Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Brief Report
Case Report
Case Series
Commentary
Editorial
Images
Letter to Editor
Media and News
Original Article
Review Article
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Brief Report
Case Report
Case Series
Commentary
Editorial
Images
Letter to Editor
Media and News
Original Article
Review Article
View/Download PDF

Translate this page into:

Case Report
ARTICLE IN PRESS
doi:
10.25259/JNRP_5_2022

Bilateral idiopathic optic nerve sheath meningocele: A case report and literature review

Department of Neuroscience, University of Turin, Turin, Italy
Department of Radiology, CTO Hospital, Turin, Italy
Department of Neurosurgery, CTO Hospital, Turin, Italy
Corresponding author: Andrea Bianconi, Department of Neuroscience, University of Turin, Turin, Italy. andrea.bianconi@edu.unito.it
Licence
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Morello A, Bianconi A, Cogoni M, Borgarello S, Garbossa D, Micon BM. Bilateral idiopathic optic nerve sheath meningocele: A case report and literature review. J Neurosci Rural Pract, doi: 10.25259/JNRP_5_2022

Abstract

Optic nerve (ON) sheath meningocele is an enlargement of the ON sheath, consisting in a cerebrospinal fluid collection along the perineural space of the optic nerve. It should be considered primary when it is not associated with orbital-cerebral neoplasm or with cranio-orbital junction malformations. Here, we report a case of bilateral primary idiopathic ON meningocele with gradual vision loss, treated with acetazolamide, which showed a maintained visual recovery and partial improvement during a 6-month follow-up period. The literature review retrieved eight cases of primary idiopathic ON sheath meningocele: ON sheath fenestration is considered in patients with progressive and severe vision loss, otherwise, acetazolamide treatment is indicated with good results on symptoms control, as confirmed in our case report.

Keywords

Optic nerve
Meningocele
Vision loss

INTRODUCTION

Optic nerve (ON) sheath dilatation or meningocele is a rare condition described as an enlargement and dilation of primarily the ON sheath.[1] It generally consists of a collection of cerebrospinal fluid (CSF) along the perineural space of the ON and should be considered primary when it is not associated with orbital-cerebral neoplasm or with cranio-orbital junction malformations. We describe a case of bilateral primary idiopathic ON meningocele with gradual vision loss and treated with acetazolamide, which showed a maintained visual recovery and partial improvement during a 6-month follow-up period.

CASE REPORT

A 46-year-old female presented with a 7-year history of blurring of vision in the right eye, chronic headache, and periorbital pain episodes. Her medical history included Hashimoto’s thyroiditis, gastric bypass surgery, and cholecystectomy. On examination, her pupil reactions were normal, and her ocular motility was unrestricted. Her best-corrected visual acuity was 9/10 in both eyes. A first visual field test reported a partial temporal hemianopsia in the right eye. Visual evoked responses revealed a conduction delay in the right eye. A first color vision was tested with Ishihara color plates and it was normal on both sides. Anterior segment examination was normal in both eyes. Examination of the fundus reveled bilateral optic atrophy; there was no disk swelling. Her intraocular pressure was measured at 16 mmHg in both eyes.

After 6 months, a second visual evoked responses confirmed evidence of pathway delay in the right eye, equal to the first examination. Otherwise, color vision was partially reduced in the right eye with a score of 16 correct responses out of the first 21 Ishihara plates. There was no evidence of a hyperopic shift in her refraction, any evidence of choroidal folds and currently macular pathology has not been noted.

Investigations including thyroid function tests, full blood count, serum B12, folate, urea and electrolytes, erythrocyte sedimentation rate, and a treponemal screen were normal. Anti-nuclear antibodies were negative. A lumbar puncture was performed with an opening pressure of 29 cm of water.

The patient underwent a brain magnetic resonance imaging (MRI) scan that ruled out conditions that can lead to chiasmal compression and excluded a case of idiopathic intracranial hypertension (IIH). MRI showed bilateral ON sheath dilatation and enlargement, with normal sized optic nerves and with no associated inflammation, orbital, or cerebral neoplasm at the apex of the orbit [Figures 1 and 2]. Except for empty sella, MRI did not reveal imaging features that support the diagnosis of IIH, and diagnostic criteria for IIH were not satisfied. Subsequently, the patient underwent a phase-contrast cine MRI which demonstrated the absence of hyperdynamic flow of CSF through the aqueduct.

Figure 1:: T2-weighted axial view showing the optic nerve meningocele.
Figure 2:: Coronal T2-weighted image showing the “bull’s eye” appearance.

The patient is being followed conservatively with serial visual examinations and with a course of acetazolamide 250 mg twice daily (Tablets) for 3 months. At present, with this therapy, she did not report a further vision loss.

DISCUSSION

The term “ON head meningocele” (ONHM) was first coined in 1990 in Garrity et al.’s landmark paper in which 13 patients were described with this condition:[1] They all had dilated ON sheaths with an expanded CSF space and with no associated inflammation, orbital or cerebral neoplasm at the apex of the orbit. The pathophysiology of ONHM is not well understood. One theory relies on the difference in osmotic gradient between the cerebral subarachnoid space and perioptic subarachnoid space; in fact, a raised protein level was found in the CSF drained from an ON cyst in a 1997 case report.[2] Another theory is that congenital narrowing of the optic or cranial-orbital junction could cause the CSF accumulation in the perioptic subarachnoid space.[3] Cases of ONHM have spanned both sexes and all age groups.[1] The presentation symptoms are visual disturbance (either a drop in visual acuity or a field disturbance), headache, proptosis, and periorbital pain.[3,4] On ocular examination, many patients have a visual field defect with optic disk pallor or edema.[2] Some authors have noticed a subgroup of ONHM that consists of middle-aged men with progressive hyperopia, choroidal folds, and macular pathology.[2] Other authors have noticed a subgroup of cases with elevated CSF pressure.[1,4,5] In a case series by Dailey et al., four out of the seven patients reported with hyperopia and choroidal folds had ON meningoceles.[6] ON sheath enlargement can be seen in cases of neurofibromatosis Type I, Marfan syndrome, or IIH.[7-10] The diagnosis is usually made by obtaining MRI of the orbits. The dilated ON sheath which is filled with CSF can easily be visualized. Coronal T2-weighed images can show the so-called bull’s eye appearance, which represents expanded CSF spaces around the ON.[1] MRI is useful to rule out conditions that can lead to secondary enlargement of ON sheath such as orbital masses and ON gliomas. The prognosis for this condition varies. Progressive visual loss can occasionally be seen. Treatment is usually tailored to the patient’s vision. Carbonic anhydrase inhibitors can be beneficial in some cases: Three patients on acetazolamide therapy reported no new loss of vision.[3,11,12] Surgical interventions in the form of ON sheath fenestration may be of benefit in cases of progressive vision loss. In a 1997 case review, 13 of 33 patients with ON sheath meningocele had some type of surgical decompression – four frontal craniotomies, one pterional craniotomy, and eight lateral orbitotomies. Five of the 13 patients who had the procedure experienced improvement of their symptoms while six had no change in their symptoms.[2] In a 2017 case report, an ON sheath fenestration was performed in a 10-year-old boy, and he experienced an improvement and stabilization of vision during a 1-year follow-up period.[13]

The current evidences are summarized in [Table 1].

Table 1:: Summary table of cases reported in the literature.
Author, year Type of article Cases (sex) Presentation Cerebrospinal fluid pressure Patients underwent a surgical procedure Associated findings Associated medical conditions
Garrity
et al., 1990
Review 13 patients
(7 M-6F)
6 Visual deficit 4 headaches 3 both Elevated in 2 patients 3 Postoperatively, one patient improved 3 patients had type I neurofibromatosis; 5 patients had optic nerve type defects
Lunardi
et al., 1997
Review 33 patients Visual deficit and headache - 13 Postoperatively, 5 patients improved 9 patients presented hyperopia
Shanmuganathan et al., 2002 Case report 1 M Visual deficit, orbital pain and proptosis Elevated - - Unilateral cystoid macular edema
Mesa-Gutiérrez
et al., 2008
Case report 1 M Visual deficit Normal - With acetazolamide, not reported new loss of vision Choroidal folds
Halimi
et al., 2013
Case report 1 F Visual deficit and periorbital pain Normal - With acetazolamide, not reported new loss of vision Optic disk drusen and pseudopapilledema
Mahatma
et al., 2017
Case report 1 M Visual deficit - 1 Postoperatively, patient improved Bilateral colobomatous cavitary disk anomalies
Algarni
et al., 2018
Case report 2 (1 M – 1 F) Visual deficit Elevated - - Swelling of the optic disk and choroidal folds
Jain
et al., 2019
Case report 1 F Visual deficit and proptosis - - With acetazolamide, not reported new loss of vision Hyperopia and choroidal folds
Shaikh
et al., 2019
Case report 1 F Soft-tissue mass covering eye - - - Patient had type I neurofibromatosis

CONCLUSION

ON sheath meningocele refers to dilatation of the ON sheath, which can have variable presentation. ON dysfunction can be seen, and it can range in severity from subtle involvement to a progressive vision loss. The diagnosis is made with orbit MRI. ON sheath fenestration may be an option in patients with progressive and severe vision loss; otherwise, acetazolamide treatment is indicated with good results on symptoms control, as confirmed in our case report.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

  1. , , , , , , et al. Optic nerve sheath meningoceles. Clinical and radiographic features in 13 cases with a review of the literature. Ophthalmology. 1990;97:1519-31.
    [CrossRef] [Google Scholar]
  2. , , , , , . Surgically verified case of optic sheath nerve meningocele: Case report with review of the literature. Neurosurg Rev. 1997;20:201-5.
    [CrossRef] [PubMed] [Google Scholar]
  3. , , . Optic nerve sheath meningocele. Clin Ophthalmol. 2008;2:661-8.
    [CrossRef] [PubMed] [Google Scholar]
  4. , , , . Bilateral idopathic optic nerve sheath meningocele associated with unilateral transient cystoid macular oedema. Eye (Lond). 2002;16:800-2.
    [CrossRef] [PubMed] [Google Scholar]
  5. , , . Optic nerve sheath meningocele. Int Med Case Rep J. 2018;11:213-5.
    [CrossRef] [PubMed] [Google Scholar]
  6. , , , , . The natural history and CT appearance of acquired hyperopia with choroidal folds. Ophthalmology. 1986;93:1336-42.
    [CrossRef] [Google Scholar]
  7. , , , . Dural ectasia of the optic nerve: A rare presentation in neurofibromatosis Type I. J Neurosci Rural Pract. 2019;10:349-51.
    [CrossRef] [PubMed] [Google Scholar]
  8. , , , , . Dural ectasia of the optic nerve sheath in neurofibromatosis Type 1: CT and MR features. J Comput Assist Tomogr. 1994;18:728-30.
    [CrossRef] [PubMed] [Google Scholar]
  9. , , , , . Idiopathic intracranial hypertension: The validity of cross-sectional neuroimaging signs. Neuroradiology. 2006;48:521-7.
    [CrossRef] [PubMed] [Google Scholar]
  10. , , , . Dural ectasia of optic nerve-an important clinical finding in marfan's syndrome. Open J Clin Med Case Rep. 2016;2:1130.
    [Google Scholar]
  11. , , , , , . Optic nerve sheath meningocele: A case report. Neuroophthalmology. 2013;37:78-81.
    [CrossRef] [PubMed] [Google Scholar]
  12. , , . Optic nerve sheath meningocele with optic disc pit: A rare finding. Ophthal Plast Reconstr Surg. 2019;35:e85.
    [CrossRef] [PubMed] [Google Scholar]
  13. , , , , . Stabilization of visual function after optic nerve sheath fenestration for optic nerve meningocele. Ophthalmic Plast Reconstr Surg. 2017;33:e160-1.
    [CrossRef] [PubMed] [Google Scholar]
Show Sections