Bedside optic nerve ultrasonography can help diagnose increased intracranial pressure
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Bedside optic nerve ultrasonography is a noninvasive, quick and easy method to help diagnose increased intracranial pressure, according to findings published in the Annals of Internal Medicine.
“Increased intracranial pressure is a disaster, and the end result is herniation and death,” Saleh A. Almenawer, MD, a clinical researcher at McMaster University in Hamilton, Ontario, Canada, told Healio Primary Care. “It’s something that we want to pick up very early ... to give the diuretics to decrease the pressure from inside of the brain.”
Just last week, former President Jimmy Carter underwent surgery for increased intracranial pressure that occurred as a result of bleeding in his brain caused by recent falls.
Almenawer explained that currently, the methods used to diagnose increased intracranial pressure — including spinal taps and CT scans — are either invasive or expose patients to excess radiation. He noted that previous studies have shown that optic nerve ultrasonography could be an alternative, noninvasive method to help diagnose intracranial pressure, but few physicians routinely use it.
Almenawer and colleagues conducted a systematic review and meta-analysis of prospective studies of optic nerve ultrasonography diagnostic accuracy in 13 databases through May 2019.
A total of 71 studies, involving 4,551 patients, were considered eligible and included in analyses. Of those, 35 were determined to have a low risk for bias. The studies included patients with traumatic brain injury, nontraumatic brain injury, or a mix of patients with both types of brain injury.
For patients with traumatic brain injury, the pooled sensitivity of optic nerve ultrasonography was 97% (95% CI, 92-99) and the pooled specificity was 86% (95% CI, 74-93). The positive likelihood ratio was 6.93 (95% CI, 3.55-13.54), and the negative likelihood ratio was 0.04 (95% CI, 0.02-0.1).
Among patients with nontraumatic brain injury, the pooled sensitivity was 92% (95% CI, 86-96), and the pooled specificity was 86% (95% CI, 77-92). The positive likelihood ratio was 6.39 (95% CI, 3.77-10.84) in this population, and the negative likelihood ratio was 0.09 (95% CI, 0.05-0.17), according to the researchers.
The specificity and sensitivity were similar when stratified by patient age, level of sonography training, cause of brain injury and reference standard.
Researchers found that the optimal cutoff for optic nerve sheath dilation on ultrasonography was 5 mm.
“We’re not saying ‘cancel your intracranial monitor, cancel your CT scan,’” Almenawer said. “We’re saying just add this useful tool. It has zero side effects, it’s easy to use, and it could eliminate unnecessary CT scans and unnecessary need for reinserting the intracranial monitor.”
In an editorial accompanying the study, Kathleen Y. Ogle, MD, assistant professor of emergency medicine at George Washington University School of Medicine and Health Sciences, and Resa E. Lewiss, MD, vice chair of point-of-care ultrasound at Thomas Jefferson University Hospital, noted that the 5 mm cutoff should be approached with caution.
“Given that disease processes manifest differently in men and women, a cutoff should be determined for both sexes and should account for other characteristics, such as race,” they wrote.
Ogle and Lewiss explained that future efforts should focus on the development of a standardized approach that includes transducer type and orientation, patient position, imaging protocol and means of measurement. – by Erin Michael
References:
The Carter Center. President Carter Admitted to Emory University Hospital. https://www.cartercenter.org/news/pr/2019/statement-111119.html. Accessed Nov. 18, 2019.
Koziarz A, et al. Ann Intern Med. 2019;doi:10.7326/M19-0812.
Ogle KY, Lewiss RE. Ann Intern Med. 2019;doi:10.7326/M19-2928.
Disclosures: Almenawer reports no relevant financial disclosures. Please see study for all other authors’ relevant financial disclosures. Lewiss and Ogle report no relevant financial disclosures.