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Biomedical subjects

H F Flanigin

Publications and source records attributed to H F Flanigin.

At least 19 recordsLinked to original sources
PubMed1995

Intraoperative hippocampal cooling and Wada memory testing in the evaluation of amnesia risk following anterior temporal lobectomy.

OBJECTIVE: To determine the efficacy of memory testing following localized thermal inactivation (cooling) of the hippocampus during epilepsy surgery to assess risk for postoperative memory decline. DESIGN: Memory was assessed after intraoperative thermal inactivation of the hippocampus and during the Wada procedure to help determine the clinical utility of each procedure. SETTING: A university hospital, comprehensive epilepsy surgery program. PATIENTS: Individuals undergoing unilateral temporal lobectomy for relief of intractable seizures. PROCEDURE: After temporal tip resection, iced liquid was irrigated into the temporal horn of the lateral ventricle until the hippocampus was "cooled." MAIN OUTCOME MEASURES: Multiple neuropsychological measures of learning and memory. RESULTS: Wada memory testing suggested risk for memory impairment in 15 patients while cooling indicated risk in only five patients. Predictions arising from the two procedures were concordant in 13 patients and discordant in 12 patients. Among the 12 inconsistent predictions, hippocampal cooling suggested adequate contralateral memory support in 11 (92%) of 12 patients, and none of these 11 patients had a postoperative anterograde amnesia. CONCLUSION: Intraoperative hippocampal cooling may be useful in determining the risk of postoperative memory disorder among selected patients undergoing epilepsy surgery.

Adult↗
PubMed1995

Intraoperative thermal inactivation of the hippocampus in an effort to prevent global amnesia after temporal lobectomy.

In an effort to assess the risk of amnesia after anterior temporal lobectomy (ATL), we conducted localized thermal inactivation (cooling) of the hippocampus with memory testing. Thirty-three ATL patients whose preoperative evaluation suggested risk for postoperative amnesia underwent hippocampal cooling. Cooling consisted of inserting a catheter in the temporal horn and irrigating it with an iced solution until a stable hippocampal temperature of approximately 20 degrees C was reached. Memory was assessed before and after cooling. In 12 of the 33 patients, memory testing was either aborted or suggested poor contralateral support, and the hippocampus was resected in 2 of these patients. The remaining 21 patients showed evidence of contralateral memory support, and the hippocampus was resected in 18. No patient became amnestic. These results suggest that intraoperative hippocampal cooling may be useful in selected cases. However, even among many patients who could cooperate with testing, discomfort, sedation, attentional deficits, confusion, and anxiety made test interpretation difficult.

Adolescent↗
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

Hippocampal contribution to verbal recent memory following dominant-hemisphere temporal lobectomy.

The effects of hippocampal encroachment in the language dominant-hemisphere were studied in 41 patients who underwent previous temporal lobectomy (TL). Patients undergoing dominant-hemisphere TL including anterior hippocampus (n = 13) performed significantly worse than nondominant TL patients (n = 16) on a verbal learning test (Selective Reminding; p less than or equal to .00001), thereby confirming the sensitivity of this procedure to lateralized temporal-lobe dysfunction. However, no significant difference was present on this or other primary measures of material-specific memory when contrasting dominant TL patients in whom the anterior hippocampus was spared (n = 12) to those in whom anterior hippocampus was resected. These data suggest that more extensive and posterior mesial temporal-lobe resection is not necessarily associated with a greater verbal material-specific memory deficit following dominant-hemisphere temporal lobectomy.

Adult↗
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

Material specific learning during electrical stimulation of the human hippocampus.

Material specific learning was assessed during unilateral electrical stimulation of the hippocampus through intracerebrally implanted electrodes in 30 patients with unilateral temporal lobe epilepsy (TLE). Verbal learning significantly decreased in patients with right TLE after stimulation of the left, but not the right, hippocampus. No verbal learning impairment was observed in left TLE patients following stimulation of either hippocampus. Visuospatial memory performance significantly decreased following stimulation of the right hippocampus regardless of the side of seizure onset. Results suggest that the contralateral "nonepileptic" hippocampus does not assume the material specific mnestic functions of the dysfunctional hippocampus associated with longstanding epilepsy.

Analysis of Variance↗
PubMed1990

Crossed aphasia in a patient with complex partial seizures: evidence from intracarotid amobarbital testing, functional cortical mapping, and neuropsychological assessment.

We report a right-handed patient who became transiently aphasic following a right temporal lobectomy for control of intractable complex partial seizures. Preoperative intracarotid amobarbital testing revealed right-hemisphere language dominance, although bilateral language representation was present. Memory testing during unilateral electrical hippocampal simulation with depth electrodes indicated reliance on left-hemisphere mesial temporal lobe structures for verbal memory. Functional mapping for language during surgery established several right perisylvian regions that, when stimulated, produced speech arrest and/or paraphasic substitution. One-year follow-up neuropsychological assessment demonstrated an increase in verbal learning and decrease in visual memory, a pattern associated with patients who have undergone right temporal lobectomy. These data demonstrate that (1) right cerebral language dominance can be observed when ipsilateral seizure onset is present (2) verbal memory and language dominance are not necessarily linked, and (3) some reported cases of crossed aphasia may in fact have bilateral language representation.

Adult↗
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

The intracarotid amobarbital procedure as a predictor of memory failure following unilateral temporal lobectomy.

We investigated the efficacy of the intracarotid amobarbital procedure to accurately predict post-temporal lobectomy anterograde amnesia. We presented items at 2 separate times during amobarbital assessment; both early and late item recall were decreased during the injection contralateral to seizure onset indicating sensitivity to bilateral temporal lobe dysfunction. Ten patients for whom follow-up neuropsychological assessment was available failed either the early or late item recognition portions of their amobarbital evaluation ipsilateral to seizure onset, but had hippocampus included in the temporal lobectomy by virtue of satisfactory performance on other tests of hippocampal function. None of these 10 patients displayed postoperative anterograde amnesia, although there was a reduction in material-specific memory in some patients. These results indicate that relying solely on amobarbital memory testing to assess the functional ability of the contralateral temporal lobe to sustain global memory prior to temporal lobectomy may needlessly exclude patients from a viable therapeutic option.

Amnesia↗
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↗
PubMed1990

MR imaging in patients with intractable complex partial epileptic seizures.

Detailed neurologic studies, high-field-strength MR imaging, and CT scanning were performed preoperatively in 53 patients with intractable complex partial seizures who underwent surgical treatment for epilepsy. Macroscopic structural (tumoral or vascular) lesions were found in 28% of patients. The remainder had pathologic findings consistent with mesial temporal gliosis. Tumors were found in 22% of the patients and were benign or of low-grade malignancy in every case. MR was accurate in the preoperative diagnosis of structural lesions, including very small occult tumors and cryptic vascular malformations. In patients with mesial temporal gliosis, there was correlation between the MR observation of a unilaterally dilated anterior temporal horn and the EEG-identified seizure focus and side of temporal lobectomy. However, MR demonstrated T2-weighted signal abnormalities correlating with the epileptogenic focus in only 8% of cases of mesial temporal gliosis. MR provided useful information in 28% of patients who underwent surgery for refractory complex partial epilepsy. MR obviated invasive EEG monitoring in 93% of the patients with structural lesions. MR was useful in only 8% of the patients with pathologic changes of mesial temporal gliosis.

Adolescent↗
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↗
PubMed1988

Spectral power of human limbic evoked potentials: relationship to seizure onset.

Limbic evoked potentials were recorded from intracerebral electrodes bilaterally implanted in the hippocampi of 16 epileptic patients undergoing evaluation for surgical resection of a seizure focus. Spectral analysis of the limbic evoked potentials revealed consistently lower spectral power of both low-band (1-12.6 Hz) and high-band (13-20 Hz) components recorded form the hippocampus that was associated with the electrographically confirmed seizure focus as compared to the contralateral side. Limbic evoked potential recordings appear to be useful in the determination of a focal functional deficit and thus in identifying the site of epileptogenic pathology. Further, the results support the hypothesis of a local generator for limbic evoked potentials and demonstrate that limbic evoked potentials in humans include not only low-frequency, high-amplitude electric field changes, but also a high-frequency component.

Adolescent↗