Background Continuous spike wave in sleep (CSWS) is an electroencephalogram (EEG) pattern associated with developmental and epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS). This etiologically heterogeneous syndrome may occur because of genetic factors and congenital or acquired brain lesions. We studied the pattern of clinical presentation and underlying etiologies in patients with DEE-SWAS that respond to resective surgery. Methods We reviewed our clinical and research databases for patients who had resolution of CSWS following surgical resection of a focal lesion. Results We identified 5 patients meeting inclusion criteria. In 3 of 5, an epileptogenic structural abnormality was not apparent on brain magnetic resonance imaging (MRI). In all 3 patients, focal cortical dysplasia was identified through intracranial EEG monitoring. Significance DEE-SWAS may be a secondary bilateral network epilepsy syndrome, which can be treated with resection of the inciting focal lesion. In patients with drug-resistant CSWS, clinicians should consider a complete epilepsy presurgical workup, including intracranial EEG monitoring.

Surgically Remediable Secondary Network Epileptic Encephalopathies With Continuous Spike Wave in Sleep: Lesions May Not Be Visible on Brain Magnetic Resonance Imaging (MRI)

Epilepsies, especially mesiotemporal epilepsy in adulthood, are frequently associated with chronic cognitive loss, psychiatry symptoms and conditions. We aim to present the pathophysiology of interictal psychiatric comorbidities interlocked with cognitive loss; severely compromising the quality of life of epilepsy patients. We will present the mechanism of cognitive harm related to interictal spiking; and the abnormalities of brain networks in epilepsy, especially of the default mode network, briefly looking into psychosocial and pharmacology effects, too.
In addition to seizures, interictal epileptic activity, mainly in sleep, may exert chronic cognitive harm, increasing the risk for primarily non-cognitive psychotic conditions as well. Interictal spikes and pathological high frequency oscillations curiously resemble normal memory traces; enabling them to “behave” and be mistaken for engrams by the memory process. Epileptic activity impairs the white and grey matter of the brain; likely contributing to brain network changes. The epileptic network changes resemble those seen in non-epileptic psychiatry conditions, offering a network-interpretation of psychiatric comorbidity.

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A Review on the Pathomechanism of Interictal Psychiatry Comorbidities in Epilepsy

Childhood idiopathic regional (polyfocal) hyperexcitability conditions (HIECs) are held to be developmental abnormalities of genetic origin without gross structural lesions. The exact genetic background has remained unclear. These conditions start in early childhood—with some age variance—when the brain is in a plastic state. Intensive spiking during non–rapid eye movement (NREM) sleep is a typical feature. Some of the patients undergo a further increase and exaggeration of spiking during night sleep, progressing to an electrical status epilepticus leading to a serious cognitive decline. The NREM sleep activation of inrerictal epileptiform discharges (IEDs) in HIEC patients is a well-known feature. The continuous transformation of IEDs to electrical status epilepticus in sleep (ESES) occurs with variable activation, localization, synchronization, and amount, but with no basic change in the original (before ESES) IED discharge morphology. Therefore, ESES and Landau–Kleffner syndrome (LKS) are clear examples of cognitive decline caused by sleep IED activation (diffuse in ESES and regional in LKS), similar to medial temporal lobe epilepsy, in which sleep spiking interferes with memory consolidation. Although the cognitive consequences reflect an important quality change in the outcome of these children, the interictal discharges do not change, just their activation during NREM sleep.

Idiopathic Polyfocal Hyperexcitability Conditions (HIEC) of Childhood and Their Transition to Electrical Status Epilepticus in Sleep

To the Editors: I read with great interest the work of Japaridze et al in Epilepsia. They wrote: “An activation of spike and wave activity during slow sleep provides a clear argument for involvement of the thalamocortical network. Synchronization of epileptiform spikes and slow oscillation during slow sleep may involve mechanism similar to one described by Steriade and colleagues . . ..” Our question is: What is the nature of the discharges? Are they really “generalized spike-and-wave” or regional discharges? The first publications about ESES spoke explicitly about generalized spike-and-wave discharges. Not only the electromorphology was considered to be “spike-and-wave” but the recent interpretations about the pathomechanism of the discharges also went back to the classical generalized spike wave pattern, similarly to the present interpretation of Japaridze et al.. However, focal/regional discharges were frequently reported. Beaumanoir already pointed out that “during ESES, the interictal EEG abnormalities during wakefulness are similar to those before ESES, but are usually more marked.” The last overview of the Tassinari group is summarized as follows: “The EEG during wakefulness shows usually focal, or multifocal, slow spikes with frequent associated diffuse slow spikes and waves. In a proportion of cases, the EEG can show features similar to what one observes in “idiopathic” focal (“Rolandic,” frontal or, less frequently, parietooccipital) epilepsies or syndromes. Figure 9 of Tassinari et al. shows a clearcut map of a focal/regional parietotemporal discharge, nothing to do with the classical bilateral spike-wave pattern. Thus doubts can be raised about the existence of a unitary mechanism of ESES because discharges show heterogenic forms; they are bilateral spike-waves but in the majority of cases are focal/regional discharges like in Rolandic or in other focal idiopathic childhood epilepsies. The literature is astonishingly poor in studies that analyze the potential fields of the ESES discharges. In our study from the 33 (18 lesional and 15 nonlesional) children with ESES, only 3 (<10%) (two nonlesional and one lesional) showed the classical generalized spike and wave field. It was characterized by bilateral more or less symmetric distribution, with a uniform dipole (anterior negative and posterior positive half-fields) without unihemispheral phase reversal. All the other patients regardless of lesional or nonlesional etiology showed unihemispheral phase reversals of their discharges with anterior, medial, and posterior localization along the Sylvian fissure as an axis, almost equally distributed. Thus we can say that in our material showing lesional and nonlesional cases in 54.5:46.5% rate, the overwhelming majority had spike fields similar to what we observe in focal/regional childhood idiopathic hyperexcitability syndromes. This finding enlightens our lack of detailed knowledge about the nature of the discharges, and raises the possibility that the majority of the discharges might reflect a more circumscript regional network and that their electromorphology, spatial distribution, and functional properties are not similar to the classical generalized spike-wave pattern.

Comment on Neuronal networks in epileptic encephalopathies with CSWS.

OBJECTIVES A retrospective study has been done at the Bethesda Children's Hospital Epilepsy Center with those patients whose EEG records fulfilled in one or more records the criteria of electrical status epilepticus in slow wave sleep (ESES) pattern, occupying at least 75% of NREM sleep with bilateral discharges, and had detailed disease history and long term follow-up data, between 2000 and 2012. PATIENTS AND METHODS--Thirty-three patients (mean 11.1 +/- 4.2 years of age) were studied by 171 sleep EEG records. Sleep was recorded after sleep deprivation or during spontaneous sleep at least for one hour length of NREM. From the 492 EEGs, 171 sleep records were performed (average five/patient). Average follow-up time was 7.5 years. Eighty-two ESES records have been analyzed in 15 non-lesional and 18 lesional (11 with dysgenetic and seven with perinatal-asphyxic or vascular origin) patients. Variability of seizure types, seizure frequency and frequency of status epilepticus was higher in the lesional group. Impairment of the cognitive functions was moderate and partial in the non-lesional, while severely damaged in the lesional group. RESULTS EEG records of 29 patients shawed unihemispherial spike fields with a perpendicular axis (in anterior, medial and posterior variants) to the Sylvian fissure, regardless their lesional or non-lesional origin. Only three (lone nonlesional and two lesional) patients had bilateral synchronous spike-wave discharges with bilateral symmetric frontocentral spike fields. The individual discharges of the sleep EEG pattern were very similar to the awake interictal records except their extension in time and field, their increased number, amplitude, and continuity of them and furthermore in the increased trans-hemispheral propagation and their synchronity. CONCLUSIONS Assumed circuits involved in the pathomechanism of discharges during NREM sleep in ESES are discussed based on our findings.

Zsuzsa Siegler

Papers

Long term follow-up of lesional and non-lesional patients with electrical status epilepticus in slow wave sleep