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Electron Microscopic Description of the Sylvian Arachnoid Membrane

Balak, Naci MD*; Tapul, Leyla MD; Ozdemirel, Rifat MD; Koc, Sermet MD; Sam, Bulent MD; Ersoy, Gokhan MD§

doi: 10.1097/WNQ.0b013e31828cc277
Original Articles
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Background: The aim of this study was to investigate the potential role of the arachnoid membrane of the Sylvian cistern in the secretion and absorption of cerebrospinal fluid (CSF).

Materials and Methods: Arachnoid specimens including the Sylvian cistern were obtained from the widest portion of the limen insulae region and were taken from 6 human cadavers within 12 hours postmortem. For electron microscopic examinations, specimens were fixed immediately in a solution of 2.5% cacodylate-buffered glutaraldehyde. Postfixation was performed with 2% osmic acid. After fixation, the tissue was dehydrated through a graded series of alcohol and blocked with Epon 812. Thick sections of the Epon-blocked tissue were stained with toluidine blue and examined under light microscopy. Ultrathin sections of 400 to 600 Å were obtained using an ultramicrotome. The thin tissue sections were then processed with lead citrate and uranyl acetate for contrast and examined under transmission electron microscopy.

Results: The Sylvian arachnoid membrane is composed of 3 main layers. Neuroepithelial cells richly occupy the outermost layer. Ultrastructural analysis revealed electron-lucent cells, electron-dense cells, cells with cytoplasmic processes, numerous tight junctions, desmosomes, and gap junctions. There were macrophage-like cells, pinocytotic vesicles, intercellular clefts, and interdigitation. These findings suggest the potential for fluid transport. The inner layers were composed of collagen fibers and fibroblasts and separated from the outer layer by a basement membrane.

Conclusions: Our study suggests that CSF might be transported across the Sylvian arachnoid membrane. Our findings demonstrate the potential of CSF transport to function in a secretory and/or absorptive manner.

*Department of Neurosurgery, Göztepe Education and Research Hospital

Department of Forensic Medicine, National Forensic Institute of Ministry of Justice

Department of Histology, Istanbul Medical Faculty

§Department of Pathology, Institute of Forensic Medicine, University of Istanbul, Istanbul, Turkey

A portion of this work was presented as a poster presentation at the 14th European Congress of Neurosurgery, October 9–14, 2011, Rome, Italy.

The authors declare no conflict of interest.

Reprints: Naci Balak, MD, Department of Neurosurgery, Göztepe Education and Research Hospital, Kadikoy, Istanbul 34730, Turkey (e-mail: drnacibalak@yahoo.com).

© 2014 by Lippincott Williams & Wilkins