Preliminary Evaluation of Preoperative Optic Nerve Sheath Diameter and CT Mass Effect in Relation to Pre-Excision Invasive Intracranial Pressure During Intracranial Tumor Surgery.

Background: Raised intracranial pressure in intracranial tumor surgery is driven by mass effect and edema, but invasive monitoring is selectively used, and imaging may not fully reflect contemporaneous pressure. We performed a pilot evaluation of preoperative optic nerve sheath diameter and CT mass effect in relation to pre-excision invasive intracranial pressure. Methods: This retrospective pilot study included adults with available preoperative optic nerve sheath diameter, CT mass effect graded by the Gordon-Firing score, and recorded pre-excision invasive intracranial pressure. The primary analysis assessed association with continuous pre-excision intracranial pressure using correlation and linear regression. Perioperative change in invasive intracranial pressure and serial optic nerve sheath diameter were also analyzed. Threshold analyses were exploratory. Results: In total, 45 patients were included. Mean pre-excision intracranial pressure was 29.40 mmHg, and 39/45 (86.7%) had intracranial pressure > 20 mmHg. Optic nerve sheath diameter showed a modest association with pre-excision intracranial pressure (r = 0.279, p = 0.064), whereas Gordon-Firing showed a stronger association (r = 0.522, p < 0.001). In the combined model, Gordon-Firing remained associated with intracranial pressure, whereas optic nerve sheath diameter did not. Mean intracranial pressure decreased by 12.24 mmHg after tumor excision, and optic nerve sheath diameter decreased at 1 h and 6 h postoperatively. Conclusions: CT mass effect graded by Gordon-Firing showed a stronger cross-sectional relationship with pre-excision invasive intracranial pressure than optic nerve sheath diameter, whereas serial optic nerve sheath diameter appeared more useful as a perioperative marker.