Multimodal imaging biomarkers in idiopathic intracranial hypertension: associations of A-scan ultrasonography, optical coherence tomography and MRI

Idiopathic intracranial hypertension (IIH) requires repeated assessment of disease activity, yet lumbar puncture (LP) and MRI are poorly suited for longitudinal monitoring. A-scan ultrasonography (US) and optical coherence tomography (OCT) provide complementary non-invasive biomarkers of optic nerve involvement, but their interrelationship and their association with structural MRI signs of raised intracranial pressure (ICP) remain incompletely understood. In this retrospective study, patients from the Vienna IIH database fulfilling diagnostic criteria for IIH underwent standardized A-scan US, OCT, LP, and MRI. Patients with all examinations performed within 30 days constituted the primary cohort (PrimCo), whereas patients with LP outside this interval or unavailable cerebrospinal fluid opening pressure (CSF-OP) formed an exploratory cohort (ExplCo) reflecting routine clinical practice. Linear mixed-effects models assessed associations between US-derived optic nerve sheath diameter (US-ONSD), OCT metrics (peripapillary retinal nerve fiber layer [pRNFL] thickness and optic nerve head [ONH] volume), and structural MRI signs or raised ICP. Pearson correlations were used to evaluate associations with CSF-OP. Seventy-seven patients were included (PrimCo, n = 31; ExplCo, n = 46). PrimCo showed more pronounced papilledema and larger US- and MRI-derived ONSD. In the PrimCo, US-ONSD was positively associated with both pRNFL thickness (β = 0.371, p < 0.001) and ONH volume (β = 0.435, p < 0.001), whereas corresponding associations were weaker and not statistically significant in the ExplCo. Among structural MRI signs in the PrimCo, posterior globe flattening was associated with larger US-ONSD (β = 0.568, p = 0.043), whereas optic nerve tortuosity showed a trend toward a negative association (β = −0.572, p = 0.064). None of the structural MRI signs was associated with OCT metrics. CSF-OP showed no significant correlation with any imaging biomarker. Significant associations between US-ONSD and OCT-derived metrics in papilledema were most evident in the cohort with more pronounced signs of raised intracranial pressure, whereas these associations were attenuated in the more heterogeneous cohort. Structural MRI signs showed limited concordance with ophthalmic biomarkers. These findings argue against interpreting individual imaging biomarkers in isolation and emphasize the need to integrate them with the overall clinical phenotype. Not applicable.