Transient global amnesia: Only in already disrupted neuronal integrity of memory network?

Transient global amnesia is a well-described clinical syndrome; however, the pathophysiology is perplexing. Structural imaging indicates that punctuate hippocampal lesions are the representative pathophysiology, although functional neuroimaging studies have reported that the various regions comprising the episodic memory network are involved. We hypothesized that the neuronal integrity of the memory network might correlate with amnesia symptoms when there is any insult that can affect the hippocampus. Diffusion tensor images of 5 patients with variable diffusion-weighted imaging findings with or without transient global amnesia symptoms were analyzed. Diffusion tensor image analyses were performed using DTI studio software. A patient with a typical restricted diffusion involving the right hippocampus, but without memory symptoms, had more abundant cingulum fibers. However, the serial cingulum fibers of patients having experienced multiple attacks did not show a decremental tendency. The volume of fibers in the affected side was lower than that of the opposite side. This report suggests that memory-related symptoms of transient global amnesia are related to the disrupted neuronal integrity of cingulum fibers.