Artikel
The dependence of the diameter of the optic nerve sheath on the intracerebral pressure in an animal model
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Veröffentlicht: | 9. Juni 2017 |
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Gliederung
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Objective: Several studies have shown that the diameter of the optic nerve sheath depend on the intracranial pressure and can be measured with transbulbar ultrasonography. The purpose of this study was to characterize the changes of the diameter of the different components of the optic nerve sheath (optic nerve, subarachnoid space, sheath) depending on the intracranial pressure in an animal model.
Methods: Eight pigs were intubated and sedated. An external ventricular drain was placed in the third ventricle through a burrhole. The intracranial pressure was progressively raised (20, 30, 40, 50 and 60mm Hg) by infusing saline. At each pressure level the diameter of the optic nerve and the inner as well as the outer nerve sheath was measured with means of transbulbar ultrasonography.
Results: The diameter of the optic nerve, as well as the diameter of the inner and outer nerve sheath increased in parallel to the intracranial pressure. The increase of the different diameters was mainly caused by an increase of the diameter of the optic nerve, whereas the size of the subarachnoid space and the nerve sheath did not change significantly.
Conclusion: The diameter of the optic nerve sheath depends on the intracranial pressure and can be measured by transbulbar ultrasonography. The increase of the diameter of the optic nerve sheath is mainly due to an increase of the diameter of the optic nerve itself, which might be caused by a reduction of the venous drainage.