gms | German Medical Science

67th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Korean Neurosurgical Society (KNS)

German Society of Neurosurgery (DGNC)

12 - 15 June 2016, Frankfurt am Main

Mossy fibres innervate excitatory granule cells and inhibitory basket cells in hippocampi of patients with temporal lobe epilepsy

Meeting Abstract

  • Thomas M. Freiman - Klinik für Neurochirurgie, Universitätsklinikum, Goethe-Universität, Frankfurt am Main, Germany; Klinik für Neurochirurgie, Universitätsklinikum, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany
  • Kathrin Leicht - Klinik für Neurochirurgie, Universitätsklinikum, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany
  • Mortimer Gierthmuehlen - Klinik für Neurochirurgie, Universitätsklinikum, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany
  • Josef Zentner - Klinik für Neurochirurgie, Universitätsklinikum, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany
  • Carola A. Haas - Experimentelle Epilepsieforschung der Klinik für Neurochirurgie, Universitätsklinikum, Albert-Ludwigs-Universität, Freiburg im Breisgau, Germany

Deutsche Gesellschaft für Neurochirurgie. 67. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 1. Joint Meeting mit der Koreanischen Gesellschaft für Neurochirurgie (KNS). Frankfurt am Main, 12.-15.06.2016. Düsseldorf: German Medical Science GMS Publishing House; 2016. DocMI.18.04

doi: 10.3205/16dgnc345, urn:nbn:de:0183-16dgnc3451

Published: June 8, 2016

© 2016 Freiman et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.


Outline

Text

Objective: Temporal lobe epilepsy is frequently associated with hippocampal sclerosis, characterised by a selective loss of mossy cells in the hilus and of pyramidal cells in CA1. Granule cells survive, but their axons, the mossy fibres, sprout backwards to the granule cell layer, because they have lost the mossy cells as target cells, through mossy cell death. It has been suggested so far, that this leads to excitatory circuits. We examined whether sprouted mossy fibres impinge only excitatory granule cells or also inhibitory interneurons such as basket cells, which might be present in a smaller number.

Method: Resected hippocampal specimens of patients with temporal lobe epilepsy were compared with control hippocampi of patients with temporal lobe lesions, which showed only mild hippocampal sclerosis. Mossy fibres were traced with neurobiotin. In addition, double immunohistochemistry against synaptoporin (mossy fibres) and parvalbumin (basket cells) was used. Synapses were examined with electron microscopy, labelled in addition with post-embedding GABA-immunogold.

Results: We found, that sprouted mossy fibres of epileptic hippocampi innervate not only excitatory granule cells but also inhibitory parvalbuminergic interneurons, as basket cells. Further we observed, that the axonal plexus of inhibitory basket cells, which surrounds the granule cells, was preserved in hippocampal sclerosis. We quantified the connections of sprouted mossy fibres with the inhibitory axonal plexus and showed that the number of persisting inhibitory axon terminals exceeds significantly the number of newly sprouted excitatory mossy fibre terminals.

Conclusions: We conclude that this might lead to an increased inhibition and synchronisation of granule cells because the preserved basket cells show an additional innervation through sprouted mossy fibres, which results in an instability of a previously balanced network.