Paroxysmal EEG Activity Research Articles

The influence of vigilance states on paroxysmal EEG activities and clinical seizures in children

We studied the relationships between clinical variables and those related to the states of vigilance in 18 cases of benign partial epilepsy with centro-temporal spike-waves, 22 cases of definite symptomatic partial epilepsy, and 16 cases of undetermined partial epilepsy. The time of day during which the seizures appeared and the paroxysmal activity densities during non-REM and REM sleep are not distributed differently among the 3 electro-clinical types. However, the benign epilepsy with centro-temporal spikes group had more patients with sleep-sensitive paroxysmal activities. Patients who mainly had nocturnal seizures were found to have more frequent generalized seizures and a greater sleep-sensitive paroxysmal activity. Three cases demonstrated continuous spike-waves during sleep. The patients who had little or no paroxysmal activity during sleep were the youngest. This study illustrates that sleep-sensitive seizures and paroxysmal activities are not specific to benign childhood epilepsy with centro-temporal spikes, and that seizures and paroxysmal activities are two manifestations associated with epilepsy, affected in different ways by states of vigilance.

Cholinergic system disturbance in the West syndrome

The effects of drug on the cholinergic system (atropine and physostigmine) were evaluated in acute tests in 12 infant patients with the West syndrome (WS) and in 12 older ones who had suffered from WS at typical ages, displaying various types of epileptic symptoms. In both groups paroxysmal EEG activity was inhibited by physostigmine and enhanced by atropine. In two infants who had frequent clinical seizures, the seizures were temporarily blocked by physostigmine. These effects in WS are different from those reported in some other experimental and clinical epilepsies, where physostigmine has a proepileptic and atropine often an antiepileptic effect, thus indicating that a cholinergic system disturbance may occur in patients with WS.

Relationship between the distribution of paroxysmal EEG activity and sleep structure

Relationship between the distribution of paroxysmal EEG activity and sleep structure

Anticonvulsant effects of localized chronic infusions of GABA in cortical and reticular structures of baboons

We studied the effects of chronic (7 day) infusions of GABA (100 and 20 μg/μl, 10 μl/h) applied in different cerebral structures of baboons made photosensitive by a subconvulsant dose of allylglycine. The GABA infusion has partial anticonvulsant effects when applied to the motor cortex, reticular magnocellular nucleus (RMC), or substantia nigra (SN), but when directed to the prefrontal cortex (area 8) it has no effect. These anticonvulsant effects of GABA infusion are more important when GABA is infused into the motor cortex, where paroxysmal discharges (PDs) originate, than when it is infused into the RMC. In contrast, the anticonvulsant effects on lightinduced generalized seizures are more pronounced when GABA is infused into the RMC than when it is infused into the motor cortex. GABA infusion into the SN has no effect on PDs and myoclonia and blocks seizures less effectively than the RMC infusion. These results are in accordance with the role of the motor cortex as a generator of PDs and of RMC in the generalization of seizures. Focal paroxysmal EEG and clinical activities, previously reported to appear at the end of the motor cortex GABA infusion, were not observed after RMC or SN infusions. However, behavioral hyperactivity occurring at the end of subcortical GABA infusions was observed. These behavioral signs could correspond to the clinical expression of a GABA withdrawal syndrome.

Acute effects of sodium valproate on epileptic photosensitivity in the lateral geniculate-kindled cat.

Epileptic photosensitivity was acquired as a result of kindling in the lateral geniculate body (GL), and a GL-kindled cat pretreated with DL-allylglycine was found to be a useful model of epilepsy for assessing the efficacy of anticonvulsant drugs. In the present study the acute anticonvulsant effects of sodium valproate (VPA) were examined in the GL-kindled cat under DL-allylglycine. An intravenous injection of VPA at 50 mg/kg induced a protective action against photically induced seizures and paroxysmal EEG activities. This protection persisted for up to 4 hours of the observation period and corresponded to plasma concentrations (61 to 123 micrograms/ml) similar to those considered therapeutic in humans. The present findings are consistent with those obtained in other animal models of photosensitive epilepsy, and lend experimental support to the idea that VPA possesses antiepileptic activity in human photosensitive epilepsy.

Effects of a behavioral intervention on epileptic seizure behavior and paroxysmal activity: a systematic replication of three cases of children with intractable epilepsy.

Three children with very frequent refractory epileptic seizures underwent a behavioral intervention consisting of symptom discrimination, countermeasures, contingent relaxation, and positive reinforcement for correct responses in a systematic replication series. The studies involved a 6-h nonintervention base rate, a 6-h treatment phase, and a 6-h nonintervention follow-up under laboratory conditions for each child. Neurophysiologic and behavioral measures of the effects of treatment were made using electroencephalogram (EEG)-video equipment. Effects of treatment were assessed by using a random sample of EEG-video sequences in base rate and follow-up. Results showed that no significant reduction of either seizure behavior or paroxysmal EEG activity was found subsequent to training in discrimination of early paroxysmal activity and/or sensations preceding seizures. Both seizure behavior and paroxysmal activity were significantly reduced in all three cases following intervention with an adapted countermeasure technique. No additional effects could be noted subsequent to the application of either contingent relaxation or positive reinforcement for correct responses. Paroxysmal EEG changes and seizure behavior were highly correlated. Reduction of the clinical manifestation or seizure response by behavioral manipulation was accompanied by a reduction of the total amount of paroxysmal activity as measured by the EEG.

Progressive Supranuclear Palsy

Progressive supranuclear palsy (PSP) was first recognized as a distinct morbid entity by Richardson, Steele and Olszewski a quarter century ago. Subsequent experience has confirmed and extended their original observations. PSP has become familiar as a chronic progressive disorder with extrapyramidal rigidity, bradykinesia, gait impairment, bulbar palsy, dementia and a characteristic supranuclear ophthalmoplegia. It is an important cause of parkinsonism. Its etiology remains obscure. Familial concentrations have not been observed. Some cases exhibit no oculomotor dysfunction. Dementia is usually mild. Recent neuropsychological studies have defined features consistent with frontal lobe cortical dysfunction. Seizures and paroxysmal EEG activity may occur. CT and MRI scans show midbrain atrophy early and later atrophy of the pontine and midbrain tegmentum and the frontal and temporal lobes. PET scans have shown frontal hypometabolism and loss of striatal D-2 dopamine receptors. Postmortem studies have documented involvement of both dopaminergic and cholinergic systems. Treatment remains palliative and unsatisfactory.

Sodium Valproate

Sodium valproate has been reported to be effective in the treatment of recurrent major affective and schizoaffective disorders. The records of 36 consecutive patients with various psychiatric diagnoses, who received valproate at our center, were retrospectively reviewed. None of these patients displayed a diagnosable neurologic disorder or paroxysmal EEG activity. Sixteen (44%) of the 36 patients experienced a moderate to marked response to valproate. The diagnoses of bipolar or schizoaffective disorder and the presence of non-paroxysmal EEG abnormalities both predicted a favorable response. The authors conclude that valproate deserves further study as a possible treatment for major affective disorder.

Carbamazepine in clinical psychiatric practice

The general use of carbamazepine in psychiatry is briefly surveyed. It is concluded that carbamazepine has clinical efficacy in patients suffering from various psychiatric syndromes. The compound is probably most effective in diseases with an episodic course, e.g. psychiatric syndromes associated with focalizations of paroxysmal EEG activity, affective disorders, and certain paroxysmal or arrhythmic syndromes. The clinical picture of the disorders responding to carbamazepine treatment may mimic paranoid psychosis, schizophrenia, or manic-depressive psychosis. Clinical guidelines are provided for carbamazepine treatment in psychiatry. Monitoring of the serum drug concentrations is recommended to check patient compliance and avoid toxic concentrations.

The peripheral benzodiazepine receptor ligand Ro 5-4864 induces supraspinal convulsions in rabbits. Reversal by the central benzodiazepine antagonist Ro 15-1788.

The peripheral BDZ receptor ligand Ro 5-4864 was administered to rabbits in doses ranging from 0.2 to 7 mg/kg IV. Changes in electrocortical activity appeared within 1 min after administration, characterized by trains of slow waves in the posterior sensorimotor and optic cortices (0.6-2 mg/kg) and by grand mal seizures (2-10 mg/kg). The low doses also induced alterations in the basic rhythms both of the hippocampus (reduced amplitude and spike-like waves) and of the nucleus ventralis of thalamus (trains of slow waves), not associated with observable behavioural changes. The paroxysmal EEG activity observed at higher doses of the drug was first recorded in the cortical areas and then spread to the subcortical structures. No change in electrical activity could be observed in the spinal cord. The paroxysmal activity was associated with tonic-clonic convulsions and scialorrea. The EEG and behavioural manifestations were inhibited by administration of Ro 15-1788. This drug at doses of 0.6 and 6 mg/kg antagonized the effects of Ro 5-4864 at doses of 0.6-5 mg/kg and 6-7 mg/kg, respectively. This effect began 1-3 min after administration of the antagonist, and led to EEG synchronization. These data suggest that in rabbits the convulsant effect of Ro 5-4864 is due to interference of the drug at the GABA-BDZ-picrotoxin receptor oligomeric complex. Such an effect seems to be mediated at least in part by central BDZ receptors.

Kopfschmerzen und generalisierte epileptische EEG-Aktivität unter starker Lichtexposition

The case of a 16 years old girl with bilateral headache attacks and simultaneous generalised paroxysmal activity in EEG triggered by light is reported. Headache intensity as well as the number of generalised spike wave discharges under photic stimulation depended on intensity of light whereas wavelength of used light had no influence. Paroxysmal activity was most intensive at a flash light frequency of 25 Hz.

GABAergic agents as anticonvulsants in baboons with photosensitive epilepsy

GABAergic agents have been evaluated for acute anticonvulsant activity in baboons, Papio papio with photosensitive epilepsy. The potent GABA A agonists muscimol and THIP are proconvulsant. (−)Baclofen, 2 mg/kg suppresses myoclonic responses; higher doses facilitate EEG paroxysmal activity. (S)γ- vinyl GABA, 100–200 mg/kg, suppresses myoclonic responses for more than 24 h. Some derivatives of esters of β-carboline-3-carboxylate that bind to the benzodiazepine receptor, e.g. ZK 91296 and ZK 93423, suppress myoclonus with a potency at least as great as diazepam.

Valproic acid and intractable seizures in severely brain-damaged patients.

We treated 52 mentally retarded patients with intractable seizures by adding valproic acid (VPA) to other drug regimens. Sixty-one percent improved clinically. VPA significantly reduced the frequency of generalized tonic-clonic seizures, generalized myoclonus, absence and atonic seizures. There was a significant correlation between clinical improvement and reduction of EEG paroxysmal activity.

Enregistrement continu de l'EEG

A continuous EEG recording device (Oxford Medical System) was utilized in 158 patients with overt epileptic seizures and atypical fits of questionable origin. This technique proved a valuable tool in assessing EEG paroxysmal activity. The validity of the results is discussed and emphasis is laid on the numerous pitfalls and obvious limitations of the method which do not allow a temporal correlation between EEG findings and clinical events. Un système d'enregistrement continu de l'EEG (Oxford Medical System) a été utilisé chez 158 patients épileptiques connus ou présentant des phénomènes critiques d'étiologie indéterminée. Cette technique s'est révélée valable dans la détection des anomalies paroxystiques électroencéphalographiques. La discussion porte sur la validité des résultats. L'accent est mis sur les nombreuses causes d'erreur et les limites évidentes de la méthode: elle ne permet pas une corrélation dans le temps entre les phénomènes électroencéphalographiques observés et les événements cliniques.

Cerebral Blood Flow During Paroxysmal EEG Activation Induced by Sleep in Patients with Complex Partial Seizures

Cerebral blood flow (CBF) measurements were combined with sleep polysomnography in nine patients with complex partial seizures. Two methods were used: the 133Xe method for measuring regional (rCBF) and the stable xenon CT method for local (LCBF). Compared to nonepileptic subjects, who show diffuse CBF decreases during stages I-II, non-REM sleep onset, patients with complex partial seizures show statistically significant increases in CBF which are maximal in regions where the EEG focus is localized and are predominantly seen in one temporal region but are also propagated to other cerebral areas. Both CBF methods gave comparable results, but greater statistical significance was achieved by stable xenon CT methodology. CBF increases are more diffuse than predicted by EEG paroxysmal activity recorded from scalp electrodes. An advantage of the 133Xe inhalation method was achievement of reliable data despite movement of the head. This was attributed to the use of a helmet which maintained the probes approximated to the scalp. Disadvantages were poor resolution (7 cm3) and two-dimensional information. The advantage of stable xenon CT method is excellent resolution (80 mm3) in three dimensions, but a disadvantage is that movement of the head in patients with seizure disorders may limit satisfactory measurements.

Seizures induced by thinking

A patient with generalized convulsions noted that seizures were reliably precipitated by mental arithmetic. The interictal electroencephalogram revealed only a mild, diffuse, nonspecific disturbance, but bursts of generalized epileptiform activity with no obvious clinical expression accompanied efforts at mental arithmetic with a significantly high incidence. Tasks involving multiplication, division, and manipulation of spatial information were significantly associated with discharges, but few, if any, discharges appeared when addition and subtraction tasks of equivalent difficulty were performed. Tasks involving the retention of numerical information in short-term memory (e.g., immediate repetition of a series of 8 digits) were never associated with paroxysmal EEG activity. It is argued that generalized epilepsy of this kind may be related to focal dysfunction in a manner analogous to the involvement of the occipital lobe in cases of pattern-sensitive epilepsy.

Interhemispheric differences in photosensitive epilepsy. I. Pattern sensitivity thresholds

A group of 15 volunteers with both photosensitive epilepsy and pattern sensitivity were shown patterns of stripes in the left and right visual hemifields. In the majority of patients the resulting paroxysmal epileptiform EEG activity was maximal in the posterior temporal and occipital regions contralateral to the stimulus. Patterns in the upper and lower hemifields were also presented and in two patients there was a difference in the vertical distribution of the response such as to suggest that in these patients the discharges were largely confined to the striate and prestriate cortex. The probability with which paroxysmal activity was evoked was usually different for the two lateral hemifields. This difference between the hemifields (which was dramatic in some patients) was mirrored in a lateralisation of the responses to diffuse intermittent photic stimulation. The association between the asymmetries in pattern sensitivity and in the responses to photic stimulation suggests that the two cerebral hemispheres often differed in hyperexcitability. It is therefore interesting that the putative differences in hyperexcitability were observed in patients with primary generalised epilepsy as well as those with other types.

Observation d'un syndrome photomyoclonique chez Macaca nemestrina

Out of a group of 12 M. nemestrina (originating from Malaysia), 9 adults had shown clinical signs induced by ILS at 25 c/sec. Six of them (3 males, 3 females) were very photosensitive; however, only 2 presented eyelid and/or head jerks after the end of ILS (level 4), but never a generalized seizure. Tactile periorbital stimuli favoured myoclonus. In all but the two of level 4, the intensity of clinical signs varied from one day to the next. In all implanted adult macaques, spontaneous paroxysmal EEG activities were seen during slow sleep in mostly anterior areas, but also during waking and REM sleep in some of them; however, their occurrence depended upon the individual and were not in all cases related to their level of photosensitivity. During ILS, paroxysmal discharges (spikes and waves and/or polyspikes and waves), isolated or in bursts at 3-4/sec were bilateral and symmetrical. They started in fronto-rolandic regions, then became generalized. This observation constitutes a new fact since the discovery, in 1966, of the photomyoclonic syndrome of Papio papio, Macaca nemestrina being another species of subhuman primates with a marked predisposition to photosensitive epilepsy.

Successfully suppressed paroxysmal EEG activity after brain injuries with anticonvulsants : D. Mintchew (Plovdiv, Bulgaria)

Successfully suppressed paroxysmal EEG activity after brain injuries with anticonvulsants : D. Mintchew (Plovdiv, Bulgaria)

Cyclic nucleotide metabolism in mouse brain during seizures induced by bicuculline or dibutyryl cyclic guanosine monophosphate

In adult male C57 black mice, intracortical injection of bicuculline (10 μg) elevated cGMP concentrations and produced contralateral clonic seizures. After intraperitoneal injection, bicuculline (10 mg/kg) elevated cGMP concentrations at the earliest time at which paroxysmal EEG activity could be detected. Changes in cAMP concentration followed those events. Further elevations of cGMP concentrations (and now of cAMP as well) were observed during clonic and tonic seizures. Intracortical injections of dibutyryl cGMP produced behavioral and EEG seizures. These data suggest that cGMP plays an important role in bicuculline seizures.