Use of the sonographic diameter of optic nerve sheath to estimate intracranial pressure.

Background And Aims: An increase in the intracranial pressure (ICP) might aggravate patient outcomes by inducing neurologic injuries. In patients with increased ICP the optic nerve sheath diameter (ONSD) increases due to its close association with the flow of cerebrospinal fluid. The present study was an attempt to evaluate the efficacy of sonographic ONSD in estimating ICP of patients who are candidates for lumbar puncture (LP).

Materials And Methods: In this descriptive prospective study, the ONSD was measured before LP using an ultrasonography in 50 nontraumatized patients who were candidates for LP due to varies diagnoses. Immediately after the sonography, the ICP of each patient was measured by LP. Correlation tests were used to evaluate the relationship between ICP and the sonographic diameter of the optic nerve sheath. Receiver operating characteristic curve was used to find the optimal cut-off point in order to diagnose ICP values higher than 20 cm H(2)O.

Results: The means of the ONSD were 5.17 ± 1.01 and 5.19 ± 1.06 mm on the left and right sides, respectively (P = .552). The mean ONSD for the patients with increased ICP and normal individuals were 6.66 ± 0.58 and 4.60 ± 0.41 mm, respectively (P < .001). This mean was significantly correlated with ICP values (P < .05; r = 0.88). The ONSD of greater than 5.5 mm predicted an ICP of ≥20 cm H(2)O with sensitivity and specificity of 100% (95% CI, 100-100) (P < .001).

Conclusion: The sonographic diameter of the optic nerve sheath might be considered a strong and accurate predicting factor for increased intracranial pressure.