Automated CT perfusion analysis reveals medial temporal perfusion abnormalities during transient global amnesia

Introduction: The underlying pathophysiology of Transient global amnesia (TGA) remains elusive. Reports of perfusion abnormalities in TGA were inconsistent, but semi-automated analysis of perfusion CT (CTP) may improve reliability and precision of perfusion deficit detection. Methods: Per institutional protocol, all TGA patients undergo multiphasic contrast-CT with arch to vertex CT angiography, intracranial CT venography, MRI, and EEG upon admission. During the study period consecutive patients diagnosed with TGA underwent CTP during the early acute amnestic phase. We retrospectively reviewed the clinical and radiological findings. Results: Five patients (3 female. median age 71, range 47–74) fulfilled entry criteria. Automated CTP analysis revealed the absence of an ischemic core (defined by CBF < 30%) or conventionally defined clinically relevant hypoperfusion area (defined by Time-to-maximum (Tmax) >6 s) in any of the patients. However, four of the five patients demonstrated territories of benign oligemia defined as Tmax>4 s in areas supplied by the Posterior Cerebral Artery. Three of these four patients had clear involvement of the bilateral medial temporal lobes. None of the patients had epileptic activity on their EEG. Both CTA and MRI were normal apart for small foci of restricted diffusion in the hippocampus of four patients. Discussion: Deficits in perfusion were found in the hippocampi of 60% of patients in the acute phase of TGA using automated image analysis software. This method may provide a quick and simple method to detect these abnormalities. These perfusion abnormalities could help solidify the diagnosis at an early stage and may advance our understanding of this elusive syndrome.