Temporal effects of bitemporal electroconvulsive therapy

The College’s professional practice guidelines (Weiss et al., 2019) for the administration of electroconvulsive therapy (ECT) emphasise a cost:benefit model (i.e. examining ways ‘to minimise cognitive side-effects while maintaining the high efficacy of ECT’). This model goes to the heart of the issue. In terms of benefit, the first author has long observed many patients (generally with melancholic or psychotic depression) respond completely to ECT after failing to obtain benefit from multiple drug regimes, while he continues to prescribe its use in certain circumstances, and thus has no intrinsic anti-ECT view.

Turning to the ‘cost’ side, in the last decade, the first author has been referred 3–6 patients/year for management of their ‘treatment resistant depression’ and who report having had ECT without benefit or with only transient benefit and who also report substantive and ongoing cognitive sequelae. Searching for signals for such a consequence, the seemingly most common element has been that the patient received bitemporal (BT) ECT throughout or at a later period within their course.

In terms of electrode placement, the College guidelines note that those ‘commonly in use are right unilateral (RUL), BT, and bifrontal (BF)’, thus effectively according bitemporal placement equal primary status. Later, however, the authors note that ‘retrograde memory changes, including autobiographical impairment, are more likely with BT placement and can last for weeks to months’ and that ‘long-term autobiographical memory impairment may persist permanently’, referencing a paper by Sackheim et al. (2007). The first author had difficulty in reconciling these two statements and turned to the second author (with high expertise in the field of ECT and a co-author of the guidelines paper) for clarification.

The second author notes that complexities of ECT prescribing have developed rapidly over the last three decades. From a prior ‘one size fits all’ model, with use of a default electrode placement, a single dose setting for all patients and all treatments and no electroencephalography (EEG) monitoring, considerable sophistication has been brought to ECT prescribing, based on knowledge gains from clinical research. These include selection from a choice of electrode placements, various settings of the stimulus pulse width, dosing individualised for each patient relative to their empirically determined seizure threshold and close monitoring of response, cognitive side-effects and seizure quality over the ECT course to inform ongoing adjustment of ECT dose. Importantly, it is the combination of the above factors that is critical in determining efficacy and cognitive outcomes, rather than any one parameter.

While it is true that bitemporal ECT results in more direct stimulation of the hippocampus (Bai et al., 2017), the risk of adverse memory effects also depends on ECT dosage (level and number of treatments) and pulse width. Indeed, research (Sackeim et al., 2008) has shown that pulse width has greater impact on memory outcomes than electrode placement (unilateral vs. bitemporal). Bitemporal ECT remains in common usage in the United Kingdom, Europe and Asia, but careful selection of when and how to use it is essential to its safe and effective use.

A related issue is that of ‘transient benefit’ after ECT. The literature shows that careful management of ECT (including tapering of treatments) and pharmacotherapy after the acute treatment phase is also essential in attaining lasting benefit (Gill and Kellner, 2019). Insufficient attention is often paid to this critical aspect of ECT treatment, with the result that the patient is left with no lasting benefit and, in the worst-case scenario, is left with cognitive deficits also.

The College has requirements for ECT in its registrar training programme. However, given the pace of development of knowledge in the field, any psychiatrist who has not updated his or her skills and knowledge in ECT in the last 5 years may not be equipped for best practice prescribing of ECT. It is incumbent on each psychiatrist prescribing ECT to familiarise himself or herself with the issues outlined above when directing ECT treatment. Furthermore, it is essential that all ECT services develop robust systems for monitoring clinical and cognitive outcomes both during and after an acute course and a system of clinical governance that facilitates regular review of those data, as well as careful oversight in relation to any potentially ‘unusual practices’ in order to facilitate optimisation of clinical outcomes informed by advances in research.