Jiri Lukavsky

Different Surgical Approaches for Mesial Temporal Epilepsy: Resection Extent, Seizure, and Neuropsychological Outcomes

Background: Surgical therapy of intractable mesial temporal lobe epilepsy (MTLE) is an effective and well-established treatment. Objectives: We compared two different surgical approaches, standard microsurgical anterior temporal resection (ATL) and stereotactic radiofrequency amygdalohippocampectomy (SAHE) for MTLE, with respect to the extent of resection or destruction, clinical outcomes, and complications. Material and Methods: 75 MTLE patients were included: 41 treated by SAHE (11 right sided, 30 left sided) and 34 treated by ATL (21 right sided, 13 left sided). Results: SAHE and ATL seizure control were comparable (Engel I in 75.6 and 76.5% 2 years after surgery and 79.3 and 76.5% 5 years after procedures, respectively). The neuropsychological results of SAHE patients were better than in ATL. In SAHE patients, no memory deficit was found. Hippocampal (60.6 ± 18.7%) and amygdalar (50.3 ± 21.9%) volume reduction by SAHE was significantly lower than by ATL (86.0 ± 12.7% and 80.2 ± 20.9%, respectively). The overall rate of surgical nonsilent complications without permanent neurological deficit after ATL was 11.8%, and another 8.8% silent infarctions were found on MRI. The rate of clinically manifest complications after SAHE was 4.9%. The rate of visual field defects after SAHE was expectably less frequent than after ATL. Conclusion: Seizure control by SAHE was comparable to ATL. However, SAHE was safer with better neuropsychological results.

Stereotactic radiofrequency amygdalohippocampectomy: Two years of good neuropsychological outcomes

PURPOSEnTo provide two-year seizure and neuropsychological outcomes in patients treated by stereotactic radiofrequency amygdalohippocampectomy (SAHE), an alternative, minimally invasive method for the treatment of mesial temporal lobe epilepsy (MTLE).nnnMATERIAL AND METHODSnThirty-seven MTLE patients treated by SAHE (26 left-sided, 11 right-sided) were included. Patients underwent neuropsychological evaluation by the Wechsler Adult Intelligence Scale-Revised and the Wechsler Memory Scale-Revised preoperatively, 1 year and 2 years after SAHE.nnnRESULTSnTwo years after SAHE twenty-eight (75.5%) patients were assessed as Engel Class I and seven (18.9%) patients as Engel Class II. In two patients (5.4%) treatment failed, one of them was classified as Class III and one as Class IV. Irrespective of the laterality of the procedure, the group improved significantly in Global and Verbal Memory Quotients, Attention, Delayed Recall, Semantic Long-term memory subtest and Working Memory. Additionally, increases in Full-scale, Verbal and Visual Intelligence Quotients were detected on the group level.nnnCONCLUSIONnIn the present study we report good seizure control and neuropsychological outcomes after SAHE in our patients. We hypothesize that good neuropsychological results were achieved by the incomplete destruction of target structures, sparing the lateral temporal neocortex, and also partially by practice effect. Treatment failures in seizure control may be attributed to larger epileptogenic zones.

Stereotactic radiofrequency amygdalohippocampectomy for the treatment of temporal lobe epilepsy: do good neuropsychological and seizure outcomes correlate with hippocampal volume reduction?

Temporal lobe surgery bears the risk of a decline of neuropsychological functions. Stereotactic radiofrequency amygdalohippocampectomy (SAHE) represents an alternative to mesial temporal lobe epilepsy (MTLE) surgery. This study compared neuropsychological results with MRI volumetry of the residual hippocampus. We included 35 patients with drug-resistant MTLE treated by SAHE. MRI volumetry and neuropsychological examinations were performed before and 1 year after SAHE. Each year after SAHE clinical seizure outcome was assessed. One year after SAHE 77% of patients were assessed as Engel Class I, 14% of patients was classified as Engel II and in 9% of patients treatment failed. Two years after SAHE 76% of subjects were classified as Engel Class I, 15% of patients was assessed as Engel II and in 9% of patients treatment failed. Hippocampal volume reduction was 58±17% on the left and 54 ± 27% on the right side. One year after SAHE, intelligence quotients of treated patients increased. Patients showed significant improvement in verbal memory (p=0.039) and the semantic long-term memory subtest (LTM) (p=0.003). Patients treated on the right side improved in verbal memory, delayed recall and LTM. No changes in memory were found in patients treated on the left side. There was a trend between the larger extent of the hippocampal reduction and improvement in visual memory in speech-side operated.

Relationship between remnant hippocampus and amygdala and memory outcomes after stereotactic surgery for mesial temporal lobe epilepsy.

Background and purpose Mesial temporal structures play an important role in human memory. In mesial temporal lobe epilepsy (MTLE), seizure activity is generated from the same structures. Surgery is the definitive treatment for medically intractable MTLE. In addition to standard temporal lobe microsurgical resection, stereotactic radiofrequency amygdalohippocampectomy (SAHE) is used as an alternative MTLE treatment. While memory impairments after standard epilepsy surgery are well known, it has been shown that memory decline is not a feature of SAHE. The aim of the present study was to correlate the volume of the remnant hippocampus and amygdala in patients treated by SAHE with changes in memory parameters. Materials and methods Thirty-seven MTLE patients treated by SAHE (ten right, 27 left) were included. Patients underwent magnetic resonance imaging examinations including hippocampal and amygdalar volumetry and neuropsychological evaluation preoperatively and 1 year after surgery. Results Using Spearman correlation analyses, larger left-sided hippocampal reductions were associated with lower verbal memory performance (ρ=−0.46; P=0.02). On the contrary, improvement of global memory quotient (MQ) was positively correlated with larger right-sided hippocampal reduction (ρ=0.66; P=0.04). Similarly, positive correlations between the extent of right amygdalar reduction and verbal MQ (ρ=0.74; P=0.02) and global MQ change (ρ=0.69; P=0.03) were found. Thus, larger right hippocampal and amygdalar reduction was associated with higher global and verbal MQ change after SAHE. Conclusion Larger left-sided hippocampal reductions were associated with lower verbal memory performance. This finding is in accordance with the material-specific model of human memory, which states that the dominant hemisphere is specialized for the learning and recall of verbal information. We hypothesize that larger right-sided ablations enable the left temporal lobe to support memory more effectively, perhaps as a consequence of epileptiform discharges spreading from remnants of right mesiotemporal structures to the left.

Predicting eye movements in multiple object tracking using neural networks

In typical Multiple Object Tracking (MOT) paradigm, the participants task is to track targets amongst distractors for several seconds. Understanding gaze strategies in MOT can help us reveal attentional mechanisms in dynamic tasks. Previous attempts relied on analytical strategies (such as averaging object positions). An alternative approach is to find this relationship using machine learning technique. After preprocessing, we assembled a dataset with 48,000 datapoints, representing 1534 MOT trials or 2.5 hours. In this study, we used feedforward neural networks to predict gaze position and compared predicted gaze with analytical strategies from previous studies using median distance. Our results showed that neural networks were able to predict eye positions better than current strategies. Particularly, they performed better when we trained the network with all objects, not targets only. It supports the hypothesis that people are influenced by distractor positions during tracking.

Models of eye movements in multiple object tracking with many objects

During everyday tasks, people often have to focus on several objects at once. As eye movements and attention are closely related, modeling eye movements can help us understand, where people attend to. In this study, we conducted an experiment in which participants had to track several moving objects at once while their eye gaze is being measured. We investigated, whether consistency of eye movements was affected by increasing number of objects on the scene during repeated presentations. We employed and extended several top-down models for predicting the eye gaze during such tasks. Results show that the presence of additional objects did not affect the coherence of scan patterns. The model accounting for the crowding effect yielded the best performance. Our results address the question of how the presence of visual clutter affects human eye behavior.

Robustness of metrics used for scanpath comparison

In every quantitative eye tracking research study, researchers need to compare eye movements between subjects or conditions. For both static and dynamic tasks, there is a variety of metrics that could serve this purpose. It is important to explore the robustness of the metrics with respect to artificial noise. For dynamic tasks, where eye movement data is represented as scanpaths, there are currently no studies regarding the robustness of the metrics. In this study, we explored properties of five metrics (Levenshtein distance, correlation distance, Fréchet distance, mean and median distance) used for comparison of scanpaths. We systematically added noise by applying three transformations to the scanpaths: translation, rotation, and scaling. For each metric, we computed baseline similarity for two random scanpaths and explored the metrics sensitivity. Our results allow other researchers to convert results between studies.

Contents Vol. 92, 2014

s 2014 Biennial Meeting of the American Society for Stereotactic and Functional Neurosurgery Washington, D.C., USA, May 31–June 3, 2014 Guest Editors: Slavin, K.V. (Chicago, Ill.); Sharan, A.D. (Philadelphia, Pa.); Gross, R.E. (Atlanta, Ga.); Lee, K.H. (Rochester, Minn.); Rezai, A.R. (Columbus, Ohio) (available online only)