Focal Spikes Research Articles

A SURVEY OF ADOLESCENTS WITH EPILEPSY

Thirty-four adolescents with epilepsy, controls matched for age and sex (A) and controls matched for age, sex and general ability (B), were studied. The adolescents with epilepsy were more likely to arrive at school by car or taxi and to have more difficult behaviour in class. Competitive sports were less popular with them and significantly fewer anticipated ever driving a car. Illness and parental marital problems were not a feature of their families. Their comprehension of reading material was significantly poorer than that of control group A. Within the group, the lowest over-all reading scores were found in children with myoclonic seizures, partial seizures with secondary generalisation, or generalised tonic-clonic seizures; and in those whose EEG findings included two-per-second spike and wave, photosensitivity, generalised slow waves, or generalised spike and wave of non-specific frequency. Right focal slow waves, sharp waves and spikes on EEG were associated with problems of comprehension, even when the over-all reading score was acceptable.

Dipole Reversal: An Ictal Feature of Benign Partial Epilepsy with Centrotemporal Spikes

Benign epilepsy with centrotemporal spikes (BECTS) is characterized by brief stereotypical partial seizures with motor and/or sensory symptoms with frequent secondarily generalized seizures. The interictal EEG shows slow, disphasic, high-voltage spikes in the centrotemporal areas. The few published examples of ictal tracings depict focal rhythmic sharp waves and spikes without significant postictal slowing. We report an ictal event in BECTS that is unusual in the evolution and polarity of the ictal discharges. In this subclinical seizure, ictal multiple spike and wave discharges appear as a dipole: they are electropositive in T3-C3 and negative in F3. These surface positive epileptic discharges are unique and require explanation. We postulate that the seizure discharge arises in the depths of the sylvian fissure involving folded cortical areas. This occurs in such a way that the negative component of the discharges is concealed from the scalp electrodes. Thus, a relative positivity is recorded on the surface. This represents a dipole reversal relative to the interictal discharges (characteristic of BECTS). This geometrical explanation allows us to avoid postulating an unusual mechanism of generation of this seizure.

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.

Eye movements in acute, chronic, and remitted schizophrenics

Eye movements in 10 acute schizophrenics, 50 chronic schizophrenics, 20 remitted schizophrenics, 25 methamphetamine psychotics, 21 temporal lobe epileptics with left-sided spike focus (l-focus), 12 temporal lobe epileptics with right-sided spike focus (r-focus), and 50 normal controls were examined with an eye mark recorder while they viewed geometric figures. The eye movements while viewing an original “S”-shaped figure for 15 sec were analyzed. Each schizophrenic group and methamphetamine psychotics had significantly less eye fixations than the normal controls and temporal lobe epileptics (r-focus and l-focus). The chronic schizophrenics had significantly shorter mean eye scanning length (MESL) than the other six groups. Each subject was then shown two other figures slightly different from the original and was requested to compare them with the original. After comparing them, the subjects were asked the question, “Are there any other differences?” The 5-sec eye movements during the response to this question were scored using the Responsive Search Score (RSS). The schizophrenic groups had a significantly lower RSS than the nonschizophrenic patient groups and the normal controls. In the chronic schizophrenics, there was a significant negative correlation between the RSS and negative symptoms. These results suggest that the MESL can be an indicator of a chronic process of schizophrenia, and that lowering of the RSS may be nosologically specific indicator for schizophrenia.

Quinolinic Acid Concentrations in Brain and Cerebrospinal Fluid of Patients with Intractable Complex Partial Seizures

Quinolinic acid (QUIN) is a neurotoxin and convulsant when injected directly into the brains of experimental animals and as such has been implicated in the etiology of human seizure disorders. In the present study, we quantified QUIN in cerebrospinal fluid (CSF) and in spiking (focus) and nonspiking (nonfocus) regions of surgically resected human temporal neocortex. L-tryptophan (L-TRP), the putative precursor of QUIN, was also measured in brain, along with CSF concentrations of L-TRP, 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA). In brain tissue, no differences were found in the concentrations of QUIN and L-TRP between focus and nonfocus regions in 15 pairs of samples. No differences were found in CSF, L-TRP, 5-HIAA, or HVA concentrations between 11 neurologically normal controls and 15 interictal (no seizures for greater than 24 h) and 20 postictal (within 50 min of seizure) samples from epileptic patients. However, CSF QUIN concentrations were significantly lower (32%) in the epileptic patients as compared with controls, which may indicate a generalized disturbance in brain QUIN metabolism or perhaps a response to antiepileptic drugs.

Epileptic seizures difficult to differentiate from alternating hemiplegia in infants: A case report

A child with epileptic seizures had a clinical course similar to that of alternating hemiplegia of infancy (AHI). Tonic hemiplegia began at 2 months of age, and atonic alternating hemiplegia and tetraplegic attacks began at 2 years of age. Clinical findings were paroxysmal ocular movement abnormalities, choreoathetotic involuntary movements, and severe developmental retardation. An interictal EEG at 6 years of age showed multiple independent spike discharges. An ictal EEG showed diffuse irregular spike-wave and slow wave bursts following focal spikes. The present case suggests that a long-term extensive follow-up is necessary to differentiate epileptic seizures from AHI.

Seizure prognosis and eeg evolution in complex partial seizures of childhood onset

We studied the clinical course and seizure prognosis of 126 children with complex partial seizures regularly followed up for more than 4 years in our clinic. Clinical and EEG features of 63 seizure-free patients were compared with those of 63 patients with persistent seizures. The features contributing to poor prognosis were 1) mental retardation, 2) a history of status epilepticus and 3) abnormal basic rhythm in EEG. CT abnormality, a history of febrile convulsions (FC), the clustering of seizures and association with other types of seizures did not influence prognosis. We divided the patients into four groups according to the evolutionary pattern of seizure discharges: Group A, 55 (43.7%) patients with spike focus always fixed in the same region; Group B, 20 (15.9%) patients with wandering foci; Group C, 10 (7.4%) patients with multifocal spikes; and group D, 41 (32.5%) patients with no focal discharges. There was no difference in seizure prognosis among these four groups, but the patients with a focus in the anterior temporal region in Group A evidenced the worst prognosis.

Cerebrospinal fluid shunt malfunction signaled by new or recurrent seizures

We have observed two patient groups with seizure activity as the primary presentation of shunt malfunction. Eight patients had a first-time seizure, and seven patients had a history of prior seizures, none more recently than 1 year prior to the seizure recurrence. Five of seven patients with prior seizures who seized were on anticonvulsant medication, three of these seven patients had therapeutic anticonvulsant levels. Shunt malfunction was diagnosed via a combination of tests. The electroencephalograms of nine patients were diffusely abnormal with regions of slowing and focal spike activity. Seizure activity stopped in all patients after preoperative stabilization with anticonvulsant medication and shunt revision. These 15 patients represent 2% of all patients treated for shunt malfunction during a 3-year period. The assessment of new or recurrent seizure activity in a previously stable shunted patient should include evaluation of shunt function whatever the anticonvulsant levels.

EEG changes, recorded with subdural electrodes, after thiopental injections in patients with temporal lobe seizures

Nineteen patients with temporal lobe epilepsy, examined with intracranial subdural electrodes for seizure monitoring, were subjected to intravenous thiopental injections to the level of deep narcosis. The induced EEG changes were recorded, analyzed, and correlated to the localization of the seizure-generating focus. In 14 patients with unilateral seizure onset, the thiopental injections evoked a focal spike activation on the focus side. The first suppression period in the EEG with a duration exceeding 1 s was recorded from the strip electrode overlying the focus. Only in six patients did asymmetries in the barbiturate-induced beta activity in the background EEG show lateralizing signs in concordance with the side of seizure onset. In five patients with bilateral seizure-generating foci, no significant lateralization in induced beta activity, focal spike activation, or focal suppression pattern could be found. The results are discussed, comparing similar studies performed with surface, sphenoidal, and depth electrodes.

The epileptic hippocampal slice: Involvement of NMDA receptors in epileptogenesis

An EEG epileptiform spike focus recorded with scalp electrodes is clinically localized by visual estimation of the point of maximal voltage and the distribution of its surrounding voltages. We compared such estimated voltage maps, drawn by experienced electroencephalographers (EEGers), with a computerized spline interpolation technique employed in the commercially available software package FOCUS. Twenty-two spikes were recorded from 15 patients during long-term continuous EEG monitoring. Maps of voltage distribution from the 28 electrodes surrounding the points of maximum change in slope (the spike maximum) were constructed by the EEGer. The same points of maximum spike and voltage distributions at the 29 electrodes were mapped by computerized spline interpolation and a comparison between the two methods was made. The findings indicate that the computerized spline mapping techniques employed in FOCUS construct voltage maps with similar maxima and distributions as the maps created by experienced EEGers. The dynamics of spike activity, including correlations, are better visualized using the computerized technique than by manual interpretation alone. Its use as a technique for spike localization is accurate and adds information of potential clinical value.

Transient impairment of visual perception induced by single interictal occipital spikes.

We have previously reported that focal occipital interictal epileptiform discharges (spikes) cause transiently prolonged reaction time (RT) and increased nonperception of stimuli, especially in the visual field contralateral to the spike. One subject with very frequent spikes was capable of carrying out a visual recognition task along with the RT task. During central fixation, computer-generated random digits were flashed for 150 ms at random locations on a screen. Some stimuli were delivered during spikes, by means of an amplitude-threshold trigger, whereas control stimuli were delivered at random times between spikes. Following each stimulus, the subject had to press a button for RT and then report the digit perceived. There was a statistically significant increase in nonresponse rate (nonperception) during spikes compared to controls, and this effect was maximal contralateral to the spike. Moreover, among the responses, perceptual accuracy (correct vs incorrect) was significantly impaired during spikes, again predominantly in the visual field contralateral to the spike. Thus, not all focal interictal spikes are necessarily "subclinical;" at least some induce a transient cortical dysfunction of the same kind as produced more enduringly from a structural lesion in the same location. These findings may have clinical relevance in patients, especially children, with very frequent epileptiform discharges and higher cortical dysfunction.

Significance of Bisynchronous Spike‐Waves in Patients with Temporal Lobe Spikes

We examined the clinical significance of bisynchronous spike-wave complexes which appear in EEGs of some patients with focal spikes in one or both temporal lobes. Few features distinguished patients with bisynchronous spike-waves from those with only focal temporal spikes: a higher incidence of patients with more than two grand mal seizures a year (43 vs. 7%) and a younger age at last recording (22.5 vs. 28.3 years) were the only statistically reliable factors. Proportion of patients with complex partial seizures (CPS) (100%), age of CPS onset, incidence of febrile convulsions, intellectual level, and normal neurologic examination were features common to the two groups. In contrast to other studies which did not exclude influencing variables such as extratemporal spike foci, our group with bisynchronous spike-waves fared equally well after temporal lobectomy as did patients with temporal spikes alone. All 6 patients with spike-waves obtained a reduction of at least 50% in seizure frequency and 5 of the 6 (83%) had a greater than 90% reduction. Sixteen of 17 patients (94%) without spike-waves had a reduction of at least 50% and 14 of the 17 (82%) had a greater than 90% reduction of seizures.

Neocortical propagation in temporal lobe spike foci on magnetoencephalography and electroencephalography.

Propagation of the neuronal population of the interictal epileptic spike was quantified in 5 patients with complex partial epilepsy arising from temporal lobe using electroencephalography and magnetoencephalography. During the spike complex in each patient there was a spike at the deep sphenoidal electrode and a spike at the superficial scalp electrode on spontaneous electroencephalography. In each patient the sphenoidal spike had a different peak latency than the scalp spike, consistent with spike propagation. Electroencephalography was used to trigger two magnetoencephalographic averages of stereotyped spikes during the sphenoidal peak and the scalp peak. Magnetoencephalography discriminated the centers of two cortical spike populations at different latencies, showing deeper localization with sphenoidal trigger and more superficial localization with scalp trigger in each patient (p less than 0.05). Latency differences and propagation distances of spikes were consistent with the conduction velocity of corticocortical fibers. Noninvasive estimates of the cortical surface area of the spikes agreed with estimates obtained by electrocorticography over temporal neocortex. These findings indicate propagation of neuronal populations active during human interictal spikes between deep and superficial cortex of temporal lobe, likely by monosynaptic or oligosynaptic pathways. This interictal system appears to be partly independent of the hippocampal interictal system in complex partial epilepsy.

Interictal and ictal activity recorded with subdural electrodes during preoperative evaluation for surgical treatment of epilepsy

A total of 94 subdural strip electrodes were implanted in 22 patients during preoperative EEG evaluation for surgery of epilepsy. Eighteen patients had temporal lobe seizure onset, three had frontal lobe seizure onset, and one had occipital lobe seizure onset. Most electrodes (total, 83) were localized over the temporal lobe cortex, but in four cases additional strip electrodes (total, 11) covered the frontal, parietal, and occipital lobe cortexes. The electrodes were left in place for up to 28 days. No complications occurred. Interictally, focal spiking was recorded subtemporally, mostly without being seen in electrodes recording from the lateral temporal cortex. In three patients studied with simultaneous subdural and sphenoidal wire electrodes, spiking recorded from subdural electrodes was often not seen in the sphenoidal recording. There were 151 seizures recorded (with or without simultaneous video monitoring). The mean number of seizures per patient was 6.7 (range, 0–21). The seizures were classified as having focal (80 seizures) or local (71 seizures) onset. It is concluded that subdural electrodes are safe and have a sufficient selectivity with regard to localization of interictal spiking and seizure onset in patients with mesial temporal epileptic lesions. In such cases, electrodes have to be placed subtemporally. Other cortical areas may also be explored with these electrodes.

Landau-Kleffner Syndrome: A Case Study with a Fourteen-Year Follow-Up

In a 14-year follow-up the improvement of language functions and the decrease of EEG abnormalities are described in a girl with the Landau-Kleffner syndrome. In this case, the results of subsequent EEG recordings do not permit conclusions about the course of the aphasia. Disappearance of focal spike and waves, bilateral paroxysms and slow background activity lack synchronicity with improvement of language. Finally, subtle language deficits were still present 14 years after the onset of the aphasia; the lastly recorded EEG showed mild abnormalities.

Stability of source estimates in rolandic spikes.

The interictal spike discharges present in rolandic epilepsy has a dominant horizontal dipolar topography, centered near the rolandic area. In order to examine the generator configuration of this focus, we investigated the variation of spike topography in 20 children with rolandic epilepsy of childhood by the dipole localization method (DLM). A quantitative measure ("stability index" or SI) of the degree of source fluctuation was devised, based on the consistency of the source parameters (location, direction and magnitude) over contiguous time points. A high SI was associated with overlapping source locations and parallel directions over many time points, while a low SI was seen with poor and variable solutions. At the peak and trough of the spike, the corresponding sources were found to have different locations. If the patients were separated into those with and without neurological findings, the mean times at which stable sources existed were significantly different: 35 and 150 ms respectively after the spike apex. Further, the group without abnormal neurological findings tended to have higher values of SI. These results suggest that such stability analysis allows measurement of the spatial and temporal extents of source estimates. These results further support the hypothesis that the topographic behaviour of a spike focus is closely associated with its clinical characteristics.

Laplacian Evaluation of Epileptic Spike Foci

Laplacian Evaluation of Epileptic Spike Foci

Focal spike discharges in children not suffering from clinical epilepsy.

Focal spike discharges in children not suffering from clinical epilepsy.

Nuclear magnetic resonance relaxometry in a penicillin model of focal epilepsy.

Magnetic resonance imaging (MRI) is effective in demonstrating pathologic lesions in patients with epilepsy. It has been suggested that MRI might also reveal functional abnormalities at an interictal epileptic focus when no gross structural change such as gliosis or tumor is present. Experimental epileptic foci were produced by topical application of penicillin to the cortex of rats. In vitro proton nuclear magnetic resonance (NMR) relaxometry of tissue excised from the experimental foci revealed an increase in spin-echo relaxation time as compared to that in control tissue. The elevated relaxation times occurred in tissue samples from areas of active electroencephalographic (EEG) spiking. This is the first direct demonstration of an alteration in proton magnetic resonance parameters by functional abnormalities (focal interictal spike activity) in the brain, supporting the concept that MRI might be similarly affected.

Morphology of spikes in spike-and-wave complexes

The morphology of spikes of spike-and-wave complexes from 9 patients with primary generalised epilepsy was studied from the scalp recordings of electrodes placed over their fields of maximum expression. Using a 4 × 4 grid electrode placement, selected epochs of the EEG were digitised and stored by a computer program which determined the times of the troughs and peak of the spike as well as its slope, amplitude and duration. Morphological parameters corresponding to those studied for focal spikes in other works gave similar values suggesting a close resemblance between spikes of generalised spike-and-wave complexes and focal spikes. In this study, second half-wave duration exceeded first half-wave duration and amplitudes of the second half-waves were either equal to or greater than those of the first half-waves. Our measures of slope resolved an apparent discrepancy among earlier studies: the entire first half-wave slope was usually equal to or greater than the second half-wave slope while the slopes of the upper half of the spike were usually equal or greater for the second half-wave than for the first. The first half-wave: second half-wave slope ratio was greatest at electrode positions with the maximum spike amplitude (the midline frontal electrodes), and therefore more closely resembled electrocorticogram spikes at these positions.