Assessment of Optic Nerve Sheath Diameter and Its Postoperative Regression among Patients Undergoing Brain Tumor Resection in a Tertiary Care Center.

Bedside measurement of optic nerve sheath diameter (ONSD) using ultrasonography (USG) is a useful method for detecting raised intracranial pressure (ICP). The primary and main objective of this study is to estimate ONSD among patients with brain tumor and its regression post tumor resection to assess the correlation as well as diagnostic accuracy of the same.  This prospective observational study was performed in a tertiary health care center over a span of 3 months on 68 adults of either sex, out of which 30 were nonneurosurgical patients, taken as control group. Rest 38 were neurosurgical patients posted for brain tumor resection. Normal ONSD in our population was determined by calculating average ONSD using transorbital USG in individuals of control group. ONSD in neurosurgical patients taken as case group was recorded before surgery, intraoperatively immediately post tumor resection, as well as 12 and 24 hours post surgery. These values were analyzed to see the correlation of ONSD with tumor resection.  The mean (±standard deviation) binocular ONSD in our population was 4.28 ± 0.28 mm. The mean preoperative binocular ONSD in cases using transorbital USG came out to be 5.43 ± 0.37 mm with 88.23% sensitivity and 100% specificity. Postoperatively, transorbital ONSD showed significant regression at 12 and 24 hours as compared with preoperative values ( -value < 0.05).  Transorbital ultrasonographic measurement of ONSD could be considered as an indirect indicator of ICP in neurosurgical patients perioperatively. The technique is quick to perform at bedside, feasible in critical patients, and without any harmful effects.