Evaluation of optic nerve sheath diameter by ultrasonography in patients with intracranial pressure elevation in intensive care unit

Intracranial pressure elevation can occur due to various reasons such as TBI, ischemic or hemorrhagic stroke, intracranial masses, among others. In the management of these patients, monitoring and treatment of ICP play a crucial role. There are various invasive and non-invasive methods for detecting increased ICP. Factors such as the cost of invasive methods, risk of infection, and the need for surgical expertise have led clinicians to prefer non-invasive techniques for ICP assessment. Ultrasonographic measurement of ONSD has gained popularity in recent years as a non-invasive method due to its safety, ease of repeatability, bedside applicability, and lower cost. In our study, we aimed to evaluate the effect of changes in optic nerve sheath diameter on prognosis and to assess the correlation between cranial CT findings and ONSD increase in patients with confirmed intracranial pressure elevation by cranial CT. ONSD measurements were taken bilaterally from 3 mm behind the vitreoretinal junction in both eyes of patients diagnosed with intracranial pressure elevation by cranial CT between June-December 2023 in our intensive care unit. The study included 50 patients with brain injury in intensive care follow-up and 36 healthy volunteers. ONSD was found to be higher in the patient group with imaging findings consistent with increased ICP compared to the healthy group. Patients with midline shift and edema on cranial CT had higher ONSD measurements compared to other CT findings. Additionally, higher ONSD was observed in patients with ventricular compression as a tomographic finding on the 3rd and 5th days of intensive care follow-up. Optic nerve sheath diameter was found to be significantly associated with mortality rates, GKS, and FOUR scores, but not with APACHE II and SOFA scores. ONSD was measured higher in patients who were intubated upon admission to the intensive care unit, while lower measurements were found in patients intubated during follow-up. Mortality rates were found to be associated with all scoring systems in our study. In conclusion, we believe that ONSD measurements can be used in the detection of intracranial pressure elevation in intensive care and can be used in prognosis estimation. Especially in patients who are hemodynamically unstable or unable to undergo CT imaging, intracranial pressure elevation can be monitored with ultrasonographic ONSD measurement. Keywords: Brain Injury, Intracranial Pressure Elevation, Cranial Computed Tomography, Optic Nerve Sheath Diameter, Ultrasonography