Purpose or Case Report: Optic nerve aplasia (ONA) is a very rare developmental anomaly characterized by absence of optic nerve, retinal ganglion, and optic nerve vessels. The majority of reported ONA cases are unilateral. The rarer cases of bilateral ONA are often associated with additional brain anomalies. ONA is considered distinct from optic nerve hypoplasia. Both environmental and genetic factors have been hypothesized to contribute to ONA, and several genetic mutations have been identified, including PAX6, OTX2, CYP26A1, or CYP26C1. We report a case of bilateral ONA in an otherwise healthy infant with mild hypoplasia of the corpus callosum without dysplasia, and macrocephaly.
A 13-month-old male presented for evaluation of macrocephaly and global developmental delay that was attributed to cortical blindness. He was born full-term without complications, however mother felt no fetal movement for one week prior to delivery. Abnormal roving eye movements were noted since the early neonatal period. There was no family history of any congenital diseases. Examination revealed conjugate non-purposeful rapid eye movements without nystagmus, bilateral lens opacification, and absence of the pupillary light response, startle reflex, and red reflex. The remainder of the physical exam was normal.
MRI of the brain and obits demonstrated absence of the bilateral optic nerves, optic chiasm, and the optic tracts. The globes were normal in size and appearance, although with the right minimally larger than the left. The corpus callosum was relatively thin, but intact, suggesting mild hypoplasia without dysplasia. In contrast to the majority of reported bilateral ONA cases that have associated CNS anomalies (polymicrogyria, corpus callosum agenesis, hypopituitarism, hydrocephalus, microphthalmus), our patient was only noted to have macrocephaly and mild hypoplasia of the corpus callosum. No other brain structural abnormalities were present. Initial genetics evaluation with a microarray was normal, therefore further testing with exome sequencing is planned. We report an extremely rare case of bilateral ONA in an otherwise healthy infant and review the literature for the associated radiologic and genetic findings.
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