Diagnostic accuracy of ultrasonography of optic nerve sheath diameter for detecting raised intracranial pressure

Optic nerve sheath diameter, intensive care unit admission and COVID-19-related-in-hospital mortality

BACKGROUND

Hypoxia and hypercapnia due to acute pulmonary failure in patients with coronavirus disease 2019 (COVID-19) can increase the intracranial pressure (ICP). ICP correlated with the optic nerve sheath diameter (ONSD) on ultrasonography and is associated with a poor prognosis.

AIM

We investigated the capability of ONSD measured during admission to the intensive care unit (ICU) in patients with critical COVID-19 in predicting in-hospital mortality.

METHODS

A total of 91 patients enrolled in the study were divided into two groups: survivor (n = 48) and nonsurvivor (n = 43) groups. ONSD was measured by ultrasonography within the first 3 h of ICU admission.

RESULTS

The median ONSD was higher in the nonsurvivor group than in the survivor group (5.95 mm vs. 4.15 mm, P < 0.001). The multivariate Cox proportional hazard regression analysis between ONSD and in-hospital mortality (contains 26 covariates) was significant (adjusted hazard ratio, 4.12; 95% confidence interval, 1.46-11.55; P = 0.007). The ONSD cutoff for predicting mortality during ICU admission was 5 mm (area under the curve, 0.985; sensitivity, 98%; and specificity, 90%). The median survival of patients with ONSD >5 mm (43%; n = 39) was lower than those with ONSD ≤5 mm (57%; n = 52) (11.5 days vs. 13.2 days; log-rank test P = 0.001).

CONCLUSIONS

ONSD ultrasonography during ICU admission may be an important, cheap and easy-to-apply method that can be used to predict mortality in the early period in patients with critical COVID-19.

Observer Variability as a Determinant of Measurement Error of Ultrasonographic Measurements of the Optic Nerve Sheath Diameter: A Systematic Review

BACKGROUND

Ultrasonographic measurements of the diameter of the sheath of the optic nerve can be used to assess intracranial pressure indirectly. These measurements come with measurement error.

OBJECTIVE

Our aim was to estimate observer's measurement error as a determinant of ultrasonographic measurement variability of the optic nerve sheath diameter.

METHODS

A systematic search of the literature was conducted in Embase, Medline, Web of Science, the Cochrane Central Register of Trials, and the first 200 articles of Google Scholar up to April 19, 2021. Inclusion criteria were the following: healthy adults, B-mode ultrasonography, and measurements 3 mm behind the retina. Studies were excluded if standard error of measurement could not be calculated. Nine studies featuring 389 participants (median 40; range 15-100) and 22 observers (median 2; range 1-4) were included. Standard error of measurement and minimal detectable differences were calculated to quantify observer variability. Quality and risk of bias were assessed with the Guidelines for Reporting Reliability and Agreement Studies.

RESULTS

The standard error of measurement of the intra- and interobserver variability had a range of 0.10-0.41 mm and 0.14-0.42 mm, respectively. Minimal detectable difference of a single observer was 0.28-1.1 mm. Minimal detectable difference of multiple observers (range 2-4) was 0.40-1.1 mm. Quality assessment showed room for methodological improvement of included studies.

CONCLUSIONS

The standard errors of measurement and minimal detectable differences of ultrasonographic measurements of the optic nerve sheath diameter found in this review with healthy participants indicate caution should be urged when interpreting results acquired with this measurement method in clinical context.

Assessing ultrasonographic optic nerve sheath diameter in animal model with anesthesia regimens

Purpose:

To determine the normal optical nerve sheath (ONS) diameter ultrasonography (ONSUS) and evaluate the possible effects of drugs on ONS diameter during anesthetic induction in healthy pigs.

Methods:

Healthy piglets were divided into three groups: a control group, that received xylazine and ketamine (X/K); other that received xylazine, ketamine and propofol (X/K/P); and a third group that received xylazine, ketamine, and thiopental (X/K/T). The sheath diameter was assessed by ultrasonography calculating the average of three measurements of each eye from the left and right sides.

Results:

118 animals were anesthetized (49 X/K 33 X/K/P and 39 X/K/T). Mean ONS sizes on both sides in each group were 0.394 ± 0.048 (X/K), 0.407 ± 0.029 (X/K/P) and 0.378 ± 0.042 cm (X/K/T) (medians of 0.400, 0.405 and 0.389, respectively). The ONS diameter varied from 0.287–0.512 cm (mean of 0.302 ± 0.039 cm). For group X/K, the mean diameter was 0.394 ± 0.048 cm. Significant differences in ONS sizes between the groups P and T (X/K/P > X/K/T, p = 0.003) were found. No statistically significant differences were detected when other groups were compared (X/K = X/K/P, p = 0.302; X/K = X/K/T, p = 0.294).

Conclusions:

Sedation with thiopental lead to significative ONS diameter reduction in comparison with propofol. ONSUS may be useful to evaluate responses to thiopental administration.

Pediatric idiopathic intracranial hypertension - Is the fixed threshold value of elevated LP opening pressure set too high?

BACKGROUND

Idiopathic intracranial hypertension (IIH) in children is a rare condition of unknown etiology and various clinical presentations. The primary aim of this study was to evaluate if our pediatric IIH study group fulfilled the revised diagnostic criteria for IIH published in 2013, particularly with regard to clinical presentation and threshold value of an elevated lumbar puncture opening pressure. Additionally we investigated the potential utilization of MR-based and fundoscopic methods of estimating intracranial pressure for improved diagnosis.

PATIENTS AND METHODS

Clinical data were collected retrospectively from twelve pediatric patients diagnosed with IIH between 2008 and 2012 and revised diagnostic criteria were applied. Comparison with non-invasive methods for measuring intracranial pressure, MRI-based measurement (MR-ICP) and venous ophthalmodynamometry was performed.

RESULTS

Only four of the twelve children (33%) fulfilled the revised diagnostic criteria for a definite diagnosis of IIH. Regarding noninvasive methods, MR-ICP (n = 6) showed a significantly higher mean of intracranial pressure compared to a healthy age- and sex-matched control group (p = 0.0043). Venous ophthalmodynamometry (n = 4) showed comparable results to invasive lumbar puncture.

CONCLUSION

The revised diagnostic criteria for IIH may be too strict especially in children without papilledema. MR-ICP and venous ophthalmodynamometry are promising complementary procedures for monitoring disease progression and response to treatment.