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57th Annual Meeting of the German Society of Neurosurgery
Joint Meeting with the Japanese Neurosurgical Society

German Society of Neurosurgery (DGNC)

11 - 14 May, Essen

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Connectivity of the hippocampal mossy fibre system in patients with temporal lobe epilepsy

Neuronale Verbindung des Moosfasersystems im Hippocampus von Patienten mit Temporallappenepilepsie

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  • corresponding author T.M. Freiman - Neurochirurgische Klinik, Albert-Ludwigs-Universität Freiburg
  • M. C. Müller - Neurochirurgische Klinik, Albert-Ludwigs-Universität Freiburg
  • J. Zentner - Neurochirurgische Klinik, Albert-Ludwigs-Universität Freiburg
  • C. Haas - Abt. Experimentelle Epilepsieforschung, Neurochirurgische Klink, Albert-Ludwigs-Universität Freiburg
  • M. Frotscher - Abteilung für Neuroanatomie, Institut für Anatomie und Zellbiologie, Albert-Ludwigs-Universität Freiburg

Deutsche Gesellschaft für Neurochirurgie. Japanische Gesellschaft für Neurochirurgie. 57. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), Joint Meeting mit der Japanischen Gesellschaft für Neurochirurgie. Essen, 11.-14.05.2006. Düsseldorf, Köln: German Medical Science; 2006. DocP 02.9

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/meetings/dgnc2006/06dgnc226.shtml

Published: May 8, 2006

© 2006 Freiman et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

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Objective: Temporal lobe epilepsy is frequently associated with Ammon’s horn sclerosis which is characterised by neuronal death and sclerosis in the hippocampal regions CA1 and hilus. Additionally, there is a reorganisation of mossy fibres in the dentate gyrus, known as mossy fibre sprouting. This sprouting is characterised by an abnormal projection of granule cell axon collaterals backwards to the granule cell layer. It has been proposed that sprouting contributes to seizure generation by forming a local excitatory feedback circuit of granule cells. However, data obtained in animal models show also a connection of sprouted mossy fibres with inhibitory basket cells.

Methods: We examined the connectivity of mossy fibres in neurosurgical specimens of patients with temporal lobe epilepsy using a novel tracing technique. In addition, double immunolabeling and electron microscopy were applied to identify putative target cells of the sprouting mossy fibres.

Results: We have shown that excitatory granule cell axons (mossy fibres) impinge both on excitatory granule cells and inhibitory interneurons. Granule cells were identified by direct tracer application and synaptoporin IHC; inhibitory interneurons (basket cells) were identified by parvalbumin IHC and GABA-postembedding immunogold electron microscopy.

Conclusions: These results suggest that backsprouted mossy fibres do not only lead to an excitatory feedback circuit but also innervate inhibitory basket cells. We hypothesise that this aberrant innervation of interneurons not only results in an increased inhibition of dentate granule cells, but may contribute to the synchronisation of this network.

Supported by the Deutsche Forschungsgemeinschaft: TR-3 and Graduiertenkolleg 843