Article
Anatomical landmarks in the retroclival region during endoscopic third ventriculostomy: the clival line
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Authors
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Peter Kurucz
- Department of Neurosurgery, Klinikum Stuttgart, Stuttgart, Deutschland; Laboratory for Applied and Clinical Anatomy, Department of Anatomy, Semmelweis University, Budapest, Hungary,
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Laszlo Barany
- Laboratory for Applied and Clinical Anatomy, Department of Anatomy, Semmelweis University, Budapest, Hungary
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Oliver Ganslandt
- Klinikum Stuttgart, Neurochirurgische Klinik, Stuttgart, Deutschland
| Published: | June 9, 2017 |
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Outline
Text
Objective: Endoscopic third ventriculostomy (ETV) is a well-accepted treatment option in selective cases of obstructive hydrocephalus instead of ventriculoperitoneal shunt placement. A sufficient flow from the ventricular system to the subarachnoid spaces requires perforation of the arachnoid membranes located in the retroclival region. This maneuver is a generally known critical point to achieve an optimal long-term outcome. Our goal was to investigate the complex arachnoid relations in the retroclival region from the viewpoint of ETV and define some landmarks which can be useful during the subarachnoid dissections.
Methods: 50 fresh human cadaveric specimens were dissected under macroscopic, microscopic and endoscopic control to describe the arachnoid relations in the retroclival region.
Results: We could verify the existence of multiple arachnoid layers perimesencephally above-, in the level-, as well as below the tentorial edge. This construct was completed ventrally by the Liliequist´s membrane complex and the anterior pontine membranes located parallel to and on both sides of the basilar artery. The basal attachment of these ventrally located membranes forms a white-grey thickening on the inner surface of the outer arachnoid and has an inverted U-shape. The base of the U-shape located in the level of the dorsum sellae. We refer this structure as “clival line” according to its anatomical location. During ETV if the arachnoid dissections were performed ventrally to the clival line the outer arachnoid was opened and the basilar artery trunk could not be visualised which resulted only a limited flow to the subarachnoid spaces (mainly ventriculo-subdural). If the perforation on the arachnoid membranes was placed directly behind (dorsal to) the clival line the top of the prepontine cistern could be directly reached through the Liliequist´s membrane complex without opening the outer arachnoid and creating an involuntary retroclival subdural shunting. This approach provides an optimal route to the relevant arachnoid membranes of the retroclival region and they could be surely perforated to visualise the basilar artery trunk. This step is mandatory to secure a free flow between the ventricular system and the interpeduncular as well as prepontine cisterns.
Conclusion: Among many other factors the sufficient arachnoid dissection is a critical point to achieve satisfactory long-term outcome after ETV. The clival line is an important anatomical landmark which helps to perform these dissection safely to achieve an optimal flow through the third ventricular floor into the basal cisterns.
