Dependence of the optic nerve sheath diameter on acutely applied subarachnoidal pressure - an experimental ultrasound study.

Purpose: To determine the distensibility and elastic characteristics of the optic nerve sheath for development of a basic understanding of ultrasound studies aimed to measure optic nerve sheath diameter (ONSD) for detection of acutely elevated intracranial pressure (ICP).

Methods: Isolated human optic nerves preparations obtained from autopsies were submitted to predefined pressure alterations, and consecutive changes in ONSD were measured by B-scan ultrasound under defined conditions.

Results: Following submission to pressure, the diameter of the nerve sheath increased up to 140% of its baseline value.