A study by researchers at Jilin University in Changchun, China, furthers the case for orbital/optic nerve ultrasound’s potential as an alternative to lumbar puncture for measuring changes in intracranial pressure (ICP).1 Previously, the researchers confirmed that ultrasonographic measurements of optic nerve (ON) sheath diameter could be used to identify patients with elevated ICP.2
Dynamic assessments. For this study, the researchers measured both ON sheath diameter and ICP in 60 patients who had been admitted for lumbar puncture. Of those, 37 were found to have elevated ICP, most caused by cerebral infection. One month later, following treatment, the 25 patients not lost to follow-up underwent an additional round of measurements.
In both situations—upon admission and after treatment—the ON sheath diameter and lumbar puncture measurements were strongly correlated. What’s more, there was no difference in mean ON sheath diameter between patients with higher or lower levels of elevated ICP.
The researchers speculated that the elasticity of the ON sheath may explain why sheath diameter examinations can be used to dynamically assess variations in ICP. They also noted that the technique is easy to learn, has high interobserver reliability, and may be generalizable and applicable in a variety of potential clinical settings.
Clinical implications. “This study adds further evidence [supporting] the sensitivity and specificity of ultrasonography for the purpose of determining in a noninvasive manner whether or not there is elevated ICP,” said Andrew G. Lee, MD, at the Blanton Eye Institute at Houston Methodist Hospital.
In fact, Dr. Lee said in an accompanying editor’s note, he has used orbital ultrasound as either an adjunct or surrogate to actual direct measurement of ICP in a number of common clinical circumstances.3 Among them: differentiating difficult cases of pseudopapilledema from papilledema, and following patients who either refuse or cannot undergo lumbar puncture.
Nevertheless, Dr. Lee noted that the technique “is still in development.” And he agreed with the researchers that larger studies are needed, in part to determine whether the results are generalizable at ICP levels outside the study’s parameters. The maximum ICP value in the study was 400 mm H2O, so the accuracy of the technique at higher levels is not clear.
Despite ultrasonography’s potential as a noninvasive alternative to lumbar puncture, Dr. Lee said, “Direct measurements of ICP remain the gold standard.”
1 Wang L et al. JAMA Ophthalmol. 2018;136(3):250-256.
2 Wang L et al. PLoS One. 2015;10(2):e0117939.
3 Lee AG. JAMA Ophthalmol. 2018;136(3):256.
Relevant financial disclosures—Dr. Lee: None.
For full disclosures and the disclosure key, see below.
Full Financial Disclosures
Dr. Lee: None.
Dr. Moutray: Bayer: C; Novartis: C.
Dr. Smith: None.
Dr. Wong: None.
||Consultant fee, paid advisory boards, or fees for attending a meeting.
||Employed by a commercial company.
||Lecture fees or honoraria, travel fees or reimbursements when speaking at the invitation of a commercial company.
||Equity ownership/stock options in publicly or privately traded firms, excluding mutual funds.
||Patents and/or royalties for intellectual property.
||Grant support or other financial support to the investigator from all sources, including research support from government agencies (e.g., NIH), foundations, device manufacturers, and/or pharmaceutical companies.
More from this month’s News in Review