To evaluate the inter-rater reliability of idiopathic intracranial hypertension (IIH) neuroimaging criteria in patients with refractory (IIH). 

The lack of operational cut-off values for the current IIH imaging diagnostic criteria causes potential variation in radiological interpretations. A standardized neuroimaging protocol was developed and investigated for its utility.  

Brain MRI/MRV from 15 refractory IIH patients were reviewed independently by three experienced neuroradiologists at Thomas Jefferson University Hospital. Standardized neuroimaging interpretation criteria were utilized: sella herniation grade, posterior globe flattening (PGF), protrusion at the optic nerve head (ONP), optic nerve horizontal/vertical tortuosity (ONHT/ONVT), distention of the optic nerve subarachnoid space (ONSAS)≥2mm, distention of the optic nerve sheath diameter (ONSD) ≥5.5mm, index of transverse sinus stenosis (ITSS), and transverse sinus of either unilateral ≥50% stenosis with contralateral hypoplasia (≥40% narrower) or bilateral stenosis. Sequence utilization and inter-rater reliability (intraclass correlation coefficient) were assessed. 

Several IIH imaging features showed high agreement: ONSAS≥2mm (1.00), ONSD≥5.5mm (0.72, 95%CI 0.29-0.91), ONVT (0.88, 95%CI 0.68-0.92), sella herniation grade (0.75, 95%CI 0.38-0.92), ITSS (0.85, 95%CI 0.63-0.95), 50% venous sinus stenosis (0.87, 95%CI 0.69-0.95) and pituitary height<4.8mm (0.75, 95%CI 0.38-0.92). Other imaging features showed low agreement: tonsil descent≥5mm, ONHT, PGF, and ONP. Quality assessment of imaging sequences showed only 5 (35.7%) axial orbit T2 thin-cut fat-saturated, and 6 (42.8%) coronal orbit T2 thin-cut fat-saturated were available.   

IIH imaging features showed high agreement justifying the use of standardized criteria in IIH assessments. Inter-rater discrepancy exists in particularly assessing orbits. Standardizing imaging protocol, especially including axial high-resolution T2w sequence, in our experience, will not only improve inter-rater reliability for certain low agreement criteria, including ONHT and PGF, but also will further improve objective measurements of ON sheaths reported above.