HIPPOCAMPAL REVERSIBLE LESIONS IN A CASE OF TRANSIENT GLOBAL AMNESIA

PURPOSE: We present a case of transient global amnesia (TGA) onset in a 52-year-old male with a medical history of migraine. METHODS: Patient was taken to ER by his colleagues which reported that after an emotional stress he suddenly appeared perplexed and started asking repetitive questions. In ER a neurological examination excluded other neurological signs or symptoms and it was confirmed that cognitive impairment was limited to the amnesia domain; electroencephalography was unremarkable and he had no history of epileptic seizures or head trauma. At the neurologic examination Capland and Hodges criteria were fulfilled and the diagnostic hypothesis of TGA was placed. He underwent to a brain CT (Siemens SOMATOM Definition AS+ 128) and later he underwent to a brain MRI (GE Signa HDxt 1,5T). MRI protocol includes sagittal and axial T2w Fast Recovery Fast Spin Echo (FRFSE), axial and coronal T2w FLuid attenuated Inversion Recovery (FLAIR), axial T1w Fast Spin Echo (FSE), axial T2*w Gradient Echo (GE) and axial Echo-Planar Diffusion Weighted Imaging (EP-DWI, using a b value of 0 and 1000s/mm2). RESULTS: Brain CT and conventional MRI sequences did not show any relevant pathological findings but diffusion weighted imaging (DWI) showed two small areas of restricted diffusion in the right hippocampus. The amnesic syndrome resolved spontaneously within 24h; in a brain MRI follow-up performed two week later those findings were no more appreciable. CONCLUSION: DWI is very sensitive identifying the typical TGA lesions especially when a high b value (b > 1000s/mm2) is used combined to a thin section thickness (<5mm). Even if the diagnosis of TGA is primarily clinical, MRI can give a positive diagnostic support. The etiology and pathogenesis of this rare neurologic syndrome is still unclear: several factors, such as migraine-related mechanism, focal ischemia, venous flow abnormalities, and epileptic-like phenomena, have been suggested and/or hypothesized. Further studies are needed but it’s plausible that more advanced imaging techniques and will help to better understand the underlying mechanisms.