Common and distinctive patterns of cognitive dysfunction in children with benign epilepsy syndromes

Dazhi Cheng, Xiuxian Yan, Zhijie Gao, Keming Xu, Xinlin Zhou, Qian Chen.   Common and distinctive patterns of cognitive dysfunction in children with benign epilepsy syndromes. Pediatric Neurology. Article in Press.

Abstract

BACKGROUND

Childhood absence epilepsy (CAE) and benign childhood epilepsy with centrotemporal spikes (BECTs) are the most common forms of benign epilepsy syndromes. Although cognitive dysfunctions occur in children with CAE or BECTs, the similarity between their patterns of underlying cognitive impairments is not well understood. To describe these patterns, we examined multiple cognitive functions in children with CAE and BECTs.

METHODS

In this study, 43 children with CAE, 47 children with BECTs, and 64 controls were recruited; all received a standardized assessment (i.e., computerized test battery) assessing processing speed, spatial skills, calculation, language ability, intelligence, visual attention and executive function. Groups were compared in these cognitive domains. Simple regression analysis was used to analyze the effects of epilepsy-related clinical variables on cognitive test scores.

RESULTS

Compared to controls, children with CAE and BECTs showed cognitive deficits in intelligence and executive function, but performed normally in language processing. Impairment in visual attention was specific to patients with CAE, whereas impaired spatial ability was specific to the children with BECTs. Simple regression analysis showed syndrome-related clinical variables did not affect cognitive functions.

CONCLUSIONS

This study provides evidence of both common and distinctive cognitive features underlying the relative cognitive difficulties in children with CAE and BECTs. It is suggested that clinicians should pay particular attention to the specific cognitive deficits in children with CAE and BECTs, to allow for more discriminative and potentially more effective interventions.

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From the article 

In fact, there is evidence that CAE and BECTs have specific cognitive dysfunctions . CAE is known to affect multiple cognitive functions related to academic and functional difficulties , such that CAE shows impairments in visual spatial skill , verbal memory , and presents with comorbid psychiatric conditions. More recent articles suggest that CAE also impairs attention and executive function  6  , even when the seizures are well-controlled. BECTs, although frequently associated with a good prognosis and remission of seizures before adulthood, is still associated with deficits in cognitive abilities such as language, memory, and attention. Therefore, there are cognitive dysfunctions in both disorders, but how they compare is unclear, since they have only been assessed separately…

The results of the cognitive tests for the CAE, BECTs, and HC groups are presented in Table 2 . There were no significant group differences in language abilities ( F = 1.55, p = 0.217 for word semantics; F = 0.50, p = 0.608 for word rhyming). For visual attention, the CAE group performed significantly worse than the HC group ( F = 6.33, p = 0.002), but the BECTs group was not significantly different from either group (vs. CAE group, p = 0.413; vs. HC group, p = 0.153). For spatial ability and calculation, the BECTs group performed significantly worse than the HC group ( F = 6.50, p = 0.002 and F = 4.78, p = 0.017 after pairwise comparison, respectively), whereas the CAE group did not differ from either the BECTs group ( p = 0.861 and p = 1.000, respectively) or the HC group ( p = 0.076 and p = 0.060, respectively). Both the CAE and BECTs groups performed significantly worse than controls in processing speed, intelligence, and executive function, (CAE group, p = 0.006, p = 0.033, and p < 0.001, respectively; BECTs group, p = 0.012, p = 0.001, and p < 0.001, respectively. However, the CAE and BECTs groups were not significantly different from each other ( p = 1.000; p = 0.985; and p > 0.999, respectively)…

Previous studies suggested that children with CAE and BECTs might have common cognitive deficits. Two recent studies examined memory and intelligence in children with CAE and BECTs, noting that children with both CAE and BECTs exhibited impairment in verbal subtests of intellectual scales, but were intact in terms of memory function. Two other neuropsychological studies on CAE indicated that patients with CAE had deficits in attention and executive function or specifically in executive attention  22  . Few studies have described shared deficits in both CAE and BECTs, though; and while assessment of syndrome-related comorbidities in epilepsy is logical, much remains unknown regarding specific cognitive abnormalities because of the absence of population-based investigations that incorporate standardized comprehensive assessments.

The current investigation found that both CAE and BECTs exhibited impairments in intelligence. Raven's Progressive Matrices test was used to assess figure reasoning ability, which belongs to nonverbal intelligence. However, recent comparative research found that children with CAE and BECTs had common deficits in verbal intelligence, as opposed to nonverbal intelligence. It is possible that these epileptic syndromes have disrupted the function of select overlapping prefrontal cortical areas. Because processing speed is an important component of verbal intelligence (i.e., as seen in the Wechsler Intelligence Scale;  both  groups with epileptic syndromes would have been negatively impacted in verbal intelligence.

Deficits in executive function were also observed in both CAE and BECTs. This result is consistent with other studies concerning the neurobehavioral comorbidities of epilepsy related to executive function. Impairments of executive functions in children with CAE have been repeatedly demonstrated in neuropsychological investigations. A recent study proposed that children with BECTs may also show a range of neuropsychological impairments particularly centered on executive attention.    The present study directly supports the concept that children with CAE and BECTs share a deficit in executive attention, suggesting that it could be a typical cognitive characteristic in epilepsy...

The children with CAE and BECTs tested here also showed distinctive cognitive deficits. Specifically, patients with CAE exhibited impaired performance in visual attention, which is in accordance with the strong association between CAE and attention deficits related to absence seizures. The computerized test battery study demonstrated that patients with CAE are impaired in in many aspects of attention. Furthermore, patients with BECTs with interictal epileptiform discharges exhibited an intrinsic activity abnormality in the middle frontal gyrus and superior parietal gyrus, areas which relate to spatial ability and simple calculation, suggesting that our distinctive deficits are consistent with those found by other research… 

In conclusion, this study demonstrated that children with CAE and BECTs shared cognitive deficits such as intelligence and executive functions, whereas they also showed cognitive deficits distinguishing each syndrome. The data imply that some of these cognitive comorbidities appear in a wide range of epilepsy syndromes, though others have specific expression in different genetic epileptic syndromes. These data could be helpful for improving clinical intervention and therapy when needed. Indeed, clinicians have considerable experience in tailoring AED therapy to CAE or BECTs specifically. This study could allow for similar tailoring of cognitive interventions for these patients.