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Abstract
Major depressive disorder (MDD) is one of the most prevalent psychiatric disorders worldwide. The most effective treatment of MDD is electroconvulsive therapy (ECT). Despite the high efficacy of ECT, its use has been limited due to its side effects, particularly cognitive side effects. Currently, the standard unilateral ECT electrode placement used in clinical practice is the temporoparietal (TP) placement but no study has shown that TP ECT is necessarily superior to other unilateral variants. This Masters thesis sought to investigate alternative unilateral placements to further optimise ECT clinical outcomes. In the first study, a systematic review was conducted to compare different unilateral placements with regards to efficacy and cognitive effects. After screening against the study inclusion criteria, a total of 29 studies were included for review. Results showed different unilateral placements have comparable efficacy but varied cognitive side effect profiles. Relative to TP placement, ECT with frontofrontal (FF) and frontoparietal (FP) placements were suggestive of better cognitive outcomes. In the second study, a pilot randomised controlled trial was implemented to compare TP ECT and FP ECT coupled with ultrabrief pulsewidth (UBP) and brief pulsewidth (BP) waveforms. Nine participants were randomised to a sequence of four different ECT conditions. Preliminary results suggested that, in relation to reorientation time, BP TP condition was associated with relatively longer time to reorientation than the other three conditions. Regarding memory outcomes for material learnt immediately before ECT (i.e., retrograde amnesia), UBP ECT seemed to be associated with better performance compared to BP ECT, irrespective of electrode placement. However, with the small sample size of this pilot study, no significant conclusions could be drawn yet. The implication of the systematic review is unilateral variants such as FF placement, despite the potential advantage of less visual memory side effects, were poorly understood, which warrants further research into such alternative unilateral variants. In addition, the preliminary results from the pilot study showed some advantage of UBP over BP ECT with both FP and TP placements in less acute retrograde memory side effects. This provides support for the optimisation of unilateral ECT through modifying the waveform.