Abstract text (incl. figure legends and references)

Question: In idiopathic intracranial hypertension (IIH), certain MRI features are promising diagnostic markers, but whether these have prognostic value is controversially discussed.

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.
Two endpoints of headache outcome were defined 12 months after IIH diagnosis: headache improvement (reduction of headache severity and/or frequency by ≥50%) and freedom of headache (Multivariate regression models were calculated regarding headache improvement/freedom with IIH MRI features as independent variables adjusted for sex, age at diagnosis, symptom duration, body mass index [BMI], and chronic headache at baseline (>15 days/month for ≥3 months).

Results: We included 84 IIH patients (88% female, mean age 33.5 years, median BMI 30.8, 6% IIH without papilledema). At baseline, headache was present in 84.5% (54.8% chronic). Headache improvement was achieved in 83.8%, freedom of headache in 25.7%. 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%).
In multivariate models, neither any single IIH MRI feature nor ≥1, ≥3 or a combination of features were associated with headache improvement or freedom. Chronic headache at baseline was significantly associated with lower likelihood of headache freedom (odds ratio 0.23, p<0.001), but not headache improvement.

Conclusions: IIH MRI features are not prognostic of headache outcome. Chronic headache at diagnosis is an unfavourable predictor of headache outcome.