Prolonged vision return after radiosurgery for an optic nerve-sheath meningioma

Abstract

Objective

To report a case of prolonged vision return after stereotactic radiosurgery for an optic nerve-sheath meningioma.

Design

Case report

Intervention

Ophthalmologic examination followed by stereotactic radiosurgery for an optic nerve-sheath meningioma.

Main outcome measures

Ophthalmologic examination and MRI findings.

Results

We report the case of 59-year-old female with visual deterioration and progressive proptosis five years after subtotal resection of a left optic nerve-sheath meningioma. Because of progression to blindness (no light perception), the patient underwent Gamma Knife® stereotactic radiosurgery to the intraorbital meningioma in order to achieve tumor-growth control. Remarkably, within one year, her vision in the ipsilateral eye improved to 20/25, and her MRI scan showed significant tumor regression. Excellent vision persisted for eight years. After that, the left eye vision again decreased to hand movement only. At ten years after radiosurgery her ophthalmological exam confirmed severe optic neuropathy.

Conclusions

Radiosurgery provided a paradoxical benefit in this patient who had complete blindness but had restoration of vision for more than eight years. Delayed eventual visual loss likely resulted from optic nerve long-term adverse radiation effect despite persistent long-term tumor growth control.

1. INTRODUCTION

Although intracranial meningiomas are common, optic nerve-sheath meningiomas (ONSM) account for only 1-2% of all meningiomas. [1-3] Management of such tumors remains controversial because of the need to retain vision as long as possible regardless of the strategy selected. ⁷ Individualized plans that include surgery, fractionated external-beam radiation therapy, radiosurgery, and observation represent therapeutic options. [1, 2, 4-7] Because of the risk of blindness, complete surgical resection can only be considered in patients who are already blind. [7] We report a patient who had dramatic and prolonged restoration of vision in her eye after undergoing stereotactic radiosurgery. Despite tumor regression, further deterioration in vision eventually occurred, perhaps related to long term delayed adverse radiation effect (ARE).

2. CASE REPORT

A 59-year-old female presented with progressive left eye visual deterioration and mild proptosis. Neuro-diagnostic imaging including both magnetic resonance imaging (MRI) and computed tomography scans (CT) revealed a left optic nerve-sheath meningioma with extension into the optic canal. The patient had progressive proptosis as well. After an initial left frontotemporal craniotomy and optic nerve-sheath decompression, the patient had improvement in her visual acuity and visual fields. Over the next five years, she had progressive visual loss from a visual acuity of 20/30 in her left eye to eventual complete blindness (no light perception). Initial ophthalmologic testing before radiosurgery determined there was no vision in the left eye (Fig 1).

Figure 1.

Ophthalmologic exam findings before Gamma knife® stereotactic radiosurgery (GKSRS) disclosed that the patient had no vision (no light perception) in the left eye.

Her macula, vessels and retina all appeared to be normal. Because of increasing tumor size and progressive proptosis, the patient underwent stereotactic radiosurgery using the Leksell Gamma Knife 5 years after surgical resection (Fig 2). The minimal tumor dose was 14 Gy and the maximal tumor dose was 28 Gy. The patient’s visual acuity improved gradually over the course of one year to 20/25 in the ipsilateral eye. An MRI revealed significant volumetric tumor regression (Fig 3). Seven years after radiosurgery, she again noticed a gradually progressive decline in her vision. By eight years after radiosurgery, her left eye vision decreased to hand movement only (Fig 4). By ten years after radiosurgery, no light perception was found in the left eye. Her last ophthalmologic exam demonstrated an anisocoria and a left afferent pupillary defect (Table 1). Extraocular movements were normal. There was no increase in proptosis, and the patient had no pain, no headache, no numbness nor other neurological findings. The patient has a past medical history of well-controlled high blood pressure and type 1 diabetes mellitus.

Figure 2.

Axial (A), coronal (B), and sagittal (C) T1-weighted contrast-enhanced MR images of the Gamma Knife ® treatment plan in 2001. To provide a three dimensional coverage of the tumor , six 8 mm collimator beams were used with a special blocking pattern to give a 14 Gy minimal tumor dose at the margin. The optic nerve and chiasm dose, external to the tumor, received a dose less than 1.9 Gy.

Figure 3.

Post contrast MRI showed no significant enlargement in the tumor size at one, three, five, eight, and ten years after GKSRS.

Figure 4.

Ophthalmologic exam eight years after radiosurgery decreased to hand movement.

Table 1.

ophthalmologic examination results

Date	Left Eye	Right Eye
10/15/2001*	No light perception	20/15
10/21/2002	20/30	20/15
8/9/2004	20/30	20/15
8/16/2006	20/40	20/25
3/14/2009	Hand movement only	20/20
7/23/2011	No light perception

^*Date represents last examination day before stereotactic radiosurgery

3. DISCUSSION

The management options selected for patients with ONSM must be individualized. Clinical decision making must take into account the patient’s visual status as well as the potential cosmetic effects of progressing proptosis in growing tumors. Complete resection of an optic nerve-sheath meningioma may solve proptosis but cannot be recommended as an initial strategy in patients with preserved vision because of invariable blindness that results. [1, 6, 8] Fractionated external-beam radiation therapy has been proposed as an alternative that may result in tumor growth control and potentially preserve useful vision. [9-12] Our patient initially benefited from subtotal surgical removal but eventually had gradual vision deterioration to complete blindness in the left eye. In order to achieve tumor growth control and potentially reduce cosmetic proptosis using a minimally invasive technique, the patient underwent Gamma Knife radiosurgery. Long-term tumor growth control and proptosis reduction were achieved. Remarkably, however, this patient had a paradoxical and dramatic improvement in her visual acuity for more than eight years, but then eventually progressed to blindness in the absence of tumor enlargement. Today no proven treatment exists for optic atrophy. Use of high dose steroids as well as oxygen therapy has been reported with various degrees of success but no significant studies have been done on this topic. [13]

The initial response and restoration of vision may reflect an early and unexpected biological response of the tumor itself, despite the high dose delivered to the optic nerve itself, which was encased by the tumor. We suspect that delayed and gradual visual deterioration in the absence of further tumor progression may reflect the long-term adverse radiation effects although optic neuritis can be occurred as another complication of optic nerve sheath meningioma. In radiosurgery, the optic nerve itself would receive a much higher dose than even the lateral tumor margin. Our data suggests that optic neuropathy can be significantly reduced in radiosurgery for patients with parasellar tumors when the optic nerve receives less than 8 Gy in a single radiosurgical procedure. [13-15] However, such doses likely are insufficient to result in long-term tumor growth control of meningiomas.[14, 16] The patient’s initial dramatic improvement in vision may reflect tumor-growth control, but delayed visual deterioration may reflect the long-term risk of microvessel or nerve damage related to ARE. [9, 17] Although fractionated external-beam radiation therapy, now often done with intensity modulated radiation therapy or image-guided radiation therapy techniques, may improve the long term visual preservation rates in patients who have useful vision prior to radiation, major improvement in visual quality is extremely rare after radiation therapy. [6, 8, 18-20] Long term vision preservation after fractionated radiation therapy is still poorly documented. [21-23]

In patients with ONSM, radiosurgery may be a valuable option to prevent further tumor growth and achieve tumor regression thereby relieving proptosis. [9-12, 24] In isolated cases, such as the one we present, dramatic, if not long-lasting visual improvement may be seen.

4. ACKNOWLEDGEMENTS

The work described in this report was funded by a research grant to Dr. Kano from AB Elekta, Stockholm, Sweden.

5. CONFLICT OF INTEREST NOTIFICATION

Drs. Lunsford is a consultant and a stock holder for AB Elekta.