Asymmetric papilledema in idiopathic intracranial hypertension.

BACKGROUND Very asymmetric papilledema in idiopathic intracranial hypertension (IIH) is rare, and few studies have dealt with this atypical presentation of IIH. Our aim was to describe the clinical and radiologic features of patients with IIH and very asymmetric papilledema. METHODS We identified all adult patients from our IIH database with very asymmetric papilledema defined as a ≥2 modified Frisén grade difference between the 2 eyes. Demographic data and initial symptoms were collected, and all brain imaging studies performed at our institution were reviewed. RESULTS Of the 559 adult patients with definite IIH, 20 (3.6%; 95% confidence interval [CI], 2.3-5.6) had very asymmetric papilledema at initial evaluation. They were older (39 vs 30 years; P < 0.001), had lower cerebrospinal opening pressure (35.5 vs 36 cm of water; P = 0.03), and were more likely to be asymptomatic compared with patients with symmetric papilledema (27% vs 3%; P < 0.001). Visual fields were worse on the side of the highest-grade papilledema (P = 0.02). The bony optic canal was smaller on the side of the lowest-grade edema in all 8 patients (100%) in whom the imaging was sufficient for reliable measurements (P = 0.008). CONCLUSIONS IIH with very asymmetric papilledema is uncommon. Very asymmetric papilledema may result from differences in size of the bony optic canals, supporting the concept of compartmentation of the perioptic subarachnoid spaces.