Is Language Impairments a Symptom of Nocturnal Epileptiform Activity? Studies exploring the relationship between nocturnal epileptiform activity and language impairments

Abstract

Evidence and experience indicate that children with isolated epileptiform activity during sleep (nocturnal epileptiform activity [NEA]) often have language impairments. However, this relationship is not fully understood. Therefore, the overall aim of this PhD project was to explore the relationship between NEA and language impairments. Increased knowledge about language impairment in children with NEA could, among others, strengthen pedagogical interventions for these children. For some children, the language impairments would be the only or the first symptom of NEA because epileptic seizures are absent or follow the language impairments. However, there is no consensus related to which language impairments should be regarded as symptom of NEA. Therefore, the project’s prolonged goal was to gain such knowledge to support the early identification of children with NEA. Early identification of NEA is crucial because it could indicate course of treatment. Based on the overall aim and the prolonged goal, three hypotheses were developed: The main hypothesis was that NEA plays a role in children’s language development. The second hypothesis was that specifically NEA is a contributing factor in the development of language impairments in particular. The last hypothesis was that NEA affects certain aspects of language. Two studies are comprised in the PhD project: one focusing on the NEA dimension and one focusing on the language impairments dimension. First, by conducting a systematic review, the prevalence of NEA in children with language impairments was explored. 55 studies (eight studies with control groups) were included in a meta-analysis and showed that isolated epileptiform activity (IEA) were more common in the language-impaired children than it was in the control group children. The overall pooled prevalence of IEA in children with language impairments was 27.3 %. However, the prevalence varied widely between the studies. The results implied that IEA during sleep (in other words NEA) are more common than IEA during wakefulness, and that children with language regression and language impairments are more likely to have IEA than children with speech impairments. Second, by conducting an empirical study with a cross-sectional design, the presence of language impairments in children with NEA was explored by comparing them with several comparison groups (typically developing children matched on age, typically developing children matched on language ability and language-impaired children without NEA). Also, the aims were explored both thorough prospective data (language and linguistic-cognitive tests and electroencephalograms [EEGs]) and retrospective data (parental questionnaires and medical records). The results indicate that children with NEA have delayed language abilities and that these impairments seem to be confined to the language domain. Moreover, it seems like children with NEA have specifically poor skills in phonology and naming speed. Last, the results indicate that an early indicator of NEA would be alterations in language development. Also, the results showed that symptoms other than language impairments could be indicators of NEA. Together with epileptic seizures, cognitive impairments (such as difficulties with executive functioning, particularly if alterations in functioning is involved), sleep problems and sound sensitivity could be early indicators of NEA. As a whole, the results confirm the three hypotheses articulated in the projects: NEA plays a role in children’s language development; specifically NEA is a contributing factor in the development of language impairments in particular; NEA affects certain aspects of language. The results could have several implications. Results showing that children with NEA have overall delayed language abilities and particularly difficulties with verbal processing could guide pedagogical practice. Results showing that a considerable prevalence of children with language regression and language impairments have NEA, and that cognitive impairments, sleep problems and sound sensitivity could be indicators of NEA, could guide us in identifying which children to refer to EEGs.