Nancy Foldvary

Semiological seizure classification

Summary: We propose an epileptic seizure classification based exclusively on ictal semiology. In this semiological seizure classification (SSC), seizures are classified as follows:

The localizing value of ictal EEG in focal epilepsy

Objective: To investigate the lateralization and localization of ictal EEG in focal epilepsy. Methods: A total of 486 ictal EEG of 72 patients with focal epilepsy arising from the mesial temporal, neocortical temporal, mesial frontal, dorsolateral frontal, parietal, and occipital regions were analyzed. Results: Surface ictal EEG was adequately localized in 72% of cases, more often in temporal than extratemporal epilepsy. Localized ictal onsets were seen in 57% of seizures and were most common in mesial temporal lobe epilepsy (MTLE), lateral frontal lobe epilepsy (LFLE), and parietal lobe epilepsy, whereas lateralized onsets predominated in neocortical temporal lobe epilepsy and generalized onsets in mesial frontal lobe epilepsy (MFLE) and occipital lobe epilepsy. Approximately two-thirds of seizures were localized, 22% generalized, 4% lateralized, and 6% mislocalized/lateralized. False localization/lateralization occurred in 28% of occipital and 16% of parietal seizures. Rhythmic temporal theta at ictal onset was seen exclusively in temporal lobe seizures, whereas localized repetitive epileptiform activity was highly predictive of LFLE. Seizures arising from the lateral convexity and mesial regions were differentiated by a high incidence of repetitive epileptiform activity at ictal onset in the former and rhythmic theta activity in the latter. Conclusions: With the exception of mesial frontal lobe epilepsy, ictal recordings are very useful in the localization/lateralization of focal seizures. Some patterns are highly accurate in localizing the epileptogenic lobe. One limitation of ictal EEG is the potential for false localization/lateralization in occipital and parietal lobe epilepsies.

Seizure outcome after temporal lobectomy for temporal lobe epilepsy A Kaplan-Meier survival analysis

Objective: To determine seizure outcome and its predictors in patients with medically refractory temporal lobe epilepsy (TLE) after temporal lobectomy (TL). Background: TL is the most common surgical procedure performed in adolescents and adults for the treatment of medically refractory TLE. Seizure outcome has been reported extensively during the first few postoperative years, but little is known beyond that time. Methods: The authors analyzed seizure outcome in 79 patients who underwent TL for epilepsy at the Duke University Medical Center from 1962 through 1984. Patients with less than 2 years of follow-up and degenerative disorders were excluded. Predictors of seizure outcome were analyzed using Kaplan-Meier survival analyses. Results: The mean follow-up was 14 years (range, 2.1 to 33.6 years). Using Engel’s classification, 65% of patients were class I, 15% were class II, 11% were class III, and 9% were class IV. At least one postoperative seizure occurred in 55% of subjects. The majority of recurrences (86%) took place within 2 years of surgery. Later recurrences tended not to lead to medical intractability. Higher monthly preoperative seizure frequency was associated with poor seizure outcome. A seizure-free state at 2 years was found to be a better predictor of long-term outcome than the 6-, 12-, and 18-month landmarks. Conclusions: TL provides sustained, long-term benefit in patients with medically refractory TLE. Seizure-free status at 2 years from the time of surgery is predictive of long-term remission.

Temporal lobe epilepsy due to hippocampal sclerosis in pediatric candidates for epilepsy surgery

Objective: To characterize the clinical, EEG, MRI, and histopathologic features and explore seizure outcome in pediatric candidates for epilepsy surgery who have temporal lobe epilepsy (TLE) caused by hippocampal sclerosis (HS). Methods: The authors studied 17 children (4 to 12 years of age) and 17 adolescents (13 to 20 years of age) who had anteromesial temporal resection between 1990 and 1998. Results: All patients had seizures characterized by decreased awareness and responsiveness. Automatisms were typically mild to moderate in children and moderate to marked in adolescents. Among adolescents, interictal spikes were almost exclusively unilateral anterior temporal, as opposed to children in whom anterior temporal spikes were associated with mid/posterior temporal, bilateral temporal, extratemporal, or generalized spikes in 60% of cases. MRI showed hippocampal sclerosis on the side of EEG seizure onset in all patients. Fifty-four percent of children and 56% of adolescents had significant asymmetry of total hippocampal volumes, whereas the remaining patients had only focal atrophy of the hippocampal head or body. Subtle MRI abnormalities of ipsilateral temporal neocortex were seen in all children and 60% of adolescents studied with FLAIR images. On histopathology, there was an unexpectedly high frequency of dual pathology with mild to moderate cortical dysplasia as well as HS, seen in 79% of children and adolescents. Seventy-eight percent of patients were free of seizures at follow-up (mean, 2.6 years). A tendency for lower seizure-free outcome was observed in patients with bilateral temporal interictal sharp waves or bilateral HS on MRI. The presence of dual pathology did not portend poor postsurgical outcome. Conclusions: TLE caused by HS similar to those in adults were seen in children as young as 4 years of age. Focal hippocampal atrophy seen on MRI often was not reflected in total hippocampal volumetry. Children may have an especially high frequency of dual pathology, with mild to moderate cortical dysplasia as well as HS, and MRI usually, but not always, predicts this finding. Postsurgical seizure outcome is similar to that in adult series.

Epileptogenicity Correlated with Increased N‐Methyl‐d‐Aspartate Receptor Subunit NR2A/B in Human Focal Cortical Dysplasia

Summary: Purpose: Human cortical dysplasia (CD) is a frequent cause of medically intractable focal epilepsy. The neurotransmitter mechanisms of epileptogenicity in these lesions have been attributed to changes in various glutamate receptor subtypes. Increased N‐methyl‐d‐aspartate (NMDA) receptor (NR) 2A/B coassembled with NRI subunits has been shown in focal epileptic CD. The purpose of this study is to correlate in situ CD epileptogenicity and the expression of various glutamate receptor subtypes.

The Effects of Lamotrigine on Sleep in Patients with Epilepsy

Summary:  Purpose: The older antiepileptic drugs (AEDs) have a variety of effects on sleep, including marked reduction in REM, slow‐wave sleep (SWS) and sleep latency, and increased percentage of light sleep. The effects of the newer AEDs on sleep are unknown. Our purpose was to study the effect of lamotrigine (LTG) on sleep.

Correlation of Hippocampal Neuronal Density and FDG-PET in Mesial Temporal Lobe Epilepsy

Summary: Purpose: Interictal [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) reveals regional hypometabolism in 60–80% of patients with mesial temporal lobe epilepsy (MTLE). The extent of hypometabolism generally extends beyond the epileptogenic zone. The pathophysiology underlying this widespread change is unknown. This study evaluated the relation between hippocampal neuronal loss and hypometabolism in patients with MTLE.

Clinical and electrographic manifestations of lesional neocortical temporal lobe epilepsy

To determine whether lesional neocortical temporal lobe epilepsy (NTLE) can be differentiated from mesial temporal lobe epilepsy (MTLE) during the noninvasive presurgical evaluation, we compared the historical features, seizure symptomatology, and surface EEG of 8 patients seizure free after neocortical temporal resection with preservation of mesial structures and 20 patients after anterior temporal lobectomy for MTLE. Seizure symptomatology of 107 seizures (28 NTLE, 79 MTLE) was analyzed. One hundred one ictal EEGs(19 NTLE, 82 MTLE) were reviewed for activity at seizure onset; presence, distribution, and frequency of lateralized rhythmic activity (LRA); and distribution of postictal slowing. Seizure symptomatology and EEG data were compared between groups, and sensitivity, specificity, and positive and negative predictive values were determined for variables that differed significantly. Multiple logistic regression was used to determine whether patients could be correctly classified as having MTLE or NTLE. MTLE patients were younger at onset of habitual seizures and more likely to have a prior history of febrile seizures, CNS infection, perinatal complications, or head injury. NTLE seizures lacked features commonly exhibited in MTLE, including automatisms, contralateral dystonia, searching head movements, body shifting, hyperventilation, and postictal cough or sigh. NTLE ictal EEG recordings demonstrated lower mean frequency of LRA that frequently had a hemispheric distribution, whereas LRA in MTLE seizures was maximal over the ipsilateral temporal region. We conclude that it may be possible to differentiate lesional NTLE from MTLE on the basis of historical features, seizure symptomatology, and ictal surface EEG recordings. This may assist in the identification of patients with medically refractory nonlesional NTLE who frequently require intracranial monitoring and more extensive or tailored resections.

A new epileptic seizure classification based exclusively on ictal semiology

Historically, seizure semiology was the main feature in the differential diagnosis of epileptic syndromes. With the development of clinical EEG, the definition of electroclinical complexes became an essential tool to define epileptic syndromes, particularly focal epileptic syndromes. Modern advances in diagnostic technology, particularly in neuroimaging and molecular biology, now permit better definitions of epileptic syndromes. At the same time detailed studies showed that there does not necessarily exist a one‐to‐one relationship between epileptic seizures or electroclinical complexes and epileptic syndromes. These developments call for the reintroduction of an epileptic seizure classification based exclusively on clinical semiology, similar to the seizure classifications which were used by neurologists before the introduction of the modem diagnostic methods. This classification of epileptic seizures should always be complemented by an epileptic syndrome classification based on all the available clinical information (clinical history, neurological exam, ictal semiology, EEG, anatomical and functional neuroimaging, etc.). Such an approach is more consistent with mainstream clinical neurology and would avoid the current confusion between the classification of epileptic seizures (which in the International Seizure Classification is actually a classification of electroclinical complexes) and the classification of epileptic syndromes.

Periictal diffusion-weighted imaging in a case of lesional epilepsy.

Summary: Purpose: Diffusion‐weighted MR imaging (DWI) has been used for the early diagnosis of acute ischemic lesions in humans and in animal models of focal status epilepticus. We hypothesized that DWI may be a sensitive, noninvasive tool for the localization of the epileptogenic area during the periictal period.