Risk factors for spatial memory impairment in patients with temporal lobe epilepsy Jana Amlerova a , Jan Laczo a, b , Kamil Vlcek b, c , Alena Javurkova d , Ross Andel b, e , Petr Marusic a, ⁎ a Department of Neurology, Charles University in Prague, 2nd Faculty of Medicine, University Hospital Motol, Prague, Czech Republic b International Clinical Research Center, St. Anne's University Hospital Brno, Brno, Czech Republic c Department of Neurophysiology of Memory, Institute of Physiology Academy of Sciences of the Czech Republic v.v.i., Prague, Czech Republic d Department of Psychology, University Hospital Motol, Prague, Czech Republic e School of Aging Studies, University of South Florida, Tampa, Florida, USA abstract article info Article history: Received 15 August 2012 Revised 19 September 2012 Accepted 8 October 2012 Available online 3 December 2012 Keywords: Spatial navigation Spatial memory Temporal lobe epilepsy Epilepsy onset Epilepsy duration Intelligence level At present, the risk factors for world-centered (allocentric) navigation impairment in patients with temporal lobe epilepsy (TLE) are not known. There is some evidence on the importance of the right hippocampus but other clinical features have not been investigated yet. In this study, we used an experimental human equiv- alent to the Morris water maze to examine spatial navigation performance in patients with drug-refractory unilateral TLE. We included 47 left-hemisphere speech dominant patients (25 right sided; 22 left sided). The aim of our study was to identify clinical and demographic characteristics of TLE patients who performed poorly in allocentric spatial memory tests. Our results demonstrate that poor spatial navigation is significantly associated with younger age at epilepsy onset, longer disease duration, and lower intelligence level. Allocentric navigation in TLE patients was im- paired irrespective of epilepsy lateralization. Good and poor navigators did not differ in their age, gender, or preoperative/postoperative status. This study provides evidence on risk factors that increase the likelihood of allocentric navigation impairment in TLE patients. The results indicate that not only temporal lobe dysfunction itself but also low general cog- nitive abilities may contribute to the navigation impairment. © 2012 Elsevier Inc. All rights reserved. 1. Introduction Spatial memory is a cognitive ability with an important impact on everyday life. Two basic strategies for spatial navigation – egocentric and allocentric – have been described [1]. Using the egocentric strategy, individuals determine the position of targets in an environment relative to their body and independently of distant landmarks. Using the allocentric strategy, landmarks and their spatial relationship to the target are used to create a cognitive map of the environment [2,3]. Egocentric navigation is localized extra-temporally, in the parietal cortex and in the striatum [4,5], while the allocentric navigation is controlled by the mesial temporal lobe structures, especially the hippocampus, parahippocampus, and adjacent regions [6,7]. A human equivalent to the Morris water maze has been found to reliably differentiate between the egocentric and allocentric components of spatial navigation [8,9]. Patients with temporal lobe epilepsy (TLE), more frequently those with right-sided epilepsy, were found to have impaired allocentric navigation [6,10–12]. However, recent studies have indicated that cooperation of both temporal regions is required for successful spatial navigation and that left-sided TLE patients may also be impaired [13–16]. We used the Hidden Goal Task, a human equivalent to the Morris water maze, in a large series of patients with drug-refractory unilater- al TLE. The aim of our study was to identify demographic and clinical characteristics of TLE patients associated with allocentric spatial memory impairment. 2. Methods 2.1. Participants We recruited 47 patients with TLE (25 right sided; 22 left sided) who underwent temporal lobe resection for drug-refractory epilepsy. Preoperative evaluation was performed at the Epilepsy Centre, Uni- versity Hospital Motol in Prague using a noninvasive protocol — neurological history/examination, routine EEG, long-term video-EEG monitoring, MRI, neuropsychological testing, and bilateral carotid sodium amobarbital/methohexital testing or fMRI for language. According to electro-clinical findings, all patients had a diagnosis of Epilepsy & Behavior 26 (2013) 57–60 Abbreviations: TLE, temporal lobe epilepsy; FSIQ, full scale IQ; VIQ, verbal IQ; PIQ, performance IQ. ⁎ Corresponding author at: Department of Neurology, Charles University in Prague, 2nd Faculty of Medicine, University Hospital Motol, V Uvalu 84, Prague 5, Motol, 150 06, Czech Republic. Fax: +420 224436875. E-mail address: petr.marusic@fnmotol.cz (P. Marusic). 1525-5050/$ – see front matter © 2012 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.yebeh.2012.10.025 Contents lists available at SciVerse ScienceDirect Epilepsy & Behavior journal homepage: www.elsevier.com/locate/yebeh