Introductory Remarks on Neuropsychological testing in Childhood Epilepsy

INTRODUCTORY REMARKS ON NEUROPSYCHOLOGICAL TESTING IN CHILDHOOD EPILEPSY

Agathe Laurent, Faustine Ilski-Lecoanet and Alexis Arzimanoglou

Neuropsychological evaluation of epilepsies considers everything that is essential or necessary for being able to identify specific abilities that are dysfunctional in children with a given type of epilepsy. Neuropsychological assessment seeks to evaluate adaptive behavioural deficits and abnormal developmental trajectories by considering key variables, including the type, number, combination and degree of any cognitive deficits, the presence or absence of associated or contributory impairments, the known or suspected aetiology, and the significance of any ability-related strengths. The aim is to be able, whenever possible, to suggest adequate measures for rehabilitation.

In children, dynamic epileptic processes interfere with typical maturational ones

The study of cognitive functions in children with epilepsy involves an examination of how the brain transforms environmental signals, processes and ‘builds’ information, and programs adaptive behaviour (including cognitive state). Consequently, it is necessary to take into account ‘maturation’ which refers to a dynamic process, of unknown duration, involving interactions between genetics and environment at every level, from molecules to the behaviour of the organism.

Schematically, cognitive development relies on the interaction between cerebral maturation and stimulation from the environment: typical developmental cognitive processes emerge from interactions between neural preorganization and environmental constraints, anticipated and selected by the neural organization.

The resulting new neural organization interacts, in turn, with new features of the environment. If no ‘accident’ occurs during this period of development, these snowball processes lead to cerebral functional specialization that will be more or less the same in all individuals. The time at which functional specialization becomes irreversible differs, according to the domains of cognitive development and to the kinds of networks involved.

Epilepsy also is a dynamic process that can start at any age and can result in morphological and functional localized/generalized cerebral network modifications. As a result, the pathological epileptic process interferes with normal cerebral development. It is known that structural damage to the brain associated with epilepsy differs, according to whether the first seizures occurred early in childhood or later in life. Onset during childhood has a more widespread structural effect on the brain than onset in adulthood. Brain connectivity reduction, as measured by volumetric reduction of white matter in the whole brain and the corpus callosum, seems to be greater in individuals with early rather than with late epilepsy onset. In individuals with early-onset epilepsy, the white matter volumetric reductions were found to be significantly associated with lower cognitive performances in some, but not all, cognitive domains. This pattern of results was not observed in patients with late-onset epilepsy (Hermann et al. 2002, 2003; Camfield and Camfield 2003; Ciumas et al. 2014).

Neuropsychological assessment should be performed as early as possible during the course of the disease

As in adults, many studies have shown the impact of epilepsy in children on various and specific aspects of somesthesic, olfactory, visual, auditory, spatial and temporal regulation and cognition, speech, and language, including arithmetic, social and emotional cognition, attention and memory, decision making, and reasoning. It is acknowledged that a variety of factors contribute to the development of those cognitive deficits. These factors include underlying neuropathology, age at onset, psychosocial problems, origin of seizures, treatment side effects, genetic factors, and sleep disturbances. For each child, the neuropsychological assessment should consider all the factors above, including the exact type of epilepsy.

More recent studies suggest that cognitive abnormalities may be present at baseline in children with new-onset epilepsies (Herman et al. 2006; Jackson et al. 2013; Kellermann et al. 2015). Some of those are remediable when appropriately treated early in the course of the disorder, reinforcing the need for an early neuropsychological assessment and regular follow-ups.

Neuropsychological assessment including cognitive and mood regulation evaluation

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