Optic nerve sheath diameter and its implications in the evaluation of cerebral venous sinus thrombosis

Purpose
To ascertain the role of optic nerve sheath diameter (ONSD) in the evaluation of cerebral venous sinus thrombosis (CVST).

Material and methods
A retrospective study with convenient sampling was done during the period November 2018 to January 2020. Forty-one patients across all age groups with magnetic resonance venography (MRV) diagnosis of CVST and 82 gender-matched controls were included in the study. ONSD was measured on axial T2-weighted magnetic resonance images. CVST was identified on axial TOF-MRV including the stage, degree, and location. Intraparenchymal infarction and haemorrhage were also noted with their stage and size. The distribution of values for ONSD was tested for equality of variances using independent samples t-test. A cut-off value for ONSD was derived using ROC analysis.

Results
The mean difference between ONSD of cases and controls was 0.84 mm (95% CI: 0.61-1.06) and was statistically significant at p < 0.001. Mean ONSD in cases was 5.33 ± 0.66, and in the control group it was 4.49 ± 0.31. The cut-off value for ONSD was taken as 4.57 mm, derived using the ROC analysis (AUC was 0.876 suggesting good diagnostic accuracy). ONSD showed a sensitivity of 87% and a negative predictive value of 89% in predicting CVST. However, we found no statistical significance between ONSD in patients with acute or chronic thrombosis or in those with neuroparenchymal complications.

Conclusions
ONSD is a valid triage tool with high sensitivity and negative predictive value, and it can be used in the evaluation of CVST.