Optic nerve sheath meningioma and optic neuropathy: A clinical and diagnosis crossroad

Abstract

Optic nerve sheath meningiomas (ONSMs) are rare, benign tumors of the central nervous system that arise from arachnoid cap cells. They most commonly affect middle-aged women and account for approximately 2% of orbital tumors. ONSMs typically present with slowly progressive, painless, ipsilateral optic neuropathy; however, atypical acute or subacute onset may mimic inflammatory optic neuritis. We describe the case of a 45-year-old woman who presented with a 1-month history of progressive visual blurring in the left eye, accompanied by retro-orbital pain and optic disc swelling. Initial clinical and paraclinical findings were suggestive of optic neuritis, and high-dose corticosteroid therapy was initiated, leading to transient improvement. Recurrence of symptoms, lack of sustained steroid response, and magnetic resonance imaging (MRI) findings showing circumferential thickening of the optic nerve sheath with the characteristic “tram-track” appearance on axial views and the “doughnut” sign on coronal sections ultimately led to the diagnosis of ONSM. The patient was managed conservatively with regular ophthalmologic and radiologic follow-up. This case underscores the diagnostic challenge of distinguishing ONSM from inflammatory optic neuropathies and highlights the pivotal role of magnetic resonance imaging (MRI) in confirming the diagnosis, avoiding unnecessary biopsy, and guiding therapeutic decisions.

Introduction

Optic nerve sheath meningiomas (ONSMs) are rare, benign tumors of the central nervous system. Primary ONSMs originate from the cap cells of the arachnoid layer and can develop at any point along the optic nerve, most commonly within the intraorbital segment [1]. They typically cause a gradual, progressive, and ipsilateral optic neuropathy. Although their growth is generally slow and indolent, the anatomical location of these tumors is of critical importance, as they directly affect the anterior visual pathway and can lead to severe visual impairment.

ONSMs account for approximately 2% of all orbital tumors and 1% of all meningiomas [2,3]. Similar to their intracranial counterparts, they show a marked predilection for middle-aged females [1]. The clinical presentation varies, but the classic triad of visual loss, optic atrophy, and optociliary shunt vessels is characteristic, although not all patients display all 3 features [2,4].

Diagnosis is primarily established through magnetic resonance imaging (MRI), particularly using gadolinium-enhanced fat-suppressed sequences, which have become the gold standard, minimizing the need for invasive tissue biopsy. On MRI, ONSMs demonstrate the characteristic “tram-track” appearance on axial views and the “doughnut” sign on coronal sections. However, it should be noted that similar enhancement patterns of the optic nerve sheath can also occur in other conditions, such as optic perineuritis (OPN) [5].

Management should be individualized based on the patient’s clinical status. Observation is appropriate in cases with stable visual function, while therapeutic options for progressive disease include surgical resection, radiotherapy, or optic nerve decompression. The present case report highlights the clinical and radiological diagnostic challenges posed by ONSMs and underscores the essential role of MRI in differential diagnosis and management planning.

Case presentation

The present report describes the case of a 45-year-old woman who presented to the emergency department with a 1-month history of rapidly progressive visual blurring in the left eye. The visual disturbance was associated with ocular pain exacerbated by eye movement, as well as mild, left-sided hemicranial headaches. Importantly, there were no accompanying neurological or systemic symptoms, such as scotoma, diplopia, vomiting, sensory or motor deficits, or any other neurological manifestations.

The patient’s medical history was notable for hypertension, managed with a daily dose of 5 mg of amlodipine. No other relevant medical or surgical history was reported. On initial examination, visual acuity was 20/20 in the right eye and 20/40 in the left eye. There was no evidence of dyschromatopsia or a relative afferent pupillary defect. Ocular motility was full, and no ophthalmoplegia, ptosis, or exophthalmos was observed. Fundus examination and fluorescein angiography of the right eye were unremarkable, while the left eye demonstrated marked optic disc swelling. Humphrey visual field testing revealed central nonspecific defects in the left eye, with preservation of the peripheral field. The neurological examination showed no additional abnormalities.

The full-field pattern-reversal visual evoked potentials revealed the absolute values of the bilateral P100 latencies to be within the normal range; however, an interside difference of significant latency prolongation was observed on the left side. A brain MRI with sections on the optic nerves revealed a distended thickening of the left retrobulbar optic nerve in T2, Flair hypersignal and diffusion, which was enhanced after injection of contrast (Fig. 1). Spinal MRI revealed no abnormalities.

Fig. 1.

Axial magnetic resonance imaging (MRI) of the brain and orbits. (A, B) Axial T2-weighted image and FLAIR sequence showing distended thickening and hyperintensity of the left optic nerve. (C) Contrast-enhanced sequence showing parallel linear enhancement of the left optic nerve sheath.

A cerebrospinal fluid examination revealed normal cell counts and protein levels and did not detect oligoclonal bands. Conversely, no antibodies against aquaporin-4 or myelin oligodendrocyte glycoprotein (MOG) were detected. The serologic test results were negative for syphilis, the human immunodeficiency virus, and toxoplasma, and the levels of serum markers for immunity and inflammation were found to be normal, including antineutrophil cytoplasmic antibody, immunoglobulin G(IgG), and erythrocyte sedimentation rate. Consequently, a computed tomography (CT) scan of the neck, chest, abdomen, and pelvis was conducted, which revealed no evidence of sarcoidosis or malignancy.

The patient was diagnosed with optic neuritis based on clinical presentation and radiological findings. They were therefore treated with a high dose of intravenous prednisolone (1 g/d) for 5 days, which resulted in partial improvement in visual acuity, rising from 20/40 to 30/40. The patient was discharged with a follow-up appointment scheduled for 1 month later. One month later, the patient’s symptoms worsened in the left eye, with a gradual decline in visual acuity and retro-orbital pain, but without diplopia or dychromatopsia. The examination of the left eye showed a visual acuity of 15/40. The fundus examination and fluorescein angiography showed significant swelling of the optic disc (Fig. 2). Humphrey visual field testing of the left eye showed nonspecific defects centrally, with an intact field peripherally. The neurological examination revealed no abnormalities.

Fig. 2.

Fundus examination and fluorescein angiography revealing normal findings in the right eye (A) and a swollen optic disc in the left eye (B).

MRI images reveal diffuse circumferential thickening and enhancement in the left optic nerve sheath, with a “tram-track” and “doughnut-shaped” appearance in axial and coronal MRI views, respectively (Fig. 3). Computed tomography of the orbits demonstrated no evidence of calcification along the left optic nerve sheath. Given the persistence of symptoms, the patient received high-dose intravenous methylprednisolone (1 g/d for 5 consecutive days), followed by 5 sessions of therapeutic plasmapheresis, without measurable clinical improvement. The diagnosis of ONSM was ultimately established based on the constellation of clinical findings, the absence of steroid responsiveness, and the persistent, well-defined circumferential enhancement of the optic nerve sheath on MRI. During a 6-month follow-up period, the patient’s visual function remained stable, with no evidence of further deterioration. In the event of clinical or radiological progression, invasive diagnostic confirmation via biopsy and consideration of adjuvant radiotherapy are planned.

Fig. 3.

Axial and coronal MRI of the brain and orbits. (A) Axial diffusion-weighted demonstrating hyperintensity of the left optic nerve. (B, C, and D) Contrast-enhanced, fat-suppressed T1-weighted magnetic resonance imaging (MRI) of the brain and orbits showing parallel linear enhancement along the left optic nerve in the axial view and circumferential enhancement in the coronal view, consistent with the characteristic “tram-track” and “doughnut” sign.

Discussion

ONSMs are primary benign tumor derived from meningothelial cells. It has been determined that approximately 95% of ONSM is unilateral [2,6]. Rare bilateral tumors have been observed in patients diagnosed with neurofibromatosis type 2 [2,6]. The prevalence of these tumors is observed to be highest in middle-aged females [2].

The development of these tumors originates from the meningeal cells (arachnoid cap cells) that line the optic nerve sheath. The growth of these structures typically occurs circumferentially around the optic nerve, with the potential to exert significant compression on the pial vascular supply. These tumors characteristically follow the path of least resistance, which can result in invasion of the entire optic nerve, from the optic canal posteriorly to the globe anteriorly [3,7].

ONSM is typically characterized by slow, painless, and progressive vision loss of the affected eye. In 1975 [8], Walsh described a pathognomonic triad of optic nerve meningiomas. It is associated with a decline in visual acuity, optic atrophy, and optociliary shunt vessels. The last 2 signs appear late in the course of the meningioma, at a time when the patient’s visual acuity is already very poor and the functional prognosis for the eye is poor. The diagnosis must therefore be made at an earlier stage so that patients can be offered treatment to stabilize or even recover their visual acuity.

In the case of inflammatory disease, the decline in visual acuity generally sets in rapidly over 2-3 days and is associated with pain when the ocular globe is mobilized. ONSM damage, on the other hand, is progressive, leading to an insidious decline in visual acuity over several months or even years. In our patient, however, the clinical evolution was unusually rapid, occurring over approximately 1 month, which contrasts with the typical indolent course of ONSM. This accelerated progression could be explained by transient vascular compromise or ischemic insult to the optic nerve secondary to compression of the pial vessels by the expanding meningioma. Similar subacute presentations have been reported in the literature and are often attributed to tumoral edema or secondary inflammation within the sheath, mimicking an inflammatory optic neuritis. The initial partial response to corticosteroids in this patient may further support the presence of a reactive peritumoral inflammatory component rather than a true demyelinating process.

It is therefore essential to carry out a meticulous search, upon questioning, for a progressive decline in visual acuity prior to that which prompted the emergency consultation. The pain experienced during globe movement is present in our patient and in 92% of ONM cases but is not very common in ONSM cases [9]. This unusual occurrence of pain in our case further supports the possibility of local inflammatory irritation or perineural edema surrounding the meningioma, which could have contributed to the atypically fast decline in vision.

The response to intravenous corticosteroids is a strong clinical argument for accepting or rejecting the diagnosis of retrobulbar optic neuritis. In fact, spontaneous visual recovery in cases of retrobulbar optic neuritis is generally expected and is accelerated after bolus corticosteroids [9]. On the other hand, meningiomas do not respond to corticosteroids unless there is an associated inflammatory component (peritumoral edema), which may then constitute an additional diagnostic trap. In this case, the partial and transient improvement after corticosteroids may have been due to a temporary reduction in tumor-associated edema rather than demyelination, which initially misled the diagnosis toward optic neuritis. This highlights the diagnostic overlap between inflammatory and neoplastic optic nerve disorders, particularly when the tumor induces secondary inflammatory phenomena.

A diagnosis of ONSM is confirmed by MRI, particularly by gadolinium-enhanced fat-suppression sequences. The MRI has become the gold standard for diagnosis and has obviated the need for tissue biopsy.

On an MRI, a meningioma of the optic nerve appears as an enlargement of the optic nerve sheath, isointense on T1-weighted sections, and slightly hyperintense on T2. ONSM is a sensitive lesion to gadolinium contrast, showing strong enhancement which contrasts with the optic nerve which does not enhance. On axial MRI images, the characteristic “tram-track” sign is present, corresponding to the enhancing outer ONSM encircling the inner nonenhancing optic nerve. On coronal images, this appears as a “doughnut” or “nonenhancing dot” sign [1]. The typical appearances of ONSMs on imaging include tubular expansion of the meninges surrounding the optic nerve (62%), globular (23%), fusiform (11%), and focal enlargement of the optic nerve (4%) [1,10]. Inflammation of OPN in patients often spreads to the surrounding orbital fat tissue outside the optic nerve sheath, contrasting with the MRI findings for ONSM. These characteristics can provide important clues for distinguishing ONSM from OPN.

Meningiomas are benign tumors and are never life-threatening. The therapeutic approach is guided by visual and functional prognosis. As meningiomas usually progress slowly, it is not uncommon to forgo treatment in favor of clinical and radiological surveillance. If there is an acute drop in visual acuity, oral corticosteroid therapy may be prescribed to reduce the associated inflammation.

Initially, surgery was the only treatment option, but other alternatives have since emerged [11,12]. For optic nerve meningiomas, surgery is currently only considered in very specific cases. Removing the tumor is difficult due to the proximity of the optic nerve and its feeder vessels. Worsening visual acuity is a postoperative complication that must be weighed against the low rate of progression. It is recommended that a repeat MRI be performed every year [13].

A transnasal endoscopic optic nerve decompression can also be used. This technique has shown disease stabilization and, in some cases, improvement in baseline visual deficits [14,15]. Conventional radiotherapy has been used pre- and postoperatively for many years [16], but more recently, stereotactic radiotherapy has been employed as an alternative to surgery with very promising results. In cases where visual function deteriorates, stereotactic radiotherapy (STR) has become the treatment of choice, as it delivers the appropriate amount of radiation to the tumor in a localized fashion. However, risks of radiation-induced retinopathy or optic neuropathy are prevalent [17,18].

Conclusion

ONSMs are progressive optic neuropathies that should be distinguished from retrobulbar optic neuritis. The age of the patient, the painless, long-standing, and progressive nature of the loss of visual acuity, and its resistance to corticosteroid therapy should direct the work-up toward an imaging search for a compressive process of the optic nerve. MRI diagnosis of a meningioma compressing the anterior optic tract is facilitated by frontal and sagittal images centered on the optic nerve, including T1 sequences with gadolinium injection and fat suppression. The clinical and radiologic features of ONSM and OPN may overlap, resulting in late diagnosis and treatment. This should be considered by clinicians when making a differential diagnosis for patients with optic nerve sheath enhancement.

List of abbreviations

MOG, Myelin oligodendrocyte glycoprotein; MRI, Magnetic resonance imaging; ONSM, Optic nerve sheath meningioma; OPN, Optic perineuritis; ONM, Optic neuritis/Optic neuropathy (selon contexte, ici utilisé pour Optic Neuritis dans comparaison clinique)

Patient consent

Written informed consent was duly obtained from the patient for using her data and images for publication of this case report.