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David Patterson, Jacqueline A Leavitt, Nathan Smischney, Sara Hocker, Eelco Wijdicks, Mai Ho, David Hodge, John Jing-Wei Chen; Evaluating tools of measuring intracranial pressure. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4554.
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© ARVO (1962-2015); The Authors (2016-present)
An indirect and non-invasive method of detecting increased intracranial pressure (ICP) would be an invaluable tool in multiple facets of medicine. The purpose of this study is to evaluate and compare the efficacy of ocular ultrasonography (US) in detecting increased ICP via measurement of the optic nerve sheath diameter (ONSD) and MRI measurements of the ONSD and sella in patients with idiopathic intracranial hypertension (IIH).
We performed a retrospective and prospective analysis comparing the ONSD of patients with papilledema from IIH (n= 18) and patients with pseudopapilledema without increased ICP (n=15). The ONSD was measured by both US and MRI at a distance of 3 mm posterior to the globe. Secondarily, a ratio of pituitary gland height compared to sella turcica height on MRI was used to assess for the “empty sella” sign commonly seen in patients with IIH.
Patients with IIH had a significantly larger ONSD by US (mean 5.1 mm, STD 0.6) compared to patients with pseudopapilledema (mean 4.2 mm, STD 0.6, p<0.001). Similarly, MRI measurements of ONSD were significantly larger for the IIH group (mean 6.4 mm, STD 1.3) compared to the pseudopapilledema group (mean 4.6 mm, STD 0.7, p<0.001). Analysis of pituitary/sella ratio yielded a significantly smaller ratio in the IIH group (mean 0.3, STD 0.2) compared to the pseudopapilledema group (mean 0.7, STD 0.2, P<0.001). There was a strong correlation between MRI and US measured ONSD (r=0.68, p<0.001). Using an ONSD cutoff of >4.7 mm, the sensitivity and specificity for detecting IIH were 81% and 86% via US and 89% and 61% via MRI. Using a pituitary/sella cutoff of <0.47 on MRI led to a sensitivity of 78% and specificity of 79% for identifying IIH. Having an abnormal value on any one of the three measurements led to 100% sensitivity, but a lower specificity of 46%. Conversely, having an abnormal value on all three measurements provided a sensitivity of 50% and a specificity of 100% for identifying IIH.
The ONSD measured by US and MRI significantly differs between patients with IIH and those with pseudopapilledema, despite some overlap in ONSD ranges between the groups. The empty sella sign on MRI can also be quantified and used to differentiate patients with IIH from patients with pseudopapilledema. Combining all three measurements can increase the ability to accurately diagnose patients with IIH.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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