The ultrasound of the optic nerve sheath diameter (ONSD) is a non-invasive tool used in the detection of intracranial hypertension and other neurological conditions. The aim of this research is to evaluate the correlation between the ultrasound measurement of the optic nerve sheath diameter and the side of neurological focus in the physical examination of adult patients evaluated in emergency departments.

II. Hypothesis The ultrasound measurement of the optic nerve sheath diameter correlates with the side of neurological focus in the physical examination of adult patients evaluated in emergency departments.

III. Objectives Estimate the correlation between the ultrasound measurement of the optic nerve sheath diameter and the side of neurological focus in the physical examination of adult patients evaluated in emergency departments.

Determine the sensitivity and specificity of the ultrasound measurement of the optic nerve sheath diameter for predicting the side of neurological focus.

IV. Methodology

Study design:

A observational study will be conducted in a secondary care hospital.

Population and sample:

Adult patients (≥18 years) presenting to the emergency department with neurological symptoms, such as headache, altered level of consciousness, motor or sensory deficit, among others, will be included. Patients with contraindications for ocular ultrasound or with a history of previous ocular surgery will be excluded.

Procedures:

1. Informed consent will be obtained from patients who meet the inclusion criteria.
2. A neurological physical examination will be performed to identify the side of neurological focus.
3. The optic nerve sheath diameter will be measured using ultrasound with a high-frequency linear transducer (7.5-12 MHz).
4. Demographic, clinical, and ultrasound data will be recorded for the patients.

Data analysis:

The correlation between the ultrasound measurement of the optic nerve sheath diameter and the side of neurological focus will be calculated using Pearson's or Spearman's correlation coefficient, depending on the distribution of the data. Additionally, sensitivity, specificity, positive and negative predictive values, and 95% confidence intervals will be calculated to determine the diagnostic utility of the ultrasound measurement of the optic nerve sheath diameter in identifying the side of neurological focus.

V. Ethical considerations The ethical guidelines established by the Declaration of Helsinki will be followed, and the privacy and confidentiality of patients will be protected. The protocol will be approved by the hospital's Research Ethics Committee before its implementation.

Inclusion Criteria:

• Patients with suspected acute ischemic stroke
• CT scan negative to hemorrhagic stroke
• Informed consent

Exclusion Criteria:

• Contraindications to perform ocular ultrasound
• Patients with ocular surgery

The study aims to include a diverse adult population, encompassing various ages, genders, and ethnic backgrounds, reflective of the general demographic seen in emergency departments with suspected ischemic stroke. By doing so, the study seeks to enhance the generalizability of its findings across different subgroups within the adult population.