Answer:
Optic nerve sheath arachnoid cyst.
Findings:
Well demarcated intraconal cystic lesion present in continuous with optic nerve sheath. The optic nerve is visible at the proximal aspect of cyst, thereafter displaced medially and inferiorly indicating asymmetric dilatation of optic nerve sheath.
Discussion
Arachnoid cyst of the optic nerve is a lesser recognized entity. Similar to the intracranial arachnoid cysts, they follow fluid signal intensity on all sequences.
They are seen as a saccular dilatation of the meninges surrounding the orbital portion of the optic nerve. They are also called as optic neural sheath meningocele, optic nerve sheath cyst, perioptic hygroma.
May occur primarily or secondarily in association with other orbital processes, such as meningioma, optic nerve pilocytic astrocytoma, and hemangioma.
Not to be confused with simple optic nerve sheath dilatation caused by intracranial hypertension, hydrocephalus and optic nerve hydrops. The dilatation of optic nerve sheath is asymmetric with arachnoid cyst in contrary to these above mentioned lesions causing eccentric displacement of optic nerve within the sheath.
Contributed By:
Dr. Karunakaran M. Kalathi MD, Dr. Arun Chelladurai MD
Consultant Radiologists, Aarthi Scans, Thirunelveli, Tamilnadu, India
Optic nerve sheath arachnoid cyst.
Findings:
Well demarcated intraconal cystic lesion present in continuous with optic nerve sheath. The optic nerve is visible at the proximal aspect of cyst, thereafter displaced medially and inferiorly indicating asymmetric dilatation of optic nerve sheath.
Discussion
Arachnoid cyst of the optic nerve is a lesser recognized entity. Similar to the intracranial arachnoid cysts, they follow fluid signal intensity on all sequences.
They are seen as a saccular dilatation of the meninges surrounding the orbital portion of the optic nerve. They are also called as optic neural sheath meningocele, optic nerve sheath cyst, perioptic hygroma.
May occur primarily or secondarily in association with other orbital processes, such as meningioma, optic nerve pilocytic astrocytoma, and hemangioma.
Not to be confused with simple optic nerve sheath dilatation caused by intracranial hypertension, hydrocephalus and optic nerve hydrops. The dilatation of optic nerve sheath is asymmetric with arachnoid cyst in contrary to these above mentioned lesions causing eccentric displacement of optic nerve within the sheath.
Contributed By:
Dr. Karunakaran M. Kalathi MD, Dr. Arun Chelladurai MD
Consultant Radiologists, Aarthi Scans, Thirunelveli, Tamilnadu, India