gms | German Medical Science

64th Annual Meeting of the German Society of Neurosurgery (DGNC)

German Society of Neurosurgery (DGNC)

26 - 29 May 2013, Düsseldorf

Morphological and functional changes in the human hippocampus in temporal lobe epilepsy

Meeting Abstract

  • Thomas M. Freiman - Department of Neurosurgery, University Medical Centre, Albert-Ludwigs-University, Freiburg, Germany
  • K. Leicht - Department of Neurosurgery, University Medical Centre, Albert-Ludwigs-University, Freiburg, Germany
  • Jessica Eismann-Schweimler - Department of Neurosurgery, University Medical Centre, Albert-Ludwigs-University, Freiburg, Germany
  • Michael Frotscher - Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Albert-Ludwigs-University, Freiburg, Germany

Deutsche Gesellschaft für Neurochirurgie. 64. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC). Düsseldorf, 26.-29.05.2013. Düsseldorf: German Medical Science GMS Publishing House; 2013. DocMO.07.10

doi: 10.3205/13dgnc061, urn:nbn:de:0183-13dgnc0610

Published: May 21, 2013

© 2013 Freiman et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: Temporal lobe epilepsy is characterized by a sclerosis of the hippocampus (Ammon’s horn sclerosis) with a specific loss of pyramidal cells in CA1 and mossy cells in the hilus. Excitatory granule cells survive, but show a reorganization of their axonal connections. Their axons, the mossy fibres, loose their target cells due to mossy cell death and sprout backwards into the granule cell layer. It was suggested so far, that this leads to a recurrent, excitatory circuit. The aim of this study was to examine the target cells of mossy fibre sprouting, and determine whether mossy fibres impinge only on granule cells or also on other neurons, in particular inhibitory interneurons (basket cells).

Method: 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 gamma-aminobutyric-acid (GABA)-immunogold.

Results: In human epileptic hippocampi sprouted mossy fibres innervated not only excitatory granule cells but also inhibitory interneurons. In addition, we show that the inhibitory axonal plexus around granule cells is preserved and that the number of inhibitory axon terminals exceeds the number of excitatory sprouted mossy fibre terminals on granule cells.

Conclusions: Sprouting of mossy fibres does not simply results in an excitatory circuit of granule cells because recurrent mossy fibres also innervate inhibitory interneurons. This might lead to increased inhibition and synchronization of granule cells because the extensive inhibitory axonal plexus is preserved and shows an additional innervation through sprouted mossy fibres.