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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effects of age on the limbic and scalp P3 in 45 patients with intracranial electrodes implanted for pre-surgical investigation of focal seizures. Scalp P3 data from a reference group of 24 healthy control subjects were also analyzed for comparison. An auditory oddball paradigm with infrequent stimuli being presented with a probability of 0.20 was used. In normals P3 latency increased by 1.34 msec/year (r = 0.60, P less than 0.01). In the patients limbic and scalp P3 latency increased linearly as a function of increasing age at a rates of 3.85 msec/year (r = 0.58, P less than 0.001) and 2.71 msec/year (r = 0.56, P less than 0.01), respectively. The rate of increase of P3 latency with age was significantly lower in the normal controls, as compared to both the patient scalp (t = 1.79, P less than 0.05) and depth (t = 2.25, P less than 0.005) ERP data. There was no significant difference between the slopes of the patient P3 latency versus age scalp and depth data (t = 1.09, P greater than 0.1). Unlike for normal controls, there was no relationship between age and limbic P3 amplitude (r = 0.02, P greater than 0.1) or age and scalp P3 amplitude (r = 0.17, P greater than 0.1). The differences between controls and patients could be due to: (i) effects of chronic seizures; (ii) long-term effects of anticonvulsant use; (iii) the use of a relatively long inter-stimulus interval which may have selectively affected the patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparative effects of age on limbic and scalp P3. 247 97

Long latency auditory event-related potentials have been shown to change in patients with cerebral dysfunction. Some seizure patients with no evidence of brain damage or mental retardation show altered interictal cognitive and memory function. Long-latency auditory event-related potentials to tone stimulation were recorded in nineteen control subjects and seventeen patients with complex partial or partial and secondarily generalized seizures who had no evidence of brain damage, retardation, or drug intoxication, and whose seizures were controlled when studied. The latencies of N2 and P3 components were significantly longer in seizure patients than control subjects, and the P3 waveform was significantly greater in amplitude in epileptics. These findings suggest that cognitive event-related potentials are affected by partial epilepsy. The changes may be related to the recently reported involvement of the hippocampus in ERP generation, or to loss or alteration of modulatory functions, possibly cholinergic in nature, in the temporal lobe consequent upon epileptogenesis.
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PMID:Long-latency auditory event-related potentials in epilepsy. 308 37

The study of working memory often utilizes a delayed matching to sample paradigm (DMS). Typically in the matching condition, the test and sample stimuli are identical, raising the possible confound of retinotopic projections for the matching stimuli in contrast to the non-matching stimuli. In the present study, 65 healthy subjects performed a modified delayed matching to sample task while monitoring their ERP waveforms. The stimuli consisted of 60 different sample stimuli (S1) and 60 different test stimuli (S2). Half of the S2s were complementary to the sample stimuli (Fit), the other half of the S2s were not complementary (Nonfit). After S2, the subjects pressed one of the buttons to indicate whether the test stimulus fits the sample stimulus. Our statistical results indicated that the ERPs to sample stimuli differed from the ERPs to test stimuli from 200 ms poststimulus to the end of the recording epoch. The ERPs to fitting stimuli were significantly different from those to non-fitting stimuli from 200 to 400 ms poststimulus. The ERP patterns in the present study may reflect ERP mnemonic effect for working memory. Our results ruled out the retinotopic confound as a potential mediator variable, and are in agreement with other animal or human neurophysiological studies on memory.
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PMID:Reflection of working memory: ERP mnemonic effects. 940 97

There are current attempts to replace the WADA test for pre-surgical evaluation of hemispheric language capabilities by one of the methods of functional brain imaging. Recent PET and fMRI studies using verbal cognitive tasks like verb generation, semantic monitoring or semantic ('deep') encoding of words showed asymmetries of activation in the fronto-lateral cortex. In a previous ERP study subjects were required to indicate whether pronounceable non-words and abstract geometric figures were presented for the first time ('new item') or whether they had been shown before ('old item'). Group analyses of this study showed significant material-specific hemispheric asymmetries with ERPs being more negative-going in recordings of the posterior part of the left hemisphere with verbal material (CP5/6) but more negative-going in recordings of the right hemisphere with the spatial material (P7/8). The aim of the present study was to test statistically ERP lateralization effects in individual healthy subjects as well as WADA-tested patients suffering from seizures of the mesio-temporal lobe (MTL). In all subjects ERP lateralization with verbal material was tested in the electrode pair CP5/6, and ERP lateralization with figures in the electrode pair P7/8. Statistical analyses of single trials showed that in 20 out of 24 subjects ERPs with verbal material started to be more negative-going in CP5 as compared to CP6 in the period between 100 and 200 ms after stimulus onset or the subsequent time epoch (200-300 ms). In one subject not CP5/6 but the closely adjacent electrode pair P7/P8 showed this verbal material-related hemispheric effect. In patients language dominance as indicated by ERPs was not always consistent with the data of the WADA test. In one patient with left MTL seizures ERPs with verbal material and figures were found to be significantly lateralized to the right hemisphere although the WADA test assigned this patient to have a language-dominant left hemisphere.
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PMID:Language-related hemispheric asymmetry in healthy subjects and patients with temporal lobe epilepsy as studied by event-related brain potentials and intracarotid amobarbital test. 960 16

Two classes of functional neuroimaging methods exist: hemodynamic techniques such as PET and fMRI, and electromagnetic techniques such as EEG/ERP and MEG. In order to fusion these images with anatomical information, co-registration with volumetric MRI is needed. While such co-registration techniques are well established for hemodynamic images, additional steps are needed for electromagnetic recordings, because the activity is only recorded on the scalp surface and inverse solutions based on specific head models have to be used to estimate the 3-dimensional current distribution. To date most of the experimental and clinical studies use multi-shell concentric sphere models of the head, solve the inverse problem on this simplistic model, and then co-register the solution with the MRI using homogeneous transform operations. Contrary to this standard method, we here propose to map the MRI to the spherical system by defining transformation operations that transform the MRI to a best-fitting sphere. Once done so, the solution points are defined in the cerebral tissue of this deformed MRI and the lead field for the distributed linear inverse solutions is calculated for this solution space. The method, that we call SMAC (Spherical Model with Anatomical Constrains) is tested with simulations, as well as with the following real data: 1) estimation of the sources of visual evoked potentials to unilateral stimulation from data averaged over subjects, and 2) localization of interictal discharges of two epileptic patients, one with a temporal, the other with an occipital focus, both confirmed by seizure freedom after resection of the epileptogenic region.
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PMID:Electromagnetic inverse solutions in anatomically constrained spherical head models. 1115 1

Lamotrigine (LTG) as both effective against a wide range of seizure types and epileptic syndromes and well tolerated drug is being used in mono--as well as in polytherapy of pharmacoresistant epilepsy. The aim of this study was to evaluate the efficacy, safety and neuropsychological functioning after LTG (mean daily dose: 316 mg) as long-term monotherapy (12 mo) in 24 young adult out-patients (22.5 ys) with newly recognised and not-previously treated epilepsy in an open, non-comparative trial. 67% of patients were responders (above 50% reduction in seizure frequency) and 42% reported seizures remission. The best were results in patients with generalised convulsive fits (87% with remission). Adverse events in the early phase of medication in 21% of patients typically concerned CNS and gastrointestinal system (headache, asthenia, insomnia, nausea, gastric aches) and resolved spontaneously without treatment discontinuation. Biochemical examinations were normal and transient leucopenia and diminishion of MCV were clinically not significant. Neurodynamic abilities, neuropsychological examination results, memory verbal and visual tests and organic evaluation in organic triada tests did not show deterioration after LTG treatment. Slight difficulties in abstractive and operative thinking and some focal symptoms of fronto-temporal origin should be considered a result of drug but also the epilepsy per se. No significant differences in latencies and amplitudes of evoked potentials (VEP, BAEP, SEP and especially ERP-300) were measured after LTG. Preliminary results obtained in this study supported good efficacy and tolerability and especially lack of unfavourable influence of LTG on neuropsychological functioning in young previously untreated patients with epilepsy.
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PMID:Long-term monotherapy with lamotrigine in newly diagnosed epilepsy in adults. 1197 53

We studied 14 patients with well-characterized refractory temporal lobe epilepsy (TLE), 7 with right temporal lobe epilepsy (RTE) and 7 with left temporal lobe epilepsy (LTE), on a word repetition ERP experiment. Much prior literature supports the view that patients with left TLE are more likely to develop verbal memory deficits, often attributable to left hippocampal sclerosis. Our main objectives were to test if abnormalities of the N400 or Late Positive Component (LPC, P600) were associated with a left temporal seizure focus, or left temporal lobe dysfunction. A minimum of 19 channels of EEG/EOG data were collected while subjects performed a semantic categorization task. Auditory category statements were followed by a visual target word, which were 50% "congruous" (category exemplars) and 50% "incongruous" (non-category exemplars) with the preceding semantic context. These auditory-visual pairings were repeated pseudo-randomly at time intervals ranging from approximately 10-140 seconds later. The ERP data were submitted to repeated-measures ANOVAs, which showed the RTE group had generally normal effects of word repetition on the LPC and the N400. Also, the N400 component was larger to incongruous than congruous new words, as is normally the case. In contrast, the LTE group did not have statistically significant effects of either word repetition or congruity on their ERPs (N400 or LPC), suggesting that this ERP semantic categorization paradigm is sensitive to left temporal lobe dysfunction. Further studies are ongoing to determine if these ERP abnormalities predict hippocampal sclerosis on histopathology, or outcome after anterior temporal lobectomy.
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PMID:Reduced sensitivity of the N400 and late positive component to semantic congruity and word repetition in left temporal lobe epilepsy. 1219 60

Chemosensory function is determined by the interplay of numerous sensory modalities. The present study aimed to evaluate the possible influence of electrical stimulation of the left-sided vagal nerve on gustatory and olfactory function in patients with vagal nerve stimulation (VNS). Gustation and olfaction were tested using psychophysical techniques; olfactory function was additionally evaluated using event-related potentials. A total of 11 subjects participated (six men and five women, aged 21 to 56 years). The vagal stimulator was run in "rapid cycle mode" in 10 patients, whereas one patient was treated with "normal mode" VNS. Subjects participated in two sessions, with the vagal stimulator switched on and off, respectively. The sequence of the two sessions was randomized across all participants. Using air-dilution, olfactometry event-related potentials to the specific olfactory stimulant H2S were recorded. Psychophysical tests were performed using the "Sniffin' Sticks" test kit, a test for retronasal olfactory function, and a gustatory test based on impregnated filter paper. The study yielded the following major results: (1) VNS produced a prolongation of P2 latencies of olfactory ERP, and (2) patients with therapeutic benefit from VNS in terms of seizure control had larger amplitudes during the on period than during the off period. In conclusion, using electrophysiological measures of olfactory function, the present study indicated a significant role of VNS in the processing of olfactory information.
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PMID:Chemosensory function in patients with vagal nerve stimulators. 1562 28

We report an investigation of P300 measures of information processing in patients with generalized epilepsy of the absence type and those with complex partial epilepsy. Studies have demonstrated that absence patients perform more poorly than complex partial patients on behavioral tests of sustained attention (the Continuous Performance Test, or CPT). Duncan [Duncan, C.C., 1988. Application of event-related brain potentials to the analysis of interictal attention in absence epilepsy. In: Myslobodsky, M.S., Mirsky, A.F. (Eds.), Elements of Petit Mal Epilepsy. Peter Lang, New York, pp. 341-364] reported that P300 was significantly reduced in a group of absence patients as compared with healthy controls. The present investigation was undertaken to compare the attention deficit in absence patients to that in complex partial seizure patients. Thus, ERPs were recorded while participants with absence seizure disorder, complex partial seizure disorder, and healthy controls performed auditory and visual versions of the CPT. A significant reduction in the amplitude of P300 on the visual CPT was observed in both groups of seizure patients as compared to controls. In contrast, P300 on the auditory CPT was reduced only in the group with absence seizures. These ERP data support and amplify previous behavioral findings of the impaired capacity of absence patients to mobilize and sustain attentional resources. Auditory sustained attention seems to be more affected by the pathophysiology of absence epilepsy than visual attention. Two possible factors may be involved: (a) There are separate visual and auditory attention systems in the brain, and the latter is more vulnerable than the former [Duncan, C.C., Kosmidis, M.H., Mirsky, A.F., 2005. Closed head injury-related information processing deficits: An event-related potential analysis. Int. J. Psychophysiol. 58, 133-157]; and (b) Auditory processing depends on intact mechanisms in the brainstem, which are dysfunctional in patients with absence seizures.
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PMID:Assessment of the attention impairment in absence epilepsy: comparison of visual and auditory P300. 1941 47

The prevalence of psychological distress, especially depressive and anxiety disorders, is higher in epilepsy than in other chronic health conditions. These comorbid conditions contribute even more than epileptic seizures themselves to impaired quality of life in patients with epilepsy (PWE). The link between these comorbidities and epilepsy appears to have a neurobiological basis, which is at least partly mediated by stress through psychological and pathophysiological pathways. The impact of stress in PWE is also particularly important because it is the most frequently reported seizure trigger. It is therefore crucial for clinicians to take stress-related conditions and psychiatric comorbidities into account when managing PWE and to propose clinical support to enhance self-control of stress. Screening tools have been specially designed and validated in PWE for depressive disorders and anxiety disorders (e.g. NDDI-E, GAD-7). Other instruments are useful for measuring stress-related variables (e.g. SRRS, PSS, SCS, MHLCS, DSR-15, ERP-R, QOLIE-31) in order to help characterize the individual "stress profile" and thus orientate patients towards the most appropriate treatment. Management includes both pharmacological treatment and nonpharmacological methods for enhancing self-management of stress (e.g. mindfulness-based therapies, yoga, cognitive-behavioral therapies, biofeedback), which may not only protect against psychiatric comorbidities but also reduce seizure frequency.
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PMID:Stress regulation in drug-resistant epilepsy. 2849 23


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