ECT-induced amnesia and postictal EEG suppression

Electroconvulsive Treatment: Hypotheses about Mechanisms of Action

No consensus has been reached on the mode of action of electroconvulsive treatment (ECT). We suggest that two features may aid in the delineation of the involved mechanisms. First, when effective, ECT would be likely to affect brain functions that are typically altered in its primary recipient group, people with severe depression. Central among these are the frontal and temporal lobes, the hypothalamus-pituitary-adrenal (HPA) stress axis, and the mesocorticolimbic dopamine system. Second, the involved mechanisms should be affected for a time period that matches the average endurance of clinical effects, which is indicated to be several days to a few weeks. To identify effects upon frontal and temporal lobe functioning we reviewed human studies using EEG, PET, SPECT, and fMRI. Effects upon the HPA axis and the dopamine system were assessed by reviewing both human and animal studies. The EEG studies indicate that ECT decelerates neural activity in the frontal and temporal lobes (increased delta and theta wave activity) for weeks to months. Comparable findings are reported from PET and SPECT studies, with reduced cerebral blood flow (functional deactivation) for weeks to months after treatment. The EEG deceleration and functional deactivation following ECT are statistically associated with reduced depression scores. FMRI studies indicate that ECT flattens the pattern of activation and deactivation that is associated with cognitive task performance and alters cortical functional connectivity in the ultra slow frequency range. A common finding from human and animal studies is that ECT acutely activates both the HPA axis and the dopamine system. In considering this evidence, we hypothesize that ECT affects the brain in a similar manner as severe stress or brain trauma which activates the HPA axis and the dopamine system and may compromise frontotemporal functions.

Management of poor postictal suppression during electroconvulsive therapy with propofol anesthesia: a report of two cases

There is increasing evidence that a greater degree of postictal suppression (the abruptness and magnitude of the EEG voltage drop at the end of the seizure) may be associated with better clinical response to electroconvulsive therapy. Retrospective studies have shown better postictal suppression when propofol is used for induction rather than the more commonly used methohexital. We report two patients in whom poor postictal suppression was rectified by switching from methohexital to propofol. The clinical significance of this improvement in postictal suppression is unclear, and prospective studies will be needed to clarify any clinical benefits.

Short bursts of weak pulses break postictal inhibition in the neocortex of Wistar rats

PURPOSE

Postictal inhibition (PI) is a decrease in excitability that follows an epileptic seizure and decreases probability of new seizure occurrence. PI may involve both increased inhibition and persisting elevated excitation. Our experiments tested whether shorter trains of weak stimuli are able to unmask this residual increase of excitability during the PI.

METHODS

Four epileptic afterdischarges (ADs) were evoked by intense electrical stimulation (20 s, 8 Hz, current intensity at 5x threshold) of the neocortex in two groups (A, B) of Wistar rats. Before the first AD and during the 10-min interictal period, 8-Hz trains of four weak pulses (half of the intensity used for the AD triggering; 4P) were applied every 20 s in group B and a single pulse with similar parameters in group A.

RESULTS

The number of interictal epileptiform events evoked by 4P in the group B was significantly higher than that in the group A (evoked by single pulses) except after the second AD. Epileptic events were triggered by 4P also immediately after the AD termination.

CONCLUSIONS

It is apparent that weak stimulation can trigger epileptic phenomena during PI. Our results indicate that it is no longer possible to perceive PI only as persisting extreme and active inhibition. An appropriate stimulation can reveal more subtle (but important) excitatory events contributing to the functional status during the postictal period.

Spikes immediately after electroconvulsive therapy in psychotic patients

The goal of this study was to assess the spikes systematically and to clarify an epileptc abnormality induced by electroconvulsive therapy (ECT). Our subjects were 20 psychotic patients with no spikes on prior EEGs. ECT was performed by applying electrical current to both sides of the patient's temple every 2 or 3 days for a period of between 1-4 weeks. The first EEG examination was performed either on the day that the ECT course was completed or on the following day. Subsequent EEG examinations were performed at intervals of 2 or 3 days. Thirteen of the 20 patients showed spikes. There were no significant differences in age, gender, diagnosis, or type of ECT. Patients with spikes had significantly more ECT sessions than those without spikes. The spikes were present in the frontal, temporal and central areas, predominantly frontal, anterior temporal and mid-temporal region, and almost disappeared in 1-3 weeks. The occurrence of spikes immediately after ECT was demonstrated. Although this abnormality was transient, it could indicate that in humans ECT causes the early stage of kindling phenomenon as a result of repeated application, and that the temporal lobe seems to play a major role in order to induce the phenomenon.

Mechanism underlying the therapeutic effects of electroconvulsive therapy (ECT) on depression

Electroconvulsive therapy (ECT) is used to treat drug-resistant depressive disorders. The results of studies on the mechanism underlying the effectiveness of ECT on depression are still controversial. ECT stimulus is usually larger than the threshold of induction of seizures and activation of whole-brain is believed to be necessary to produce therapeutic effects. A single ECT session induces alterations of the electroencephalogram (EEG) including initial epileptic discharges, then slow waves, and finally flattened EEG. Repeated ECT results in an increasing number of slower waves in the EEG for as long as a month. ECT-induced changes in various neurotransmitter systems have also been reported. Serotonin (5-hydroxytryptamine, 5-HT) is one of the most important neurotransmitters involved in depressive illness, and ECT alters several 5-HT-receptor subtypes in the central nervous system. 5-HT1A receptors in post-synaptic neurons are sensitized by repeated ECT, but those in pre-synaptic neurons (auto-receptors) are not changed. In addition, our electrophysiological studies have shown that ECT increases sensitivity to 5-HT of 5-HT3 receptors in the hippocampus, resulting in an increase in release of neurotransmitters such as glutamate and gamma-aminobutyric acid. In contrast, ECT decreases the auto-receptor functions in noradrenergic and dopaminergic neurons in the locus coeruleus and substantia nigra, respectively, resulting in an increase in release of noradrenaline and dopamine. In conclusion, 5-HT1A-receptor sensitization may be important for explaining the effectiveness of ECT, as this change induces a decrease in the number of 5-HT2A receptors that are elevated in depressive patients. Facilitation of neurotransmitter releases due to 5-HT3-receptor sensitization by ECT may also play an important role in effective treatment of depressive patients refractory to therapeutic drugs.

Electrophysiological and hormonal responses to three types of electroconvulsive therapy

Patients were treated with three different types of electroconvulsive therapy in random order in the first three sessions of their courses. Anaesthetic and muscle relaxants were administered in standard doses, and treatment applied a set time after bolus injection. Electroencephalographic recordings were undertaken before, during, and after treatment, and hormonal measures before and after. The responses to treatment differed between the three types of current in both EEG and prolactin measures. It is suggested that the quality of the convulsive response varies with different currents.