Abstract text (incl. figure legends and references)

Question: In idiopathic intracranial hypertension (IIH), certain MRI features are promising diagnostic markers, but their prognostic value is controversial.

Methods: We analyzed patients from the Vienna-Idiopathic-Intracranial-Hypertension (VIIH) database with definitive IIH according to Friedman criteria and cranial MRI performed at diagnosis. Presence of empty sella (ES), optic nerve sheath distension (ONSD), optic nerve tortuosity (ONT), posterior globe flattening (PGF) and transverse sinus stenosis (TSS) was assessed by a senior neuroradiologist with experience in IIH imaging. Impaired visual outcome was defined as a combined endpoint of visual acuity ≥0.1 logMAR and/or mean deviation <-2.0 dB in static threshold perimetry 12 months after diagnosis. Visual worsening was defined as worsening by ≥0.2 logMAR and/or ≥2.0 dB. Multivariate binary logistic regression models were calculated regarding poor visual outcome/visual worsening with IIH MRI features as independent variables adjusted for sex, age at diagnosis, symptom duration, BMI and visual dysfunction at baseline.

Results: We included 84 patients (88% female, mean age 33.5 years, median body mass index 30.8, 6% IIH without papilledema). At baseline, visual impairment was present in 70.2%. Impaired visual outcome occurred in 57.1% and visual worsening in 11.9%.At least one IIH MRI feature was found in 78.6% and 52.9% had ≥3 features with ONSD most frequent (64.3%) followed by TSS (60.0%), ONT (46.4%), ES (44.0%) and PGF (25.0%).Neither any single IIH MRI feature nor ≥1, ≥3 or a combination of features were associated with impaired visual outcome or visual worsening. Visual dysfunction at baseline predicted impaired visual outcome (odds ratio 7.6, p=0.001), but not visual worsening.

Conclusions: IIH MRI features are neither prognostic of impaired visual outcome nor further visual worsening from the time of IIH diagnosis. Visual impairment at diagnosis remains the only established predictor of visual outcome.