Bilateral paediatric optic nerve sheath meningioma
- 1 Ophthalmology, Children's Health Ireland at Temple Street, Dublin, Ireland
- 2 Neurology, Children's Health Ireland at Temple Street, Dublin, Ireland
- Correspondence to Dr Daire John Hurley; dairehurley@gmail.com
Abstract
At birth, the patient was noted to have microphthalmia and optic atrophy in her left eye with no apparent cause. In early childhood, the vision in that eye began to deteriorate. A few years later, disc swelling was noted in the contralateral right eye. Neuroimaging was normal and a subsequent lumbar puncture found borderline high opening pressure. Vision and visual fields in the right eye remained stable until the patient was in early adolescence when she started to complain of blurred vision. Her pattern visual evoked potential showed a 75% reduction in P100 amplitude compared with the previous year. Repeat neuroimaging was suggestive of bilateral meningiomas and a biopsy was performed to confirm this. Subsequently, the patient was treated with proton beam therapy to salvage vision in her right eye. This is a novel case of meningioma presenting with enophthalmos due to contraction of the retrobulbar optic nerve.
Background
We describe a rare case of a young girl recently diagnosed with bilateral optic nerve sheath meningiomas (ONSMs) that presented with enophthalmos. One eye was noted to have optic atrophy present from birth and appeared microphthalmic. The other eye remained unaffected until middle childhood when disc swelling was noted.
ONSMs involve proliferation meningothelial cells within the nerve sheath of the orbital or intracanalicular portion of the optic nerve. They are rare in the paediatric population, accounting for less than 5% of total ONSMs.1 The presence of bilateral ONSMs is equally rare, comprising 5% of OSNMs.2 They are particularly aggressive tumours in the paediatric population with progressive, painless decline in visual acuity. Owing to their anatomical location, surgical excision is a hazardous procedure. The gold standard of treatment is radiotherapy, which may stabilise or improve visual function. Until recently, this took the form of stereotactic frequency radiotherapy (SRF), but advances in proton beam radiotherapy make it a promising treatment option.
Case presentation
From birth, the patient was noted to have microphthalmia in her left eye. In early childhood, the vision in that eye was found to be deteriorating. A period of patching of the right eye followed in order to reverse suspected amblyopia, but ultimately, the vision continued to decline to non-perception of light within a couple years. Contrast MRI brain and orbits showed an atrophic left optic nerve without an observed cause or a focal mass (figure 1). Examination revealed a left relative afferent pupillary defect and a pale optic disc. No formal diagnosis was made at the time to explain the progressive visual loss.
MRI In early childhood. (A) T1 (axial). (B) T1 post contrast (coronal). This shows a retracted left eye with a slightly atrophic optic nerve. However, there is no focal mass along the optic nerve or tracts and no orbital mass.
The right eye was kept under regular surveillance. In middle childhood, disc swelling was noted in the right eye (figure 2A,B). Visual acuity at this time was 6/6, and the patient was asymptomatic with no headaches. Contrast MRI of the brain and orbits remained unchanged from a few years prior. Although no specific signs of increased intracranial pressure were noted, given the worsening acuity and new-onset disc oedema, a lumbar puncture was carried out. The opening pressure was measured to be 31 cm H2O. The local referring team made a working diagnosis of idiopathic intracranial hypertension based on the disc swelling, raised cerebrospinal fluid pressure and lack of orbital or intracranial masses or lesions. Treatment with acetazolamide (250 mg twice daily) was commenced but had no effect on the disc swelling. Additional diagnostic work-up investigating for neuroinflammatory, infectious and metabolic causes was unrevealing.
Optic disc photos 3 years before diagnosis. (A) Right eye. (B) Left eye. The right optic disc is grossly swollen, whereas the left optic disc is pale and atrophic.
A year later, the patient was commenced on a trial dose of prednisolone and admitted for intracranial pressure monitoring, which was within normal limits. This was repeated 5 months later after weaning from steroids and again the opening pressures were noted to be normal with no changes interpreted on neuroimaging. Acetazolamide was then weaned but with no effect on the disc swelling. The vision remained stable throughout this period and visual evoked potentials were unremarkable. Visual fields in the right eye were normal (figure 3).
Full-field 120-point suprathreshold test (right eye) 3 years before diagnosis. Full visual fields in the right eye which had started to develop optic disc swelling.
By early adolescence, the patient’s vision began to deteriorate in the right eye (6/12 or 0.3 logarithm of the minimal angle of resolution (logMAR)). Pattern visual evoked potentials were repeated and showed a 75% reduction in P1 100 amplitude compared with the previous year. Contrast MRI showed T2 hyperintensity and enhancement within both optic nerve sheaths with maximal intensity at the orbital apices, greater in the left than the right (figure 4A,B). Additionally, there was an enlarged left fifth cranial nerve with expansion of the left Meckel cave and peripheral enhancement (figure 5). A CT was performed the following day to better characterise this calcification. This showed thickened optic nerves, more predominantly the left optic nerve, with suggested tram track hyperattenuation (figure 6A,B). There was marked postcontrast enhancement. At this point, a working diagnosis of bilateral ONSM was made. The process in Meckel’s cave may represent a schwannoma.
MRI at diagnosis. (A) T1 post contrast (coronal). (B) T2 post contrast (coronal). This shows T2 hyperintensity and enhancement within both optic nerve sheaths with maximal intensity at the orbital apices, greater in the left than the right.
T2 MRI: expansion of the left Meckel’s cave (coronal). This shows an enlarged left fifth cranial nerve with expansion of the left Meckel cave and peripheral enhancement. This may represent a schwannoma.
CT at diagnosis. (A) Precontrast (axial). (B) Post contrast (axial). This shows thickened optic nerves, more predominantly the left optic nerve, with suggested tram track hyperattenuation.
The patient underwent a genetic work-up in the form of trio whole-exome sequencing. This was unrevealing; in particular, no abnormalities were found in NF2, SMARCE1 and SUFU genes. A biopsy was then performed on the left, non-functioning optic nerve, which showed evidence of transitional meningioma WHO grade I (figure 7). During this procedure, the optic nerve was found to be under significant tension and causing significant enophthalmos. This is evident in figure 6A, where globe retraction and posterior tenting of the sclera are evident, in addition to the microphthalmia. The presentation of an ONSM with enophthalmos represents a deviation from the more typically described exophthalmos. Postoperatively, division of the optic nerve resulted in a much improved aesthetic appearance, with resolution of the globe retraction.
Histology. (A) Meningioma circumscribing the optic nerve. (B) Psammoma body. Biopsy revealed a transitional meningioma WHO grade I. On the right, a characteristic psammoma body is shown.
Treatment
At a neuro-oncology multidisciplinary meeting, it was recommended that the patient should be offered proton beam therapy (PBT) in an attempt to control the right ONSM and stabilise the vision. The PBT has now been completed.
Outcome and follow-up
The patient has had no acute side effects with the PBT. Additionally, the visual acuity has improved from 6/19 (0.5 logMAR) prior to PBT to 6/9.5 (0.2 logMAR) a week after treatment. The patient will be regularly followed up to assess visual acuity and visual fields, in addition to neuroimaging to assess disease recurrence. Fundus examination is also required for at least 6 years following PBT to monitor for radiation retinopathy and optic neuropathy.
Discussion
ONSMs are rare tumours of the visual pathway. They account for 1.7%–10.0% of all orbital tumours3 and 33%–42% of all optic nerve tumours in all age groups.4 Ninety-two per cent of primary ONSMs arise within the intraorbital nerve sheath, while only 8% are intracanalicular.5 Bilateral ONSMs are very rare, accounting for only 5% of ONSMs.2 Bilateral ONSMs are more commonly found in patients with neurofibromatosis type 2 (NF2).6 Our patient had an MRI finding of an expansion of the left Meckel cave, which may represent a schwannoma. This created a high suspicion for NF2, but genetic testing was negative.
ONSMs are a rare entity within the paediatric population, with only 4% of cases occurring in patients under 20 years of age.5 6 Levin and Jakobiec were able to estimate the prevalence of paediatric ONSMs as only 1 in 95 000–5 25 000.7 In this age group, the lesions are more often associated with NF2, concomitantly diagnosed in 28% of paediatric patients.1 Conventionally, these tumours have been thought to be more frequently aggressive with higher rates of intracranial extension and recurrence.1 2 However, differing results were seen in a recent case series of eight paediatric ONSMs by Narayan et al.8 They found two of the eight patients retained stable vision and had no change in tumour growth at a mean follow-up of 156 months. Although, this is a very small sample size, it is the largest case series of conservatively managed paediatric ONSMs, highlighting the relative rarity of the condition. This case report is novel as it describes the presence of bilateral ONSMs in a paediatric patient.
Clinically, the classic triad of visual loss, optic atrophy and the presence of opticociliary shunt vessels is suggestive of a compressive optic nerve lesion such as ONSM.9 However, only a minority of patients present with all three signs, particularly in the paediatric population. The most common presenting symptom in ONSMs is progressive, painless decline in visual acuity (80% of patients), and this generally precedes diagnosis by 1–5 years.1 This occurs through the tumours’ mass effect on the pial vascular supply and disruption of axonal flow.10 Visual field defects have been reported in close to 50% of paediatric ONSMs at presentation.1 Examination of the fundus reveals optic disc oedema and atrophy. Other signs may include proptosis, chemosis and limitation of extraocular muscles.8 Nickel et al 11 concluded optic atrophy in a child without a recognisable cause should prompt bilateral ONSM as a differential.
In our patient, the initial presentation was thought to be congenital microphthalmia. A diagnosis of microphthalmia, however, should not produce progressive visual loss. In reality, while the globe was of reduced size in keeping with the original diagnosis of microphthalmia, it was also significantly retracted and enophthalmic as a result of tumour compression on the optic nerve. This is in stark contrast to the commonly reported presentation of proptosis. In our review of the literature, we found no case reports of such a presentation.
Neuroimaging plays an essential role in diagnosis of ONSMs, with advances in imaging making the diagnosis possible in some cases without tissue biopsy.12 CT allows visualisation of a hyperdense or isotense mass and thickened optic nerve sheath. However, the gold standard remains MRI due to its superior optic nerve detail, particularly with postgadolinium fat-suppression sequences. ONSMs are contrast-enhancing masses. The classic imaging description is of a ‘tram-track’ sign in which the thickened, calcified optic nerve sheath surrounds the non-enhancing optic nerve.13 Furthermore, electrophysiology testing may show abnormalities that precede recognisable changes on imaging. In our case, the pattern visual evoked potential showed a 75% reduction in P100 amplitude prior to any abnormality being noted on imaging.
Biopsy is necessary in atypical presentations of ONSMs, as in our case. The long-standing optic atrophy with no perception of light for many years in the fellow eye made a biopsy of this eye an easily justified step, but it remains a high-risk intervention in a seeing eye. Histology of ONSMs may take either a meningothelial pattern, whereby vascular trabeculae separate sheets of polygonal cells, or a transitional pattern, in which oval cells are arranged in whorls displaying the characteristic psammoma bodies.2 6 ONSMs may be classified according to the WHO grading system: I, benign (6.9% recurrence rate); II, atypical (34.6%); and III, malignant (72.7%).14
Treatment of ONSMs is difficult, given the proximity to the optic nerve and its vascular supply. The aim with treatment is to preserve vision and control disease burden. The conservative measure involves observation with serial imaging. It may be appropriate in cases of advanced or negligible visual decline. Additionally, it may be appropriate in certain cases in the paediatric population as shown by Narayan et al.13 However, 85% of patients will experience deterioration of vision.15 16 Delay in initiation of treatment may reduce the probability of visual improvement with treatment. In the paediatric population, there is a lack of consensus with regard to intervention timing, but certainly treatment should be initiated promptly on documentation of any visual loss. Surgical resection is particularly challenging, given how primary ONSMs circumferentially wrap around the optic nerve. It may be indicated in patients whose vision is already significantly reduced or who have extension intracranially.15 However, in Dutton’s5 review of outcomes of ONSMs following surgical excision, only 5% showed an improvement in visual acuity, with 78% of patients being left with no perception of light and 25% having further recurrences.
SRF offers good tumour control and stabilisation of visual function. Berman and Miller collated data from seven case series (75 patients) and reported disease control in 94.6% and visual improvement in 54.7%.17 Further studies since using more targeted dosing have yielded better results such as Landert et al,18 who found a visual acuity improvement in 86% of patients with doses of 50.4–54 Gy. However, severe complications may occur with SRF including early side effects of nausea, focal alopecia, local erythema, radiation retinopathy and optic neuropathy and late effects of pituitary dysfunction and cerebral small vessel disease.19
PBT displays high rates of local control and visual stability, in addition to a much safer side effect profile. It was chosen as the treatment strategy in this case of a paediatric patient as it provides better dose distribution than SRF and limits the exposure of normal tissues.20 Proton beams achieve this through a finite range and narrow beam. A retrospective study by Hage et al 21 looked at 60 patients who underwent PBT for primary ONSMs and found that 85% had either improvement or stability in their visual field examination. Among the 31 patients who underwent PBT alone without surgery in their cohort, 4 developed radiation retinopathy, of which 2 were mild with no change to visual acuity, and no patients developed a definitive radiation optic neuropathy.
Given our patient’s young age, it was agreed that PBT minimised our patient’s lifetime risk of radiation optic neuropathy and retinopathy.
Learning points
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Unexplained globe retraction and optic atrophy in a child should prompt optic nerve sheath meningioma (ONSM) as a differential and merit detailed MRI orbits with contrast.
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Full visual fields and subtle visual acuity reduction does not exclude sight threatening optic nerve pathology.
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A diagnosis of microphthalmia should not produce progressive visual loss in the absence of other pathologies.
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Visual evoked potential abnormalities may preclude optic disc damage in ONSM.
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Early intervention on any visual function deterioration is key to sight preservation.
Ethics statements
Patient consent for publication
Footnotes
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Contributors IF (ophthalmology) and DOR (neurology) were the consultants involved in the patient’s care. All authors undertook background research on the topic and contributed to data acquisition and case report planning; DJH wrote the initial draft of the manuscript; SW and IF reviewed and made edits to the initial manuscript. Upon editorial decision, we contacted DOR, who addressed all significant concerns from both reviewers. DOR made all necessary changes to the manuscript and gathered and reviewed additional neuroimaging. All authors read and agreed on the most recent version of the manuscript.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.
References
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