The intracarotid amobarbital or Wada test: unilateral or bilateral?

OBJECTIVE

In the Netherlands, presurgical screening for temporal lobe epilepsy (TLE) includes the intracarotid amobarbital procedure (IAP), consisting of two consecutive injections of amobarbital, ipsilateral and contralateral to the epileptic focus. We studied whether a bilateral IAP has added value to a unilateral, ipsilateral IAP.

METHODS

This population-based study included 183 consecutive patients referred for screening for TLE surgery who underwent bilateral IAP. Using multivariable modeling, we assessed the added value of bilateral IAP on the decision for surgery, resection size, amygdalohippocampectomy, post-operative seizure freedom, memory performance, and IQ change.

RESULTS

Given the results from the unilateral IAP, the bilateral IAP had added prognostic value for postoperative change in verbal memory (P < 0.01) and verbal IQ (P < 0.01), especially if patients had a left-sided focus. In contrast, information provided by the contralateral IAP was not associated with decision-making or surgical strategy.

CONCLUSIONS

A bilateral IAP has added value in predicting post-operative verbal memory and IQ. A bilateral IAP is currently not used to guide surgical strategy, but may be used for this purpose when verbal capacity is of particular concern in patients with a left-sided focus. In other cases, IAP is best performed unilaterally.

Overlapping neurologic and cognitive phenotypes in patients with TSC1 or TSC2 mutations

OBJECTIVE

The purpose of this study was to systematically analyze the associations between different TSC1 and TSC2 mutations and the neurologic and cognitive phenotype in patients with tuberous sclerosis complex (TSC).

METHODS

Mutation analysis was performed in 58 patients with TSC. Epilepsy variables, including EEG, were classified. A cognition index was determined based on a comprehensive neuropsychological assessment. On three-dimensional fluid-attenuated inversion recovery MR images, an automated tuber segmentation program detected and calculated the number of tubers and the proportion of total brain volume occupied by tubers (tuber/brain proportion [TBP]).

RESULTS

As a group, patients with a TSC2 mutation had earlier age at seizure onset, lower cognition index, more tubers, and a greater TBP than those with a TSC1 mutation, but the ranges overlapped considerably. Familial cases were older at seizure onset and had a higher cognition index than nonfamilial cases. Patients with a mutation deleting or directly inactivating the tuberin GTPase activating protein (GAP) domain had more tubers and a greater TBP than those with an intact GAP domain. Patients with a truncating TSC1 or TSC2 mutation differed from those with nontruncating mutations in seizure types only.

CONCLUSIONS

Although patients with a TSC1 mutation are more likely to have a less severe neurologic and cognitive phenotype than those with a TSC2 mutation, the considerable overlap between both aspects of the phenotype implies that prediction of the neurologic and cognitive phenotypes in individuals with tuberous sclerosis complex should not be based on their particular TSC1 or TSC2 mutation.

Cognitive impairment in tuberous sclerosis complex is a multifactorial condition

OBJECTIVE

In patients with tuberous sclerosis complex (TSC), associations between tuber number, infantile spasms, and cognitive impairment have been proposed. We hypothesized that the tuber/brain proportion (TBP), the proportion of the total brain volume occupied by tubers, would be a better determinant of seizures and cognitive function than the number of tubers. We investigated tuber load, seizures, and cognitive function and their relationships.

METHODS

Tuber number and TBP were characterized on three-dimensional fluid-attenuated inversion recovery MRI with an automated tuber segmentation program. Seizure histories and EEG recordings were obtained. Intelligence equivalents were determined and an individual cognition index (a marker of cognition that incorporated multiple cognitive domains) was calculated.

RESULTS

In our sample of 61 patients with TSC, TBP was inversely related to the age at seizure onset and to the intelligence equivalent and tended to be inversely related to the cognition index. Further, a younger age at seizure onset or a history of infantile spasms was related to lower intelligence and lower cognition index. In a multivariable analysis, only age at seizure onset and cognition index were related.

CONCLUSIONS

Our systematic analysis confirms proposed relationships between tuber load, epilepsy and cognitive function in tuberous sclerosis complex (TSC), but also indicates that tuber/brain proportion is a better predictor of cognitive function than tuber number and that age at seizure onset is the only independent determinant of cognitive function. Seizure control should be the principal neurointervention in patients with TSC.

[Intracranial EEG monitoring for epilepsy surgery using electrode grids--results in the first 22 Dutch patients]

OBJECTIVE

Description of initial experiences with subdural electrode grids in patients with refractory focal epilepsy as additional diagnostic tool for epilepsy surgery. Using these electrodes, the attacks were recorded during a number of days and the cerebral cortex was electrically stimulated in order to map the functional areas.

DESIGN

Retrospective.

METHOD

Data were collected from patients in whom subdural electrode grids had been placed between 1 September 1999 and 31 August 2004. All patients underwent a neurological examination and a neuropsychological test before the implantation. At the follow-up examination, the results with regard to function and the frequency of attacks were noted, as well as the complications.

RESULTS

Electrodes were placed in 22 patients: 9 women and 13 men with an average age of 27 years (range: 5-42). The implantation lasted for an average of 7 days (range: 3-10). In 4 patients, increased seizures during implantation required intravenous anticonvulsant treatment. Severe but transitory complications were seen in 4 patients (meningitis, subdural haematoma and ischaemia). 19 patients underwent a therapeutic resection. A postoperative decline in language skills was noted in 1 patient, while another 2 scored poorer in verbal tests. A permanent decline in sensorimotor function was seen in 1 patient, but this had been foreseen. Of the 16 operated patients with a duration of follow-up of at least 1 year, so were (practically) free of attacks, and another 3 patients had significantly fewer attacks.

CONCLUSION

Registration with intracranial electrodes makes it possible to treat epileptic patients surgically by excision of brain tissue near critical areas. Such intensive monitoring is, however, not without risk and this must be weighed against the potential benefits.

Cerebrovascular Reserve Capacity Is Preserved in a Population-Based Sample of Patients with Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSE

Type 2 diabetes mellitus (DM2) is associated with an increased risk of stroke. DM2 is also associated with cognitive impairments. Vascular dysfunction, such as impaired cerebrovascular reserve capacity (CVR), may be a determinant of these changes, but previous studies on CVR in DM2 have provided variable results in selected populations of patients. We aimed to examine CVR in a population-based sample of DM2 patients.

METHODS

The CO(2) reactivity of the middle cerebral artery was examined using transcranial Doppler ultrasonography in 81 DM2 patients and 38 controls. In DM2 patients CVR was correlated with diabetic parameters, vascular risk factors and cognitive functioning.

RESULTS

CVR was similar in patients and controls (51 vs. 49%). Within the DM2 group, there was no statistically significant relationship between CVR and DM duration, HbA(1c), albuminuria, blood pressure, intima-media thickness and cognition. CVR tended to be lower in diabetic patients with retinopathy [46 vs. 55%, mean difference: -7.9 (confidence interval -18.0, 2.2)].

CONCLUSION

We conclude that CVR is not impaired in unselected patients with DM2 and probably does not, therefore, play a major role in the aetiology of cognitive impairment.

Seizure Detection in Adult ICU Patients Based on Changes in EEG Synchronization Likelihood

INTRODUCTION

Seizures are common in Intensive Care Unit (ICU) patients, and may increase neuronal injury.

PURPOSE

To explore the possible value of synchronization likelihood (SL) for the automatic detection of seizures in adult ICU patients.

METHODS

We included EEGs from ICU patients with a variety of diagnoses. The gold standard for further analyses was the consensus judgment of three clinical neurophysiologists who classified 150 scalp EEG epochs as "definitely epileptiform," "definitely non epileptiform," or "uncertain." SL estimates the statistical interdependencies between two time series, such as two EEG channels. We computed the average synchronization by calculating the SL between one channel and every other channel, and taking the mean of these values.

RESULTS

The mean SL in the 38 "definitely epileptiform" epochs ranged from 0.095 to 0.386 (mean 0.189; SD 0.066). In the 34 "definitely nonepileptiform" epochs the mean SL ranged from 0.087 to 0.158 (mean 0.115; SD 0.016; p < 0.0005). The area under the ROC curve was 0.812 (95% Confidence Interval 0.725 to 0.898).

CONCLUSION

The mean SL may distinguish between seizure and nonseizure epochs, and may prove helpful to monitor epileptic activity in ICU patients.

Recovery of amplitude integrated electroencephalographic background patterns within 24 hours of perinatal asphyxia

OBJECTIVE

To assess the time course of recovery of severely abnormal initial amplitude integrated electroencephalographic (aEEG) patterns (flat trace (FT), continuous low voltage (CLV), or burst suppression (BS)) in full term asphyxiated neonates, in relation to other neurophysiological and neuroimaging findings and neurodevelopmental outcome.

METHODS

A total of 190 aEEGs of full term infants were reviewed. The neonates were admitted within 6 hours of birth to the neonatal intensive care unit because of perinatal asphyxia, and aEEG recording was started immediately. In all, 160 infants were included; 65 of these had an initial FT or CLV pattern and 25 an initial BS pattern. Neurodevelopmental outcome was assessed using a full neurological examination and the Griffiths' mental developmental scale.

RESULTS

In the FT/CLV group, the background pattern recovered to continuous normal voltage within 24 hours in six of the 65 infants (9%). All six infants survived the neonatal period; one had a severe disability, and five were normal at follow up. In the BS group, the background pattern improved to normal voltage in 12 of the 25 infants (48%) within 24 hours. Of these infants, one died, five survived with moderate to severe disability, two with mild disability, and four were normal. The patients who did not recover within 24 hours either died in the neonatal period or survived with a severe disability.

CONCLUSION

In this study there was a small group of infants who presented with a severely abnormal aEEG background pattern within six hours of birth, but who achieved recovery to a continuous normal background pattern within the first 24 hours. Sixty one percent of these infants survived without, or with a mild, disability.

Cortisol, depression and reduced cortico-cortical cross-talk in Cushing's syndrome

In the present report assumed relationships between hypercortisolism, depression and cortico-cortical cross-talk in Cushing's syndrome were investigated. Electroencephalographic (EEG) recordings and depression ratings from three patients diagnosed with mild, moderate and severe hypercortisolism were obtained. Reductions in cortico-cortical cross-talk as quantified by EEG coherence together with increases in depression were observed in the moderate and severe as compared to the mild hypercorticolism state. These findings provide preliminary evidence for the hypothesis that loss of cortico-cortical cross-talk might be linked to hypercortisolism and the severity of depressive symptoms.

Synaptosomal glutamate and GABA transport in patients with temporal lobe epilepsy

High-affinity glutamate and GABA transporters found in the plasma membrane of neurons and glial cells terminate neurotransmission by rapidly removing extracellular transmitter. Impairment of transporter function has been implicated in the pathophysiologic mechanisms underlying epileptogenesis. We characterized glutamate and gamma-aminobutyric acid (GABA) transport in synaptosomes, isolated from neocortical and hippocampal biopsies of patients with temporal lobe epilepsy (TLE). We analyzed K(+)-evoked release in the presence and absence of Ca(2+) to determine vesicular and transporter-mediated release, respectively. We also analyzed (3)H-glutamate and (3)H-GABA uptake, the effect of glutamate uptake inhibitors L-trans-pyrrolidine-2,4-dicarboxylic acid (tPDC) and DL-threo-beta-benzyloxyaspartate (TBOA), and GABA uptake inhibitor N-(4,4-diphenyl-3-butenyl)-3-piperidinecarboxylic acid (SK&F 89976-A). Neocortical synaptosomes from TLE patients did not show vesicular glutamate release, strongly reduced transporter-mediated release, and an increased basal release compared to that in rat synaptosomes. Furthermore, basal release was less sensitive to tPDC, and (3)H-glutamate uptake was reduced compared to that in rat synaptosomes. Vesicular GABA release from neocortical synaptosomes of TLE patients was reduced compared to that in rat synaptosomes, whereas transporter-mediated release was hardly affected. Furthermore, basal GABA release was more than doubled, but neither basal nor stimulated release were increased by SK&F 89976-A, which did significantly increase both types of GABA release in rat synaptosomes. Finally, (3)H-GABA uptake by synaptosomes from TLE patients was reduced significantly in hippocampus (0.19 +/- 0.04%), compared to that in neocortex (0.32 +/- 0.04%). Control experiments with human peritumoral cortical tissue suggest that impaired uptake of glutamate, but not of GABA, was caused in part by the hypoxic state of the biopsy. Our findings provide evidence for impaired function of glutamate and GABA transporters in human TLE.

Measurement of the conductivity of skull, temporarily removed during epilepsy surgery

The conductivity of the human skull plays an important role in source localization of brain activity, because it is low as compared to other tissues in the head. The value usually taken for the conductivity of skull is questionable. In a carefully chosen procedure, in which sterility, a stable temperature, and relative humidity were guaranteed, we measured the (lumped, homogeneous) conductivity of the skull in five patients undergoing epilepsy surgery, using an extended four-point method. Twenty-eight current configurations were used, in each of which the potential due to an applied current was measured. A finite difference model, incorporating the geometry of the skull and the electrode locations, derived from CT data, was used to mimic the measurements. The conductivity values found were ranging from 32 mS/m to 80 mS/m, which is much higher than the values reported in other studies. Causes for these higher conductivity values are discussed.

Collateral flow and ischemic brain lesions in patients with unilateral carotid artery occlusion

OBJECTIVE

To investigate the association between ischemic brain lesions and intracranial collateral blood flow in patients with unilateral occlusion of the internal carotid artery (ICA).

METHODS

Sixty-eight consecutive patients were included. Ischemic lesions on MRI were identified on hard copies, and volume measurements of the lesions were performed on an MR workstation. Intracranial collateral pathways were studied with MR angiography, digital subtraction angiography, and transcranial Doppler sonography.

RESULTS

The presence of collateral flow via the anterior communicating artery (ACoA) was associated with a reduction in prevalence (p = 0.01) and volume (p = 0.008) of internal border zone infarcts in the hemisphere ipsilateral to the occluded ICA. Absence of collateral blood flow via the circle of Willis was associated with an increase in prevalence (p = 0.007) and volume (p = 0.005) of internal border zone infarcts. No association between any collateral flow pattern in the circle of Willis and periventricular lesions or lacunar, territorial, or external border zone infarcts was found. No association between collateral flow via the ophthalmic artery or leptomeningeal vessels with any type of ischemic lesion was found.

CONCLUSION

Collateral flow via the ACoA is associated with a reduction of the prevalence and volume of internal border zone lesions but not with any other type of ischemic lesion. The presence of a functional posterior communicating artery or secondary collateral pathways is not associated with the prevalence of any type of ischemic lesion.

Quantitative cerebral perfusion MRI and CO2 reactivity measurements in patients with symptomatic internal carotid artery occlusion

Quantitative perfusion MRI is a promising new technique capable of offering information on cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, it is still unclear how these perfusion parameters relate to the underlying physiological indicators and how they compare to conventional techniques. The purpose of this study was to investigate how quantitative perfusion MRI is related to the cerebrovascular reactivity as measured by transcranial Doppler ultrasonography (TCD) in combination with a CO2 stimulus in patients with a symptomatic occlusion of the internal carotid artery (ICA). Thirty-nine patients with transient or minor disabling retinal or hemispheric ischemic symptoms and an occlusion of the ICA underwent quantitative perfusion MRI and CO2 reactivity measurements by TCD. Perfusion parameters were correlated with cerebrovascular reactivity measurements and compared with measurements of control subjects. The results of this study show a negative correlation between the cerebrovascular reactivity and the time to bolus peak (TBP) both for gray (r = -0.26, P = 0.035) and white matter (r = -0.28, P = 0.026). No correlation between resting CBV, CBF, or MTT and cerebrovascular reactivity was found. Our results indicate that an increase in TBP reflects a poor development of collateral flow, which is supported by a relatively low CO2 reactivity in these patients.

Diazepam-enhanced beta activity in Sturge Weber syndrome: its diagnostic significance in comparison with MRI

OBJECTIVES

This study was performed to assess the extent of functional involvement of the affected hemisphere in Sturge Weber syndrome in comparison with the uninvolved hemisphere. To this end beta activity in the electroencephalogram (EEG) was measured, both before and after administration of diazepam intravenously (i.v.).

METHODS

In 9 patients asymmetry in beta band activity was studied before and after diazepam administration. Several beta bands and asymmetry parameters were calculated. beta band asymmetries were compared with structural abnormalities (magnetic resonance imaging, MRI).

RESULTS

Total beta activity was reduced in the involved hemisphere in all patients after diazepam administration. In 3 patients functional abnormalities were found in brain regions that were structurally intact.

CONCLUSIONS

Decreased diazepam-enhanced beta activity in the EEG is a sensitive criterion of functional abnormality. In patients with subtle structural abnormalities diazepam-enhanced EEG may have added value in diagnosing functional involvement and in monitoring disease progression in patients.

The existence of two sources in rolandic epilepsy: confirmation with high resolution EEG, MEG and fMRI

In benign rolandic epilepsy seizure semiology suggests that the epileptic focus resides in the lower sensorimotor cortex. Previous studies involving dipole modeling based on 32 channel EEG have confirmed this localization. These studies have also suggested that two distinct dipole sources are required to adequately describe the typical interictal spikes. Since in benign epilepsy invasive validation is prohibited, this study tries to further establish these results using a multi-modal approach, involving 32 channel EEG, high resolution 84 channel EEG, 151 channel MEG and fMRI. From one patient interictal spikes were recorded and analyzed using the MUSIC algorithm in a realistic volume conductor model. In an fMRI experiment the same patient performed voluntary tongue movements, thus mimicking a typical seizure. Results show that EEC, MEG and fMRI localization converge on the same area in the lower part of the sensorimotor cortex, and that high resolution EEG clearly reveals two distinct sources, one in the post- and one in the pre-central cortex.

EEG evidence for shunt requirement during carotid endarterectomy: optimal EEG derivations with respect to frequency bands and anesthetic regimen

Currently there is no consensus on the derivations that should be used for EEG monitoring during carotid endarterectomy (CEA). The aim of this study was to determine which derivations distinguish the best between patients requiring a shunt and patients who do not need a shunt. Four predefined frequency bands and two regimens for general anesthesia (isoflurane versus propofol) were used. EEG data (16 channels) were obtained from 152 EEGs recorded during carotid endarterectomy. Analog EEG signals of preclamp and clamp periods of 100 seconds were digitized to compute power spectra. Changes in power during clamping were calculated for all possible derivations in four predefined frequency bands and were expressed as Z-scores. For each derivation, the area under the receiver operating characteristics curve was calculated. Derivations with the greatest area under the receiver operating characteristics curve were considered to distinguish the best between the shunt and the nonshunt groups formed in retrospect on the basis of consensus between three independent and experienced board-certified electroencephalographers. The two different anesthetic regimens resulted in different patterns of EEG changes because of clamping. The optimal derivations to differentiate between the shunt and the nonshunt groups also differed for the two anesthetic regimens, although for both conditions, anterior head regions were especially preferred. The optimal derivations are given for each anesthetic regimen.

Activation of interictal spiking in mesiotemporal lobe epilepsy by propofol-induced sleep

The objective of this study was to test whether low-dose propofol increases the number of interictal spikes in patients with mesiotemporal lobe epilepsy, and to determine whether this is the result of intrinsic properties and is restricted to the primary epileptogenic focus. Controlled infusion of propofol in step-up/-down target concentrations of 0, 0.3, 0.6, and 0.8 mg/L was administered to 10 patients during a 3.5-hour daytime EEG registration. The number of spikes were counted and related to propofol concentration and sleep level. Results were compared with a spontaneous, nocturnal first sleep cycle in 9 of 10 patients. All patients entered nonrapid eye movement 1 sleep during propofol administration, and 8 reached nonrapid eye movement 2 sleep. In 7 patients who showed spikes, spikes were related to sleep (P < 0.05) and not to increasing (P = 0.1) or decreasing (P = 0.5) propofol concentration. Six of nine patients showed more spikes during spontaneous (nocturnal) sleep than during propofol-induced sleep. Contralateral spiking was not suppressed selectively. Low-dose propofol is a safe means of increasing spiking in these patients because it induces sleep. There were no signs of an intrinsic epileptogenicity of propofol or a selective effect on ipsilateral spikes. Controlled sleep induction will increase the yield of interictal spikes during short interictal recordings such as in magnetoencephalography.

Sustained bilateral hemodynamic benefit of contralateral carotid endarterectomy in patients with symptomatic internal carotid artery occlusion

BACKGROUND AND PURPOSE

We sought to investigate whether in patients with a symptomatic internal carotid artery (ICA) occlusion, endarterectomy of a severe stenosis of the contralateral carotid artery can establish long-term cerebral hemodynamic improvement.

METHODS

Nineteen patients were studied on average 1 month before and 6 months after contralateral carotid endarterectomy (CEA). Volume flow in the main extracranial and intracranial arteries was measured with MR angiography. Collateral flow via the circle of Willis and the ophthalmic arteries was studied with MR angiography and transcranial Doppler sonography, respectively. Cerebral metabolism and CO(2) vasoreactivity were investigated with MR spectroscopy and transcranial Doppler sonography, respectively. Twelve nonoperated patients with a symptomatic ICA occlusion and contralateral ICA stenosis, who were matched for age and sex, served as control patients.

RESULTS

In patients who underwent surgery, flow in the operated ICA increased significantly (P:<0.05) and flow in the basilar artery decreased significantly (P:<0.01) after CEA. On the occlusion side, mean flow in the middle cerebral artery increased significantly from 71 to 85 mL/min (P:<0.05) after CEA. The prevalence of collateral flow via the anterior communicating artery to the occlusion side increased significantly (47% before and 84% after CEA; P:<0.05), while the prevalence of reversed ophthalmic artery flow on the operation side decreased significantly (42% before and 5% after CEA; P:<0.05). In the hemisphere on the side of the ICA occlusion, lactate was no longer detected after CEA in 80% of operated patients, whereas it was no longer detected over time in 14% of nonoperated patients (P:<0.05). CO(2) reactivity increased significantly in operated patients in both hemispheres (P:<0.01).

CONCLUSIONS

Contralateral CEA in patients with a symptomatic ICA occlusion induces cerebral hemodynamic improvement not only on the side of surgery but also on the side of the ICA occlusion.

Recurrent ischemia in symptomatic carotid occlusion: prognostic value of hemodynamic factors

OBJECTIVE

To identify hemodynamic factors that predict recurrence of ipsilateral cerebral ischemic events in patients with symptomatic carotid artery occlusion (CAO).

PATIENTS AND METHODS

The authors studied 117 consecutive patients with CAO and corresponding recent (</=6 months) ischemic symptoms of the brain or eye that were transient or at most mildly disabling. They determined, using Cox proportional hazards analysis, the prognostic value for recurrence of ipsilateral cerebral ischemic events of 1) clinical features believed to indicate hemodynamic compromise, 2) collateral blood flow pattern, and 3) transcranial Doppler CO(2)-reactivity.

RESULTS

None of the 24 patients with symptoms of retinal ischemia alone had a recurrent cerebral ischemic event. In the 93 patients with cerebral ischemic symptoms on entry, recurrence of these symptoms was independently predicted by 1) the nature of the initial symptoms being of purported hemodynamic origin (limb-shaking, precipitation of symptoms by rising, exercise or low blood pressure, retinal claudication) (hazard ratio [HR] 3.8, 95% CI 1.5 to 9.5), 2) continuing symptoms after the CAO had been documented, but before inclusion in the study (HR 5.9, 95% CI 2.2 to 16.1), and 3) the presence of collateral blood flow via leptomeningeal vessels (HR 4.1, 95% CI 1.3 to 13.1). CO(2)-reactivity did not predict recurrence of cerebral ischemic events.

CONCLUSIONS

Having cerebral in contrast to retinal ischemia, clinical features suggestive of hemodynamic compromise, continuing symptoms after demonstration of the CAO, and presence of leptomeningeal collaterals may help to identify patients with symptomatic CAO at high risk of future cerebral ischemia.

A longitudinal study of collateral flow patterns in the circle of Willis and the ophthalmic artery in patients with a symptomatic internal carotid artery occlusion

BACKGROUND AND PURPOSE

The purpose of the present study was to assess whether the direction of flow via the circle of Willis and the ophthalmic artery (OphA) changed over time in patients with a symptomatic occlusion of the internal carotid artery (ICA) who did not experience recurrent cerebral ischemic symptoms.

METHODS

Sixty-two patients with a symptomatic ICA occlusion were investigated within 6 months after symptoms occurred. The investigations were repeated after 6 and 12 months. The directions of flow in the A1 segment and the posterior communicating artery (PCoA), both on the side of the symptomatic ICA occlusion, were assessed with the use of magnetic resonance angiography. The pattern of collateral flow via the circle of Willis was categorized as via the A1 segment only, via the PCoA only, via the A1 segment plus the PCoA, or no collateral flow via the circle of Willis. The direction of flow in the OphA was investigated with transcranial Doppler sonography. CO(2) reactivity was determined with transcranial Doppler sonography to investigate whether changes in flow patterns were accompanied by changes in cerebrovascular reactivity.

RESULTS

There were no statistically significant changes over time in the direction of blood flow in the A1 segment and the PCoA or in the pattern of collateral flow via the circle of Willis. On average, 72% of patients with a unilateral ICA occlusion (n=41) had willisian collateral flow compared with 37% of patients with a bilateral ICA occlusion (n=21; P<0.05). Patients with a unilateral ICA occlusion tended to a lower prevalence of reversed flow via the OphA over time. CO(2) reactivity did not change significantly in any patient group. In patients with a unilateral ICA occlusion, decreased CO(2) reactivity was associated with a higher prevalence of absent willisian collateral flow and a lower prevalence of collateral flow via the A1 segment plus the PCoA.

CONCLUSIONS

The absence of recurrent cerebral ischemic symptoms in patients with a symptomatic ICA occlusion is not associated with an improvement in collateral flow via the circle of Willis or the OphA during 1.5-year follow-up.

Glutamate and gamma-aminobutyric acid content and release of synaptosomes from temporal lobe epilepsy patients

During surgical intervention in medically refractory temporal lobe epilepsy (TLE) patients, diagnosed with either mesial temporal lobe sclerosis (MTS)- or tumor (T)-associated TLE, biopsies were taken from the anterior temporal neocortex and the hippocampal region. Synaptosomes, isolated from these biopsies were used to study intrasynaptosomal Ca(2+) levels ([Ca(2+)](i)), and glutamate and gamma-aminobutyric acid (GABA) contents and release. All synaptosomal preparations demonstrated a basal [Ca(2+)](i) of about 200 nM, except neocortical synaptosomes from MTS-associated TLE patients (420 nM). K(+)-induced depolarization resulted in a robust increase of the basal [Ca(2+)](i) in all preparations. Neocortical synaptosomes from TLE patients contained 22.9 +/- 3.0 nmol glutamate and 4.6 +/- 0.5 nmol GABA per milligram synaptosomal protein, whereas rat cortical synaptosomes contained twice as much glutamate and four times as much GABA. Hippocampal synaptosomes from MTS-associated TLE patients, unlike those from T-associated TLE patients, contained about 70% less glutamate and 55% less GABA than neocortical synaptosomes. Expressed as percentage of total synaptosomal content, synaptosomes from MTS-associated TLE patients exhibited an increased basal and a reduced K(+)-induced glutamate and GABA release compared to rat cortical synaptosomes. In MTS-associated TLE patients, only GABA release from neocortical synaptosomes was partially Ca(2+)-dependent. Control experiments in rat synaptosomes demonstrated that at least part of the reduction in K(+)-induced release can be ascribed to resection-induced hypoxia in biopsies. Thus, synaptosomes from MTS-associated TLE patients exhibit a significant K(+)-induced increase in [Ca(2+)](i), but the consequent release of glutamate and GABA is severely impaired. Our data show that at least part of the differences in glutamate and GABA content and release between human biopsy material and fresh rat tissue is due to the resection time.

The use of preoperative transcranial Doppler variables to predict which patients do not need a shunt during carotid endarterectomy

OBJECTIVES

to analyse whether preoperative transcranial Doppler (TCD) variables can predict intraoperative shunt requirement.

DESIGN AND METHODS

the blood-flow velocity (BFV) in the major basal cerebral arteries was measured preoperatively with TCD, in 178 patients scheduled for CEA. Carotid artery compression and CO2 reactivity tests were also performed. Intraoperative electroencephalography was used to decide whether a shunt was needed. Differences in the probability of shunt requirement between the categories of variables were assessed with crosstabs statistics.

RESULTS

preoperative TCD criteria clearly identified a subgroup of 59 patients (33%) who did not require a shunt. In general, these patients appeared to have adequate collateral flow through the anterior communicating artery. In contrast, prediction of the need for a shunt was less reliable. TCD variables could predict the need for a shunt with a probability of only 60%.

CONCLUSIONS

preoperative TCD can be used to identify patients who do not require a shunt during carotid endarterectomy.

The need for correct realistic geometry in the inverse EEG problem

For accurate electroencephalogram-based localization of mesial temporal and frontal sources correct modeling of skull shape and thickness is required. In a simulation study in which results for matched sets of computed tomography and magnetic resonance (MR) images are compared, it is found that errors arising from skull models based on smooth and inflated segmented MR images of the cortex are of the order of 1 cm. These errors are comparable to those found when overestimating or underestimating skull conductivity by a factor of two.

Characterization of neocortical and hippocampal synaptosomes from temporal lobe epilepsy patients

To investigate epilepsy-associated changes in the presynaptic terminal, we isolated and characterized synaptosomes from biopsies resected during surgical treatment of drug-resistant temporal lobe epilepsy (TLE) patients. Our main findings are: (1) The yield of synaptosomal protein from biopsies of epilepsy patients was about 25% of that from rat brain. Synaptosomal preparations were essentially free of glial contaminations. (2) Synaptosomes from TLE patients and naive rat brain, quickly responded to K(+)-depolarization with a 70% increase in intrasynaptosomal Ca(2+) ([Ca(2+)](i)), and a 40% increase in B-50/GAP-43 phosphorylation. (3) Neocortical and hippocampal synaptosomes from TLE patients contained 20-50% of the glutamate and gamma-aminobutyric acid (GABA) contents of rat cortical synaptosomes. (4) Although the absolute amount of glutamate and GABA released under basal conditions from neocortical synaptosomes of TLE patients was lower than from rat synaptosomes, basal release expressed as percentage of total content was higher (16.4% and 17.3%, respectively) than in rat (11.5% and 9. 9%, respectively). (5) Depolarization-induced glutamate and GABA release from neocortical synaptosomes from TLE patients was smaller than from rat synaptosomes (3.9% and 13.0% vs. 21.9% and 25.0%, respectively). (6) Analysis of breakdown of glial fibrillary acid protein (GFAP) indicates that resection time (anoxic period during the operation) is a critical parameter for the quality of the synaptosomes. We conclude that highly pure and viable synaptosomes can be isolated even from highly sclerotic human epileptic tissue. Our data show that in studies on human synaptosomes it is of critical importance to distinguish methodological (i.e., resection time) from pathology-related abnormalities.