Optic nerve sheath diameter in patients undergoing intracranial tumour resection: Perioperative changes and contributing factors - A prospective observational study.

BACKGROUND AND AIMS

Ultrasonographic (USG) optic nerve sheath diameter (ONSD) provides a real-time, non-invasive method for assessing intracranial pressure. This study investigates perioperative ONSD variations and contributing factors in patients undergoing elective intracranial tumour resection.

METHODS

A prospective observational study was conducted on 94 adults with intracranial tumours, excluding orbital lesions and sellar/suprasellar tumours. Preoperative symptoms, Glasgow coma scale scores, and radiological findings were noted. USG-ONSD was assessed in the transverse and sagittal plane on each eye, with an average of three readings at the following time-points: pre-induction, post-induction, post-extubation, and 24-hour post-tumour resection. The presence of ventriculo-peritoneal (VP) shunt, duration of surgery/anaesthesia, intraoperative position, use of osmotic agents, and complications during surgery were noted. The data were analysed using linear regression and general linear modelling in R software.

RESULTS

ONSD increased significantly ( = 0.001) immediately after surgery and decreased 24 hours after surgery ( < 0.001) compared to preoperative values. Although the trend of ONSD changes was similar for both supratentorial and infratentorial tumours, supratentorial tumours consistently showed higher values ( = 0.549). Higher American Society of Anesthesiologists physical status, nausea/vomiting, visual field affection, midline shift, mass effect, and larger tumour size were associated with higher preoperative values. Similarly, large-size tumours ( < 0.001), shorter duration of symptoms ( = 0.001), and lateral intraoperative positioning ( = 0.028) showed significantly higher values and greater changes, whereas the presence of VP shunt, use of osmotherapy, and sitting position for surgery showed a lower trend of ONSD postoperatively.

CONCLUSION

USG-ONSD demonstrates dynamic changes in patients undergoing intracranial tumour resection. ONSD is affected by the size of the tumour, duration of symptoms, and intraoperative positioning, though the trend is homogenous among supratentorial and infratentorial tumours.