SEP 27, 2011
This prospective study evaluated the efficacy of optic nerve ultrasonography at distinguishing papilledema from pseudopapilledema in 44 patients. Ultrasonography findings on optic nerve width (ONW) correlated well with final diagnosis, especially when the upper limit of the normal ONW was set at 3.0 mm.
Researchers evaluated all patients with bilateral optic disc swelling who underwent a complete neuro-ophthalmological examination. Suitable patients were referred for neuroimaging (computerized tomography or magnetic resonance imaging) and lumbar puncture. They underwent optic nerve ultrasonography (A-mode and B-mode), and the findings were compared with the final clinical assessment.
Ultrasonography detected papilledema with a high degree of sensitivity (85 percent) when the normal ONW was set at 3.3 mm or less, and with an even higher degree of sensitivity (95 percent) when the normal ONW was set at 3.0 mm or less. Ultrasonography had a high negative predictive value for detecting papilledema: 83 percent when the normal ONW was set at 3.3 mm or less and 93 percent when it was set at 3.0 mm or less. There was a significant correlation between the ultrasonography findings and the final diagnosis (P < 0.001) when the upper limit of the normal ONW was set at 3.0 mm.
Compared to other noninvasive procedures used for examining bilateral optic nerve swelling, including fundoscopy and imaging tests, ultrasonography had the highest sensitivity and negative predictive value. It also had the best correlation with the final diagnosis and proved to be the only test whose correlation to the final diagnosis reached a level of significance. General ophthalmologic examination (including fundoscopy) and imaging tests (CT and MRI) were more specific than ultrasonography. However, the calculated sensitivities of these tests were lower than those of ultrasonography for the purposes of papilledema screening. While diagnostic tools of high specificity could be useful for confirming a diagnosis of papilledema, those with high sensitivity rather than high specificity could be useful screening tools for indicating which patients require additional invasive tests to confirm the final diagnosis.
This study is limited by its small size and possibly biased by the fact that it relied on the talents of a single, very experienced ultrasonographer to perform all measurements. Nevertheless, the authors conclude that ultrasonography could be a useful noninvasive technique for differentiating papilledema from other causes of optic disk edema.