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Biomedical subjects

A M Murro

Publications and source records attributed to A M Murro.

35 records · Page 2Linked to original sources
PubMed1993

Localization of temporal lobe seizures with quantitative EEG.

In this study, we describe a quantitative EEG method for localization of seizure onset in 29 patients with temporal lobe epilepsy. We used right-left differences in relative power and a logistic regression to predict the side of seizure onset. The optimum bipolar channels were T4-T6/T3-T5 and the optimum frequency band was 4-10.5 Hz. Using a threshold probability of 0.75 for classification, the best quantitative EEG method classified 23 patients (79%) correctly, 2 patients (7%) incorrectly, and 4 patients (14%) as undetermined localization. In comparison, 3 electroencephalographers visually interpreted these same EEGs and classified 20-25 patients (69-86%) correctly, 1 patient (3%) incorrectly and 3-8 patients (10-28%) as undetermined localization. In the 8 patients classified as undetermined localization by at least one interpreter, the quantitative EEG method classified 5 patients correctly, 1 patient incorrectly and 2 patients as undetermined localization. These results suggest that quantitative EEG might improve the reliability of ictal EEG localization and potentially reduce the need for invasive intracranial EEG monitoring.

Adolescent↗
PubMed1993

Seizure localization in temporal lobe epilepsy: a comparison of scalp-sphenoidal EEG and volumetric MRI.

We determined the accuracy of volumetric MRI (based on identification of unilateral hippocampal atrophy) and scalp-sphenoidal EEG (based on concordant interpretations of scalp-sphenoidal ictal EEG by three independent interpreters) for seizure focus localization in 20 patients with temporal lobe epilepsy. All patients became seizure-free or had rare seizures following temporal lobectomy. Among the 20 patients, nine (45%) met both MRI and EEG localization criteria, six (30%) met MRI localization criteria alone, three (15%) met EEG localization criteria alone, and two patients (10%) did not meet either localization criteria. In the 18 patients meeting MRI or EEG localization criteria, the predicted localization agreed with the side of temporal lobectomy. These results suggest that a noninvasive approach combining MRI and EEG will correctly localize the side of seizure onset in most patients with temporal lobe epilepsy.

Adolescent↗
PubMed1993

Wada memory testing and hippocampal volume measurements in the evaluation for temporal lobectomy.

We examined the relationship of Wada memory performance and MRI hippocampal volume measurements to laterality of ultimate seizure localization in 20 patients with complex partial seizures who later underwent temporal lobectomy. Discriminant function analysis employing both Wada memory test asymmetries and hippocampal volume asymmetries correctly classified 100% of the patients into left and right temporal lobe groups. Wada memory asymmetries alone correctly classified 90% of the sample (80% of the sample when the discriminant function included all patients except the one being classified), and hippocampal volume asymmetries alone correctly classified 90% of the patients. A significant correlation was present between Wada memory asymmetries and hippocampal volume asymmetries (r = 0.78), indicating that structural evidence of reduced hippocampal volume has a functional correlate reflected by Wada memory performance. These data suggest that the combination of functional and structural measures is of value in the preoperative evaluation for epilepsy surgery.

Adult↗
PubMed1992

Comparison of CT- versus MRI-guided, computer-assisted depth electrode implantation.

Fourteen candidates for ablative seizure surgery underwent CT-guided, computer-assisted stereotactic depth electrode implantation and 21 underwent MRI-guided, computer-assisted implantation. A hand-held computer with no graphic capability was used for CT-guided procedures. A computer work station which included a high-resolution color graphics terminal with touchscreen interfacing and software capable of simulating targets and trajectories in single or multiple views was used for MRI-guided procedures. Previous phantom studies done with a 1.5-tesla MR scanner suggested acceptable localization error. Localizing information was obtained in 10 (71.4%) of 14 of the CT-guided implants and in 16 (76.2%) of 21 of MRI-guided cases. In the CT group, 7 (70%) were seizure-free and 8 (80%) were greater than 90% improved at 1 year follow-up. In the MRI group, 8 (80%) were seizure-free and 9 (90%) were greater than 90% improved at latest follow-up.

Computer Graphics↗
PubMed1992

Differential effects of left versus right seizure focus on human hippocampal evoked responses.

Hippocampal evoked potentials were recorded using the P3 tonal oddball paradigm in 30 patients with unilateral temporal lobe seizure focus. Spectral power of the evoked potentials was decreased on the side of seizure focus, but this reduction was much greater when the focus was on the left. The effect of left/right focus does not appear to be due to group differences in age, sex, seizure duration, or operative pathology. Remote or finer left/right structural differences or differential left/right hippocampal processing for the sequential tonal task are possible explanations.

Adolescent↗
PubMed1991

Computerized seizure detection of complex partial seizures.

In this study, we describe a computerized method that uses 3 quantified EEG features and discriminant analysis to automatically detect seizure EEG. The quantified EEG features were relative amplitude, dominant frequency and rhythmicity. Using EEGs recorded from intracranial electrodes, the seizure detection method was applied to consecutive non-overlapping 2-channel EEG epochs. A seizure detection sensitivity, ranging from 90% to 100%, was associated with a false positive detection rate of 1.5-2.5/h. The performance of the seizure detection method remained stable for EEG recorded over variable time periods.

Discriminant Analysis↗
PubMed1991

Behavioral state-specific changes in human hippocampal theta activity.

Although there has been extensive examination of the behavioral and physiologic correlates of hippocampal theta activity in animals, the human literature consists of a single case study. We investigated the differential effects of four behavioral states on human hippocampal theta activity in 16 epilepsy surgery patients. Behavioral conditions included resting eyes closed (RC), resting eyes open (RO), eyes open with auditory word activation (AW), and eyes open with visuospatial activation (VS). Hippocampal theta activity decreased during both RO and VS compared to both RC and AW. There were reciprocal changes in delta activity. Comparisons of RO to VS and of RC to AW were nonsignificant. The results demonstrate state-specific changes in human hippocampal theta and are consistent with the animal literature that relates hippocampal theta to sensorimotor integration and forebrain volitional mechanisms.

Adolescent↗
PubMed1990

Adaptive smoothing: an improved method for spectral analysis and its application to seizure EEG.

We describe the data adaptive smoothing method, an improved method for multichannel spectral analysis of seizure EEG. After Fast Fourier Transform of EEG data, spectra were computed by smoothing over adjacent frequency components. Using cross-validatory maximum likelihood criteria, unsmoothed spectral data were used to select the level of smoothing (spectral window effective bandwidth) required to minimize bias and variance errors. The statistical assumptions of this method are consistent with the statistical properties of seizure EEG. On computer simulation of seizure EEG, the smoothing level predicted by this method correlates strongly with the optimum smoothing level. The utility of the method is demonstrated by application to seizure EEG. The consistency of the method's statistical assumptions, the success in selection of the optimum smoothing level, and the variability in optimum smoothing required for seizure EEG suggest that the adaptive smoothing method is a useful method for multichannel spectral analysis.

Electroencephalography↗
PubMed1990

Cerebral language lateralization: evidence from intracarotid amobarbital testing.

Cerebral language lateralization was investigated in 103 patients undergoing intracarotid amobarbital testing as part of their diagnostic work-up for epilepsy surgery. Inclusion criteria included adequate bilateral intracarotid amobarbital studies and no radiologic lesion in areas other than the temporal lobe. Language was evaluated with respect to strict presence or absence of language representation, in which a patient was considered to have bilateral language despite potentially having asymmetric language representation, and with respect to forced relative hemispheric dominance, in which a single side could be considered dominant despite bilateral language representation. Seventy-nine patients displayed exclusive left hemisphere language representation, two patients showed exclusive right hemisphere language representation, and 22 patients had language represented in each hemisphere. In the 22 patients with bilateral language, an asymmetry was present in 17 cases (13 L greater than R, 4 R greater than L). These data indicate that language restricted only to the right hemisphere is rare, and that in the absence of purely left hemisphere language, most patients exhibit bilateral representation. Previously reported incidence of exclusive right hemisphere language may be an artifact of dichotomizing a continuous variable.

Amobarbital↗
PubMed1990

An 8-year experience with depth electrodes in the evaluation of ablative seizure surgery candidates.

Stereotactically implanted depth electrodes are one means of localization of seizure foci. Unilateral seizure focus localization was obtained in 72.7% mesial temporal (MT) implants and 50% of focus/extramesial temporal (MT-XMT) implants. Recent increase in localization to over 80% in MT implants was possible because a larger percentage of patients had MT-XMT implants. Increased localization to 60% in MT-XMT implants was related to using more XMT electrodes per patient and to orienting electrodes to monitor larger limbic XMT and neocortical areas. Since MT foci were localized in 25% of MT-XMT cases, MT electrodes should be included with all MT-XMT implants. Depth electrography can also be used to rule out certain patients as surgical candidates. Therefore, a surgical decision can be reached in a very high percentage of patients undergoing depth implantation. Surgical results are comparable to those in our overall series.

Brain Mapping↗
PubMed1990

Human hippocampal EEG: effects of behavioral activation.

We studied spectral components of human hippocampal EEG in relation to behavioral status in 19 patients with intractable complex partial seizures who had depth electrodes implanted into the anterior hippocampi as a part of their preoperative evaluations. Behavioral conditions included: eyes closed resting, eyes open resting, eyes open with a verbal task, and eyes open with a visuospatial task. Hippocampal EEG spectral power uniformly decreased during behavioral activation. EEG activation was quantitatively different among the 3 activated conditions, with the most prominent change occurring during the visuospatial task. The degree of EEG activation corresponded inversely with the site of epileptic focus during the verbal task. The results demonstrate the response of human hippocampal EEG to behavioral activation. The magnitude of EEG change may reflect the degree of functional activation of the given hippocampus.

Adult↗
PubMed1989

Surgical management of epilepsy.

About 300,000 people in the United States suffer from medically uncontrolled focal epilepsy. It is estimated that about 40,000 of these patients are candidates for surgery. Underuse of surgical treatment of epilepsy is reflected by the fact that only about 1% of these candidates are operated on. Candidates for ablative surgery (ie, removal of seizure focus) must have a focus demonstrated by either extracranial or intracranial electrode recordings. Nearly half of the patients who have ablative surgery become seizure-free, and nearly two thirds have no seizures or only rare ones. Candidates for corpus callosotomy are those patients with multiple seizure types and nonfocal EEG abnormalities. Almost half of these patients have at least a 50% reduction in seizure frequency. Patients with infantile hemiplegia and seizures may have marked improvement in seizure control after physiologic hemispherectomy.

Corpus Callosum↗
PubMed1987

Analysis of a four-year experience with depth electrodes and a two-year experience with subdural electrodes in the evaluation of ablative seizure surgery candidates.

Chronically implanted depth and subdural electrodes have both been shown to be satisfactory means of localizing epileptogenic foci. Utilizing bilateral mesial temporal depth electrodes, we have localized mesial temporal foci in a large percentage of patients. Depth electrode investigation of a more limited number of patients with suspected extramesial temporal foci has not been as reliable in giving localizing information. We have more recently used subdural electrodes to investigate this latter category of patients, and preliminary findings suggest that this technique may be of localizing value in several subcategories.

Electrodes, Implanted↗
PubMedDate not supplied

Effects of scopolamine on visual evoked potentials in aging and dementia.

The unusual combination of a normal pattern reversal VEP and a delayed flash VEP has been reported in patients with dementia of Alzheimer's type (DAT). Hyoscine hydrobromide has been reported to produce a similar VEP abnormality in young, healthy subjects. In the present study, we assessed the relative sensitivity of DAT patients and healthy young, middle-aged and elderly subjects to temporary cholinergic blockade. We report VEP latency values following 3 doses of scopolamine and after a peripheral anticholinergic agent. Flash P2 latency was not significantly slower in DAT patients than in the healthy elderly. Scopolamine increased P2 latency in the young controls but did not affect any other group. The pattern reversal P100 was normal in DAT, and a significant increase in latency occurred following scopolamine administration in both the control and patient groups.

Adult↗
PubMedDate not supplied

Corpus callosotomy for the treatment of intractable epilepsy.

Twenty-five patients underwent anterior corpus callosotomy (ACC) for treatment of uncontrolled seizures. Two patients died, and 6 patients experienced perioperative complications which resolved. A statistically significant reduction of generalized tonic-clonic seizures (17 patients; P less than 0.05) and complex partial seizures (11 patients; P less than 0.05) occurred following ACC. A single patient with atonic seizures became free of atonic seizures. Two patients had a greater than 50% reduction in seizures resulting in falls, a single patient became free of episodes of status epilepticus, and in 2 patients the seizures changed from generalized tonic-clonic seizures to hemiconvulsive seizures. Thus ACC appears to decrease the severity and frequency of disabling seizures in some patients with uncontrolled seizures.

Adolescent↗
PubMedDate not supplied

Amnesia after unilateral temporal lobectomy: a case report.

We report a mixed handed (L > R) patient with exclusive right cerebral language representation who developed a permanent anterograde amnestic syndrome after right anterotemporal lobectomy. Preoperative neuropsychological performance consisted of impaired verbal memory and normal nonverbal memory. Wada memory performance was asymmetrical for objects presented soon after amobarbital injection in conjunction with no memory asymmetry for items presented later in the Wada evaluation. Pre- and postoperative magnetic resonance imaging (MRI) scans showed no structural lesions; however, postoperative MRI hippocampal volume measurements suggested decreased hippocampal volume for the nonresected temporal lobe. These results confirm the risk of anterograde amnesia after unilateral temporal lobectomy and demonstrate that baseline neuropsychological testing may falsely literalize material-specific memory functions in patients with atypical cerebral language dominance.

Adult↗