Alexander C. van Huffelen

Reduction of Sympathetic Hyperactivity by Enalapril in Patients with Chronic Renal Failure

BACKGROUND Inhibition of angiotensin-converting enzyme (ACE) reduces the risk of cardiovascular problems in patients with chronic renal failure. This effect may be due in part to a decrease in sympathetic nervous activity, but no direct evidence of such an action is available. METHODS We studied muscle sympathetic-nerve activity in 14 patients with hypertension, chronic renal failure, and increased plasma renin activity before, during, and after administration of the ACE inhibitor enalapril. Ten other patients with similar clinical characteristics were studied before and during treatment with the calcium-channel blocker amlodipine. Normal subjects matched for age and weight were included in both studies. RESULTS At base line, mean (+/-SD) muscle sympathetic-nerve activity was higher in the group of patients who received enalapril than in the control subjects (35+/-17 vs. 19+/-9 bursts per minute, P=0.004). The baroreflex curve, which reflects changes in muscle sympathetic-nerve activity caused by manipulations of blood pressure with sodium nitroprusside and phenylephrine, was shifted to the right in the patients, but baroreflex sensitivity was similar to that in the control subjects (-2.1+/-1.9 and -2.7+/-1.3 bursts per minute per mm Hg, respectively; P=0.36). A single dose of the sympatholytic drug clonidine caused a greater fall in blood pressure in the patients than in the control subjects. Treatment with enalapril normalized blood pressure and muscle sympathetic-nerve activity (at 23+/-10 bursts per minute) in the patients and shifted the baroreflex curve to the left, reflecting normal blood-pressure levels, without significantly changing sensitivity (-2.3+/-1.8 bursts per minute per mm Hg, P=0.96). In the patients who received amlodipine, treatment also lowered blood pressure but increased muscle sympathetic-nerve activity, from 41+/-19 to 56+/-14 bursts per minute (P=0.02). CONCLUSIONS Increased sympathetic activity contributes to hypertension in patients with chronic renal disease. ACE inhibition controls hypertension and decreases sympathetic hyperactivity.

Effect of Treatment of Subclinical Neonatal Seizures Detected With aEEG: Randomized, Controlled Trial

OBJECTIVES: The goals were to investigate how many subclinical seizures in full-term neonates with hypoxic-ischemic encephalopathy (HIE) would be missed without continuous amplitude-integrated electroencephalography (aEEG) and whether immediate treatment of both clinical and subclinical seizures would result in a reduction in the total duration of seizures and a decrease in brain injury, as seen on MRI scans. METHODS: In this multicenter, randomized, controlled trial, term infants with moderate to severe HIE and subclinical seizures were assigned randomly to either treatment of both clinical seizures and subclinical seizure patterns (group A) or blinding of the aEEG registration and treatment of clinical seizures only (group B). All recordings were reviewed with respect to the duration of seizure patterns and the use of antiepileptic drugs (AEDs). MRI scans were scored for the severity of brain injury. RESULTS: Nineteen infants in group A and 14 infants in group B were available for comparison. The median duration of seizure patterns in group A was 196 minutes, compared with 503 minutes in group B (not statistically significant). No significant differences in the number of AEDs were seen. Five infants in group B received AEDs when no seizure discharges were seen on aEEG traces. Six of 19 infants in group A and 7 of 14 infants in group B died during the neonatal period. A significant correlation between the duration of seizure patterns and the severity of brain injury in the blinded group, as well as in the whole group, was found. CONCLUSIONS: In this small group of infants with neonatal HIE and seizures, there was a trend for a reduction in seizure duration when clinical and subclinical seizures were treated. The severity of brain injury seen on MRI scans was associated with a longer duration of seizure patterns.

Epilepsy Surgery in Tuberous Sclerosis: A Systematic Review

Summary:  Purpose: Tuberous sclerosis complex (TSC) is often associated with intractable epilepsy. Although epilepsy surgery has gained interest in recent years uncertainties exist about which patients are good surgical candidates. A systematic review of the available literature has been undertaken to assess the overall outcome of epilepsy surgery and identify risk factors of seizure recurrence.

Electrocorticographic discharge patterns in glioneuronal tumors and focal cortical dysplasia.

Summary:  Purpose: To determine whether highly epileptiform electrocorticographical discharge patterns occur in patients with glioneuronal tumors (GNTs) and focal cortical dysplasia (FCD) and whether specific histopathological features are related to such patterns.

Identification of the Epileptogenic Tuber in Patients with Tuberous Sclerosis: A Comparison of High‐resolution EEG and MEG

Summary:  Purpose: We compared epileptiform activity recorded with EEG and magnetoencephalography (MEG) in 19 patients with tuberous sclerosis complex (TSC) and epilepsy.

Detection of subclinical electroencephalographic seizure patterns with multichannel amplitude-integrated EEG in full-term neonates

OBJECTIVE To compare the seizure pattern detection rate of single-channel and multichannel amplitude-integrated EEG (aEEG), using conventional EEG (cEEG) as a gold standard, in full-term neonates with hypoxic-ischemic encephalopathy. The optimal electrode derivation for seizure detection with single-channel aEEG was also investigated. METHODS Twelve infants with cEEG seizure patterns (10s) were investigated. cEEG signals were transformed into aEEG signals. Seizure patterns and the number of patients identified with 1 seizure patterns were calculated for single- and multichannel aEEG. RESULTS On cEEG, 121 seizure patterns with a mean duration of 58s were identified, 68% of which occurred over the centrotemporal region. The sensitivity of aEEG for the detection of seizure patterns was 30% (C.I.: 0.22-0.38) for single-channel aEEG and 39% (C.I.: 0.31-0.48) for multichannel aEEG. Multichannel aEEG identified all patients with 1 seizure pattern (C.I.: 0.75-1.00), whereas single-channel aEEG (with C4-C3 as the optimal electrode derivation) identified all but one of the patients (C.I.: 0.66-0.99). CONCLUSIONS Seizure pattern detection rate is slightly better with multichannel aEEG compared with single-channel (C4-C3) aEEG. Multichannel aEEG identified correctly all patients with 1 seizure pattern in this small selection of patients. SIGNIFICANCE Single-channel aEEG may detect most patients (in a selected group) with severe neonatal seizures patterns; patient identification can be improved using multichannel recordings.

The Added Value of [18F]-Fluoro-D-deoxyglucose Positron Emission Tomography in Screening for Temporal Lobe Epilepsy Surgery

Purpose:[18F]‐Fluoro‐d‐deoxyglucose positron emission tomography (FDG‐PET) is an expensive, invasive, and not widely available technique used in the presurgical evaluation of temporal lobe epilepsy. We assessed its added value to the decision‐making process in relation to other commonly used tests.

High-resolution source imaging in mesiotemporal lobe epilepsy: a comparison between MEG and simultaneous EEG.

Summary Magnetic source imaging is claimed to have a high accuracy in epileptic focus localization and may be a guide for epilepsy surgery. Non-lesional mesiotemporal lobe epilepsy (MTLE), the most common form of epilepsy operated on, has different etiologies, which may affect the choice of surgical approach. The authors compared whole-head magnetoencephalography (MEG) with high-resolution EEG for source identification in MTLE. Nineteen patients with unilateral, nonlesional MTLE underwent a simultaneous 151-channel CTF MEG (CTF Systems, Inc., Port Coquitlam, British Columbia, Canada) and 64-channel EEG recordings with sleep induction. Three independent observers selected spikes from the EEG and MEG recordings separately. Only when there was interobserver agreement (kappa>0.4) on the presence of spikes in recordings were consensus spikes averaged. EEG and MEG equivalent current dipoles (ECD) were then integrated in the head model of the patient reconstructed from MRI. The results were compared with intraoperative electrocorticography findings. Spikes were detected in 32% of MEGs and 42% of EEGs. No patient showed MEG spikes only. Equivalent current dipole modeling correctly localized the source to the temporal lobe in four out of five MEG and three out of eight EEG recordings. MEG localized sources were more superficial and EEG localized sources were deeper. Unfortunately, basal temporal lobe areas were only partially covered by the sensor helmet of the MEG setup. Best correlation between EEG or MEG findings and electrocorticography findings was between horizontal EEG dipole orientation and prominent neocortical spiking; these patients also had a less favorable prognosis. Magnetic source imaging is currently unlikely to alter the surgical management of MTLE. The yield of spikes is too low, and ECD modeling shows only partial correlation with electrocorticography findings. Moreover, the whole-head MEG helmet provides insufficient coverage of the temporal lobe.

Prognosis after temporal lobe epilepsy surgery: The value of combining predictors

Purpose: Although several independent predictors of seizure freedom after temporal lobe epilepsy surgery have been identified, their combined predictive value is largely unknown. Using a large database of operated patients, we assessed the combined predictive value of previously reported predictors included in a single multivariable model.

Modality-specific spike identification in simultaneous magnetoencephalography/electroencephalography: A methodological approach

Summary Epileptiform spikes may have a different morphology and signal-to-noise ratio in simultaneously recorded EEGs and magnetoencephalograms (MEGs) that may lead to differences in the identification of spikes if both the modalities are presented separately. Moreover, there are no criteria for MEG spikes. It is unknown to which extent the visual assessment of MEG data yields consistent and meaningful results. Nineteen patients were selected with mesial temporal lobe epilepsy who underwent whole-head simultaneous MEG/EEG. These data were split into MEG and EEG files and were assessed independently by three observers for the occurrence of spikes. Interobserver kappa values were calculated. A mean kappa value greater than 0.5 was taken as a criterion for the presence of unequivocal spikes. Index cases from the resulting four subgroups were studied further. One patient had unequivocal spikes in both modalities, one in EEG only, one in MEG only, and one did not show any unequivocal spike. Spikes on which at least two observers agreed were then subjected to a template match algorithm to test for equal morphology and distribution. Equal spikes were averaged and electrical and magnetic field maps were plotted. Unequivocal spikes were found in both MEG and EEG in one patient, in MEG only in two patients, in EEG only in two patients, and no spikes in either modality were seen in 14 patients. In the four index patients, MEG showed 50 to 80% more spikes than EEG. After averaging identical consensus spikes, MEG spikes revealed a concomitant spike in the EEG, but the reverse was not always true. Even in the patient with MEG and EEG spikes that met all selection criteria, simultaneous field maps showed unexpected inconsistencies. In most patients with mesial temporal lobe epilepsy, there are no unequivocal spikes during MEG/EEG. In some cases, however, experienced electroencephalographers can identify MEG spikes reliably. Because of a better signal-to-noise ratio, more spikes could be identified in MEG than in EEG. Simultaneous MEG/EEG recordings do not simply ensure the best of both, but one modality may improve the identification of spikes in the other. In addition, different aspects of a complex source can be revealed. Our three-step approach to combined data ensures a reproducible selection of spikes for source modeling.