Non-invasive estimation of cerebrospinal fluid pressure in idiopathic intracranial hypertension: magnetic resonance imaging analysis of optic nerve and eyeball.

Purpose: Invasive methods such as lumbar puncture and intraventricular catheters are commonly used to measure intracranial pressure (ICP). This study aims to develop quantitative and non-invasive techniques to measure ICP in patients with Idiopathic Intracranial Hypertension (IIH) using magnetic resonance imaging (MRI) findings.

Methods: MRI data obtained from 50 patients with IIH and 30 age- and sex- matched controls were analyzed and optic nerve sheath diameter (ONSD), eyeball transverse diameter (ETD) and optic nerve diameter (OND) were measured. ONSD, ONSD/ETD and OND/ONSD indexes were calculated according to different ONSD measurement distances. Correlations of MRI findings with ICP were calculated. Sensitivity and specificity of all methods were analyzed.

Results: ONSD and ONSD/ETD index at 3 mm and 10 mm behind the eyeball were significantly higher (p < 0.001) and OND/ONSD index at 3 mm behind the eyeball was significantly lower (p < 0.001) in the IIH group. The ONSD/ETD index at 3 mm had the highest area under the curve (AUC) value (0.898) with a cut-off of 0.27 mm (82% sensitivity and 91.67% specificity) for predicting high cerebrospinal fluid (CSF) pressure, followed by ONSD measurements at 3 mm (AUC = 0.886) with a cut-off of 6.17 mm (83% sensitivity and 86.67% specificity). The OND/ONSD index at 3 mm posterior to the eyeball decreased significantly as ICP increased, and the strength of the relationship was moderate (p < 0.001; r = -0.358).

Conclusions: ONSD and ONSD/ETD index measured on MRI sequences are potentially useful in detecting elevated ICP. The OND/ONSD index correlates with CSF pressure and these techniques may be helpful in diagnosing IIH.