Undiagnosed elevated intracranial pressure could lead to brain damage in Intensive Care Unit patients. Recently, ultrasound diagnostic has been proved to be a sure and cost-effective way to get data otherwise difficult to obtain during primary evaluation in Emergency and Critical Care Medicine settings. The optic nerve sheath diameter is enlarged in patients with intracranial hypertension and its increase correlates with data of non-invasive and invasive measurements of intracranial pressure and head computed tomography scan findings. Thus, the optic nerve sonography can serve as an additional non-invasive diagnostic tool of elevated intracranial pressure preceding the emergency computed tomography or the decision to start the invasive monitoring of intracranial pressure.