Exceptionally high initial seizure threshold in a patient treated with electroconvulsive therapy: a case report

Seizure threshold in electroconvulsive therapy (ECT) is defined as the smallest dose of electrical stimulus that produces a generalized seizure of at least 25 to 30 seconds as recorded by electroencephalography. Seizure thresholds vary considerably, with some patients demonstrating an exceptionally high initial seizure threshold. This case report describes a patient with schizoaffective disorder and an initial seizure threshold exceeding 1100 millicoulombs (mC), higher than can be delivered by the ECT device used.

A review of the literature was carried out to identify other reports of the phenomena.

Six articles reporting on 9 patients with mental illness and exceptionally high initial seizure thresholds were identified. These reports were of mainly elderly patients treated for severe depression. The initial seizure thresholds ranged from 335 to 896 mC. In 6 of the 9 cases, ECT was given bilaterally; and in these cases, the median initial seizure threshold was 624 mC (interquartile range, 274 mC).

Patients with exceptionally high initial seizure thresholds are rare, and few have been reported in the literature. The initial seizure threshold described in this case report is well in excess of others previously reported. The report highlights the potential for raised seizure thresholds in those taking mood-stabilizing antiepileptic medication.