Point of Care Optic Nerve Sheath Ultrasound to Assess Intracranial Pressure

Elevated intracranial pressure (ICP) is one of the most common symptoms encountered in a variety of traumatic injuries and diseases. Any tissue swelling within the rigid confines of the skull results in increased ICP, which may lead to life-threatening structural alterations in the brain or cerebral blood flow, thus causing oxygen deprivation and ischemia in the brain.

Methods for ICP monitoring can be divided into invasive and noninvasive approaches. In fluid-based systems, external ventricular drainage (EVD) has been considered the gold standard.

Clinicians have found several noninvasive methods that can be used as surrogates for invasive methods for ICP measurement. The optic nerve, as part of the central nervous system, is wrapped by the dural sheath. The optic nerve sheath (ONS) is the continuation of the subarachnoid space at the optic nerve, and its tissues are connected with the subarachnoid space. Thus, an increase in ICP results in a corresponding elevation of the ONS diameter (ONSD).

Hypertonic solutions such as mannitol and hypertonic saline (HTS) are recommended early in the management of ICH after severe TBI . They provide therapeutic benefit along with a wide therapeutic margin. The most recent BTF guidelines stated "although hyperosmolar therapy may lower intracranial pressure, there was insufficient evidence about effects on clinical outcomes to support a specific recommendation, or to support use of any specific hyperosmolar agent".