Abstract
We read with great interest the review by Zhang et al (2017) concerning the invasive and noninvasive means of measuring intracranial pressure. We would like to congratulate the authors for their interesting paper, but we were a bit disappointed reading the section dedicated to the role of ultrasound in the measurement of the optic nerve sheath diameter (ONSD).
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In this section, 'ONSD assessment', the authors stated that 'ONSD assessment has been discussed and developed by multiple researchers (e.g. Borchert and Lambert (2000) and Rajajee et al (2011))' and 'Enlargement of the optic nerve sheath has been described in patients with increased ICP (Soldatos et al 2008)'.
We were a bit surprised to read this, because ultrasound has been used routinely to measure the ONSD and to differentiate optic nerve lesions for a long time, since the late 70s when Karl Ossoinig showed how to measure it (Ossoinig et al 1981, Ossoinig 1990).
To support this statement, as we routinely evaluate the optic nerve with ultrasound, not only were we able to make a diagnosis of optic nerve leukemic infiltration in 1993 (Camera et al 1993), but, in 2003, five years before Soldatos, we published a case where ultrasound was essential in making a diagnosis of increased benign intracranial pressure (BIH) (Rosa et al 2003).
The real problem is that when we deal with ocular structure, acquiring precise measurements is mandatory, because a few microns can make a difference (Rosa et al 2005) and this is difficult with a B-scan.
Zhang et al ignored the use of standardized A-scans that, as we clarified in several reports (De Bernardo and Rosa 2017, Iaconetta et al 2017, Rosa and De Bernardo 2017a, 2017b, Tenuta et al 2017), can be more valuable and precise than B-scans in detecting and differentiating ON lesions, also thanks to the so-called 30° test developed by Ossoinig et al (1981). This test consists in a measurement of the ONSD in straight gaze and in maximal eye abduction (30° gaze). If this test shows a decrease greater than 5% in the ONSD, a diagnosis of increased intracranial pressure is made. In case no decrease in the ONSD is detected, a diagnosis of solid thickening of the sheaths (e.g. in Graves orbitopathy, in optic nerve sheath meningiomas, or leukemic infiltration of the optic nerve), or swelling of the pial and arachnoidal sheaths with engorged vessels in cases of severe orbital congestions (e.g. in arteriovenus fistulas or in acute orbital inflammation, can be made.
So, in conclusion, we hope that in the case of future papers, the authors will address the role of standardized A-scan examination in the differential diagnosis of ONSD enlargement.