A case of recurrent transient global amnesia: don't forget the hippocampal punctuate diffusion restriction

Abstract

Transient global amnesia (TGA) is a syndrome characterized by reversible impairment of short-term memory. TGA itself is a benign disease, however, it is reasonable to investigate and exclude sinister causes of global amnesia; such as stroke or a seizure activity. A case of TGA is presented here with special emphasis on the typical TGA lesion that was detected on the patient's magnetic resonance imaging (MRI) of Brain. In patients with TGA, the typical MRI Brain finding is a tiny focus of diffusion restriction in the mesiotemporal lobe. This finding can potentially aid in early diagnosis and management of TGA. Although in overwhelming majority of cases, the TGA episode occurs only once, yet a second TGA episode can occur rarely. This patient, two years later, had a recurrence of TGA episode, albeit with a normal MRI brain, and without residual changes from prior episode.

Figure 1:

(a) Axial MRI brain, DWI sequence shows punctuate high signal in medial temporal lobe, as pointed out by white arrow. (b) Corresponding ADC mapping shows signal loss as pointed out by black arrow

Figure 2:

Axial MRI brain, T2 weighted imaging (a) and FLAIR sequences (b) do not reveal any residual signal changes at corresponding location of the prior right medial temporal lobe DWI lesion.