Use of A-scan Ultrasound and Optical Coherence Tomography to Differentiate Papilledema From Pseudopapilledema.

SIGNIFICANCE Differentiating papilledema from pseudopapilledema reflecting tilted/crowded optic discs or disc drusen is critical but can be challenging. Our study suggests that spectral-domain optical coherence tomography (OCT) peripapillary retinal nerve fiber layer thickness and retrobulbar optic nerve sheath diameter (ONSD) measured by A-scan ultrasound provide useful information when differentiating the two conditions. PURPOSE To evaluate the use of A-scan ultrasound and spectral-domain OCT retinal nerve fiber layer thickness (RNFLT) in differentiating papilledema associated with idiopathic intracranial hypertension from pseudopapilledema. METHODS Retrospective cross-sectional analysis included 23 papilledema and 28 pseudopapilledema patients. Ultrasound-measured ONSD at primary gaze, percent change in ONSD at lateral gaze (30 degrees test), and peripapillary RNFLT were analyzed. Receiver operating characteristic curves were constructed using one eye from each subject. RESULTS Compared with pseudopapilledema, papilledema eyes showed larger mean ONSD (5.4 0.6 vs. 4.0 +/- 0.3 mm, P < .0001), greater change of ONSD at lateral gaze (22.4 +/- 8.4% vs. 2.8 +/- 4.8%, P < .0001), and thicker retinal nerve fiber layer (219.1 +/- 104.6 vs. 102.4 +/- 20.1 m, P < .0001). Optic nerve sheath diameter and 30 degrees test had the greatest area under the receiver operating characteristic curve, 0.98 and 0.97, respectively; followed by inferior quadrant (0.90) and average RNFLT (0.87). All papilledema eyes with Frisen scale greater than grade II were accurately diagnosed by ONSD, 30 degrees test, or OCT. In mild papilledema (Frisen scale grades I and II, n = 15), area under the receiver operating characteristic curve remained high for ONSD (0.95) and 30 degrees test (0.93) but decreased to 0.61 to 0.71 for RNFLT. At 95% specificity, sensitivities for ONSD, 30 degrees test, and RNFLT were 91.3%, 91.3%, and 56.5%, respectively, for the entire papilledema group and 80.0%, 86.7%, and 13.3% for the mild papilledema subgroup. CONCLUSIONS Retinal nerve fiber layer thickness can potentially be used to detect moderate to severe papilledema. A-scan may further assist differentiation of mild papilledema from pseudopapilledema.