Diffusion tensor imaging of the optic disc in idiopathic intracranial hypertension

To study optic disc in idiopathic intracranial hypertension (IIH) with diffusion tensor imaging. Prospective study was carried out on 31 consecutive patients with IIH and 17 age and sex-matched controls that underwent diffusion tensor imaging of optic nerve. Fractional anisotropy (FA) and mean diffusivity (MD) of optic disc were measured by two readers. Grades of papilledema and visual field defects were evaluated by ophthalmologist. FA of optic disc was significantly lower in IIH than controls (p = 0.001) with excellent inter-observer agreement (K = 0.93) of both readers. The cutoff FA used to differentiating IIH from controls were 0.28 and 0.29 with area under curve (AUC) of 0.921 and 0.914, accuracy 92% and 91%, and sensitivity 97% and 96%. MD of optic disc were significantly higher in IIH than in controls (p = 0.001) with excellent inter-observer agreement (K = 0.91) of both readers. The cutoff MD used to differentiating IIH from controls was 1.51 and 1.22 x 10^-3 mm²/s with AUC 0.943 and 0.922, and accuracy 94% and 92% respectively. FA of optic disc was significantly lower in early than advanced papilledema and visual field defects (p = 0.001, 0.001) respectively. The MD of optic disc was significantly higher in early than advanced papilledema and visual field defects (p = 0.001, 0.001) respectively. Diffusion tensor imaging parameters of optic disc are non-invasive reliable imaging parameters that can be used for diagnosis of IIH and well correlated with papilledema and visual field defects. (orig.)