Electrocorticographic discharge patterns in glioneuronal tumors and focal cortical dysplasia.

Purpose: To determine whether highly epileptiform electrocorticographical discharge patterns occur in patients with glioneuronal tumors (GNTs) and focal cortical dysplasia (FCD) and whether specific histopathological features are related to such patterns.

Methods: The series consists of operated patients with pharmacoresistant epilepsy because of FCD or GNT between 1992 and 2003. Electrocorticography was reviewed for presence of continuous spiking, bursts, recruiting discharges, or sporadic spikes.

Single pulse electrical stimulation for identification of structural abnormalities and prediction of seizure outcome after epilepsy surgery: a prospective study.

Background: Abnormal late responses to single pulse electrical stimulation (SPES) in patients with intracranial recordings can identify epileptogenic cortex. We aimed to investigate the presence of neuropathological abnormalities in abnormal SPES areas and to establish if removal of these areas improved postsurgical seizure control.

Methods: We studied abnormal responses to SPES during chronic intracranial recordings in 40 consecutive patients who were thereafter operated on because of refractory epilepsy and had a follow-up period of at least 12 months.

Treatment of interictal epileptiform discharges can improve behavior in children with behavioral problems and epilepsy.

Objectives: It is generally agreed that children should be treated for epilepsy only if they have clinical seizures. The aim of this study was to examine whether suppressing interictal discharges can affect behavior in children with epilepsy.

Study Design: In a double-blinded, placebo-controlled, crossover study, 61 children with well-controlled or mild epilepsy were randomly assigned to add-on therapy with either lamotrigine followed by placebo or placebo followed by lamotrigine.

Characteristics of scalp electrical fields associated with deep medial temporal epileptiform discharges.

Objective: To determine scalp characteristics of epileptiform discharges arising from medial temporal structures (MT).

Methods: Signal-to-noise ratio was increased by averaging simultaneous recordings from intracranial and scalp electrodes synchronised on discharges recorded by foramen ovale (FO) electrodes. The topography, amplitude and distribution of averaged scalp signals were analysed.

Material-specific recognition memory deficits elicited by unilateral hippocampal electrical stimulation.

Although the medial temporal lobe is thought to be critical for recognition memory (RM), the specific role of the hippocampus in RM remains uncertain. We investigated the effects of transient unilateral hippocampal electrical stimulation (ES), subthreshold for afterdischarge, on delayed item RM in epilepsy patients implanted with bilateral hippocampal depth electrodes. RM was assessed using a novel computer-controlled test paradigm in which ES to left or right hippocampus was either absent (baseline) or synchronized with item presentation.

Cognitive impairment during epileptiform discharges: is it ever justifiable to treat the EEG?

Epileptiform EEG discharges are not confined to people with epilepsy, and their frequency is only weakly related to severity. A fundamental principle of EEG practice is, therefore, to avoid overinterpretation of epileptiform activity. Epileptiform discharges not accompanied by obvious clinical events are generally regarded as subclinical or interictal.

Electrical impedance tomography of human brain function using reconstruction algorithms based on the finite element method.

Electrical impedance tomography (EIT) is a recently developed technique which enables the internal conductivity of an object to be imaged using rings of external electrodes. In a recent study, EIT during cortical evoked responses showed encouraging changes in the raw impedance measurements, but reconstructed images were noisy. A simplified reconstruction algorithm was used which modelled the head as a homogeneous sphere.

Presurgical assessment of memory-related brain structures: the Wada test and functional neuroimaging.

Medial temporal lobe structures are known to play a major role in memory processing. Recent work has revealed that extratemporal structures (e.g.

Lateralising value of neuropsychological protocols for presurgical assessment of temporal lobe epilepsy.

Purpose: To estimate the value of neuropsychological measurements in determining the side of seizure onset for presurgical assessment in patients with temporal lobe epilepsy. The lateralising value of neuropsychological protocols was evaluated for all patients and in subpopulations depending on surgical outcome with regard to seizure control, speech dominance, neuropathology, and need for intracranial EEG recordings.

Methods: A battery of neuropsychological procedures was carried out preoperatively in 125 patients who underwent left (n = 66) or right (n = 59) temporal lobectomies.

A hole in the skull distorts substantially the distribution of extracranial electrical fields in an in vitro model.

The purpose of this study was to quantify the distortion of electrical fields by skull foramina using an in vitro model. Extracranial voltage generated by current dipoles located inside a human calva immersed in saline were measured when a 4-mm hole was open and when it was blocked with paraffin wax. Dipoles were located either along the internal surface of the bone (superficial dipoles) or at increasing distances from the bone (deep dipoles).