Introduction: An orbital encephalocele is a rare variant of encephalocele in which there is a herniated mass of brain and meninges into the orbit. The encephalocele may arise through natural foramina or bony defects in the orbital roof. Most orbital encephaloceles are considered to be of congenital origin but post traumatic cases have been reported. We present a case of an orbital encephalocele which was later pathologically identified with a small focus of pilocytic astrocytoma. Pilocytic astrocytomas have been reported to occur in the optic nerve or optic chiasm but do not commonly occur in the orbit.

Methods: A 29-year-old male with a past medical history significant for a remote high-velocity motor vehicle accident and multiple sports-related concussions presented with a series of witnessed tonic-clonic seizures. A head CT performed in the emergency department revealed a right-sided encephalocele that protruded into the orbit. Further imaging included an MRI that showed strangulation with T2 signal change. Clinically, the patient had slight right-sided ptosis.

Results: The encephalocele was surgically resected and the pathological interpretation confirmed disorganized neuro-glial consistent with encephaloceles. However, there was with a 0.5 cm focus of low grade pilocytic astrocytoma encased by the encephalocele.

Conclusions: Piloid gliosis may occur as a result chronic processes like an encephalocele; however, our case exhibited increased cellularity and clearly involved the leptomeninges, which are features in favor of a pilocytic astrocytoma. It is unclear if the tumor caused bony erosion resulting in an encephalocele, or if the chronic inflammation of the encephalocele produced an environment which promoted a pilocytic astrocytoma. To our knowledge this is the first case report of a pilocytic astrocytoma within an orbital encephalocele. Although we do not know the general significance of our patient’s findings, we recommend close pathological examination of orbital encephaloceles.

Patient Care: To our knowledge this is the first report of a pilocytic astrocytoma located within the orbit not originating from the optic pathway, as well as the first case of a pilocytic astrocytoma completely contained within an encephalocele. This case suggests close pathological examination of encephaloceles for underlying disease.

Learning Objectives: 1. Illustrate the need for pathological evaluation of orbital encephaloceles

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