Brain Advance Access originally published online on December 10, 2008
Brain 2009 132(2):357-368; doi:10.1093/brain/awn336
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Transient epileptic amnesia: regional brain atrophy and its relationship to memory deficits
1 Division of Clinical Neurosciences, University of Edinburgh, Edinburgh, UK 2 Department of Surgery, Homerton University Hospital, London, UK 3 Department of Clinical Neurosciences, Addenbrooke's Hospital, Cambridge, UK 4 Wales Institute of Cognitive Neuroscience, Cardiff University, Cardiff, UK 5 Prince of Wales Medical Research Institute, University of New South Wales, Sydney, Australia 6 Department of Neurology, Peninsula Medical School, Exeter, UK
Correspondence to: Dr C. R. Butler, Bramwell-Dott Building, Department of Clinical Neurosciences, Western General Hospital, Edinburgh EH4 2XU, UK E-mail: chris.butler{at}ed.ac.uk
Transient epileptic amnesia (TEA) is a recently recognised form of epilepsy of which the principle manifestation is recurrent, transient episodes of isolated memory loss. In addition to the amnesic episodes, many patients describe significant interictal memory difficulties. Performance on standard neuropsychological tests is often normal. However, two unusual forms of memory deficit have recently been demonstrated in TEA: (i) accelerated long-term forgetting (ALF): the excessively rapid loss of newly acquired memories over a period of days or weeks and (ii) remote autobiographical memory loss: a loss of memories for salient, personally experienced events of the past few decades. The neuroanatomical bases of TEA and its associated memory deficits are unknown. In this study, we first assessed the relationship between subjective and objective memory performance in 41 patients with TEA. We then analysed MRI data from these patients and 20 matched healthy controls, using manual volumetry and voxel-based morphometry (VBM) to correlate regional brain volumes with clinical and neuropsychological data. Subjective memory estimates were unrelated to performance on standard neuropsychological tests but were partially predicted by mood, ALF and remote autobiographical memory. Manual volumetry identified subtle hippocampal volume loss in the patient group. Both manual volumetry and VBM revealed correlations between medial temporal lobe atrophy and standard anterograde memory scores, but no relation between atrophy and ALF or remote autobiographical memory. These results add weight to the hypothesis that TEA is a syndrome of mesial temporal lobe epilepsy. Furthermore, they suggest that although standard anterograde memory test performance is related to the degree of mesial temporal lobe damage, this is not true for ALF and autobiographical amnesia. It is possible that these unusual memory deficits have a more diffuse physiological basis rather than being a consequence of discrete structural damage.
Key Words: transient epileptic amnesia; memory; epilepsy; MRI; voxel-based morphometry
Abbreviations: ALF, accelerated long-term forgetting; EMQ, everyday memory questionnaire; MTL, medial temporal lobe; MAMI, Modified Autobiographical Memory Interview; TIV, total intracranial volume; TLE, temporal lobe epilepsy; TGA, transient global amnesia; TEA, transient epileptic amnesia; VBM, voxel-based morphometry
Received July 18, 2008. Revised October 18, 2008. Accepted November 14, 2008.