Unilateral Optic Nerve Hypoplasia with Contralateral Optic Pathway Hypoplasia: A Case Report

Abstract

Optic nerve hypoplasia is diagnosed by the ophthalmoscopic appearance of the fundus of the eye and by standard magnetic resonance imaging of the brain. The ability to study eyes with optic nerve hypoplasia by magnetic resonance diffusion tensor imaging has improved the evaluation of the optic pathways. The authors report a case of unilateral optic nerve hypoplasia with hypoplasia of the contralateral optic pathway. The entire visual pathway of this patient was examined by magnetic resonance and magnetic resonance diffusion tensor imaging. The images show a decrease of the volume of the optic radiation contralateral to the optic nerve abnormality and also pre- and post-chiasmal abnormalities.

Keywords: Magnetic resonance diffusion tensor imaging; optic pathway hypoplasia; unilateral optic nerve hypoplasia.

FIGURE 1

Fundus photographs of the optic discs of a 3-year-old boy. (a) Right optic disc is normal. (b) Left optic disc is small and shows the double-ring sign (Note: Figures 1, 4, and 5 of this article are available in colour online at www.informahealthcare.com/oph).

FIGURE 2

Axial T2-weighted magnetic resonance image (MRI) of the optic pathway of a 3-year-old boy. MRI shows that the left optic nerve is thinner than the right.

FIGURE 3

Coronal T2-weighted MRI of the optic pathway. (a) Optic nerve of his left eye is thinner than that of the right. (b) No asymmetry can be seen in the chiasma. (c) The optic tract of the right (contralateral) side is thinner.

FIGURE 4

Fractional anisotropy (FA) map of a 3-year-old boy. FA of the right optic radiation shows a lower value than that of the left side. Arrows point to the thinner optic radiation on the right side (contralateral to the optic nerve hypoplasia).

FIGURE 5

Diffusion tensor visualizer image of a 3-year-old boy. MRDTI shows a reduction of the optic radiation of the right side. Arrow points to the right optic radiation.

FIGURE 6

Diagram of our hypothesis. Septo-optic dysplasia (SOD) with unilateral optic tract dysplasia, all of the optic nerve fibres decussate to the contralateral optic tract at the chiasm. This would result in reduced volume of the contralateral optic tract and radiation.