Transorbital Ultrasonography Can Noninvasively Measure Intracranial Pressure

Optic nerve subarachnoid space area (ONSASA) measured using ultrasonography can serve as a rapid noninvasive method to evaluate intracranial pressure (ICP), according to the findings of a prospective observational study published in the British Journal of Ophthalmology.

Patients (N=90) with neurological diseases who were undergoing invasive ICP monitoring at the Beijing Tongren Hospital and Beijing Xuanwu Hospital in China between 2015 and 2018 were recruited for this study. Results from invasive assessment were compared with noninvasive ultrasonography data and the best predictive model was formulated. Patients were randomly assigned to training (n=63) and test (n=27) cohorts.

The training cohort consisted of 31 men and 32 women, (meanage, 49.27 years; mean ICP, 13.21 mm Hg) and the test cohort consisted of 13 men and 14 women (mean age, 50.11 years; mean ICP, 13.19 mm Hg).

Among the training cohort, ICP was correlated with ONSASA (r, 0.953; P <.0001), optic nerve sheath diameter (ONSD; r, 0.672; P <.0001), ONSASA width at 3 mm from the optic nerve head (r, 0.605; P <.0001), mean blood pressure (MABP; r, 0.627; P <.0001), and BMI (r, 0.426; P <.0001).

In the linear regression analysis, ICP was associated with ONSASA (β, 2.050; P <.001) and MABP (β, 0.036; P =.015).

On the basis of these data, the best noninvasive method for calculating ICP was using the equation ICP=2.050xONSASA-0.051xBMI+0.036xMABP-5.837, according to the researchers. This formula had an area under the receiver operating characteristic curve of 0.960, sensitivity of 1.00, and specificity of 0.92. The best cutoffs for predicting ICP of higher than 20 mm Hg was 19.96.

The major limitation of this study was the implicit inaccuracy of ultrasound equipment.

“Measurement of the ONSASA by ultrasonography has potential as a method for rapid quantification of the ICP. With a mathematical formula, this noninvasive technique might be used to assess the ICP accurately. It is also possible to have the potential value for detection and evaluation [of] the pathogenesis of normal tension glaucoma,” the study authors report.