IS THERE AN OPTIMAL ELECTRODE PLACEMENT FOR PATIENTS WITH SCHIZOPHRENIA UNDERGOING ELECTROCONVULSIVE THERAPY?
Authors: Tan *Weng Jun , Foo Jenies Hui Xin , Choo Kimberly Wan Xin , Tor Phern Chern 
Published: February 2025

Abstract

Background
Electroconvulsive therapy (ECT) using the 3 common electrode placements, namely bitemporal, bifrontal and right unilateral (RUL) modalities, has been shown to be efficacious in symptom-reduction in patients with schizophrenia (Ali et al., 2019). However, the most efficacious modality for the treatment of schizophrenia has not been ascertained. Furthermore, the benefit of switching ECT modalities after poor response to the initial electrode placement has not been well-studied.

Aims And Objectives
We hypothesise that different patients with schizophrenia respond well to a particular ECT modality but not to another. These patients would benefit from switching ECT modalities once a lack of response to the initial modality is identified. Hence, we aim to illustrate the twin issues of the optimal ECT modality and the effect of switching ECT modalities after initial non-response in patients with schizophrenia.

Method
We report a case series of two distinct patients with schizophrenia who underwent multiple courses of both bifrontal and RUL ECT. Their response to ECT was objectively assessed by comparing their scores on the Brief Psychiatric Rating Scale (BPRS) and the Global Assessment of Functioning (GAF) scale prior to the commencement of ECT with their scores after the 6th and 12th sessions of ECT. The Montreal Cognitive Assessment (MoCA) was used to assess for cognitive side effects of ECT.

Results
Both patients showed good response to at least one previous course of bifrontal ECT. Subsequently, they were given 6 sessions of RUL ECT with the aim to minimise cognitive side effects, but their response to RUL ECT was poor. However, after they were switched back to bifrontal ECT, they showed marked improvement in their BPRS and GAF scores. Furthermore, one of the patients had a better MoCA score after he was switched back to bifrontal ECT than when he had received RUL ECT.

Discussion And Conclusion
As both patients had lacked response to RUL ECT but consistently responded well to bifrontal ECT, we believe that different patients with schizophrenia only respond well to a certain type of ECT modality. This is possibly because the pattern and degree of brain stimulation can be affected by the type of electrode placement which influences the strength and distribution of the electric field generated by the ECT stimulus (Bai et al., 2017; Bai et al., 2019; Lee et al., 2010), as well as anatomical differences such as head-size and skull-thickness (Bai et al., 2019; Fridgeirsson et al., 2021). In conclusion, there is no optimal ECT modality for the treatment of schizophrenia currently. Patients present with a variety of demographics, anatomy and severity of symptoms, and hence we believe that the prescription of ECT should be individualised, rather than employ a “one size fits all” approach. If response to a particular type of ECT modality is insufficient after 6 sessions, a switch to a different modality should be strongly considered as adequate response may only be achieved using a different ECT modality that is unique to the individual patient.

References
[1]Ali, SA. et al. (2019) ‘Electroconvulsive therapy and schizophrenia: a systematic review’, Mol Neuropsychiatry. 5(2), pp. 75-83. doi:10.1159/000497376.
[2]Bai, S. et al. (2017) ‘Computational models of bitemporal, bifrontal and right unilateral ECT predict differential stimulation of brain regions associated with efficacy and cognitive side effects’, Eur Psychiatry. 41, pp. 21-29. doi:10.1016/j.eurpsy.2016.09.005.
[3]Bai, S. et al. (2019) ‘Computational comparison of conventional and novel electroconvulsive therapy electrode placements for the treatment of depression’, Eur Psychiatry. 60, pp. 71-78. doi:10.1016/j.eurpsy.2019.05.006.
[4]Lee, WH. et al. (2010) ‘Regional electric field induced by electroconvulsive therapy: a finite element simulation study’, Annu Int Conf IEEE Eng Med Biol Soc. 2010, pp. 2045-2048. doi:10.1109/IEMBS.2010.5626553.
[5]Fridgeirsson, EA. et al. (2021) ‘Electric field strength induced by electroconvulsive therapy is associated with clinical outcome’, Neuroimage Clin. 30, pp. 102581. doi:10.1016/j.nicl.2021.102581.