Intraorbital optic nerve coloboma: Neurosurgical considerations from two rare cases.

Background: Coloboma or colobomatous cyst of the optic nerve coloboma (ONC) is a rare congenital anomaly commonly associated with microphthalmia or anophthalmia. Neurosurgeons usually treat orbital lesions surgically; however, in some centers, neuro-ophthalmologists and other surgical specialties may also be involved in these procedures. Given this context, neurosurgeons must be familiar with various intraorbital lesions, including ONC. Here, emphasizing the clinical, pathological, and radiological aspects, we report two uncommon pediatric cases of ONC to enhance neurosurgeons' awareness and recognition of this condition. Case Description: The first case involved a 2-year and 9-month-old boy who presented with proptosis, palpebral ptosis, visual impairment, and exotropia of the right eye. Magnetic resonance imaging (MRI) showed an intraorbital retrobulbar cystic lesion without microphthalmia. A right front-orbital craniotomy was performed with total removal of the cystic lesion and with improved proptosis, maintaining the visual deficit. The second case involved a 7-year-old and a 9-month-old girl with congenital exotropia and visual impairment in the right eye. MRI revealed a cystic optic nerve associated with microphthalmia. She underwent a cyst puncture and clinical and MRI follow-up. The histology studies confirmed ONC in both cases. Conclusion: Although often unfamiliar to neurosurgeons, these two presentations of ONC (with and without microphthalmia) should be included in the differential diagnosis of retrobulbar lesions, especially in pediatric patients.