Electroconvulsive therapy (ECT) is a highly effective treatment for severe psychiatric disorders. Despite its high efficacy, the use of ECT would be greater if the risk of cognitive side effects were reduced. Over the last 20 years, developments in ECT technique, including improvements in the dosing methodology and modification of the stimulus waveform, have allowed for improved treatment methods with reduced adverse cognitive effects. There is increasing evidence that the electrode placement is important for orienting the electrical stimulus and therefore modifying treatment outcomes, with potential for further improvement of the placements currently used in ECT.

We used computational modelling to perform an in-depth examination into regional differences in brain excitation by the ECT stimulus for several lesser known and novel electrode placements, in order to investigate the potential for an electrode placement that may optimise clinical outcomes.

High resolution finite element human head models were generated from MRI scans of three subjects. The models were used to compare regional differences in average electric field (EF) magnitude among a total of thirteen bipolar ECT electrode placements, i.e. three conventional placements as well as ten lesser known and novel placements.

In this exploratory study on a systemic comparison of thirteen ECT electrode placements, the EF magnitude at regions of interest (ROIs) was highly dependent upon the position of both electrodes, especially the ROIs close to the cortical surface. Compared to conventional right-unilateral (RUL) ECT using a temporo-parietal placement, fronto-parietal and supraorbito-parietal RUL also robustly stimulated brain regions considered important for efficacy, while sparing regions related to cognitive functions, and may be a preferrable approach to the currently used placement for RUL ECT. The simulations also found that regional average EF magnitude varied between individual subjects, due to factors such as head size, and results also depended on the size of the defined ROI.

Brief-pulse electroconvulsive therapy (ECT) is the most acutely effective treatment for severe depression though concerns persist about cognitive side-effects. While bitemporal electrode placement is the most commonly used form worldwide, right unilateral ECT causes less cognitive side-effects though historically it has been deemed less effective. Several randomized trials have now compared high-dose (>5× seizure threshold) unilateral ECT with moderate-dose (1.0–2.5× seizure threshold) bitemporal ECT to investigate if it is as effective as bitemporal ECT but still has less cognitive side-effects. We aimed to systematically review these trials and meta-analyse clinical and cognitive outcomes where appropriate.

We searched PubMed, PsycINFO, Web of Science, Cochrane Library and EMBASE for randomized trials comparing these forms of ECT using the terms ‘electroconvulsive’ OR ‘electroshock’ AND ‘trial’.

Seven trials (n = 792) met inclusion criteria. Bitemporal ECT did not differ from high-dose unilateral ECT on depression rating change scores [Hedges's g = −0.03, 95% confidence interval (CI) −0.17 to 0.11], remission (RR 1.06, 95% CI 0.93–1.20), or relapse at 12 months (RR 1.42, 95% CI 0.90–2.23). There was an advantage for unilateral ECT on reorientation time after individual ECT sessions (mean difference in minutes = −8.28, 95% CI −12.86 to −3.70) and retrograde autobiographical memory (Hedges's g = −0.46, 95% CI −0.87 to −0.04) after completing an ECT course. There were no differences for general cognition, category fluency and delayed visual and verbal memory.

High-dose unilateral ECT does not differ from moderate-dose bitemporal ECT in antidepressant efficacy but has some cognitive advantages.

To compare response, remission and switch (to other pulse width and/or electrode placement) rates and number of treatments between groups receiving right unilateral ultra-brief (RUL-UB), Bitemporal brief (BT), Bifrontal Brief (BF) and Right unilateral brief (RUL-B).

Data was collected from case notes in three centers. There were 133 in total, grouped as RUL-UB (50), BT (43), BF (23), RUL-B (17). Two of the three centers had a preferred electrode placement and pulse width.

Apart from age, the groups did not differ significantly on sex distribution, proportion of bipolar depression and psychotic symptoms. 56% of patients in RUL-UB switched compared to 12.5% in RUL-B, 4.9% in BT and none in BF (p value < 0.0001). When we considered patients who switched as treatment failures, remission rates were significantly different (p value < 0.0001) 40% in RUL-UB, 81.3% in RUL-B, 73.9% in BF and 78.0% in BT. Mean number of treatments in each group was significantly different (p value < 0.0001); 12.02 in RUL-UB, 10.2 in RUL-B, 7 in BF and 7.5 in BT. Post-hoc analysis indicated that RUL-UB differed significantly from BT and BF. Final response and remission rates including patients who switched were 98% and 82% in RUL-UB, 100% and 93.8% in RUL-B, 100% and 73.9% in BF and 97.7% and 83.7% in BT.

Majority commencing RUL-UB switched and received 4–5 more treatments compared to bilateral placements. RUL-UB ECT appears less effective and might not be appropriate as first line for all older adults as some patients at higher anaesthetic risk would benefit from having reduced number of treatments.