Primary Generalized Seizure Disorder: Correlation of Epileptiform Discharges with Seizure Frequency

Summary: The role of routine follow-up EEG in assessment of severity of a seizure disorder is not known. This retrospective chart review study of patients with primary generalized seizure disorders explored the relation between parameters of epileptiform discharge bursts on EEG and number of seizures experienced in the preced ing months. Eighty-seven such patients were found, each with one to seven EEGs and corresponding clinical records, comprising a total of 201 clinicoelectrographic epochs. The 56 chronically attending patients (more than two attendances) differed from the 31 nonchronic attenders in receiving more antiepileptic drugs (AEDs) and having fewer EEG poly spikes; otherwise, the two groups were similar and were analyzed together. We noted a strong relation between number and maximum length of epileptiform bursts in the resting EEG record and number of absence seizures reported in the months preceding the EEG. Age did not affect this relation. After stepdown regression analysis, only the maximum length of epileptiform bursts remained significantly related to the reported number of absence seizures. These findings may prove useful in assessing clinical progress, e.g., in patients whose ability to estimate numbers of attacks is suspect. Neither number nor maximum length of epileptiform bursts in the resting EEG record had a significant relation with the number of generalized tonic-clonic seizures. Presence of polyspikes on resting or "activated" EEG had no added predictive value. The presence of epileptiform bursts after activation by sleep, hyperventilation, or photic stimulation was not associated with an increased likelihood of having had seizures.     

Will a Critical Level of Hyperventilation-Induced Hypocapnia Always Induce an Absence Seizure?

We wished to determine if the degree of hypocapnia correlates with increased frequency of absence seizures and if there is a critical pCO² at which absence seizures are reliably provoked. Twelve untreated children with newly diagnosed absence epilepsy were continuously monitored by EEG and end-expiratory CO₂ recording during quiet respiration and hyperventilation (to absence seizure or exhaustion) while breathing four gas mixtures: (a) room air, (b) 100% O₂, (c) 4% CO₂ in room air, or (d) 4% CO₂+ 96% O₂. In quiet respiration, a reduction in number of spike and wave bursts and total seconds of spike and wave was noted in children breathing supplemental CO₂ (gases c and d vs. gases a and b), p < 0.05. Supplemental O₂ had no effect. Eight subjects had absence seizures elicited with each trial of hyperventilation. All subjects had their own critical pCO₂, ranging from 19 to 28 mmHg. Three children had no seizures, two despite hypocapnia to pCO₂ of 19 and 21 and 1 who achieved a pCO₂ of only 25. In 1, absence seizures were provoked in only six of nine hyperventilation trials to pCO₂ of 17–23. In 67% of subjects, absence seizures were reliably provoked by hypocapnia. Critical pCO₂ varied among children with absence. Determination of whether variation in sensitivity to hypocapnia may be helpful in determining response to antiepileptic drugs (AEDs) or remission of seizures will require further study.     

Epilepsy with Typical Absence Seizures with Onset During the First Year of Life

Absence epilepsy with multiple daily seizures and onset at the age of 6 and 1/2 months in a healthy female child with normal development is described. EEG-video recording revealed typical absence seizures (vacant staring and interruption of motor activity) and complex absences (as above, plus raising of the eyeballs, slight beatings of the eyebrows, and forward propulsion of head and shoulders). The absences were accompanied by bilateral symmetrical 3-Hz spike-wave discharges preceded, and at times followed, by bilateral frontoparietal theta activity coinciding with onset and termination of the absence seizures. The seizures regressed with nitrazepam therapy. At age 3-years, the child is seizure-free and shows normal neurologic development.     

Some Genetic Aspects of Idiopathic and Symptomatic Absence Seizures: Waking and Sleep EEGs in Siblings

Epileptic activity was recorded in the waking and sleep EEG of 62.5% of 80 siblings of 38 patients with absence seizures. Epileptic discharges were noted in waking only in 8.7%, in waking as well as sleep in 28.8%, and in sleep only in 25%. Generalized, partly irregular, and slow spike-wave complexes were found, twice with lateral emphasis. Spike-wave complexes were recorded in 72% of 50 siblings of patients with idiopathic absence and in 46.7% of 30 siblings of patients with symptomatic absence. One epileptic discharge was observed every 108.6 s on the average, without striking differences between siblings of patients with idiopathic (99.7 s) and symptomatic absence (119.3 s). Without any differences between siblings of children with idiopathic and symptomatic absence, the most epileptic discharges were activated in sleep stages C and D, followed by stages A and B. The highest activation rate was observed in the 7-14-year-old group (73.5%) and to a somewhat lesser degree in the group between 15 and 20 years of age (66.7%); fewer epileptic discharges were recorded in younger (25%) and older patients (28.6%). The higher activation rates in the male sex were significant only in siblings of patients with idiopathic absence. Although only five patients (13.2%) were photosensitive, a photosensitivity was found in 24% of siblings of children with idiopathic absence and in 20% of siblings of patients with symptomatic absence. Three siblings of patients with idiopathic absence also had absence seizures; in one of them a febrile seizure occurred at an earlier age. All of them showed generalized spike wave discharges in waking as well as sleep. Occipital theta delta activity with generalization was observed more frequently in siblings of patients with idiopathic absence (82.2%) than in those of patients with symptomatic absence (63.6%). Our waking and sleep EEG recordings prove that concerning etiology-genetic factors play a striking role in idiopathic absence, but are also of considerable significance in the symptomatic types.     

Absence Seizures and Carbamazepine in Adults

Summary: Carbamazepine (CBZ) therapy was associated with development of absence seizures in 4 adults with generalized epilepsy. Two patients had new appearance of absence seizures and 2 patients had recrudesence of remote absence seizures. The seizures abated after discontinuation of CBZ therapy or addition of ethosuximide (ESM) in 1 patient intolerant of valproate (VPA).     

钙调素拮抗剂对癫痫动物模型抗痫作用的研究

目的 了解钙调素拮抗剂有无抗痫作用,为临床上开发新型的抗痫药以进一步控制癫痫提供理论依据。方法 采用记录小鼠脑电图同时观察其行为的方法,观察钙调素桔抗剂W—7对L型钙离子通道激动剂±Bayk—8644致痫小鼠行为和脑电图的影响。结果 钙调素拮抗剂明显延长了痫性发作和痫波发放的潜伏期,减轻了痫性发作程度,减少了痫波发放频率;同时还发现钙调素拮抗剂有一定的镇静作用。结论 钙调素拮抗剂对±Bayk-8644致痫小鼠有抗痫作用。     

Mirror Focus: Function of Seizure Frequency and Influence on Outcome After Surgery

Summary: The concept of the mirror focus (MF) implies that an actively discharging epileptiform region may induce similar paroxysmal behavior in a homologous site. In a group of patients with complex partial seizures (CPS) we investigated whether occurrence of a MF was influenced by certain clinical factors and whether surgical out-come was influenced by the presence of an MF. Factors studied included age at onset, duration, and total number of seizures. Patients had had CPS for >3 years and had pathologically proven temporal lobe neoplasms. Seizure frequency was estimated by the history-taking physician. We estimated total seizure number by multiplying frequency by duration. Seven patients had MF, and 15 did not. Mean age at onset of seizures, duration of seizure disorder, and total seizure number did not vary statistically between the two groups of patients. All patients with an MF except 1 were seizure-free at follow-up. Ten of the 15 patients without MF were seizure-free. Three patients who were not seizure-free had had subtotal resection owing to tumor overlap with eloquent cortex. We conclude that an MF is not a contraindication to operation even when the preponderance of interictal spike activity is contralateral to the tumor or when seizures appear to arise from the MF on scalp EEG.     

A Study of Unilateral Brief Focal Atonia in Childhood Partial Epilepsy

We studied unilateral brief focal atonia (BFA) in seven patients with childhood partial epilepsy. BFA was observed as a transient dropping of one arm lasting from 100 to 150 ms when patients were asked to keep both arms outstretched in front of the body. Close examination using simultaneous video-polygraphic recordings showed dropping of the arm to correspond exactly with a single sharp and slow wave complex arising from the contralateral centrotemporoparietal region. The BFA occasionally would progress to atonic seizures or atonic absence seizures, when the localized epileptic discharge evolved into generalized discharges. In one patient we found a positive correlation between the intensity of BFA and the amplitude of the contralateral epileptic discharges. A higher amplitude corresponded to more pronounced BFA and a lower amplitude to less pronounced BFA. These results led us to conclude that the apparently interictal single sharp and slow wave complex in the rolandic region may inhibit contralateral motor control, thus producing BFA that corresponds with the spike amplitude.     

Benign Partial Epilepsy with Secondarily Generalized Seizures in Infancy

Summary: Seven infants with benign idiopathic partial epilepsy presented with apparently generalized tonic-clonic seizures (GTCs) which proved to be partial seizures evolving to secondarily generalized seizures. All were easily controlled with phenobarbital (PB) or carbamazepine (CBZ), and remained seizure-free >3 years even after discontinuation of medication, and had a normal developmental outcome. The initial seizure manifestation consisting of motion arrest, staring or blank eyes, or crying associated with focal paroxysmal discharges was followed by GTCs in accordance with generalization of paroxysmal discharges. Four infants had a family history of benign type of childhood convulsions. The term "benign partial epilepsy in infancy" is proposed to combine this syndrome with the previously described benign infantile epilepsy with complex partial seizures.     

NIRS‐measured oxy‐ and deoxyhemoglobin changes associated with EEG spike‐and‐wave discharges in a genetic model of absence epilepsy: The GAERS

Purpose: Absence epilepsy may be severe and is frequently accompanied by cognitive delay, yet its metabolic/hemodynamic aspects have not been established. The Genetic Absence Epilepsy Rats from Strasbourg (GAERS) are an isomorphic, predictive, and homologous model of human absence epilepsy. We studied hemodynamic changes related to generalized spike‐and‐wave discharges (GSWDs) in GAERS by using a technique with high temporal resolution: near‐infrared spectroscopy (NIRS). We hypothesized that conflicting results from other techniques might be due to the averaging of a biphasic response such as the one we described in children. Methods: NIRS is particularly suitable for monitoring changes in the concentrations of oxy‐, deoxy‐, and total hemoglobin (HbO₂, HHb, and HbT), using the specific absorption properties of living tissues in the near infrared range. We obtained concomitant high quality electroencephalography (EEG)–NIRS recordings in six GAERS (total of 444 seizures), and tested whether the discharges were related to changes in cardiac or respiration rates. Results: The onset of GSWDs was preceded by a deactivation, followed by an activation that was possibly due to seizure‐suppression mechanisms. The end was marked by a deactivation. The onset of GSWDs was associated with a decrease and the end with a brief increase in respiratory rate. Discussion: Our results differ partially from those of previous studies on hemodynamic aspects of GSWDs (many of which describe a simple deactivation), probably due to differences in temporal resolution and data processing; however, they are consistent with metabolic studies, functional magnetic resonance imaging (fMRI) studies on WAG/Rij rats, and some results in children with absence epilepsy.     

Lateralized Postictal EEG Delta Predicts the Side of Seizure Surgery in Temporal Lobe Epilepsy

PURPOSE: The concordance of lateralized EEG postictal polymorphic delta activity (PPDA) to the side of seizure origin in temporal lobe epilepsy (TLE) has received limited study. Our objective was to study the lateralizing value of PPDA in patients with documented TLE. METHODS: A cohort of consecutive adults with TLE, detailed presurgical evaluation before temporal lobectomy, and minimal follow-up of 2 years were included. One author masked the ictal rhythm of presurgical EEGs and randomly presented 20 s of preictal and the postictal EEG to two electroencephalographers who were blind to all clinical data. They independently assigned PPDA to one of three categories: not present, bilateral, or lateralized (defined as newly appearing or an amplitude >50% of the preictal record). RESULTS: Eighty seizures from 29 patients were studied. Fifteen patients had a left, and 14 had a right temporal lobectomy. Twenty-three patients were seizure free or substantially improved (defined as simple partial or nocturnal seizures only). Lateralized PPDA was present in 64% of all EEGs and at least one record from 22 (76%) patients. Lateralized PPDA, when present, was concordant with the side of surgery in 96% of the EEGs. CONCLUSIONS: Lateralized PPDA is highly predictive of the side of ultimate temporal lobectomy, and by inference the side of seizure origin.     

Reactive Occipital Epileptiform Activity: Is It Benign?

Occipital epileptiform activity that is almost continuous and reactive to eye opening has been associated with a childhood epilepsy syndrome and basilar migraine with seizures. An association of these syndromes with a benign course had been disputed. In this study, a retrospective investigation of reactive occipital epileptiform activity (ROEA) was performed to determine the prognostic value of this distinctive EGG pattern. The EEG and hospital record of patients with ROEA were reviewed with an observation period of 6 months to 8 years. The patients were divided into good and poor outcome groups based on response to treatment. Of 33 patients, 12 (36.4%) had complete seizure control; 21 (63.6%) continued to have poorly controlled seizures. Only 3 (9.1%) patients were able to discontinue antiepileptic drugs (AEDs) without seizure recurrence. Analysis of clinical and EEG variables showed that a history of perinatal difficulties, abnormal neurologic findings, and abnormal EEG background activities occur significantly more frequently in the poor outcome group. This study suggests that ROEA is not uniformly associated with a benign course and that other factors are involved in determining prognosis of the epilepsy.     

Visual Cognitive Disturbance During Spike-Wave Discharges

Cognitive functions of patients showing slow spike-wave discharge in EEG without obvious absence seizures were investigated using tachistoscopic stimuli triggered by spike-waves. Response times obtained during spike-waves and during non-spike-waves were compared for three tests (tapping, simple reaction, and morphological discrimination). We present one case of Lennox-Gastaut syndrome in which the test results could be statistically confirmed. The tapping test was interrupted by the occurrence of spike-waves. Response times during spike-waves were more delayed than during non-spike-waves in both the simple reaction tests and morphological discrimination tests. The differences in response times measured during spike-waves and during non-spike-waves were significantly greater in the morphological discrimination test than in the simple reaction test. The positive correlation between the length of spike-waves and response time in the discrimination test was significantly more pronounced than in the reaction test. These results were also confirmed in two other patients with Lennox-Gastaut syndrome. We conclude that spike-wave discharges may impair cognitive processing more intrinsically than motor functions.     

Frontal Lobe Seizure Propagation: Scalp and Subdural EEG Studies

PURPOSE: To study propagation properties of focally originating frontal lobe seizures: principally direction and promptness of ictal spread. METHOD: Forty-eight scalp EEG-recorded and 17 subdurally recorded seizures in two separate groups of patients were visually scrutinized. RESULTS: Initial propagation was directed more commonly to contiguous frontal cortex than to the opposite hemisphere in both studies: 58% and 86% for scalp and subdural recordings, respectively. Eighteen (38%) of scalp EEG seizures propagated within 5-10 s of apparent onset, whereas 16 (33%) did so after 11-20 s; no evidence of propagation could be discerned in the remaining 14 (29%). Of subdurally recorded attacks, only four (24%) propagated in the first 4 s; six (35%) did so after a delay of 5-10 s; six (35%) either failed to propagate or did so after > or =20-s latency. Latency to initial propagation was between 5 and 20 s in 41 (63%) of the 65 seizures in both studies. Ictal activity remained within the frontal lobe of origin for > or =10 s in 39 (81%) of scalp-recorded seizures and 11 (65%) of subdural seizures. It remained so confined for > or =15 s in 26 (54%) and nine (53%), respectively. Twenty-four (50%) of scalp-recorded seizures displayed evidence of opposite hemisphere (bisynchronous or other contralateral) involvement, occurring 5-10 s after onset in eight (17%) seizures and 10-20 s after onset in 16 (33%). Similarly, the subdural study documented spread to the opposite hemisphere in 11 (65%) of seizures with a latency ranging from 1 to 45 s. CONCLUSIONS: Frontal lobe seizures in this study propagated less promptly than reputed, and initial spread occurred more commonly to the frontal lobe of origin than to the opposite hemisphere. Such properties underlie the good lateralizing value of clinical semiology of frontal lobe seizures.     

Caffeine Blocks Absence Seizures in the Tottering Mutant Mouse

The neurological tottering mutant mouse is characterized by frequent "absence" seizures accompanied by bilateral synchronous spike and wave EEG bursts. Under anesthesia, adult homozygous tottering mice were implanted with permanent epidural electrodes, and at least 7 days elapsed before electrocorticograms in unrestrained mice were scored for seizure incidence and duration. Caffeine (5, 10, 15 mg/kg, n = 8) injected intraperitoneally (i.p.) at the fourth hour of 8-h recording sessions significantly (p less than 0.001 for 10 and 15 mg) decreased seizure incidence as compared with control saline injections. Spike and wave bursts were eliminated during the 30 min after injection and reached 50% preinjection levels between the first and the second hour after injection. Another central nervous system (CNS) stimulating drug, amphetamine (1 mg/kg; n = 5), under identical conditions failed to decrease seizure incidence in this mutant.     

EEG and Seizure Outcome After Epilepsy Surgery

Summary: The significance of the EEG after epilepsy surgery is not fully understood. We investigated the as- sociation between postoperative EEG abnormalities and persistent seizures after epilepsy surgery as they relate to pathologic lesions. Among 254 patients who underwent epilepsy surgery between 1987 and 1991, we identified 78 patients who had mesiotemporal sclerosis (MTS) and 47 patients who had low-grade brain tumors, all of whom had 6-to 18-month postoperative follow-up including EEG. Patients who had other pathology, multiple operations, callosotomy, or hemispherectomy, or who were aged <18 years or who had insufficient EEG data, were excluded. Patients were classified as having persistent seizures or being seizure-free since operation. EEG abnormalities were abstracted from EEG reports 6–18 months postoperatively. Seizures persisted in 24% of the MTS group and in 27% of the tumor group. Of those with normal EEGs, none of the MTS patients and only 1 of the tumor patients had persistent seizures (p = 0.03 for MTS and p = 0.42 for tumor). Epileptiform discharges and focal slowing were associated with seizure persistence in both groups, but to a significant extent only in the MTS group. In the MTS group, patients who had both epileptiform discharges and focal slowing were more likely to have persistent seizures than were those with either abnormality alone.     

Effect of Chronic Electrical Stimulation of the Centromedian Thalamic Nuclei on Various Intractable Seizure Patterns: I. Clinical Seizures and Paroxysmal EEG Activity

Twenty-three patients with various intractable seizure patterns were divided into four groups based on their most frequent seizure type and their clinical and EEG response to chronic electrical stimulation of the centromedian thalamic nuclei (ESCM): group A, generalized tonic-clonic (GTC, n = 9); group B, partial motor (Rasmussen type) (n = 3); group C, complex partial seizures (CPS, n = 5); and group D, generalized tonic seizures (Lennox-Gastaut type) (n = 6). CM were radiologically and electrophysiologically localized by means of stereotaxic landmarks and by thalamically induced scalp recruitinglike responses and desynchronization. ESCM consisted of daily 2-h stimulation sessions for 3 months. Each stimulus consisted of a 1-min train of square pulses with a 4-min interstimulus interval, alternating right and left CM. Each pulse was 1.0 ms in duration at 60/s frequency and 8–15 V (400–1,250 μ-A) amplitude. Voltage (V), current flow (μA) and impedance (kΩ) at the electrode tips were kept constant. A significant decrease in the number of seizures per month and paroxysmal EEG waves per 10-s epochs occurred in group A patients between the baseline period (BL) and the ESCM period. These changes persisted for >3 months after discontinuation of ESCM (poststimulation period, Post). Post was accompanied by a significant decrease in the number of paroxysmal EEG discharges. A substantial decrease in seizures and paroxysmal discharges was also observed in patients of group B. In contrast, patients of groups C and D showed no significant changes from BL to ESCM and Post periods, except for a significant decrease in the number of seizures in group D patients from BL to Post periods.     

Eyelid Myoclonia with Absences in Adults: A Clinical and Video-EEG Study

Summary: We report clinical and video-EEG findings in 11 adults with the syndrome of eyelid myoclonia with absences (EMA). Prevalence was 2.7% among all epilepsies and 12.9% among idiopathic generalized epilepsies (IGE) with typical absences. All patients with EMA were women, with a mean age of 30.9 years and a mean age of 7.8 years at reported onset of eyelid myoclonia. The characteristic seizures, studied with video-EEG in 10 patients, began with and were mainly manifested by eyelid myoclonia, either alone if brief ( 2 s) or with associated mild impairment of consciousness if longer. The ictal EEG was characterized by polyspike and slow waves at 3-6 Hz. Ictal clinical and EEG manifestations occurred mainly after eye closure and were inhibited by total darkness. All patients were photosensitive, but photosensitivity decreased with age; nonpatient had self-induced seizures. Infrequent generalized tonic-clonic seizures (GTCS) occurred in all but the youngest patient; they were usually infrequent and were precipitated mainly by flickering lights, sleep deprivation, fatigue, and menstruation. Mild myoclonic jerks of the upper limbs occurred in 6 patients. Eyelid myoclonia was resistant to medication and persisted despite control of other seizures.