Ultrasound-measured optic nerve sheath diameter correlates well with cerebrospinal fluid pressure.

BACKGROUND

Intracranial pressure (ICP) can be raised in many neurological conditions and must be treated early to prevent poor clinical outcomes. To detect the rising ICP, it is important to measure it repeatedly using a tool that is noninvasive, safe, accurate, and portable with minimal inter- and intraobserver variability. The aim of our study was to correlate cerebrospinal fluid (CSF) pressure with ultrasound (US)-measured optic nerve sheath diameter (ONSD) and find out a measurement which correlates best with CSF pressure of >20 cm of water.

MATERIALS AND METHODS

All patients in whom lumbar puncture (LP) was indicated and CSF pressure could be measured using manometer were included in the study. Ocular US was used to measure the ONSD.

RESULTS

A hundred patients were included in the study out of which 81% were males. The mean age was 60.5 years (±15.6) with a range of 26-90 years. Significant positive correlation was found between the ONSD and CSF pressure. Correlation coefficient (r) was 0.715 (P < 0.001). Receiver's operating characteristic curve was used to find out the ONSD value correlating with a CSF pressure of >20 cm of water. An ONSD >0.63 cm had a sensitivity of 77.3% [95% confidence interval (CI) 54.6-92.1] and specificity of 92.3% (95% CI 84.0-97.1) in predicting a CSF pressure of >20 cm of water (likelihood ratio [LR] + 10.05, LR - 0.25).

CONCLUSION

There is a positive correlation of US-measured ONSD and LP-measured CSF pressure. ONSD of >0.63 cm suggests a CSF pressure of >20 cm of water.