Real-Time Evaluation of Optic Nerve Sheath Diameter (ONSD) in Awake, Spontaneously Breathing Patients

The Effect of Different Optic Nerve Sheath Diameter Measurements Using Ultrasound to Assess Intracranial Pressure in Patients With Acute Brain Injury

BACKGROUND

Optic nerve sheath diameter (ONSD) is a promising, noninvasive invasive intracranial pressure (ICP) measurement method. This study aims to analyze the differences in ONSD between the left and right eyeballs and the differences in ultrasonic measurement between the transverse and sagittal planes.

METHODS

Data from a total of 50 eligible patients with various types of brain injury who were admitted to our hospital from May 2019 to June 2021 were analyzed. An ONSD assessment was then performed using Philips B-mode ultrasound, measuring ONSD 3 mm posterior to the eyeballs. The left and right ONSDs in the transverse and sagittal planes were measured. Intraparenchymal fiber optic sensors and catheters were inserted into the ventricles and connected to an external pressure transducer to measure ICP.

RESULTS

A total of 164 sonographic measurements of ONSD were performed in 50 patients with brain injury in a prospective observational study. Statistically significant differences were found in ONSD between the transverse and sagittal planes. The difference in the left ONSD between the transverse and sagittal planes was 0.007 ± 0.030 cm ( P = 0.003). The Spearman rank correlation test showed that the correlation coefficient between ICP and left/right ONSD in the transverse/sagittal planes was 0.495 vs 0.546 and 0.559 vs 0.605, respectively. The results showed that the areas under the curve of ONSD in the transverse and sagittal planes were 0.843 and 0.805, respectively. Medcalc software was used to compare the areas under the receiver operator characteristic curve, and the results showed that ONSD in the sagittal plane is generally better than in the transverse plane ( P = 0.0145).

CONCLUSIONS

This study found that ONSD in the sagittal plane is superior to the transverse plane regarding the comprehensive efficacy of ICP, and unilateral measurement is sufficient.

Non-Invasive Intracranial Pressure Monitoring

(1) Background: Intracranial pressure (ICP) monitoring plays a key role in the treatment of patients in intensive care units, as well as during long-term surgeries and interventions. The gold standard is invasive measurement and monitoring via ventricular drainage or a parenchymal probe. In recent decades, numerous methods for non-invasive measurement have been evaluated but none have become established in routine clinical practice. The aim of this study was to reflect on the current state of research and shed light on relevant techniques for future clinical application. (2) Methods: We performed a PubMed search for “non-invasive AND ICP AND (measurement OR monitoring)” and identified 306 results. On the basis of these search results, we conducted an in-depth source analysis to identify additional methods. Studies were analyzed for design, patient type (e.g., infants, adults, and shunt patients), statistical evaluation (correlation, accuracy, and reliability), number of included measurements, and statistical assessment of accuracy and reliability. (3) Results: MRI-ICP and two-depth Doppler showed the most potential (and were the most complex methods). Tympanic membrane temperature, diffuse correlation spectroscopy, natural resonance frequency, and retinal vein approaches were also promising. (4) Conclusions: To date, no convincing evidence supports the use of a particular method for non-invasive intracranial pressure measurement. However, many new approaches are under development.

Multimodal Neuromonitoring in Pediatric Neurocritical Care: Current Perspectives

Children with neurological illness in the critical care unit are always at higher risk of developing secondary brain injury (SBI). Brain insult can lead to changes in cerebral autoregulation, intracranial pressure (ICP), cerebral oxygenation, and metabolism. This can cause a raised ICP, cerebral ischemia, hypoxia, excitotoxicity, cellular energy failure, and nonconvulsive status epilepticus. Simultaneous and continuous assessment of these parameters will help to improve patient care and neurological outcomes. Even though clinical examination and neuroimaging can help in the initial diagnosis of the neurological illness, they may not be helpful in continuous monitoring of cerebral pathophysiological changes. The ideal single neuromonitoring device to detect these real-time changes is currently unavailable. However, a range of invasive and noninvasive monitors are available to monitor these cerebral functional parameters. Invasive monitoring techniques include invasive ICP monitoring, cerebral autoregulation monitoring, brain tissue partial oxygen pressure, and cerebral microdialysis. Noninvasive-monitoring techniques include pupillometry, brain and ocular ultrasonography, near-infrared spectroscopy, and electrophysiological monitoring. Multimodal (MM) neuromonitoring involves incorporating these techniques and tools for the early identification and treatment of primary and secondary brain insults. The utility and feasibility of most of these techniques are well described in adult neurocritical care. Even though the evidence on their usage in children is primarily available in pediatric traumatic brain injury, the emerging data help to further expand their utility in pediatric nontraumatic coma. MM neuromonitoring aims to provide clinical and pathophysiological information to the intensivists to improve their understanding of the child's neurological status and to formulate patient-specific treatment approaches.

Problems in CSF and Ophthalmic Disease Research

There has been significant interest and progress in the understanding of cerebrospinal fluid pressure and its relationship to glaucoma and other ophthalmic diseases. However, just as every physiologic fluid pressure fluctuates, cerebrospinal fluid pressure (CSFP) is similarly dynamic. Coupling this with the difficulty in measuring the pressure, there are many obstacles in furthering this field of study. This review highlights some of the difficulties in CSFP research, including fluid compartmentalization, estimation equations, and pressure fluctuation. Keeping these limitations in mind will hopefully improve the quality and context of this burgeoning field.