Optic nerve hypoplasia. Identification by magnetic resonance imaging.

High-resolution magnetic resonance images of the intracranial optic nerves and chiasm were obtained in 15 patients with severe optic nerve hypoplasia. These were compared, in a double-blind manner, with similar images from 30 age-matched controls. On both coronal and sagittal images, hypoplastic optic nerves were thin and demonstrated signal attenuation when compared with normal optic nerves. All patients with severe bilateral optic nerve hypoplasia also had diffuse chiasmal hypoplasia, which was seen best on coronal images. Patients with unilateral or asymmetrical optic nerve hypoplasia had variable chiasmal abnormalities. The degree to which the magnetic resonance diagnosis of optic nerve hypoplasia matched the clinical diagnosis was highly significant (P less than .001, Fisher's Exact Test) for both coronal and sagittal views of the intracranial optic nerves. Oblique axial and coronal views of the orbital optic nerves did not reliably distinguish optic nerve hypoplasia from normal optic nerves. High-resolution magnetic resonance imaging is a useful diagnostic modality to identify small optic nerves neuroradiologically.