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From the Department of Neurology (T.B., G.D.) and Section of Neuroradiology (K.A., S.W., A.R., O.J.), University Hospital Schleswig-Holstein, Kiel, Germany.
Address correspondence and reprint requests to Dr. T. Bartsch, Dept. of Neurology, University Hospital Schleswig-Holstein, Kiel, Schittenhelmstr. 10, 24105 Kiel, Germany t.bartsch{at}neurologie.uni-kiel.de
Objective: The pathomechanisms of transient global amnesia (TGA) remain enigmatic. Focal MR signal diffusion changes in the CA-1 sector of the hippocampus have been described in transient global amnesia, but the pathophysiologic correlate of these lesions is unknown.
Methods: We studied the metabolic spectra of diffusion lesions in the CA-1 sector hippocampus of seven patients with TGA using MR spectroscopy (MRS) between 24 and 72 hours after onset and 2 to 5 months later. The amnestic deficit was studied using a neuropsychometric test battery.
Results: Four out of seven patients with an acute TGA showed a diffusion lesion with a corresponding T2 lesion in the CA-1 sector of the hippocampus. Selective hippocampal MRS of diffusion lesions showed a lactate peak in three of four patients, but not in patients without a diffusion lesion. The NAA/creatine ratio was normal.
Conclusion: Lactate as a marker of anaerobic glycolysis indicates acute metabolic stress of CA-1 neurons in TGA whereas long-term neuronal metabolic changes are not found. This implies that the acute effect on hippocampal CA-1 neurons is the functional correlate of a transient global amnesia reflecting a transient perturbation of memory relevant circuits in the hippocampus.
Abbreviations: ACE = ACE inhibitor; ADC = apparent diffusion coefficient; artHT = arterial hypertension; asp = aspirin; CA = cornu ammonis; CHD = coronary heart disease; DWI = diffusion-weighted imaging; FOV = field of view; hypchol = hypercholesterolemia; MI = myocardial infarction; MRS = MR spectroscopy; RAVLT = Rey Auditory Verbal Learning and Recognition test; RFc = Rey-Osterrieth Complex Figure copy; RFr = Rey-Osterrieth delayed recall; TE = echo time; TGA = transient global amnesia; TI = inversion time; TR = repetition time; TSE = turbo spin echo.
Disclosure: The authors report no conflicts of interest.
Received August 19, 2007. Accepted in final form November 21, 2007.
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