It is in this context that a new diagnostic modality attractive to intensive care is circumscribed, which is a fast, easy to perform, inexpensive and available at the patient's bedside. We refer to clinical ultrasound, critical multi organic ultrasound or point-of- care ultrasound (POCUS). This includes, among many strategies, non-invasive monitoring of neurological variables such as intracranial pressure (ICP). [2]

Elevated ICP is a common complication in cancer patients and leads to unfavorable clinical outcomes or death. The prognosis depends on the patient's performance status (according to Karnofsky's scale), the occurrence of systemic complications (septic encephalopathy or acute liver failure) and the origin of the primary tumor (brain neoplasms or diffuse processes such as: hydrocephalus, cerebral edema, infection or inflammation). [1], [3] Thus, the clinical presentation suggestive of the event and brain imaging by nuclear magnetic resonance or computed axial tomography (CT) of the skull (both can be contrasted or not) are usually the diagnostic suggestions established by the specialized literature. Also the invasive monitoring of ICP through intracranial micro transducers for use in the ICU [1,2,3]

However, the disadvantage of these strategies is the need to transfer the patient to settings with neuroimaging access. On the other hand, invasive monitoring does not escape complications such as bleeding or infection.

For this reason, we believe it is convenient to introduce ultrasound  of the optic nerve sheath diameter (ONSD), which offers a detailed approximation of the ICP value. It is the most innocuous for the critically ill patient and ideal for services that do not have neuro invasive technology. The technique is easy to learn and allows real- time monitoring of ICP fluctuations. [2]

Cerebrospinal fluid and meningeal sheaths that form the optic nerve sheath (ONS) surround the optic nerve, as a structure of the central nervous system. This allows the increase in ICP to be transmitted to the cerebrospinal fluid in the subarachnoid space of the ONS, widening it. [4]

A 3 - 8 MHz linear transducer is used to measure the ONSD. Patients are examined in the supine position. The transducer is placed in an axial plane over the temporal portion of the closed upper eyelid using a thick layer of ultrasound gel. In this way, the retro bulbar portion of the optic nerve can be visualized in an axial plane showing the papilla and optic nerve in its longitudinal path. By convention, the ONSD is evaluated three millimeters (3 mm) below the papilla. At that level, the distance from outer edge to outer edge of the hyper echogenic area around the optic nerve and corresponding to the VNO is measured perpendicularly (Figure 1-2).

Figure 1: A: Axial plane projection. B: DVNO diagram. C: B- mode visualization of DVNO. Photos taken by the authors.

Figure 2: A: Axial plane projection. Patient with septic encephalopathy and elements of intracranial hypertension. Right eye: 6.3mm and left eye: 6.6mm. Photos taken by the authors.

The diagnostic accuracy for the detection of intracranial hypertension has demonstrated a good statistical correlation compared to invasive monitoring, CT and lumbar puncture [1,2] [4].

Based on what has been described above, we consider that, to date, we did not find studies evaluating ICP in oncologic patients through this method. However, ONSD ultrasound can be incorporated into Oncologic Emergency and Urgent Care Units as well as ICUs while opening up a whole field of research with encouraging results.

1. Nates JL, Price KJ eds. Oncologic Critical Care. Springer Nature Switzerland AG. 2020.
2. Sosa-Remon A, Jerez-Alvarez A, Remon-Chavez C. Ultrasonografía del diametro de la vaina del nervio optico en el monitoreo de la presion intracraneal. Rev Cubana Anestesiol Reanim. 2022; 20: e710.
3. Jafari A, Rezaei-Tavirani M, Salimi M, Tavakkol R, Jafari Z. Oncological emergencies from pathophysiology and diagnosis to treatment: a narrative review. Soc Work in Public Health. 2020; 35: 689-709.
4. Abdo-Cuza A A, Suarez-Lopez J M, Machado-Martinez R E. Neuromonitoreo no invasivo en pacientes críticos. Rev Cub Med Int Emerg. 2018; 17: 51-59.