Intralobar fibres of the occipital lobe

Francesco Vergani, Sajedha Mahmood, Cristopher M. Morris, Patrick Mitchell, Stephanie J. Forkel
Cortex. 2014-07-01; 56: 145-156
DOI: 10.1016/j.cortex.2014.03.002

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INTRODUCTION: The atlas by Heinrich Sachs (1892) provided an accurate description
of the intralobar fibres of the occipital lobe, with a detailed representation of
the short associative tracts connecting different parts of the lobe. Little
attention has been paid to the work of Sachs since its publication. In this
study, we present the results of the dissection of three hemispheres, performed
according to the Klingler technique (1935). Our anatomical findings are then
compared to the original description of the occipital fibres anatomy as detailed
by Sachs.
METHODS: Three hemispheres were dissected according to Klingler’s technique
(1935). Specimens were fixed in 10% formalin and frozen at -15 °C for two weeks.
After defreezing, dissection of the white matter fibres was performed with blunt
dissectors. Coronal sections were obtained according to the cuts originally
described by Sachs. In addition, medial to lateral and lateral to medial
dissection of the white matter of the occipital lobe was also performed.
RESULTS: A network of short association fibres was demonstrated in the occipital
lobe, comprising intralobar association fibres and U-shaped fibres, which are
connecting neighbouring gyri. Lateral to the ventricles, longitudinal fibres of
the stratum sagittale were also identified that are arranged as external and
internal layers. Fibres of the forceps major were also found to be in direct
contact with the ventricular walls. We were able to replicate all tracts
originally described by Sachs. In addition, a previously unrecognised tract,
connecting the cuneus to the lingual gyrus, was identified. This tract
corresponds to the “sledge runner”, described in tractography studies.
CONCLUSIONS: The occipital lobe shows a rich network of intralobar fibres,
arranged around the ventricular wall. Good concordance was observed between the
Klingler dissection technique and the histological preparations of Sachs.


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