Utility of Serial Optic Nerve Sheath Diameter Measurements in Patients Undergoing Cerebral Spinal Fluid Diversion Procedures for Hydrocephalus

Abstract

Functional status of cerebrospinal fluid (CSF) diversion procedure for hydrocephalus is difficult to assess on several occasions. We report the use of serial ultrasonographic measurement of optic nerve sheath diameter (ONSD) to assess the functional status of CSF diversion procedures in patients with hydrocephalus. In this prospective observational study, ultrasonographic ONSD measurement was performed preoperatively, on postoperative days 1, 3, and 7 (n= 51 at each time point) and at follow-up (n= 31) in patients undergoing ventriculoperitoneal shunt or endoscopic third ventriculostomy for hydrocephalus. Change in ONSD values during first week after CSF diversion procedure and at follow-up were correlated with ventriculoperitoneal shunt/ETV function. ONSD ≥5.5 mm strongly correlated with clinical and imaging features of raised ICP (P < 0.001). Mean ONSD progressively decreased in the postoperative period and was the lowest on postoperative day 7 (P < 0.001) with >95% of patients having ONSD <5.5 mm at that time point. At follow-up (median, 12 months; n= 31), ONSD had further reduced in 78.6% of patients. All 3 patients with shunt dysfunction had an increase in the ONSD value compared with that on postoperative day7. ONSD measurement on postoperative day 7 after CSF diversion correlates well with early surgical outcome but decreases further in many patients at a follow-up of 12 months. Rise in postoperative day 7 ONSD at follow-up correlates with failure of the CSF diversion procedure.