Abnormal EEG Power Spectra in Acute Transient Global Amnesia: A Quantitative EEG Study

Abstract

Transient global amnesia (TGA) is a clinical syndrome characterized by retrograde and anterograde amnesia without other neurological deficits. Although electroencephalography (EEG) methods are commonly used in both clinical and research setting with TGA patients, few studies have investigated neurophysiological pattern in TGA using quantitative EEG (qEEG). The main aim of the present study was to extend these previous findings by exploring EEG power spectra differences between patients with acute TGA and healthy controls using the exact low-resolution brain electromagnetic tomography software (eLORETA). EEG was recorded during 5 minutes of resting state. Sixteen patients (mean age: 66.81 ± 7.94 years) during acute TGA and 16 healthy subjects were enrolled. All patients showed hippocampal or parahippocampal signal abnormalities in diffusion-weighted magnetic resonance imaging performed from 2 to 5 days after the onset of TGA. Compared with healthy controls, TGA patients showed a decrease of theta power localized in the temporal lobe (Brodmann areas, BAs 21-22-38) and frontal lobe (BAs 8-9-44-45). A decrease of EEG beta power in the bilateral precuneus (BA 7) and in the bilateral postcentral gyrus (BAs 3-4-5) was also observed in TGA individuals. Taken together, our results could reflect the neurophysiological substrate of the severe impairment of both episodic memory and autobiographical memory which affect TGA patients during the acute phase.

Transient Global Amnesia: Risk Factors, Imaging Features, and Prognosis

“…The patients with TGA and lesions on DWI were further examined using fMRI. Similar to the results of previous studies, 12,16,17,[20][21][22][23][24][25] our findings showed that the lesions on DWI were mainly located in the hippocampal CA1 area (Figure 3). Seven of the patients with TGA and hippocampal lesions on DWI were right-handed, suggesting that the left cerebral hemisphere was dominant.…”

“…Although several studies have reported an abnormal EEG in patients with TGA, they failed to diagnose epilepsy. 21 , 37 In most studies, the EEG of patients with TGA returns to normal after the patients have recovered from TGA, so the findings are not sufficiently convincing. In our study, eight patients underwent EEG, and their results were normal.…”

Power Spectral Differences between Transient Epileptic and Global Amnesia: An eLORETA Quantitative EEG Study

“…We show one exemplary subject for each condition TEA and TGA, PSA is shown with topographies of instantaneous frequency at each band (delta, theta, alpha, beta, gamma). Moreover, for each condition we show the topography in average beta power (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Spectral activity in the TEA patient is more scattered and beta power topography appears to be more asymmetric compared to TGA patients.…”

“…According to a recent study, only a small sub-group (about 26%) might show some non-specific acute abnormalities such as bilateral slowing [13]. Other studies on EEG spectral analysis in TGA patients found a diffuse symmetric decrease of beta and theta activity during the acute phase [14]. Meanwhile, there are no quantitative EEG (qEEG) studies describing spectral activity in patients with Transient Epileptic Amnesia.…”

EPIAMNE: A New Scoring System for Differentiating Transient EPIleptic AMNEsia from Transient Global Amnesia

“…In TGA patients, a prior qEEG study demonstrated a decrease in absolute theta power in fronto-temporal regions and a decrease in absolute beta power in the parietal lobe during the acute phase [ 16 ], while another work showed a marked reduction of absolute beta 1 and alpha power in the left temporo-parietal regions far from amnesia attack when compared with healthy controls [ 17 ]. More recently, our group demonstrated an increased beta power in the uncus and parahippocampal gyrus of the affected hemisphere of patients with TEA when compared to those affected by TGA [ 18 ].…”