Acute Amnestic Syndrome in Fornix Lesions: A Case Series and a Systematic Review of The Literature

The fornix stands as a pivotal component in the intricate network of the limbic system. Its connections with the hippocampus, mammillary bodies, thalamus, and other structures emphasize its role in memory consolidation, emotional processing, and overall cognitive function(Nowrangi and Rosenberg, 2015). The overall vascular supply to the fornix is not completely defined, being the role of the sub-callosal artery (ScA) the first one to be described extensively. Acute amnestic syndromes exhibit variable epidemiology, with an annual incidence influenced by diverse etiologies. Each syndrome's occurrence is influenced by distinct risk factors, contributing to the nuanced epidemiological landscape of acute amnestic disorders. The hallmark feature is memory deficit, especially affecting episodic memory, which involves personal experiences and events not only in a temporal but also spatial context (Douet and Chang, 2015). To assess the role of the fornix in acute amnestic syndrome and the main differential diagnosis of this syndrome, we first describe two cases of acute ischemic stroke involving the fornix and then we systematically review the existing literature on the topic. we employed the use of PubMed, Scopus and Web of science. Two distinct evaluators reviewed the tittles, and titles describing fornix lesions due to iatrogenic injury were discarded. The results showed that out of 52 texts 55 clinical cases have been extracted. As expected, vascular etiology was the most common culprit, linked in 43/55 cases reported. The memory defcit observed was anterograde in the majority of patients and anterograde in a minor part of about 32% of cases, and symptoms persisted in a large number of reports. Acute amnestic syndrome is an uncommon clinical presentation and poses a significant diagnostic challenge. Apart from surgical cases, where the diagnosis is straightforward, several different etiologies should be considered. However, when the symptom onset is hyperacute, as for other neurological syndromes, the most relevant etiology is cerebrovascular disease. In particular, our study confirm that the ScA is the main culprit vessel, and, in the majority of cases, the etiology of stroke is small vessel disease. Our two cases, as well as our literature review, strengthen these findings and point to the importance of considering a vascular etiology also in young patients without obvious traditional vascular risk factors.