimaging manifestations and inconclusive electroencephalogram sometimes confuse the diagnosis to other focal epilepsies or even to non- epileptic seizures (Chauvel, 1997). However, frontal seizures share some common characteristics like the absence of aura, a fast start tending to spread widely bilaterally, short term seizures, high incidence during sleep and they are often grouped in clusters (Lee et al., 2008; Shulman, 2000). FLE is normally due to a structural/metabolic cause like traumatic brain injuries, tumours, vascular malformations or dysplasia. FLE is associated with cognitive problems, especially in areas related to frontal lobe functioning as executive functions, attention and motor skills, but with impact on memory and psychosocial adaptation (Patrikelis et al., 2009). Deficits are similar in both adults and children with FLE, although no studies, longitudinal or transverse, comparing the same research in adult and paediatric performance have been made. Therefore, this paper investigates the cognitive functioning in FLE in adult and child population through two methodologies that allows a full view of the issue: an empirical study with a sample of adults and children and a systematic review with meta-analysis about cognition in FLE in these two populations. Data are presented using the CHC cognitive factors (McGrew, 2005). A random effect meta-analysis was made using Cohen’s d and the confidence interval for each cognitive factor was calculated. 40 subjects participated in the empirical study: 20 adults and 20 children, 20 FLE subjects and 20 healthy controls. A neuropsychological protocol was designed in order to assess the different cognitive factors. The results in the meta-analysis show a general pattern of cognitive dysfunction in FLE, especially in functions related to the frontal lobe, with an influence of the duration and the age of onset of epilepsy, as well as the age of the sample used. In addition, researches in this type of epilepsy are heterogeneous, with too many different sampling and methodological characteristics, which no standard format reporting clinical sample characterization, making it difficult to study FLE in depth. The results in the neuropsychological study indicate that people with FLE are at higher risk of neuropsychological disorders. FLE is related to a pattern of cognitive dysfunction that affects mainly to complex attention, sustained attention, cognitive inhibition, verbal memory and spatial working memory and long term memory, both verbal and figurative. These changes affect both children and adults. In addition, the CHC model stands as a valid and reliable option for studying the cognition in epilepsy, with explanatory and discriminant capacity among participants with FLE and healthy controls and allows a consistent and concise interpretation of the neuropsychological profile in epilepsy. General conclusions are included at the end of this manuscript, combining both studies and giving a general explanation and interpretation of the impact of this research.