Melissa Filippini and Giuseppe Gobbi
Defining the problem: the ‘what’ and the ‘how’
Epilepsy is the most common neurological disorder in childhood (Reilly et al. 2014). In addition to recurrent seizures, psychiatric, cognitive and social-adaptive behaviour disorders are major potential sources of disability, in many cases more challenging than epilepsy itself. These complications have been recently referred to collectively as the neurobehavioural comorbidities of the epilepsies (Lin et al. 2012).
In paediatrics, findings have unequivocally documented an increased rate of psychiatric comorbities in children with epilepsy compared with both the general population and children with other medical disorders, including non-neurological disorders (Jones et al. 2007; Hermann et al. 2008). Psychiatric problems occur typically in around 24–66% of children (Rodenburg et al. 2005; 2006; Austin et al. 2011). This risk is evident in children with uncomplicated epilepsies, for example, those with normal results on neurological examination and normal IQ, also attending mainstream schools (Sillanpää and Shinnar 2010), but is especially marked in those with complicated epilepsies, for example, epilepsy plus brain lesion and/or intellectual disability (e.g. IQ < 70) and in children with active epilepsy (Reilly et al. 2014), rating over 50%, as compared with 6.6% in the general child population (Choudhary et al. 2014). Similarly, uncomplicated epilepsies show, even with a normal IQ, an increased prevalence of impairment in some aspects of cognition, such as attention, memory and language (Høie et al. 2006; Fastenau et al. 2009). Prevalent academic achievement problems have also been characterised, with significantly higher rates of school-based interventions (e.g. repeating the same grade, summer schools, tutors) (Rantanen et al. 2010). In addition, the social and psychological effects of epilepsy can be profound. Epilepsy can exert a negative effect on the child and family quality of life (QOL), because of lower social competences, more physical and functional disabilities, more unmet medical and mental health needs than children without epilepsy, exposure to real and perceived stigma, financial stress, treatment-related adverse events and the general fear of seizures (Luoni et al. 2011; Russ et al. 2012).
Even if neurobehavioural comorbidities in children with epilepsy are frequent, few are assessed by mental health professionals, probably indicating either a lack of recognition of need for referral or a lack of appropriate services to meet this particular need (Reilly et al. 2014). In the former case, it is probable that children with epilepsy are subject to a form of ‘diagnostic overshadowing’, with the neurological disorder overshadowing neurobehavioural problems (Fastenau et al. 2008). Similarly, when an intellectual disability is present, the assumption may be that the intervention is not needed because the abnormal or atypical behaviour is an inherent part of intellectual disability, leading to missed and untreated disorders (Reilly et al. 2014).
POSSIBLE BEHAVIOURAL DISORDERS
The phenomenology of psychiatric disorders associated with epilepsy is wide and variable (Choudhary et al. 2014). Adding to the diagnostic difficulty of neurobehavioural disorders in epilepsy is the fact that several psychiatric symptoms, recognised as diagnostic criteria, can occur secondary to seizure activity, EEG abnormalities or antiepileptic drugs (AEDs). Moreover, some authors have considered cognition and language as intrinsic components of behaviour since they play an important role in social functioning, as well as in the sense of competence and self-esteem (Austin and Caplan 2007). Consequently, in some articles it is difficult to discern between pure behavioural and cognitive problems.
The neurobehavioural comorbidities being various, the attempts of classification have been controversial. Some researchers contend that psychiatric syndromes in epilepsy can be characterised by atypical features that are poorly represented by conventional classification systems such as the fourth edition (text revised) of the Diagnostic and Statistical Manual of Mental Disorders (DSM IV-R) and the International Classification of disease (ICD) Version 10 (Krishnamoorthy et al. 2007). In 2007, the International League Against Epilepsy (ILAE) Commission on Psychobiology of Epilepsy developed a classification proposal of neuropsychiatric disorders in epilepsy with the aim to separate disorders comorbid with epilepsy and those that reflect ongoing epileptiform activity from epilepsy-specific disorders, and to attempt to subclassify the epilepsy-specific disorders alone (Krishnamoorthy et al. 2007). The classification was followed by international clinical practice consensus statements for the treatment of neuropsychiatric conditions associated with epilepsy, to provide guidance on the management of these conditions (Kerr et al. 2011a). These documents put together adult and childhood epilepsies.
Generally, there is a wide consensus regarding a greater association between epilepsy and the following behavioural disorders: attention-deficit–hyperactivity disorder (ADHD), autism spectrum disorders (ASD), anxiety, depression and psychosis.
ADHD is one of the most common comorbidities, being reported in about 30–40% of children with epilepsy compared to 3–6% of controls, especially in preschool and school-age children, without sex differences (Dunn and Kronenberger 2005; Hermann et al. 2007a; Parisi et al. 2010; Cohen et al. 2013; Socanski et al. 2013). Differently from children without epilepsy, children with epilepsy are most likely to present with an inattentive form (Reilly 2011). The symptoms of ADHD may not be the same as those of ADHD in other conditions, because of the comorbidity with psychiatric disorders, underlying brain abnormality, frequent epileptiform discharges, seizures and adverse effects of medication. A common pathogenic mechanism has been hypothesised: the animal models of ADHD suggest that synaptic abnormality in excitatory glutamergic transmission may contribute to vulnerability for epilepsy and ADHD (Jensen et al. 2009).
ASD have been reported in around 20% of children with epilepsy; estimates of epilepsy in autism range from 5–40%, compared to 1% of general population, depending on the samples chosen, on diagnostic criteria and on the age of participants (Berg et al. 2011c; Woolfenden et al. 2012). Indeed, there are two peaks of onset of epilepsy associated with autism: the first in infancy and the second in adolescent years. Moreover, the prevalence of autism in children with epilepsy also depends on the IQ level (the lower the IQ the higher the incidence of ASD) and on sex (being girls at higher risk) (Amiet et al. 2008; Tuchman et al. 2013). Despite the importance of this comorbidity, the rate of misdiagnosis of epilepsy is still high, typically around 20–25%, and despite the large number of studies performed, a full understanding of the possible links between epilepsy and ASD remains elusive (Uldall et al. 2006). So far, there is no evidence that typical autism can be attributed to an epileptic disorder, even in those children with a history of regression after normal early development (Deonna and Roulet 2006). The current evidence seems to point to a common underlying predisposition factor since a growing number of genetic defects leading to both conditions have been discovered (Betancur 2011; Brooks-Kayal 2011).
The increased prevalence of anxiety and depression has been found in epidemiological and clinical studies, and is frequently comorbid (Berg et al. 2011a; Russ et al. 2012). The reported prevalence of these internalising disorders from samples obtained in epilepsy clinics is higher than the prevalence reported in epidemiological surveys, namely 12–20% for depression and 10–20% for anxiety, compared to 1–7% of controls, going beyond 30% in patients with lower IQ, language delays, or neuropsychological deficits such as academic difficulties (Caplan et al. 2005b; Cushner-Weinstein et al. 2008; Ekinci et al. 2009; Austin et al. 2010b; Reilly 2011). The higher risk for anxiety includes specific phobias, panic disorder, and posttraumatic stress symptoms (Dunn et al. 2009). Age has been found to be a significant risk factor for both depression and anxiety, adolescents being more at risk than younger children, although findings are discordant (Ekinci et al. 2009). It also seems that adolescents report more symptoms than parents observe. For children and adolescents with primary depression, early age at onset and the severity of depressive symptoms are associated with non-adherence to treatment or lack of treatment and are predictive of both pharmaco-resistant epilepsy and recurrence of depressive symptoms during their adult age (Pereira and Valente 2013). The sex difference in the increased prevalence of anxiety and depression is inconsistent though the prevalence of depression is high in female adolescents (Pereira and Valente 2013). The symptoms are similar to those observed in peers without seizures (Vega et al. 2011). However, some symptoms may relate specifically to epilepsy: brief episodes of anxiety or fear can occur as an aura in children with focal epileptiform discharges frequently originating from the temporal lobe (Salpekar and Dunn 2007). For symptoms of depression and anxiety, some authors suggested distinguishing between epilepsy-related preictal, ictal, postictal and interictal symptoms and comorbid disorders unrelated to epilepsy. Specific epilepsy-related factors do not seem to be a major factor in the causation of anxiety or depression (Pereira and Valente 2013), and findings have shown that depression is more important than seizure frequency in determining perceived QOL (Hecimovic et al. 2012).
Psychosis or ‘psychotic’ features are significantly more frequent in patients with epilepsy than in the general population, with prevalence rates ranging between 2% and 8%, compared to less than 1% of controls (Helmstaedter et al. 2014). Nevertheless, in a large proportion of these reports no formal diagnosis has been made and the term is being used loosely to describe any behaviour that cannot be easily explained. No evidence of features such as hallucinations or thought disorder is provided; moreover, there is confusion surrounding the classification terms. Some authors suggested distinguishing at least four categories: psychosis related to seizures (e.g. ictal or postictal), psychosis related to seizure remission (alternative psychosis or forced normalization), interictal psychosis (i.e. psychosis between seizures without any clear time relationship to them) and iatrogenic psychosis related to AEDs or after temporal lobectomy. In adolescents, psychosis can be postictal, interictal, antiepileptic-drug induced or post-surgical; whether ictal psychosis occurs in teenagers remains open to debate.
In children occur also psychogenic non-epileptic seizures (PNES), even if no formal guidelines for diagnosing in children exist, and little is known about the clinical practice of diagnosing PNES in the paediatric setting (Wichaidit et al. 2014). PNES are paroxysmal events that resemble clinical signs and symptoms of epileptic seizures but are not associated with ictal epileptiform abnormalities in the EEG pattern. Some studies focused on the development or on the remission of PNES after cranial surgery for epilepsy, especially for right temporal dysplasia. The clinical semiology of PNES is very complex and belongs to the complicated phenomenon defined as ‘dissociation’, for example, ‘a disruption of and/or discontinuity in the normal integration of consciousness, memory, identity, emotion, perception, body representation, motor control, and behavior’ (Roberts and Reuber 2014).
Bipolar disorders are rarely diagnosed in the paediatric epilepsy population, rating around 1% (Berg 2011). Bipolar disorder symptoms have been more often reported as postictal phenomena and occasionally as ictal phenomena. The phenomenological understanding of childhood mania has changed over recent years to the extent that a bipolar disorder spectrum allows for better description of the patient presentations most commonly encountered in clinical practice. Symptoms such as explosive rage, extreme irritability, mood lability and agitation may not meet full criteria for traditional mania but may be consistent with a bipolar disorder spectrum especially in terms of treatment selection (Nishida et al. 2005; Schmitz 2005).
There does not appear to be a significant increase of oppositional defiant disorder (ODD) or conduct disorder in children with uncomplicated epilepsy, although results are not univocal (Jones et al. 2007).
Suicidal ideation has been reported in around 20% of children with epilepsy, compared to about 5% in general population (Caplan et al. 2005b; Wagner et al. 2009; Hesdorffer et al. 2012b). Adolescents with epilepsy are at higher risk, both as compared with general population and as compared with adults with older-onset epilepsy. The risk seems to be associated with the severity of epilepsy and with intellectual disability, but other factors are likely to be important and need to be discovered through further investigation and clinical practice advances (Rodenburg et al. 2011).
Compared to siblings and to children with other chronic conditions, social difficulties (e.g. difficulties in having a productive and mutually satisfying relationship with others) tend to be specific to children with epilepsy (Sillanpää and Cross 2009; Clary et al. 2010; Rantanen et al. 2009; 2012; Rodenburg et al. 2011). Measures of initiating behaviour, making conversation, responding to the actions of others, and assertiveness have proved significantly impaired (Tse et al. 2007). Poorer social competence may be related to a chronic condition or, as seen in typically developing children, peer problems may also be associated with neurocognitive functions (e.g. inattention and social cognition) (Drewel et al. 2009). Cognitive impairment or learning problems and verbal IQ are proposed to be moderators of development of social competence in children with epilepsy (Clary et al. 2010; Buelow et al. 2012; Byars et al. 2014). An individual with inadequately developed communication skills may not effectively express emotions, regulate behaviour, or develop and maintain interpersonal relationships (Clary et al. 2010). It is possible that early-onset epilepsy with comorbid cognitive impairment and a longer duration of seizures are associated with poorer social skills or delayed social skill acquisition (Cushner-Weinstein et al. 2008; Rantanen et al. 2009). Also, an abnormal family function has been shown to be strongly predictive of social skills impairment (Tse et al. 2007). Alternatively, psychosocial factors may play a role. Epilepsy remains a stigmatised condition and myths and misconceptions are still prevalent in society (Baxendale and O’Toole 2007). Because of this, children with epilepsy may feel less welcome in peer interactions and may avoid social situations for fear they may suffer a seizure or be restricted from participation by their parents and caregivers (Cheung and Wirrell 2006). Put together, findings regarding the importance of several epilepsy variables (e.g. aetiology, seizure frequency and seizure type) to be associated with problems in social competence are contradictory. The relationship between epilepsy-related variables and social competence is probably indirect rather than direct (Noeker et al. 2005). Nevertheless, problematic social skills during childhood and adolescence are related to subsequent psychopathology and may predispose to behavioural and adjustment problems in adulthood (Rantanen et al. 2012).
Consensus neurobehavioural diagnoses have been generally made using the DSM-IV criteria together with standardised scales. The ADHD Rating Scale-IV (ADHD-RS-IV; DuPaul et al. 1998) and Conners’ Rating Scales (CRS-R, Conners 1997) have been used for ADHD diagnosis. The Childhood Depression Inventory (CDI, Kovacs 1985), the Short Mood and Feelings Questionnaire (SMFQ) (Angold et al. 1987), the Child or Adolescent Symptom Inventory (Sprafkin et al. 2002), the Beck Depression Inventory (BDI) (Beck et al. 1988) and the Children Depression Rating-Scale Revised (CDRS-R) (Poznanski and Mokros 1996) have been used to rate mood disorders. So far, the instruments most commonly used to assess anxiety disorders have been the Revised Children’s Manifest Anxiety Scale (RCMAS) (Reynolds and Richmond 1985), the Multidimensional Anxiety Scale for Children (MASC, March et al. 1997), the Screen for Child Anxiety Related Emotional Disorders (SCARED, Birmaher et al. 1997).
Some studies used psychiatric diagnoses based on structured psychiatric interviews with the child or parent, such as the Child Global Assessment Scale (CGAS, Shaffer et al. 1983), the Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS) (Kaufman et al. 1997), the Diagnostic Interview Schedule for Children (Shaffer et al. 2000), the Vineland Social Maturity Scale (VSMS, Doll 1965) and the Behaviour Assessment System for children, Second Edition (BASC-2) (Reynolds and Kamphaus 2004).
Among self-rating scales, the Child Behaviour Check List (CBCL) (Achenbach 1991) for children, parent and teacher has been highly used, confirming behavioural disorders associated with epilepsy, although with different results (Rantanen et al. 2012).
To rate parenting stress in relation to children with special needs and/or epilepsy, the Parenting Stress Index (PSI) has been developed (Abidin 1990).
To assess social skills, there are the CBCL, the CRS-R and the Social Skills Rating System (SSRS, Gresham and Elliott 1990). Together with the SSRS, the Strength and Difficulties Questionnaire (SDQ, Goodman 1997) is an example of possible and practical assessment tools for a broader perspective in the assessment of social competence, since they include all aspects (Dafoulis and Kalyva 2012). Studies have also provided evidence for a high sensitivity and specificity of SDQ among children with epilepsy (Hysing et al. 2007). Furthermore, since expectations of social competence increase as a function of child’s age and developmental level, the division into subgroups according to their age has been suggested (Rantanen et al. 2012).
A novel approach using multiple instruments to assess ASD, developmental delay and behavioural/emotional difficulties has been proposed (Eom et al. 2014), including the Social Communication Questionnaire (SCQ) (Rutter et al. 2003), the Modified Checklist for Autism in Toddlers (mCHAT) (Robins et al. 2001), and the SDQ.
QOL scales specific for children with epilepsy have been developed to cover physical, psychological, social and academic functioning. Examples of tools include the Quality of Life in Epilepsy for Adolescents (QOLIE-AD-48) (Cramer et al. 1999), the Quality of Life in Childhood Epilepsy (QOLCE) (Sabaz et al. 2000), the Impact of Paediatric Epilepsy Scale (IPES) (Camfield et al. 2001) and the Impact of Childhood Illness Scale (Hoare and Russell 1995). The National Institute of Neurological Disorders and Stroke (NINDS) provided leadership to develop the Neuro-QOL, which provides psychometrically sound and clinically relevant QOL measures for children and adults with neurological disorders (Cella et al. 2012; Gershon et al. 2012).
The best way of obtaining accurate information on the prevalence of neurobehavioural comorbidities in children with epilepsy is to analyse data from well-designed, prospective epidemiological studies on large populations of children, including control groups. While interviewing patients, some strategies can be used that are both efficient and accurate (Salpekar and Dunn 2007). With younger children, a calm and reassuring stance will yield the most information, and a gradual process of general questions leading to more specific questions is often most effective. Especially for adolescents, to obtain a behavioural description every attempt should be made to interview the patient independently, since they may not reveal their symptoms in the presence of caregivers.
Nevertheless, findings may differ on the basis of the rate of the behaviour and type of measurement, which can lead to over- or underestimation of problems (Dafoulis and Kalyva 2012). Clinicians and researchers should be aware that using different rating scales may yield different results especially since they have not been designed specifically for children with epilepsy (Krishnamoorthy 2006). In addition, parents’ psychiatric status might influence what information they provide and how they communicate it: depressed and/or anxious parents might be aware of the child’s symptoms, but under- or overestimate their severity.
A lifespan perspective on behavioural disorders
Evidence has emerged suggesting bidirectional relations between epilepsy and various neurobehavioural comorbidities in paediatric epilepsy (Lin et al. 2012; Helmstaedter et al. 2014). Psychiatric disorders can either precede or follow the onset of epilepsy, which is the case for depression, anxiety, ADHD and psychosis (Jones et al. 2005; Hesdorffer et al. 2006; Wotton and Goldacre 2012). Seizure incidence has been shown to be higher in psychiatric patients, males and aged 6 to 12 years, even in those without seizure risk factors (McAfee et al. 2007).
In a study, more than 40% of children with epilepsy met diagnostic criteria for a DSM-IV disorder before the diagnosis of epilepsy and the first recognised seizure (Jones et al. 2005), even without clinical evidence of brain structural abnormalities (Almane et al. 2014). The increased prevalence may be consistent with the presence of underlying neurobiological influences independent of seizures, epilepsy syndrome and AEDs (Jones et al. 2007).
ADHD is more prevalent in new-onset epilepsy than in healthy controls (31% vs 6%), even in idiopathic syndromes (Hermann et al. 2007a). More than 15% of the children with new-onset seizures fell in the clinical range of internalising and externalising problems (Dunn et al. 2009). About 25% of children with new-onset idiopathic epilepsies need special education services before clinical seizure onset (Berg et al. 2005). Behavioural complications do not necessarily respect traditional syndrome groupings in children with new- or recent-onset epilepsy, showing shared findings in localisation-related and generalised epilepsies, even if social difficulties and internalising behaviours are more frequent in the latter (Bhise et al. 2009; Almane et al. 2014). At the time of the first seizure episodes, the child must begin to adapt to an unpredictable and frightening disorder, causing him/her persisting worries about having another seizure (Choudhary et al. 2014). Anxiety, stress and emotions can trigger seizures and increase seizure frequency. This, in turn, can also trigger anticipatory anxiety and evoke stress, anger and frustration leading to a vicious circle of anxiety and seizures fuelling each other, further increasing the risk for behavioural problems (Lathers and Schraeder 2006).
The effects of early disorders may be short-term on educational functioning and long-term on occupational, social and behavioural development. Though most studies of behaviour in children with epilepsy have been cross-sectional, several groups have assessed changes over time, finding in some cases a trend either of behavioural improvement with controlled seizures or of stability (Austin et al. 2012). However, longitudinal retesting of patients with epilepsy and controls has shown persistent neurobehavioural differences (such as lower levels of education and employment, less cognitive gaining in testing) even in adults with childhood-onset epilepsy who have been seizure free and off medication for many years and those with benign types of epilepsy. In particular, an earlier age at onset is associated with poorer cognitive function and, consequently, with an increasing risk for neurobehavioural comorbidities (Hermann et al. 2008). A 10-year follow-up population study of psychological and social outcome in well-functioning children and adolescents with childhood-onset epilepsy has shown some emotional, behavioural and social problems, especially in patients with active epilepsy (e.g. at least one seizure episode in the last 5y) and polytherapy, with a better outcome for idiopathic localization-related epilepsies (Jonsson et al. 2014). In a population-based study with a median follow-up duration of 28 years since the onset of epilepsy, compared to unaffected population, children with epilepsy with good cognitive development and without comorbidities have shown similar adult health, educational and employment outcomes but had difficulties with establishing and maintaining personal relationships (Chin et al. 2011). On the contrary, a combination of childhood epilepsy and poor cognitive development and/or comorbidities and/or difficulties in feeling accepted by peers at the age of 11 years is more likely to be associated with adverse outcomes compared to having poor cognitive development without childhood epilepsy. Consequently, a good childhood cognitive development can be considered as an important predictor of good adult outcomes. Higher IQ may relate to stronger strategies to handle with sickness, such as an active participation and compliance to pharmacological intake, reducing the specific impact of medical epilepsy-related variables, such as seizure severity (Pereira and Valente 2013). Moreover, the management of social/emotional problems around 11 years should have positive long-term impacts. It is generally recognised that the development of social competence is one of the best predictors of later social and academic success, and of present and future behavioural and emotional problems (Rantanen et al. 2012). Other studies have reported similar findings suggesting that negative societal attitudes towards epilepsy may cause isolation in later life (Camfield and Camfield 2007). With respect to factors predicting behavioural adaptation to epilepsy, early temperament (e.g. the early appearing, biologically based characteristic patterns of emotional reactivity and self-regulation) and neuropsychological functioning (especially executive functions also involved in behavioural control) in school-age children with new-onset seizures have shown to predict the outcome 3 years after seizure onset (Baum et al. 2010). In particular, novelty distress (perhaps an early marker of anxiety), unmanageability (perhaps an early marker of impulsivity and deviant behaviours) and cognitive self-regulatory difficulties may put children at risk for relatively long-term poor behaviour outcomes.
Authors have proposed that the concept of cerebral reserve might have important implications in understanding the life course of people with epilepsy who have an early brain insult, raising the question whether it confers an increased risk for disrupted cognitive development and accelerated ageing effects owing to reduced cerebral reserve (Deary et al. 2004). In the context of childhood-onset chronic epilepsy, this concept might help to conceptualise the lifespan course of cognition and brain structure in epilepsy (Hermann et al. 2008).
There are relatively few studies of the behavioural outcome of epilepsy surgery in children who have used standardised behavioural measures before and after the procedure. Moreover, homogeneous data are lacking because of groups with mixed pathology and retrospective studies. Characterising the long-term behavioural outcome for people with epilepsy previously admitted to surgery is complex, given the highly individual nature of patient response to illness and its treatment (Wilson et al. 2005). Increasing evidence supports the idea that epilepsy surgery early in life may be associated with a complex psychological process of postoperative adjustment, which persists for many years (McLellan et al. 2005).
Taken together, results show that the outcome in temporal and extra-temporal surgery is very variable, with few children improving and others deteriorating, and with a better outcome in younger children (Mclellan et al. 2005; Colonnelli et al. 2012). De novo depression is a common psychiatric sequela of temporal lobe epilepsy (TLE) surgery (McLellan et al. 2005; Wrench et al. 2009). The study of the psychological profile in childhood-onset TLE approximately 13 years after seizure onset showed that surgical non-seizure-free patients had the poorest outcome in terms of lowered mood and depression (Micallef et al. 2010), and are at higher risk for postictal psychosis (Cleary et al. 2013). Lifetime psychiatric history predicts a worse seizure outcome following temporal lobectomy (Kanner et al. 2009). The outlook for hemispherectomy does not seem better, since psychopathology has been a common result either pre- or postoperatively, without post-surgical worsening or improvement, even in seizure-free patients (Danielsson et al. 2009; Colonnelli et al. 2012). Vagus nerve stimulation seems to increase QOL, even without a change of adaptive behaviour (Mikati et al. 2009; Zamponi et al. 2011).
Theoretical models propose that psychopathology in epilepsy can stem from a complex interplay of multiple aetiological variables (Choudhary et al. 2014). The prevalence of neurobehavioural comorbidities in epilepsy across the lifespan has triggered a concerted effort to uncover their potential mediators, including various epilepsy-related variables. Moreover, psychosocial models have been developed to depict the complexity of behavioural comorbidities in childhood epilepsy. Recent neuroimaging evidence contributes to the tracing of the neurobiological underpinnings of associated disorders, providing biological markers of increased risk.
THE ROLE OF EPILEPSY-RELATED VARIABLES
Given that neurobehavioural comorbidities are especially recurrent in complicated epilepsies, it is important to distinguish the burden of the core clinical features of epilepsy. Among many possible factors, the most relevant to clinical practice include aetiology, syndrome, epileptiform discharges, seizure, age at epilepsy onset, years of epilepsy duration and prescribed drugs (Lin et al. 2012).
An assumption in the specialty is that epilepsy occurs in a fundamentally abnormal brain, which increases a person’s risk not only for seizures, but also for neurobehavioural comorbidities (Salpekar and Dunn 2007). Hence, comorbid symptoms may be directly related to epilepsy and the underlying brain disorder. Despite their variability, structural-functional relations seem to be strong in lesional epilepsy such as malformation of cortical development, even before seizure onset (Freilinger et al. 2006; Chang et al. 2012). However, removing a lesion does not always improve symptoms, suggesting that this mechanism alone is not the entire explanation (Hamiwka and Wirrell 2009).
The electro-clinical syndrome is a factor which has received particular interest. For decades, the syndromic model has served as the basis for investigating the cognitive and psychiatric domains most at risk. The importance of the behavioural implications of syndrome classification could be considered in two broad categories: first, the behavioural effects of epilepsy syndromes and, second, the behavioural associations of childhood syndromes (‘behavioural phenotypes’) in which epilepsy occurs as a prominent feature. Even if different syndromes seem to have diverse comorbidities, the same disorders have been documented across a wide range of epilepsy syndromes: for example, psychiatric complications of TLE have been documented also in benign epilepsy with centrotemporal spikes (BECTS). Consequently, the decade-long controversy regarding the unique psychiatric vulnerability of some syndromes has been replaced by the opinion that psychiatric disorders occur across diverse epilepsy syndromes. This variability within and across syndromes suggests that phenotypic presentations might be driven by other factors.
In the following, we provide a description of behavioural disorders of some syndromes which will not be discussed in detail in the next chapters of the book.