A 70-year-old man receives a course of bilateral electroconvulsive therapy for severe depression. He improves markedly but complains of difficulty recalling events from the months surrounding the treatment course. What is the most likely explanation?

• A Anterograde amnesia due to hippocampal neurogenesis
• B Drug-induced amnesia from succinylcholine
• C Permanent diffuse cortical damage from electrical current
• D Retrograde amnesia related to temporal lobe stimulation, more pronounced with bilateral electrode placement ✓

Explanation

The commonest adverse cognitive effect of ECT is retrograde amnesia for events close in time to the treatment, usually patchy and improving over months. Bilateral electrode placement produces more memory disturbance than unilateral right-sided placement, so unilateral brief-pulse ECT is preferred when cognition matters. Anterograde amnesia can also occur but is less characteristic here, and succinylcholine causes transient paralysis, not amnesia.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

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Written and medically reviewed by the StethoPrep medical team.