Impact of rater experience on detecting MRI features of idiopathic intracranial hypertension

Abstract Background: In idiopathic intracranial hypertension (IIH), certain MRI features are promising diagnostic markers, but impact of neuroradiologist’s experience and specific referral question on identifying these features correctly is unknown. Therefore, we compared ratings in real-world setting by radiologists with unknown awareness of IIH-MRI-features, with the ratings of a junior neuroradiologist aware of features but without special IIH training, and a senior neuroradiologist with experience in IIH imaging (gold standard). Methods : For comparing the 3 settings, we included patients from the Vienna-Idiopathic-Intracranial-Hypertension (VIIH) database with definitive IIH according to Friedman criteria and routine cranial MRI performed during diagnostic work-up and assessed frequencies of empty sella (ES), optic nerve sheath distension (ONSD), optic nerve tortuosity (ONT), posterior globe flattening (PGF) and transverse sinus stenosis (TSS). Results: We evaluated MRI scans of 84 IIH patients (88% female, mean age 33.5 years). By gold standard, 78.6% had ≥1 IIH-MRI-feature and 60.0% had ≥3 features with ONSD most frequent (64.3%) followed by TSS (60.0%), ONT (46.4%), ES (44.4%) and PGF (23.8%). Compared to gold standard, IIH features were described significantly less frequently in routine MRI reports (≥1 feature 64.3%, ≥3 features 15.7%, ONSD 28.6%, ONT 13.1%, PGF 4.8%, TSS 42.9%, p<0.01 respectively) except for ES (42.9%, p=0.9). Specific referral question regarding IIH increased detection rates in routine reports, but rates of ONSD, ONT and PGF were still significantly lower than by gold standard. Contrary, rating by a neuroradiologist without special training produced significantly higher frequencies of ≥1 / ≥3 MRI features (95.2% and 72.5%, p<0.01 respectively), ONSD (81.0%, p<0.01) and ONT (60.7%, p<0.01), but not ES (47.6%), PGF (29.8%) and TSS (68.1%). Conclusions: IIH-MRI-features are underestimated in routine MRI reports and partly overcalled by less experienced neuroradiologists, driven by features less well known or methodologically difficile. Reevaluation of MRI scans by an experienced rater (and to a lesser degree specific referral question) improves diagnostic accuracy.