Idiopathic focal epilepsies: the “lost tribe”

Abstract

The term idiopathic focal epilepsies of childhood (IFE) is not formally recognised by the ILAE in its 2010 revision (Berg et al., ), nor are its members and boundaries precisely delineated. The IFEs are amongst the most commonly encountered epilepsy syndromes affecting children. They are fascinating disorders that hold many “treats” for both clinicians and researchers. For example, the IFEs pose many of the most interesting questions central to epileptology: how are functional brain networks involved in the manifestation of epilepsy? What are the shared mechanisms of comorbidity between epilepsy and neurodevelopmental disorders? How do focal EEG discharges impact cognitive functioning? What explains the age‐related expression of these syndromes? Why are EEG discharges and seizures so tightly locked to slow‐wave sleep? In the last few decades, the clinical symptomatology and the respective courses of many IFEs have been described, although they are still not widely appreciated beyond the specialist community. Most neurologists would recognise the core syndromes of IFE to comprise: benign epilepsy of childhood with centro‐temporal spikes or Rolandic epilepsy (BECTS/RE); Panayiotopoulos syndrome; and the idiopathic occipital epilepsies (Gastaut and photosensitive types). The Landau‐Kleffner syndrome and the related (idiopathic) epilepsy with continuous spikes and waves in sleep (CSWS or ESES) are also often included, both as a consequence of the shared morphology of the interictal discharges and their potential evolution from core syndromes, for example, CSWS from BECTS. Atypical benign focal epilepsy of childhood also has shared electro‐clinical features warranting inclusion. In addition, a number of less well‐defined syndromes of IFE have been proposed, including benign childhood seizures with affective symptoms, benign childhood epilepsy with parietal spikes, benign childhood seizures with frontal or midline spikes, and benign focal seizures of adolescence. The term “benign” is often used in connection with the IFEs and is increasingly being challenged. Certainly most of these disorders are not associated with the devastating cognitive and behavioural problems seen with early childhood epileptic encephalopathies, such as West or Dravet syndromes. However, it is clear that specific, and sometimes persistent, neuropsychological deficits in attention, language and literacy accompany many of the IFEs that, when multiplied by the large numbers affected, make up a significant public health problem. Understanding the nature, distribution, evolution, risk and management of these is an important area of current research. A corollary to such questions regarding comorbidities is the role of focal interictal spikes and their enduring impact on cognitive functioning. What explains the paradox that epilepsies characterised by abundant interictal epileptiform abnormalities are often associated with very few clinical seizures? This is an exciting area in both clinical and experimental arenas and will eventually have imp...

Etiology, syndrome diagnosis, and cognition in childhood‐onset epilepsy: A population‐based study

“…A genetic or presumed genetic source accounts for another third of the etiologies, and the etiology is unknown in the remaining cases. It should be noted here that although genetic etiologies can be clearly defined as chromosomal and gene anomalies, presumed genetic ones are harder to delineate; the genetic basis of “idiopathic” epilepsies in general is quite well established, but that of focal “idiopathic” epilepsies specifically is more debatable …”

The role of EEG in the diagnosis and classification of the epilepsy syndromes: a tool for clinical practice by the ILAE Neurophysiology Task Force (Part 2)

“…-(2) A change in morphology of the CTS during sleep (particularly the appearance of fast spikes or polyspikes, or a marked increase in the slow component, or a brief depression of voltage) may evoke the possibility of symptomatic aetiology even when the clinical ictal features are suggestive of BRE (Dalla Bernardina et al, 2005). Rarely though, patients with electroclinical phenotypes of BRE associated with cortical dysplasia have been reported Pal et al, 2016) (supplementary figure 4.12). -(4) Runs of diffuse bilateral/generalised spike-andwave discharges, lasting for more than three seconds in wakefulness.…”

“…Atypical evolution of benign focal epilepsies in childhood This condition does not refer to children with atypical clinical and EEG features of BRE, but to a subset of children who initially appear to have a typical form of BRE (or Panayiotopoulos syndrome-PS), but subsequently present a period of severe aggravation of epileptic seizures and/or language and cognitive dysfunction, and/or behavioural disturbance (Pal et al, 2016). Aicardi and Chevrie (1982) were the first to report this unusual evolution in seven children with BRE who presented periods with new types of seizure, mainly atonic and myoclonic, associated with continuous spike-and-wave discharge in slow sleep on the EEG, and transitory deterioration in school performance; they used the term "atypical benign partial epilepsy of childhood" (ABFEC).…”

“…FLAIR MRI scan showed focal cortical dysplasia involving the left rolandic region (from Guerrini R and Pisano T;Pal et al [2016]). EEG recording of a four-year-old girl showing normal background activity with superimposed spikes in the left centro-temporal region.…”

Network analysis of prospective brain development in youth with benign epilepsy with centrotemporal spikes and its relationship to cognition

“…12 In addition, both white matter and functional discrepancies have been reported, comprising lower fractional anisotropy in left inferior frontal and supramarginal regions, and lower functional connectivity between left sensorimotor and right inferior frontal gyrus, respectively. 13,14 Similarly, although interest has been longstanding in regard to the complications of language-based abilities in children with BECTS, [15][16][17] cognitive complications of BECTS have been reported in diverse areas of mentation compared to age-matched control peers, 8,15,18,19 including not only language-related skills but intelligence, memory, attention, and executive function (for reviews, see Wickens et al, 5,20 Pal et al 20 ). Importantly, cognitive and magnetic resonance (MR) abnormalities have been reported in new onset cases as well, with the nature and range of anomalies varying across studies, [21][22][23][24] attesting that these abnormalities are not necessarily secondary to the effects of epilepsy chronicity and medication treatment.…”