Focal Epileptic Discharges Research Articles

Contribution of concurrent Doppler and EEG in differentiating occipital epileptic discharges from migraine

In a young woman, episodes of visual symptoms were accompanied by simultaneous nonspecific EEG alterations. Concurrent Doppler sonography showed increased blood flow velocity with latency of a few seconds in the posterior cerebral arteries only. This is typical for local autoregulatory hyperperfusion due to increased neuronal activity, thus indicating focal epileptic discharges and excluding migrainous attacks.

Fluctuations of interictal brain imaging in repeated 123I-IMP SPECT scans in an epileptic patient

Single photon emission computed tomography (SPECT) brain scans with N-isopropyl-(iodine 123) p-iodoamphetamine (123I-IMP) were performed three times in interictal periods in a 35-year-old man with intractable frontal lobe epilepsy and normal X-ray CT findings. The first scan showed decreased 123I-IMP uptake in the right frontal lobe. This abnormal image was regarded as the primary focus of his epilepsy on the basis of its regional agreement with focal epileptic discharges on EEGs. In the second scan, he showed normal imaging, while the third scan showed the same abnormal image as before, in the right frontal lobe. The frequency of his clinical seizures was almost unchanged during the intervals between scans and further EEGs recorded soon after each scan showed almost no changes in the basic activities and frequency of the epileptic discharges. Such fluctuations in SPECT brain imaging suggest that the severity of functional inactivation underlying the focal hypoperfusion image as an epileptic focus may fluctuate considerably in the interictal state with no relation to the clinical features of epilepsy.

Long‐Term Prognosis of the Lennox‐Gastaut Syndrome

A long-term follow-up study of 89 patients of Lennox-Gastaut syndrome (LGS) disclosed the persistent occurrence of seizures in 68 patients (76.4%) and severe mental defect in 48 (53.9%). An analysis of the correlation between the mental and seizure prognoses confirmed that the persistence of minor seizures could result in mental deterioration. An examination of the evolutional changes in EEG demonstrated that diffuse slow spike-waves characteristic of LGS gradually disappeared, while focal epileptic discharges, especially multifocal spikes, appeared in spite of the persistence of minor seizures. The diagnostic criteria were satisfied in only 31 (47.0%) of 66 patients with the persistence of minor seizures. Patients with multiple independent spike foci and minor seizures were considered to belong to a specific type of epilepsy, namely the severe epilepsy with multiple independent spike foci (the severe epilepsy with MISF). The seizure and mental prognoses were poorer in patients who evolved into the severe epilepsy with MISF than others.

Suppression of recurrent generalized tonic-clonic seizure discharges by intraventricular perfusion of a calcium antagonist

Epileptic depolarizations in single motor cortical and hippocampal neurons and focal epileptic discharges in neuronal cortical populations have been described to be decreased by calcium antagonists. In the present investigations the action of the calcium antagonists verapamil on generalized tonic-clonic seizures was studied. The experiments were performed in the anesthetized and artificially ventilated rat. Tonic-clonic seizures were induced by repeated intraperitoneal injections of pentylenetetrazol (PTZ). The calcium antagonist verapamil, dissolved in artificial cerebrospinal fluid, was applied to a lateral cerebral ventricle by means of the push-pull technique. This procedure achieved high concentrations of the drug in cerebral tissue and avoided alterations of the systemic circulatory system. Generalized tonic-clonic seizures were depressed in intensity to a great extent and often abolished during the verapamil perfusion. With this suppression seizures decreased in their rate of occurrence. The negative shift of the epicortical DC potential evoked by the PTZ injections before verapamil application became a positive displacement during verapamil perfusion. Control experiments revealed (i) that intraventricular perfusion with drug-free cerebrospinal fluid did not change tonic-clonic seizure activity, and (ii) that in experiments without epileptic activity verapamil perfusion exerted no depressive effect on the power of the spontaneous EEG and failed to shift the DC potential to the positive side. As a whole, systemic administration of the calcium antagonist verapamil depressed tonic-clonic seizures and did not depress non-epileptic cerebral activity.

Psychomotorische Anfälle bei Säuglingen und Kleinkindern

The authors analyzed the ictal clinical symptoms (in 6 cases with videotape monitoring) of 12 infants and young children, who had focal epileptic discharges in the temporal regions (fig. 3, 4, 5). The average age was 1 9/12 years with a range of 3 months to 5 years. In 6 cases the seizures were typical „psychomotor” with oral automatisms, aimless movements of the upper extremities and/or tonic versive motor manifestations (fig. 2). In 5 cases the seizures consisted of staring and arrest of any movement. In another case, automatisms of the upper extremities were accompanied by a psychomotor arrest reaction.

The prognostic value of eeg patterns in epilepsies with infantile spasms

By scoring EEG patterns (hypsarrhythmia = 10, absence of sleeping patterns = 10, focal epileptic discharge = 5, general-treatment or in whom infantile spasms never disappeared even during ACTH. A low voltage EEG did not have any ending ACTH therapy free of seizures showed lower scores compared to those infants relapsing after the end of ACTH treatment or in whom infantile spasms never disappeared even during ACTH. A low voltage EED did not have any prognostic significance. Using EEG scores it might be possible to separate non-responders and responders after 3 weeks of ACTH therapy, thus shortening ACTH treatment in non-responding infants.

Functional hemidecortication by spreading depression or by focal epileptic discharge disrupts spatial memory in rats

The importance of neocortex for the acquisition and retrieval of the water tank navigation task has been examined in 110 hooded rats. The animals were trained to swim to a small (10 cm in diameter) submersed platform 1 cm below the surface of a large pool (120 cm in diameter) of opaque water. In Experiment 1, naive rats with unilateral cortical spreading depression (SD) elicited by application of a filter paper soaked with 25% KC1 on one hemicortex were unable to find the platform during 1 min in about 50% of the 12 acquisition trials. The performance of functionally hemidecorticated rats did not improve after a single trial with the intact brain, but escape latencies were significantly shortened in rats given 2,6 or 60 pretraining trials with intact brain. Even in the overtrained rats escape latencies under unilateral SD were significantly longer (14 sec) than in intact rats after 12 acquisition trials (5 sec). In Experiment 2, development of an epileptic focus established by local penicillin application onto the exposed cortical surface was electrophysiologically monitored. Regular interictal discharge (0.2 to 0.5 Hz) disrupted acquisition of the navigation task and interfered to a lesser degree with performance in rats given 12 and 36 pretraining trials with the intact brain. The occipital foci were more disruptive than the frontoparietal ones. Performance recovered with cessation of the epileptic discharge. It is concluded that spatial memory mediating navigation in the water tank task requires coordinated activity of both cerebral hemispheres.

Contribution of calcium and calcium-dependent membrane currents to focal epileptic discharges in neocortical neurons of the rat

Contribution of calcium and calcium-dependent membrane currents to focal epileptic discharges in neocortical neurons of the rat

Regular and lasting neocortical spiking produced by systemic administration of a steroid derivative in the rat

The hypothesis was tested that sedation and stereotyped behaviour, developing in rats after the administration of the steroid derivative with γ-aminobutyric acid (GABA) antagonistic properties. R 5135, are of an epileptiform nature. Electroencephalographic (EEG) and visual evoked potentials (VEP) were recorded and behaviour was observed over not less than 5–7 hr after subconvulsive doses of R 5135. Doses of 2–4 mg/kg of the compound produced quasi-rhythmic spikes resembling experimental focal epileptic discharges in all rats. This epileptiform activity was accompanied by behavioural sedation and somnolence, followed by a build-up of stereotyped behaviour and sporadic episodes of epileptiform motor activity, developing 1–2 hr after injection. The secondary components (SNW) of the visual evoked potentials were suppressed by R 5135 and the primary potential (N 1) facilitated, virtually reducing the visual evoked potential to the form of an evoked spike. Pretreatment with the anticonvulsant GABAergic drugs γ-acetylenic GABA (GAG) (100 mg/kg). sodium valproate (VPA) (400 mg/kg) and diazepam (5 mg/kg) suppressed the motor components of seizure activity, producing severe ataxia, but not the electrographic manifestation of seizure activity. Neither γ-acetylenic GABA nor valproate significantly altered the latency to onset of spiking, although all three drugs did significantly reduce the frequency of discharges. Diazepam was the only anticonvulsant tested which completely suppressed spike activity in 3 of 5 rats. Moreover, R 5135 was found to antagonize diazepam. but not valproate induced suppression of secondary components of the visual evoked potential, suggesting that diazepam and R 5135 may compete for the same receptor.

Sustained limbic seizures induced by intraamygdaloid kainic acid in the baboon: Symptomatology and neuropathological consequences.

In Papio papio baboons chronically prepared for cortical and deep electroencephalographic recording, injection of kainic acid into the amygdala (7 animals) or temporal pole (2 animals) gave rise to focal epileptic discharges lasting 15 to 150 hours. Electrographically, the seizure activity spread ipsilaterally and contralaterally within the limbic system but did not become generalized. The principal associated motor signs were arrest of movement and oral automatisms. Histological examination after two to ten days demonstrated lesions (neuron loss and gliosis) at the injection site that varied according to the amount of kainic acid injected (2 to 68 microgram). "Remote" lesions occurred in the ipsilateral hippocampus (end-folium and Sommer sector) and neocortex (occipital and frontal regions). The hippocampal lesions were comparable to those previously described as consequent to status epilepticus.

Propagation of focal cortical epileptiform discharge to the basal ganglia

Single-unit activity was recorded in the caudate and entopeduncular nuclei of cats during penicillin-induced epileptiform discharge from the pericruciate cortex. More than 80% of responsive caudate neurons fired a burst of action potentials after the cortical interictal spikes. An even higher percentage (95%) burst during the clonic phase of electrocorticographic seizures. In the entopeduncular nucleus, approximately 45% of the cells increased their firing rate or burst with the interictal spike and 33% decreased their firing rate after the interictal spike. These results are consistent with the notion that the basal ganglia may act as an important pathway for the spread and generalization of focal epileptic discharge.

A reappraisal of “benign epilepsy of children with centro-temporal EEG foci”

A comparative study was carried out between 41 patients under the age of 15 years with typical benign epilepsy of children with centro-temporal EEG foci (BECCT) who satisfied strict criteria of both interictal epileptic discharges and clinical seizure manifestations, and 45 children with partial seizures, either elementary or complex, who served as controls. Thirty-one children whose EEG and clinical seizure characteristics only partially satisfied the diagnostic criteria of BECCT served as an intermediate group. The results were as follows:<ul><li>1)The focus of epileptic discharges on scalp EEGs corresponded with clinical seizures. There was not a single case with centro-temp oral foci who showed clinical features of a partial seizure with complex symptomatology and, conversely, no case with an epileptic focus or foci located outside the centro-temporal region who had a typical attack of those seen in "Sylvian" seizures.</li><li>2)The morbidity for convulsive disorders in siblings of probands with typical BECCT was not significantly high as compared with those of controls.</li><li>3)A bilateralization tendency during light sleep from stage 1 to 2 of focal epileptic discharges was a common feature in both typical BECCT and controls. An age factor resulting in secondary bilateral synchrony is the most possible explanation.</li><li>4)As a result of drug treatment, a complete seizure free period of more than one year was confirmed not only in BECCT (78%) but in the control groups (77% and 80%). Benignancy is not solely relevant to the clinical entity that is called BECCT.</li><li>5)All the conclusions mentioned above were obtained by excluding the patients whose EEG background activities were not within normal limits and those with any signs of retarded or deteriorated psychomotor development.</li></ul>

Relationships between electroencephalographic pattern and biochemical picture of the cobalt epileptogenic lesion after cortical superfusion with taurine

Cobalt gelatin pellets were implanted into the feline cortex pretreated with a superfusion of taurine. The following results were obtained. (i) The antiepileptic action of taurine was confirmed. Taurine superfusion remarkably delayed the onset and subsequent development of focal epileptic activity. At the end of superfusion, the taurine cortical concentration was highly increased whereas the glutamic acid level was reduced. The appearance and evolution of focal epileptic discharges was paralleled by a progressively more extensive decrease in concentration of several amino acids. A relationship between the taurine and glutamate levels and the depression of epileptic susceptibility of cortex is pointed out. In addition, the more severe alterations of cortical amino acid content in the cobalt focus in comparison with the penicillin focus under the same experimental conditions as used previously (L. Durelli et al. 1976. Exp. Neurol. 52: 30–39) are outlined. (ii) The taurine-induced prolonged suppression of focal epileptic activity was associated with epileptiform electroencephalographic abnormalities recorded in cortical regions far from the site of cobalt implantation. These extrafocal spikes occurred before the onset of the focal activity and decreased, even disappeared, simultaneously with progressive enhancement of the epileptic discharges in the cobalt area. The hypothesis is put forward that cobalt, though topically implanted, might exert an epileptogenic action diffuse to different regions of the brain. Under normal conditions the inhibition by the epileptogenic focus in the cobalt area would not allow the simultaneous development of other epileptogenic zones. The latter would, however, develop if the first zone had been previously inhibited by the local action of taurine.

Subconvulsive epileptiform discharge and behavioral impairment

Clinical and experimental reports regarding deficits in learning and memory as a result of subclinical epileptiform discharge are reviewed. The effects of focal epileptic discharge upon behavior are compared to the effects produced by nonepileptic lesions of the same brain areas. It is suggested that whether or not epileptogenic discharge has behavioral consequences similar to ablation of the same brain region depends upon the intensity of the discharge and the extent to which the discharge spreads from the focus. Data which support the hypothesis that seizure discharge impairs retrieval of information more severely than storage are discussed. The advantages and disadvantages of several methods for producing epileptiform discharge experimentally are discussed. Finally, it is suggested that relatively long term changes in background EEG activity and cortical steady potential shifts may be the underlying physiological alterations responsible for the observed deficits, rather than simply the presence of epileptiform spike and wave discharges.

Frequency-wavenumber spectrum analysis of EEG multielectrode array data.

Electroencephalographic (EEG) data consisting of visual evoked responses monitored via an array of electrodes from humans and penicillin-induced focal epileptic discharge data recorded from rat neocortex are analyzed. This procedure, previously applied to seismic array data, offers a method by which high-resolution vector velocity and, thus, direction and speed of propagating wavefronts can be estimated.

Focal Epileptic Discharges during All Night Sleep Studies

Focal Epileptic Discharges during All Night Sleep Studies

Amino acids in the cobalt-induced epileptogenic and nonepileptogenic cat's cortex.

Epileptogenic cortical foci were produced by the topical application of cobalt powder to the exposed anterior or posterior sigmoid gyrus of adult cats. Within 60–90 min after application, epileptic discharges were observed only in the area adjacent to the cobalt-treated region (focus). Twenty-four hours later, tonic and clonic epileptic convulsions occurred. These seizures disappeared by the 3rd day after treatment. The concentration of amino acids in the cortex was determined during three periods after the application of cobalt: preconvulsive period (acute), 0–360 min; convulsive period (semi-acute), 24–48 h; postconvulsive period (chronic), 30–70 days.In the cortical tissue adjacent to the site of cobalt application, glutamic acid, aspartic acid, and γ-aminobutyric acid were decreased, while there was a marked increase in glycine, threonine, serine, and taurine during the convulsive period. In the preconvulsive period, the amino acids in the superfusates of the cobalt-treated cortex were measured. The rate of release of glutamic acid increased within 90 min after cobalt application together with a corresponding decrease of the rate of release of glutamine and urea. The excitatory effect of the liberated glutamic acid may play an important role in the production of focal epileptic discharges following the application of cobalt powder to the cerebral cortex.

Epilepsias focais na infância: correlação eletro-clínica

Foram estudadas, do ponto de vista eletrencefalográfico, 37 crianças epilépticas com a finalidade de estabelecer correlação entre os diferentes aspectos das manifestações clínicas e os elementos bioelétricos paroxísticos. Os resultados mostram que as características bioelétricas da atividade paroxística não apresentam, em sua morfologia, diferenças significativas que permitam correlacioná-las com os diferentes tipos de crises clínicas. Do ponto de vista clínico as manifestações não dependem apenas do foco lesional, mas também de suas conexões com estruturas subcorticais e das vias de projeção para regiões homo e controlaterais dos hemisférios cerebrais.

Borderline cases of petit mal status.

Six cases of psychotic episodes are described which in some way or another resemble petit mal status, but differ from it in their time courses and in exhibiting focal epileptic discharge besides the b

Eurosurgical aspects of epilepsy: physiological sleep as a means for focalizing EEG epileptic discharges.

The EEGs of a group of epileptic patients with no clear signs of lateralization either in the clinical history and examination, the clinical seizure pattern, the radiological examinations, or the repeated standard EEG recordings, were registered during nocturnal physiological sleep. The appearance of clearcut focal epileptic discharges was observed during sleep in most of the patients who when awake had normal EEG or bilateral inconstantly synchronous abnormalities; no focal abnormality was found in patients showing bilateral constantly synchronous convulsive discharges during wakefulness. The possible application of these findings in the selection of patients for surgical treatment of their epilepsy is discussed.