The distal part of the orbital portion of the optic nerve was found to be significantly enlarged and had a bulb-like appearance

The distal part of the orbital portion of the optic nerve was found to be significantly enlarged and had a bulb-like appearance. arachnoid cyst, perioptic subdural hygroma, and dural ectasia of the optic nerve sheath all have been used to describe this entity since its first description Selpercatinib (LOXO-292) in 1918. 1, 2, 4The term optic nerve sheath meningocele was Selpercatinib (LOXO-292) introduced by Garrity et al in 1990. 1We prefer the term dural ectasia to describe the optic nerve sheath dilatation. Imaging of the orbit using magnetic resonance imaging (MRI) in patients with dural ectasia reveals tube-like enlargement of the optic nerve/sheath complex. 1, 2We present a patient with rapidly progressive visual loss which was related to dural ectasia of the optic nerve sheath and the vision remained unchanged despite surgical treatment. == Case report == A 36-year-old Selpercatinib (LOXO-292) female was admitted (to the Department of Neurology, Hacettepe University Medical Faculty, Department of Neurology, Neuro-ophthalmology Unit, Ankara, Turkey) with the complaints of headache and severe bilateral visual loss that had progressed rapidly in 3 months. She was found to have papilledema on examination and had been treated with acetazolamide 250 mg qid for 8 weeks elsewhere. Idiopathic intracranial hypertension (IIH) was considered in diagnosis although opening pressure was recorded normal in the lumbar puncture (LP). On our examination her visual acuity (VA) was light perception OD and 20/100 OS. There was a right afferent pupillary defect. Fundoscopy revealed pale optic nerve head with blurred margins on the right and chronic disc edema on Selpercatinib (LOXO-292) the left. She was not able to identify any of the Ishihara color plates OU. LP was performed with an opening pressure of 22 cm of H2O. CSF analysis showed protein level of 40 mg/dL and no cells. MRI studies revealed a fluid-filled dilated optic nerve sheath surrounding the optic nerves (Figure 1). There was no evidence of a space-occupying lesion. Her left VA decreased to counting fingers in a week. The CSF pressure at the repeat LP was significantly low which could not be recorded. Dural ectasia of the optic nerve is considered in diagnosis. Due to progressive dysfunction of the optic nerve despite PLAUR treatment with carbonic anhydrase inhibitors, optic nerve sheath decompression via medial transconjunctival approach was performed bilaterally by an ophthalmic surgeon (HK). The distal part of the orbital portion of the optic nerve was found to be significantly enlarged and had a bulb-like appearance. The dura was streched but otherwise looked normal. Overlying Selpercatinib (LOXO-292) dural vessels were also enlarged and tortuous. Three parallel longitudinal incisions, each measuring 2 to 2 . 5 mm in length, were made into the dura along the enlarged optic nerve. Large amount of clear fluid rapidly egressed with pressure following the first incision. The optic nerves deflated within seconds while cerebrospinal fluid continued to ooze for a while. No intraoperative complications were observed. The left optic disc edema resolved within one week and the patient remained stable over the next 3 months with the same visual acuity. == Figure 1 . == Fluid-filled dilated sheath surrounds normal optic nerves on T2-weighted axial MRI. == Discussion == A dilatation of the optic nerve sheath could be secondary to neoplasms and malformations of the orbit, like gliomas, meningiomas and arachnoid cysts involving the optic nerve sheath. 1, 2Dural ectasia of the optic nerve is a rare cause of optic nerve sheath enlargement due to the accumulation of CSF around the optic nerve with no associated pathology. The radiological examination of choice is MRI with fat suppression and high spatial resolution which shows tube-like enlargement of the optic nerve sheath isointense with cerebrospinal fluid. 2Optic nerve glioma can be associated with thickening and distention of the optic nerve which is in contrast with the appearence of meningocele. Optic nerve sheath meningioma should also be considered in the differential diagnosis because of its railroad track appearance of the optic nerve. 4Clinical examination, CSF analysis, MRI, investigations including full blood count, anti-nuclear antibodies, erythrocyte sedimentation rate, folate, serum B12 and serum angiotensin converting enzyme levels in our patient revealed no evidence of any other systemic disease or abnormalities.