Targeted prefrontal cortical activation with bifrontal ECT

Changes in postictal cerebral perfusion are related to the duration of electroconvulsive therapy-induced seizures

OBJECTIVE

Postictal symptoms may result from cerebral hypoperfusion, which is possibly a consequence of seizure-induced vasoconstriction. Longer seizures have previously been shown to cause more severe postictal hypoperfusion in rats and epilepsy patients. We studied cerebral perfusion after generalized seizures elicited by electroconvulsive therapy (ECT) and its relation to seizure duration.

METHODS

Patients with a major depressive episode who underwent ECT were included. During treatment, 21-channel continuous electroencephalogram (EEG) was recorded. Arterial spin labeling magnetic resonance imaging scans were acquired before the ECT course (baseline) and approximately 1 h after an ECT-induced seizure (postictal) to quantify global and regional gray matter cerebral blood flow (CBF). Seizure duration was assessed from the period of epileptiform discharges on the EEG. Healthy controls were scanned twice to assess test-retest variability. We performed hypothesis-driven Bayesian analyses to study the relation between global and regional perfusion changes and seizure duration.

RESULTS

Twenty-four patients and 27 healthy controls were included. Changes in postictal global and regional CBF were correlated with seizure duration. In patients with longer seizure durations, global decrease in CBF reached values up to 28 mL/100 g/min. Regional reductions in CBF were most prominent in the inferior frontal gyrus, cingulate gyrus, and insula (up to 35 mL/100 g/min). In patients with shorter seizures, global and regional perfusion increased (up to 20 mL/100 g/min). These perfusion changes were larger than changes observed in healthy controls, with a maximum median global CBF increase of 12 mL/100 g/min and a maximum median global CBF decrease of 20 mL/100 g/min.

SIGNIFICANCE

Seizure duration is a key factor determining postictal perfusion changes. In future studies, seizure duration needs to be considered as a confounding factor due to its opposite effect on postictal perfusion.

Parsing the Network Mechanisms of Electroconvulsive Therapy

Electroconvulsive therapy (ECT) is one of the oldest and most effective forms of neurostimulation, wherein electrical current is used to elicit brief, generalized seizures under general anesthesia. When electrodes are positioned to target frontotemporal cortex, ECT is arguably the most effective treatment for severe major depression, with response rates and times superior to other available antidepressant therapies. Neuroimaging research has been pivotal in improving the field's mechanistic understanding of ECT, with a growing number of magnetic resonance imaging studies demonstrating hippocampal plasticity after ECT, in line with evidence of upregulated neurotrophic processes in the hippocampus in animal models. However, the precise roles of the hippocampus and other brain regions in antidepressant response to ECT remain unclear. Seizure physiology may also play a role in antidepressant response to ECT, as indicated by early positron emission tomography, single-photon emission computed tomography, and electroencephalography research and corroborated by recent magnetic resonance imaging studies. In this review, we discuss the evidence supporting neuroplasticity in the hippocampus and other brain regions during and after ECT, and their associations with antidepressant response. We also offer a mechanistic, circuit-level model that proposes that core mechanisms of antidepressant response to ECT involve thalamocortical and cerebellar networks that are active during seizure generalization and termination over repeated ECT sessions, and their interactions with corticolimbic circuits that are dysfunctional prior to treatment and targeted with the electrical stimulus.

Noninvasive neuromodulation of the prefrontal cortex in mental health disorders

More than any other brain region, the prefrontal cortex (PFC) gives rise to the singularity of human experience. It is therefore frequently implicated in the most distinctly human of all disorders, those of mental health. Noninvasive neuromodulation, including electroconvulsive therapy (ECT), repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS) among others, can-unlike pharmacotherapy-directly target the PFC and its neural circuits. Direct targeting enables significantly greater on-target therapeutic effects compared with off-target adverse effects. In contrast to invasive neuromodulation approaches, such as deep-brain stimulation (DBS), noninvasive neuromodulation can reversibly modulate neural activity from outside the scalp. This combination of direct targeting and reversibility enables noninvasive neuromodulation to iteratively change activity in the PFC and its neural circuits to reveal causal mechanisms of both disease processes and healthy function. When coupled with neuronavigation and neurophysiological readouts, noninvasive neuromodulation holds promise for personalizing PFC neuromodulation to relieve symptoms of mental health disorders by optimizing the function of the PFC and its neural circuits. ClinicalTrials.gov Identifier: NCT03191058.

Adjunctive Nonconvulsive Electrotherapy for Patients with Depression: a Systematic Review

The efficacy and safety of adjunctive nonconvulsive electrotherapy (NET) for patients with depression are undetermined. This systematic review was conducted to examine the efficacy and safety of adjunctive NET for patients with depression. Chinese (WanFang and Chinese Journal Net) and English (PubMed, EMBASE, PsycINFO and the Cochrane Library) databases were systematically searched from their inception until Jan 27, 2021 by three independent investigators. One randomized controlled trial (RCT) with 3 treatment arms (n = 108) and two observational studies (single-group, before-after design, n = 31) were included. In the RCT, the antidepressant efficacy of NET on depression was similar to that of electroconvulsive therapy (ECT) (P > 0.05) but with significantly fewer neurocognitive impairments as measured by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) (P < 0.05). In two observational studies, the 17-item Hamilton Depression Rating Scale (HAMD-17) scores decreased significantly from baseline to post-NET (all Ps < 0.05), without adverse neurocognitive effects. In the RCT, adverse drug reactions (ADRs) were not separately reported among the 3 treatment arms but a similar rate of discontinuation was reported. The currently available limited evidence from 3 studies suggests that NET as an adjunctive treatment may be a safe, well-tolerated, effective therapy for depression without serious neurocognitive impairments.

Proton magnetic resonance spectroscopic analysis of changes in brain metabolites following electroconvulsive therapy in patients with major depressive disorder

Objectives: The aim of this study was to evaluate the metabolic changes in the anterior cingulate cortex (ACC) induced by electroconvulsive therapy (ECT) in patients with MDD via ¹H-MRS.Methods: The study was conducted on 13 MDD patients receiving ECT treatment and 14 healthy controls matched in terms of age, gender and education. The patients underwent six sessions of ECT. ¹H-MRS imaging and psychometric evaluations obtained before 1st and after the 6th sessions. The control group also went through the same procedures except for ECT. N-Acetyl aspartate (NAA), choline (Cho) and creatine (Cr) metabolite levels and the creatine to metabolite ratios were measured.Results: There was no significant difference in the ACC metabolite levels of the patients and those of the controls at the baseline. ECT associated with a statistically significant decrease in the NAA/Cr ratio in ACC. All of the patients had responded to ECT treatment as measured with the clinical scales.Conclusions: The results has suggested that indirect proof of an increase in energy metabolism without any evidence of impaired neuronal viability in the ACC induced by ECT. The relative increase in Cr levels following ECT in MDD seems to be associated with improvement in clinical severity.Key pointsECT is one the most effective method in the treatment of acute MDD.The mechanism of ECT's antidepressant activity remains unclear but it is thought to be related to the regulation of prefrontal cortical or cingulate areas.In this study the patients underwent six sessions of ECT and after ¹H-MRS imaging.The study revealed that baseline levels of metabolites in patients with MDD were not significantly different than those of control group.

A Retrospective Study of Cognitive Improvement Following Electroconvulsive Therapy in Schizophrenia Inpatients

OBJECTIVES

Findings on the cognitive effect of electroconvulsive therapy (ECT) in individuals with schizophrenia have brought mixed results, with few recent studies beginning to report cognitive improvements after treatment. Cognitive change in inpatients with schizophrenia who were referred for an acute course of ECT was examined in the current study. Furthermore, the study aimed to determine the profile of patients who experience cognitive improvement and the potential use of a brief cognitive battery to detect this positive cognitive change, if any.

METHODS

Montreal Cognitive Assessment (MoCA) was conducted at baseline and posttreatment after 6 sessions of ECT. The Brief ECT Cognitive Screen was also administered to determine its predictive ability on cognitive gain of 2 points or higher in MoCA total scores for the 2 consecutive time points.

RESULTS

A total of 81 inpatients were included in the study. Retrospective analysis revealed significant improvements in MoCA total score and domains of visuospatial/executive function and attention. Cognitive improvement was more pronounced among those who had worse pre-MoCA score before ECT.

CONCLUSIONS

The study provided support to the existing literature where cognitive improvement has been reported among individuals with schizophrenia after ECT. Future studies should consider the use of randomized controlled trials to examine the possible cognitive benefits of ECT. In a setting where there is a high volume of patients receiving ECT, the monitoring of patients' cognitive status through the course of ECT continues to be warranted and the Brief ECT Cognitive Screen may be useful as a quick measure to detect such ECT-related cognitive change.

Electroconvulsive therapy electrode placement for bipolar state-related targeted engagement

Background

Electroconvulsive therapy (ECT) is an effective treatment for all bipolar states. However, ECT remains underutilized, likely stemming from stigma and the risk of neurocognitive impairment. Neuroimaging research has identified state-specific areas of aberrant brain activity that may serve as targets for therapeutic brain stimulation. Electrode placement determines the geometry of the electric field and can be either non-focal (bitemporal) or more focal (right unilateral or bifrontal). Previous research has shown that electrode placement can impact clinical and cognitive outcomes independent of seizure activity. This review critically examines the evidence that focal (unilateral or bifrontal) electrode placements target specific aberrant circuitry in specific bipolar states to optimize clinical outcomes. We hypothesize that optimal target engagement for a bipolar state will be associated with equivalent efficacy relative to bitemporal non-focal stimulation with less neurocognitive impairment.

Methods

We performed a literature search in the PubMed database. Inclusion criteria included prospective, longitudinal investigations during the ECT series with specific electrode placements within a bipolar state from 2000 to 2018.

Results

We identified investigations that met our inclusion criteria with bipolar mania (n = 6), depression (n = 6), mixed (n = 3) and catatonia (n = 1) states. These studies included clinical outcomes and several included cognitive outcomes, which were discussed separately.

Conclusions

While the heterogeneity of the studies makes comparisons difficult, important patterns included the reduced cognitive side effects, faster rate of response, and equivalent efficacy rates of the focal electrode placements (right unilateral and bifrontal) when compared to non-focal (bitemporal) placement. Further avenues for research include more robust cognitive assessments to separate procedure-related and state-related impairment. In addition, future studies could investigate novel electrode configurations with more specific target engagement for different bipolar states.

New directions in the rational design of electrical and magnetic seizure therapies: individualized Low Amplitude Seizure Therapy (iLAST) and Magnetic Seizure Therapy (MST)

Electroconvulsive therapy remains a key treatment option for severe cases of depression, but undesirable side-effects continue to limit its use. Innovations in the design of novel seizure therapies seek to improve its risk benefit ratio through enhanced control of the focality of stimulation. The design of seizure therapies with increased spatial precision is motivated by avoiding stimulation of deep brain structures implicated in memory retention, including the hippocampus. The development of two innovations in seizure therapy-individualized low-amplitude seizure therapy (iLAST) and magnetic seizure therapy (MST), are detailed. iLAST is a method of seizure titration involving reducing current spread in the brain by titrating current amplitude from the traditional fixed amplitudes. MST, which can be used in conjunction with iLAST dosing methods, involves the use of magnetic stimulation to reduce shunting and spreading of current by the scalp occurring during electrical stimulation. Evidence is presented on the rationale for increasing the focality of ECT in hopes of preserving its effectiveness, while reducing cognitive side-effects. Finally, the value of electric field and neural modelling is illustrated to explain observed clinical effects of modifications to ECT technique, and their utility in the rational design of the next generation of seizure therapies.

Cerebellar volume change in response to electroconvulsive therapy in patients with major depression

Electroconvulsive therapy (ECT) is remarkably effective in severe major depressive disorder (MDD). Growing evidence has accumulated for brain structural and functional changes in response to ECT, primarily within cortico-limbic regions that have been considered in current neurobiological models of MDD. Despite increasing evidence for important cerebellar contributions to affective, cognitive and attentional processes, investigations on cerebellar effects of ECT in depression are yet lacking. In this study, using cerebellum-optimized voxel-based analysis methods, we investigated cerebellar volume in 12 MDD patients who received right-sided unilateral ECT. 16 healthy controls (HC) were included. Structural MRI data was acquired before and after ECT and controls were scanned once. Baseline structural differences in MDD compared to HC were located within the "cognitive cerebellum" and remained unchanged with intervention. ECT led to gray matter volume increase of left cerebellar area VIIa crus I, a region ascribed to the "affective/limbic cerebellum". The effects of ECT on cerebellar structure correlated with overall symptom relief. These findings provide preliminary evidence that structural change of the cerebellum in response to ECT may be related to the treatment's antidepressant effects.

Cognitive Effects of Bifrontal Versus Right Unilateral Electroconvulsive Therapy in the Treatment of Major Depression in Elderly Patients: A Randomized, Controlled Trial

OBJECTIVES

Bifrontal (BF) electrode placement has been explored to refine the electroconvulsive therapy (ECT) technique. No previous study has compared the cognitive effects of BF versus right unilateral (RUL) ECT by only including the subgroup that is most likely to receive it: elderly patients with major depression.

METHODS

Nondemented patients (n = 65) with major depression, aged 60 to 85 years, were randomly allocated to BF ECT and RUL formula-based ECT. Cognitive function was assessed at baseline (T1), within 1 week after a course of ECT (T2), and 3 months after T2 (T3). Six neuropsychological test measures of memory, 5 of executive function, and 3 of information-processing speed were administered.

RESULTS

According to linear mixed models, there were no significant differences between the BF and RUL groups at any time. The retrograde memory score for public facts declined more for the RUL group (P < 0.001) than the BF group (P = 0.005) from baseline to the first retest and remained stable for both groups from T2 to T3. A rapid improvement in selective attention was observed in the RUL group from T1 to T2, but the scores remained stable from T2 to T3 (P < 0.001). This measure remained stable in the BF group from T1 to T3.

CONCLUSIONS

Our findings indicate that there were negligible differences in the cognitive effects of formula-based BF or RUL ECT. The overall cognitive effects of ECT were equally favorable for each of the groups.

Nonconvulsive Electrotherapy for Treatment Resistant Unipolar and Bipolar Major Depressive Disorder: A Proof-of-concept Trial

BACKGROUND

Electroconvulsive therapy (ECT) is the most effective therapy for treatment resistant major depressive disorder (TRD); however, some individuals with TRD refuse ECT over concern about adverse cognitive effects. Clinical observation of two patients with TRD who had a therapeutic response to intended ECT despite having only one or no seizure suggested that nonconvulsive electrical stimulation may be effective in some patients.

OBJECTIVE/HYPOTHESIS

This study tested the hypothesis that electrical brain stimulation applied like standard ECT, but below seizure threshold, can have therapeutic effects on TRD with fewer adverse cognitive effects.

METHODS

Thirteen outpatients with TRD (6 unipolar, 7 bipolar) who refused ECT participated in this open label adjunctive treatment study of nonconvulsive electrotherapy (NET) at the University of Maryland Medical Center. Brief pulse bifrontal electrical stimulation was given thrice weekly with a Thymatron System IV Integrated ECT Instrument.

RESULTS

Seizure-free data were obtained from 11 of 13 subjects. Group mean Hamilton Depression Rating Scale 17-item version scores declined significantly (P = 0.001) from 20.3 to 8.6. Response and remission rates were 73% (8) and 55% (6), respectively. Cognitive testing using the Mini-Mental State Exam and the Autobiographical Memory Inventory-Short Form did not show declines typically observed with ECT.

CONCLUSIONS

The therapeutic effect of NET on TRD was similar to that of ECT. Serious adverse effects and adverse cognitive effects were not observed. These results challenge the widespread belief that a seizure is necessary for the antidepressant effect of ECT and merit further investigation to determine whether NET is a viable alternative to ECT in some patients with TRD. Clinical trial posted on www.clinicaltrials.gov, identifier: NCT01065597.

Clinical efficacy of formula-based bifrontal versus right unilateral electroconvulsive therapy (ECT) in the treatment of major depression among elderly patients: a pragmatic, randomized, assessor-blinded, controlled trial

BACKGROUND

No prior study has compared the efficacy of bifrontal (BF) vs right unilateral (RUL) electroconvulsive therapy (ECT) by including the subgroup that is most likely to receive it: only elderly patients with major depression (MD).

METHODS

This single-site, randomized, assessor-blinded, controlled trial was conducted from 2009 to 2013. Seventy-three elderly patients with MD, unipolar and bipolar, were treated with a course of formula-based BF ECT or RUL ECT. The 17-item Hamilton Rating Scale for Depression (HRSD17) was used to measure efficacy. Safety was assessed with the Mini Mental State Examination (MMSE).

RESULTS

Both electrode placements resulted in highly significant downward trends in symptom severity (all p<0.001), with a non-significant difference between methods (p=0.703). At the end of the ECT course, response rates for the BF and RUL group were 63.9% and 67.6%, respectively. Short-term remission, defined as an HRSD17 score≤7, was achieved in 14 (38.9%) patients in the BF group and 19 (51.4%) patients in the RUL group. Global cognitive function, as measured by the MMSE, did not deteriorate in the two treatment groups.

LIMITATIONS

The small number of subjects may have led to reduced power to detect real differences. The MMSE is not sufficient to ascertain the negative effect of ECT on cognition.

CONCLUSIONS

This study indicates that formula-based BF and RUL ECT are equally efficacious, and that remission rates of formula-based dosing are lower than those previously reported for titrated dosing, in a clinical sample of elderly patients with MD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01559324.

Controlling stimulation strength and focality in electroconvulsive therapy via current amplitude and electrode size and spacing: comparison with magnetic seizure therapy

OBJECTIVES

Understanding the relationship between the stimulus parameters of electroconvulsive therapy (ECT) and the electric field characteristics could guide studies on improving risk/benefit ratio. We aimed to determine the effect of current amplitude and electrode size and spacing on the ECT electric field characteristics, compare ECT focality with magnetic seizure therapy (MST), and evaluate stimulus individualization by current amplitude adjustment.

METHODS

Electroconvulsive therapy and double-cone-coil MST electric field was simulated in a 5-shell spherical human head model. A range of ECT electrode diameters (2-5 cm), spacing (1-25 cm), and current amplitudes (0-900 mA) was explored. The head model parameters were varied to examine the stimulus current adjustment required to compensate for interindividual anatomical differences.

RESULTS

By reducing the electrode size, spacing, and current, the ECT electric field can be more focal and superficial without increasing scalp current density. By appropriately adjusting the electrode configuration and current, the ECT electric field characteristics can be made to approximate those of MST within 15%. Most electric field characteristics in ECT are more sensitive to head anatomy variation than in MST, especially for close electrode spacing. Nevertheless, ECT current amplitude adjustment of less than 70% can compensate for interindividual anatomical variability.

CONCLUSIONS

The strength and focality of ECT can be varied over a wide range by adjusting the electrode size, spacing, and current. If desirable, ECT can be made as focal as MST while using simpler stimulation equipment. Current amplitude individualization can compensate for interindividual anatomical variability.

The prefrontal cortex influence over subcortical and limbic regions governs antidepressant response by N=H/(M+R)

We review the evidence for relationships between metabolic activity of cortical, subcortical and limbic brain regions in depression and the efficacy of antidepressant agents. The influence of these regions can be described by an algebraic equation, N=H/(M+R), where N represents a homeostatic level of executive function, H represents prefrontal (Brodmann areas 9, 10, 11, 12; 46) and cingulate cortex activity (24, 25; 32), M represents subcortical (hippocampus, parahippocampal gyrus) influences, and R represents limbic (amygdala) influences. This hypothesis is based on depressed prefrontal cortex and enhanced amygdala and hippocampal metabolism in major depressive disorder, and the remission of these changes by most antidepressant interventions. The therapeutic efficacy of antidepressant strategies may depend less on their presumptive molecular mechanisms of action and more on their ability to restore the predominant metabolic and executive functions of the prefrontal cortex, and dampen excessive subcortical and limbic influences.

Impaired consciousness in epilepsy

Consciousness is essential to normal human life. In epileptic seizures consciousness is often transiently lost, which makes it impossible for the individual to experience or respond. These effects have huge consequences for safety, productivity, emotional health, and quality of life. To prevent impaired consciousness in epilepsy, it is necessary to understand the mechanisms that lead to brain dysfunction during seizures. Normally the consciousness system-a specialised set of cortical-subcortical structures-maintains alertness, attention, and awareness. Advances in neuroimaging, electrophysiology, and prospective behavioural testing have shed light on how epileptic seizures disrupt the consciousness system. Diverse seizure types, including absence, generalised tonic-clonic, and complex partial seizures, converge on the same set of anatomical structures through different mechanisms to disrupt consciousness. Understanding of these mechanisms could lead to improved treatment strategies to prevent impairment of consciousness and improve the quality of life of people with epilepsy.

Effect of white matter anisotropy in modeling electroconvulsive therapy

White matter in the brain exhibits strong anisotropic conductivity. Modeling studies on electroencephalography have found that such anisotropic conductivity greatly influences the estimated dipole source. In this study, we made a detailed comparison of the effects of conductivity anisotropy using a computational model of electroconvulsive therapy (ECT). The human head model was a high resolution finite element model generated from MRI scans, implemented with tissue heterogeneity and an excitable neural model incorporated in the brain. Results showed that anisotropy in conductivity had minimal effects on the location of the brain region that was maximally activated, but it had relatively large effects on deep brain structures.

Epilepsy and the consciousness system: transient vegetative state?

Recent advances have shown much in common between epilepsy and other disorders of consciousness. Behavior in epileptic seizures often resembles a transient vegetative or minimally conscious state. These disorders all converge on the "consciousness system" -the bilateral medial and lateral fronto-parietal association cortex and subcortical arousal systems. Epileptic unconsciousness has enormous clinical significance leading to accidental injuries, decreased work and school productivity, and social stigmatization. Ongoing research to better understand the mechanisms of impaired consciousness in epilepsy, including neuroimaging studies and fundamental animal models, will hopefully soon enable treatment trails to reduce epileptic unconsciousness and improve patient quality of life.

A computational model of direct brain excitation induced by electroconvulsive therapy: comparison among three conventional electrode placements

BACKGROUND

Electroconvulsive therapy (ECT) is a highly effective treatment for severe depressive disorder. Efficacy and cognitive outcomes have been shown to depend on variations in electrode placement and other stimulus parameters, presumably because of differences in the pattern of neuronal activation. This latter effect, however, is poorly understood.

OBJECTIVE

In this study, we present an anatomically accurate human head computational model to stimulate neuronal excitation during ECT, to better understand the effects of varying electrode placement and stimulus parameters.

METHODS

Electric field and current density throughout the head, as well as direct neural activation within the brain, were computed using the finite element method. Regions representing passive volume conductors (skin, skull, cerebrospinal fluid) were extracellularly coupled to an excitable neural continuum region representing the brain. The skull was modeled with anistropic electrical conductivity.

RESULTS

Simulation results indicated that direct activation of the brain occurred immediately beneath the electrodes on the scalp, consistent with existing imaging studies. In addition, we found that the brainstem was also activated using a right unilateral electrode configuration. Simulation also demonstrated that a reduction in stimulus amplitude or pulse width led to a reduction in the spatial extent of brain activation.

CONCLUSIONS

The novel model described in this study was able to simulate direct excitation of the brain during ECT, was useful in characterizing differences in neuronal activation as electrode placement, pulse width, and amplitude were altered, and is proposed as a tool for further exploring the effects of variations in ECT stimulation approaches. Results from the simulations assist in understanding recently described clinical phenomena, in particular, the reduction in cognitive side effects with ultrabrief pulse width stimulation, and greater effects of the ECT stimulus on cardiovascular function with unilateral electrode placement.

The default mode network and altered consciousness in epilepsy

The default mode network has been hypothesized based on the observation that specific regions of the brain are consistently activated during the resting state and deactivated during engagement with task. The primary nodes of this network, which typically include the precuneus/posterior cingulate, the medial frontal and lateral parietal cortices, are thought to be involved in introspective and social cognitive functions. Interestingly, this same network has been shown to be selectively impaired during epileptic seizures associated with loss of consciousness. Using a wide range of neuroimaging and electrophysiological modalities, decreased activity in the default mode network has been confirmed during complex partial, generalized tonic-clonic, and absence seizures. In this review we will discuss these three seizure types and will focus on possible mechanisms by which decreased default mode network activity occurs. Although the specific mechanisms of onset and propagation differ considerably across these seizure types, we propose that the resulting loss of consciousness in all three types of seizures is due to active inhibition of subcortical arousal systems that normally maintain default mode network activity in the awake state. Further, we suggest that these findings support a general “network inhibition hypothesis”, by which active inhibition of arousal systems by seizures in certain cortical regions leads to cortical deactivation in other cortical areas. This may represent a push-pull mechanism similar to that seen operating between cortical networks under normal conditions.

The effect of electrode placement and pulsewidth on asystole and bradycardia during the electroconvulsive therapy stimulus

Electroconvulsive therapy (ECT) is the most effective treatment for severe depression, and different forms are increasingly used in clinical practice. This study investigated the acute cardiac effects of different forms of ECT: bitemporal and bifrontal (1.5 times seizure threshold), and right unilateral (RUL) (five times seizure threshold). For RUL ECT, the effect of stimulus pulsewidth (1.0 or 0.3 ms) was also examined. Electrocardiograms recorded just prior to and during the ECT stimulus in 476 ECT treatments in 114 patients were examined. The degree of bradycardia (any slowing of heart rate) and incidence of asystole (absence of heart beats for ≥5 s) during the ECT stimulus were measured from these traces. Regression analyses estimated the contribution of patient and ECT treatment factors to the risk of bradycardia and asystole. Bifrontal ECT was associated with less severe bradycardia than bitemporal or RUL ECT (p<0.001). Modelling showed, for a mean pre-ECT heart rate of 85 beats per minute (bpm), expected heart rates during the stimulus were 78 bpm (bifrontal), 46 bpm (bitemporal) and 35 bpm (RUL). Bifrontal ECT was also associated with a lower incidence of asystole than RUL ECT (corrected odds ratio 1:207) and bitemporal ECT (corrected odds ratio 1:24). Ultrabrief pulsewidth stimulation resulted in lesser bradycardia and asystole than standard pulsewidth stimulation for RUL ECT. Modelling showed, for a mean pre-ECT heart rate of 86 bpm, expected heart rates were 43 bpm (ultrabrief RUL) and 26 bpm (RUL). Bradycardia and asystole were relatively common side-effects during the ECT stimulus. Bifrontal ECT was associated with the lowest risk of bradycardia and asystole during ECT and should be considered for patients at risk of arrhythmias and prolonged asystole during ECT.

A computational model of direct brain stimulation by electroconvulsive therapy

Electroconvulsive therapy (ECT) is the most effective treatment for severe depressive disorder, and yet the mechanisms of its therapeutic effects remain largely unknown. A novel computational model is presented in this study to simulate and investigate direct cortical excitation caused by bitemporal electroconvulsive therapy (BT ECT), using a finite element model (FEM) of the human head. The skull was modeled with anisotropic conductivity, with an excitable ionic neural model incorporated into the brain based on the classic Hodgkin-Huxley formulation. Results suggested that this model is able to reproduce direct stimulation of the cortex during the application of ECT.

Electric field strength and focality in electroconvulsive therapy and magnetic seizure therapy: a finite element simulation study

We present the first computational study comparing the electric field induced by various electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) paradigms. Four ECT electrode configurations (bilateral, bifrontal, right unilateral, and focal electrically administered seizure therapy) and three MST coil configurations (circular, cap, and double cone) were modeled. The model incorporated a modality-specific neural activation threshold. ECT (0.3 ms pulse width) and MST induced the maximum electric field of 2.1-2.5 V cm⁻¹ and 1.1-2.2 V cm⁻¹ in the brain, corresponding to 6.2-7.2 times and 1.2-2.3 times the neural activation threshold, respectively. The MST electric field is more confined to the superficial cortex compared to ECT. The brain volume stimulated was much larger with ECT (up to 100%) than with MST (up to 8.2%). MST with the double-cone coil was the most focal, and bilateral ECT was the least focal. Our results suggest a possible biophysical explanation of the reduced side effects of MST compared to ECT. Our results also indicate that the conventional ECT pulse amplitude (800-900 mA) is much higher than necessary for seizure induction. Reducing the ECT pulse amplitude should be explored as a potential means of diminishing side effects.

Electroconvulsive therapy simulations using an anatomically-realistic head model

Electroconvulsive therapy (ECT) is a highly effective treatment for severe depressive disorder. Efficacy and cognitive outcomes have been shown to depend on variations in treatment technique. A high resolution finite element model of a human head was generated from MRI scans and implemented with tissue heterogeneity and an excitable ionic neural model incorporated in the brain. The model was used to compare the effects of three common ECT electrode configurations, including the spatial profiles of electric field and excitation in the brain. The results showed that electrode placement has a significant effect in determining the spatial extent of activation in different brain regions, which would account for differences seen in clinical outcomes.

Focal BOLD fMRI changes in bicuculline-induced tonic-clonic seizures in the rat

Generalized tonic-clonic seizures cause widespread physiological changes throughout the cerebral cortex and subcortical structures in the brain. Using combined blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 9.4 T and electroencephalography (EEG), these changes can be characterized with high spatiotemporal resolution. We studied BOLD changes in anesthetized Wistar rats during bicuculline-induced tonic-clonic seizures. Bicuculline, a GABA(A) receptor antagonist, was injected systemically and seizure activity was observed on EEG as high-amplitude, high-frequency polyspike discharges followed by clonic paroxysmal activity of lower frequency, with mean electrographic seizure duration of 349 s. Our aim was to characterize the spatial localization, direction, and timing of BOLD signal changes during the pre-ictal, ictal and post-ictal periods. Group analysis was performed across seizures using paired t-maps of BOLD signal superimposed on high-resolution anatomical images. Regional analysis was then performed using volumes of interest to quantify BOLD timecourses. In the pre-ictal period we found focal BOLD increases in specific areas of somatosensory cortex (S1, S2) and thalamus several seconds before seizure onset. During seizures we observed BOLD increases in cortex, brainstem and thalamus and BOLD decreases in the hippocampus. The largest ictal BOLD increases remained in the focal regions of somatosensory cortex showing pre-ictal increases. During the post-ictal period we observed widespread BOLD decreases. These findings support a model in which "generalized" tonic-clonic seizures begin with focal changes before electrographic seizure onset, which progress to non-uniform changes during seizures, possibly shedding light on the etiology and pathophysiology of similar seizures in humans.

Cortical and subcortical networks in human secondarily generalized tonic-clonic seizures

Generalized tonic-clonic seizures are among the most dramatic physiological events in the nervous system. The brain regions involved during partial seizures with secondary generalization have not been thoroughly investigated in humans. We used single photon emission computed tomography (SPECT) to image cerebral blood flow (CBF) changes in 59 secondarily generalized seizures from 53 patients. Images were analysed using statistical parametric mapping to detect cortical and subcortical regions most commonly affected in three different time periods: (i) during the partial seizure phase prior to generalization; (ii) during the generalization period; and (iii) post-ictally. We found that in the pre-generalization period, there were focal CBF increases in the temporal lobe on group analysis, reflecting the most common region of partial seizure onset. During generalization, individual patients had focal CBF increases in variable regions of the cerebral cortex. Group analysis during generalization revealed that the most consistent increase occurred in the superior medial cerebellum, thalamus and basal ganglia. Post-ictally, there was a marked progressive CBF increase in the cerebellum which spread to involve the bilateral lateral cerebellar hemispheres, as well as CBF increases in the midbrain and basal ganglia. CBF decreases were seen in the fronto-parietal association cortex, precuneus and cingulate gyrus during and following seizures, similar to the 'default mode' regions reported previously to show decreased activity in seizures and in normal behavioural tasks. Analysis of patient behaviour during and following seizures showed impaired consciousness at the time of SPECT tracer injections. Correlation analysis across patients demonstrated that cerebellar CBF increases were related to increases in the upper brainstem and thalamus, and to decreases in the fronto-parietal association cortex. These results reveal a network of cortical and subcortical structures that are most consistently involved in secondarily generalized tonic-clonic seizures. Abnormal increased activity in subcortical structures (cerebellum, basal ganglia, brainstem and thalamus), along with decreased activity in the association cortex may be crucial for motor manifestations and for impaired consciousness in tonic-clonic seizures. Understanding the networks involved in generalized tonic-clonic seizures can provide insights into mechanisms of behavioural changes, and may elucidate targets for improved therapies.

Clinical use of ictal SPECT in secondarily generalized tonic-clonic seizures

Partial seizures produce increased cerebral blood flow in the region of seizure onset. These regional cerebral blood flow increases can be detected by single photon emission computed tomography (ictal SPECT), providing a useful clinical tool for seizure localization. However, when partial seizures secondarily generalize, there are often questions of interpretation since propagation of seizures could produce ambiguous results. Ictal SPECT from secondarily generalized seizures has not been thoroughly investigated. We analysed ictal SPECT from 59 secondarily generalized tonic-clonic seizures obtained during epilepsy surgery evaluation in 53 patients. Ictal versus baseline interictal SPECT difference analysis was performed using ISAS (http://spect.yale.edu). SPECT injection times were classified based on video/EEG review as either pre-generalization, during generalization or in the immediate post-ictal period. We found that in the pre-generalization and generalization phases, ictal SPECT showed significantly more regions of cerebral blood flow increases than in partial seizures without secondary generalization. This made identification of a single unambiguous region of seizure onset impossible 50% of the time with ictal SPECT in secondarily generalized seizures. However, cerebral blood flow increases on ictal SPECT correctly identified the hemisphere (left versus right) of seizure onset in 84% of cases. In addition, when a single unambiguous region of cerebral blood flow increase was seen on ictal SPECT, this was the correct localization 80% of the time. In agreement with findings from partial seizures without secondary generalization, cerebral blood flow increases in the post-ictal period and cerebral blood flow decreases during or following seizures were not useful for localizing seizure onset. Interestingly, however, cerebral blood flow hypoperfusion during the generalization phase (but not pre-generalization) was greater on the side opposite to seizure onset in 90% of patients. These findings suggest that, with appropriate cautious interpretation, ictal SPECT in secondarily generalized seizures can help localize the region of seizure onset.

A critical examination of bifrontal electroconvulsive therapy: clinical efficacy, cognitive side effects, and directions for future research

Bifrontal (BF) electroconvulsive therapy (ECT), although researched less extensively than bitemporal (BT) or right unilateral (RUL) ECT, has been suggested to be comparable to the other 2 electrode placements with respect to clinical efficacy while resulting in less cognitive impairment than BT ECT. Imaging studies have indicated that seizures induced by BF ECT affect the brain differently than BT or RUL ECT, in that BF ECT increases cerebral blood flow in the frontal lobes more intensely than either of the other 2 placements. Therefore, it is possible that the cognitive impairment manifested after a course of BF ECT could also be different than the impairment seen with BT and RUL ECT. Research conducted on cognitive impairment from BF ECT to date has been inadequate due to the use of nonspecific cognitive measures (such as the Mini-Mental Status Examination) or an inordinate focus on memory functioning (which is believed to be mostly subsumed in the temporal lobes). Because BF ECT increases cerebral blood flow in the frontal lobes more intensely than either of the other placements, research must instead focus on investigating the possible effects of BF ECT on executive functioning, which is believed to be subsumed in the frontal lobes. This is especially important because of the established relationship between executive dysfunction and depression and also because of the increasing popularity of BF ECT.

Double-blind randomized controlled study comparing short-term efficacy of bifrontal and bitemporal electroconvulsive therapy in acute mania

BACKGROUND

Bifrontal electrode placement is as efficacious as bitemporal placement during electroconvulsive therapy (ECT) in depression but is associated with fewer cognitive adverse effects. There are no studies comparing these techniques in acute mania. This study compared the short-term efficacy and adverse effects of bifrontal and bitemporal ECT in the treatment of acute mania.

METHOD

Thirty-six DSM-IV mania inpatients referred for ECT were recruited for study. They were randomized to receive bifrontal (BFECT; n = 17) or bitemporal (BTECT; n = 19) ECT. None of the subjects were on mood stabilizers during the course of ECT. Severity of mania was measured on the Young Mania Rating Scale (YMRS) before beginning ECT and then on Days 3, 7, 11, 14, and 21 of treatment. Cognitive functions were assessed eight hours after the fifth ECT session using the Mini-Mental Status Examination (MMSE), Paired Associate Learning Test, Complex Figure Test, Verbal Fluency Test (animals and fruits categories), and Trail Making Test, Part A.

RESULTS

The subjects in the two groups were comparable on sociodemographic and clinical variables, including severity of mania at baseline. They were also similar in ECT parameters, including seizure threshold and seizure duration. Mean YMRS scores showed faster decline in the BFECT than in the BTECT group. Kaplan-Meier survival analysis showed that a greater proportion of subjects in the BFECT group responded (50% reduction in YMRS score) significantly earlier than in the BTECT group. There were no significant differences between the groups in performance on cognitive function tests.

CONCLUSION

In this pilot study, mania patients treated with BFECT responded faster than those treated with BTECT, with comparable cognitive adverse effects. Since ECT is usually prescribed for rapid control of symptoms, BFECT may be preferred over BTECT in the treatment of acute mania.

Bifrontal versus bitemporal electroconvulsive therapy in severe manic patients

OBJECTIVES

To compare the efficacy and safety of moderate-dose bifrontal (BF) with low-dose bitemporal (BT) electroconvulsive therapy (ECT) in the treatment of patients with severe mania.

METHODS

In a parallel, double-blind, randomized clinical trial, 28 patients with severe mania admitted to a university hospital were assigned randomly to moderate-dose BF (n = 14) and low-dose BT (n= 14) ECT. The primary outcome measures included the Mini-Mental State Examination (MMSE) and the Young Mania Rating Scale (YMRS).

RESULTS

All patients received at least 6 sessions of ECT. The 2 groups did not show any difference in their baseline MMSE or YMRS scores (P > 0.05). There was a significant difference between the MMSE scores of the BF compared with the BT group after both the sixth ECT (P < 0.05) and final ECT treatments (P < 0.05). Young Mania Rating Scale scores did not differ between the 2 groups after either the sixth or the last ECT sessions (P > 0.05).

CONCLUSIONS

Moderate-dose BF ECT was as effective as BT ECT but was associated with fewer cognitive side effects in the treatment of patients with severe mania.

Ictal electroencephalographic correlates of posttreatment neuropsychological changes in electroconvulsive therapy: a hypothesis-generation study

OBJECTIVES

Electroconvulsive therapy (ECT) has been associated with memory and neuropsychological changes, but which features of ECT are associated with those changes have not been well investigated. The aim of this hypothesis-generation study was to examine correlations between ictal electroencephalographic (EEG) characteristics and cognitive side effects after ECT.

METHODS

Eight patients with major depressive disorder were examined with the Wechsler Memory Scale-Revised (WMS-R), the Stroop test, the Trail Making Test, and verbal fluency before and after ECT treatment. Seven ictal EEG measurements (eg, slow-wave phase amplitude, postictal suppression) were manually rated by 3 independent psychiatrists. The correlations between ictal EEG measurements, changes in WMS-R subset scores, and non-memory-related neuropsychological assessments were examined with Spearman rank correlation.

RESULTS

Verbal memory, general memory, attention/concentration, delayed memory of WMS-R subset scores, and the Stroop test scores improved significantly after ECT treatment. Postictal suppression and slow-wave amplitude correlated positively with delayed memory and visual/verbal discrepancy score. Slow-wave amplitude correlated negatively with letter fluency. The longer the polyspike wave duration, the higher the attention/concentration test results.

CONCLUSIONS

Certain ictal EEG measurements were associated with changes in several neuropsychological test results that had improved 2 weeks after the final ECT treatment. A hypothesis-testing study with a larger sample is needed to verify the relationships between EEG measurements and neuropsychological test performance.

Imaging onset and propagation of ECT-induced seizures

PURPOSE

Regions of seizure onset and propagation in human generalized tonic-clonic seizures are not well understood. Cerebral blood flow (CBF) measurements with single photon emission computed tomography (SPECT) during electroconvulsive therapy (ECT)-induced seizures provide a unique opportunity to investigate seizure onset and propagation under controlled conditions.

METHODS

ECT stimulation induces a typical generalized tonic-clonic seizure, resembling spontaneous generalized seizures in both clinical and electroencephalogram (EEG) manifestations. Patients were divided into two groups based on timing of ictal (during seizure) SPECT tracer injections: 0 s after ECT stimulation (early group), and 30 s after ECT (late group). Statistical parametric mapping (SPM) was used to determine regions of significant CBF changes between ictal and interictal scans on a voxel-by-voxel basis.

RESULTS

In the early injection group, we saw increases near the regions of the bitemporal stimulating electrodes as well as some thalamic and basal ganglia activation. With late injections, we observed increases mainly in the parietal and occipital lobes, regions that were quiescent 30 s prior. Significant decreases occurred only at the later injection time, and these were localized to the bilateral cingulate gyrus and left dorsolateral frontal cortex.

CONCLUSIONS

Activations in distinct regions at the two time points, as well as sparing of intermediary brain structures, suggest that ECT-induced seizures propagate from the site of initiation to other specific brain regions. Further work will be needed to determine if this propagation occurs through cortical-cortical or cortico-thalamo-cortical networks. A better understanding of seizure propagation mechanisms may lead to improved treatments aimed at preventing seizure generalization.

Regional cerebral blood flow changes in depression after electroconvulsive therapy

A large number of studies have documented regional cerebral blood flow (rCBF) abnormalities in depression. A smaller yet significant number of studies have examined changes in rCBF before and after treatment. The findings, however, have been variable with regard to changes before and after electroconvulsive therapy (ECT). A consecutive series of patients (n=10) with drug-resistant major depressive episode according to DSM-IV with 17-item Hamilton Rating Scale for Depression (HRSD) scores greater than or equal to 14 gave their informed consent and were studied with technetium-99m ethyl cysteinate dimer single-photon emission computed tomography (99mTc-ECD SPECT) before and after a course of ECT. The results were analyzed with statistical parametric mapping version 99. No region showed significant positive correlations between rCBF patterns of changes and HRSD changes, but three clusters emerged as showing significant negative correlations. These regions corresponded with left frontopolar gyrus, left amygdala, globus pallidus and nucleus accumbens, and left superior temporal gyrus. It was speculated that ECT affected both the prefrontal cortex, commonly assumed to be involved in depression, and the amygdala, known to play a central role in the processing of emotional stimuli, through the limbic-cortical-striatal-pallidal-thalamic circuit.

Nonconvulsive seizures in electroconvulsive therapy: further evidence of differential neurophysiological aspects of bitemporal versus bifrontal electrode placement

In recent years, attention has been focused on the role of electrode placement in determining efficacy and cognitive side effects of electroconvulsive therapy (ECT). In particular, interest in bifrontal electrode placement has increased. Some evidence indicates differential therapeutic, cognitive, and neurophysiological aspects of bifrontal versus bitemporal ECT. Occasionally in ECT practice, electroencephalographic seizure activity is manifested in the absence of motor convulsive activity, a phenomenon termed nonconvulsive seizures. This probably indicates isolated prefrontal seizure activity in the absence of motor strip involvement. We reviewed our records and found that bifrontally treated patients had a significantly higher incidence of nonconvulsive seizures in ECT than did bitemporally treated patients. Seizure threshold was also higher among the bifrontal patients. We hypothesize that this provides further evidence of differential neurophysiology of seizures induced with these 2 electrode placements.

Consciousness and epilepsy: why are patients with absence seizures absent?

Epileptic seizures cause dynamic, reversible changes in brain function and are often associated with loss of consciousness. Of all seizure types, absence seizures lead to the most selective deficits in consciousness, with relatively little motor or other manifestations. Impaired consciousness in absence seizures is not monolithic, but varies in severity between patients and even between episodes in the same patient. In addition, some aspects of consciousness may be more severely involved than other aspects. The mechanisms for this variability are not known. Here we review the literature on human absence seizures and discuss a hypothesis for why effects on consciousness may be variable. Based on behavioral studies, electrophysiology, and recent neuroimaging and molecular investigations, we propose absence seizures impair focal, not generalized brain functions. Impaired consciousness in absence seizures may be caused by focal disruption of information processing in specific corticothalamic networks, while other networks are spared. Deficits in selective and varying cognitive functions may lead to impairment in different aspects of consciousness. Further investigations of the relationship between behavior and altered network function in absence seizures may improve our understanding of both normal and impaired consciousness.

Focal network involvement in generalized seizures: new insights from electroconvulsive therapy

Generalized seizures are commonly thought to involve the entire brain homogeneously. However, recent evidence suggests that selective cortical-subcortical networks may be crucial for the initiation, propagation, and behavioral manifestations of generalized seizures, while other brain regions are relatively spared. Here we review previous studies, and describe a new human model system for the investigation of generalized seizures: single-photon emission computed tomography, ictal-interictal difference imaging of generalized tonic-clonic seizures induced by electroconvulsive therapy (ECT). Bitemporal ECT activates focal bilateral frontotemporal and parietal association cortex, sparing other regions; bifrontal ECT activates mainly prefrontal cortex; while in right unilateral ECT the left frontotemporal region is relatively spared. Associated midline subcortical networks are also involved. Focal verbal memory deficits parallel the focal regions involved in these neuroimaging studies. Further studies of this kind may elucidate specific networks in generalized tonic-clonic seizures, providing targets for new therapeutic interventions in epilepsy.