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.