A-42 Case of Persistent Amnestic Syndrome due to Small Right-Sided Retrosplenial Lacunes

Abstract

Abstract Objective Lesions to the retrosplenial cortex secondary to acute stroke or tumor have been shown to disrupt Papez’s circuit due to disconnection between the anterior thalamus and hippocampus, via the posterior cingulate, producing an amnestic syndrome. This case demonstrates how small but strategic lacunes in this region may produce memory deficits. Method The patient is a 52-year-old, right-handed, African-American woman with 18 years of education who reported memory changes over the last 8 years (e.g., misplacing items, forgetting details of conversations). Her medical history was notable for BMI of 31 and borderline diabetes. She completed structural magnetic resonance imaging 6 years prior to, and concordant with, her neuropsychological evaluation. Both scans showed two small (2-3 mm) right-sided retrosplenial lacunes, without evidence of hippocampal or global volume loss over the 6-year span. Results Her neurocognitive profile was characterized by impairments in both verbal (stories, word-list) and figural memory, with relative strengths in attention, processing speed, and executive functioning. Across memory measures, she performed in the low average-to-mildly impaired range on immediate recall, mildly-to-severely impaired range on delayed recall, and did not benefit from yes-no recognition format. She demonstrated additional features of an amnestic profile, including flat learning slope, recency effect, elevated cued recall intrusion errors, and very elevated false positive errors on recognition. Conclusions Findings expand upon the existing literature to show that chronic, small retrosplenial lacunes can disrupt the connection between the anterior thalamus and hippocampus, resulting in a clinical presentation of circumscribed memory impairment that persists years beyond acute vascular changes.