The efficacy of optic nerve ultrasonography for differentiating papilloedema from pseudopapilloedema in eyes with swollen optic discs

Purpose: To evaluate the diagnostic yield of optic nerve ultrasonography (US) in distinguishing between papilloedema (swollen discs owing to raised intracranial pressure) and pseudopapilloedema. Methods: We prospectively 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 US (A-mode and B-mode), and the findings were compared with the final clinical assessment. Sensitivity, specificity and predictive values for US distinction between true papilloedema and pseudopapilloedema were calculated and compared with those of the other imaging tests. Results: Forty-four patients were enrolled. Ultrasonography detected papilloedema with a high degree of sensitivity (85%) when the normal optic nerve width (ONW) was set at ≤3.3 mm, and with an even higher degree of sensitivity (95%) when the normal ONW was set at ≤3.0 mm. Ultrasonography had a high negative predictive value for detecting papilloedema: 83% when the normal ONW was set at ≤3.3 mm and 93% when it was set at ≤3.0 mm. There was a significant correlation between the US findings and the final diagnosis (p < 0.001) when the upper limit of the normal ONW was set at 3.0 mm. Conclusions: Ultrasonography findings of the ONW correlated well with the final diagnosis of papilloedema or pseudopapilloedema, especially when the upper limit of the normal ONW was set at 3.0 mm. Ultrasonography could be a useful non-invasive technique for differentiating papilloedema from other causes for swollen discs, such as pseudopapilloedema.