Egan RA, Lessell S. A Contribution to the Natural History of Optic Nerve Sheath Meningiomas. Arch Ophthalmol. 2002;120(11):1505-1508. doi:10.1001/archopht.120.11.1505
To describe the natural history of patients with primary optic nerve sheath meningioma (ONSM) who were cared for without intervention.
A retrospective review of the medical records of 42 patients identified in the database of an academic neuro-ophthalmology unit who had been diagnosed with a unilateral ONSM. Twenty-five had been referred after treatment had been implemented, and 1 was blind at referral. The remaining 16 patients who were followed up with observation only are the focus of this study.
The study subjects were followed up for a mean of 6.2 years (range, 2-18 years). The mean follow-up from the time of the first symptom was 10.2 years (range, 3-28 years). No patient died or incurred neurological deficits other than vision loss. At diagnosis, 12 of 16 had a visual acuity of 20/100 or better; 11 had a visual acuity of 20/30 or better. At follow-up, 8 of 16 had a visual acuity of 20/100 or better; 6 had a visual acuity of 20/30 or better. Three patients had slight improvement. Visual fields remained stable in 4 patients and improved in the 3 patients whose visual acuity also improved.
Some patients with ONSM have a stable course for many years, and a few may even show slight improvement. The routine application of radiation therapy may unnecessarily expose some patients to complications and should be reserved for those patients whose visual function declines under observation.
PRIMARY OPTIC nerve sheath meningioma (ONSM) is a slow growing, benign tumor, the treatment of which remains controversial. Surgical intervention, radiation therapy, and drugs have been advocated, but their value has yet to be established. Ideally, the issue of proper management should be resolved by a prospective, randomized controlled study, but the low incidence of ONSM makes it highly unlikely that this could be accomplished. Instead, a determination must rely on the comparison of the results reported in various case series. Information on the natural history of these tumors is a requisite, but there is a paucity of such data. We are aware of only 3 publications that report case series in which patients with ONSM were followed by observation only.1- 3 We attempt to help re-address this deficiency by detailing the course in 16 consecutive patients with ONSM who were followed up without intervention or who had a period of observation prior to intervention. This series includes neither children nor adolescents, age groups in which the behavior of ONSM may be different from that in adults.
A search of the database of the neuro-ophthalmology unit of the Massachusetts Eye and Ear Infirmary in 1999 yielded the names of 42 patients who had received a diagnosis of primary ONSM since 1973 when computed tomographic scanning became available. Their medical records were reviewed. All 25 patients who at the time of their initial evaluation had been treated or who were about to be treated by the referring physician and one whose eye was blind at first evaluation were excluded from the analysis since we could not make inferences from them about the natural history of their disease.
The other 16 patients, all of whom had unilateral tumors, had been diagnosed by clinical and radiological criteria without recourse to a biopsy by one or both senior neuro-ophthalmologists in the unit. All patients had undergone computed tomographic scanning and/or magnetic resonance imaging. The diagnosis of primary ONSM was made by a neuroradiologist. None of the patients had clinical evidence of neurofibromatosis type 1 or type 2, and none developed a systemic disorder such as sarcoidosis, which would suggest an alternative explanation for the optic nerve lesion. However, we acknowledge that, except for the 2 patients who had later resections (described in the "Results" section), the diagnosis of ONSM was based solely on the clinical and imaging findings, and it is conceivable that our putative diagnosis was in error in some of the cases.
All patients were informed that they had a benign tumor that appeared to arise from the covering of the optic nerve and that tumor resection would almost certainly cause blindness in that eye. They were told that some experts favored radiation treatment but that the value of radiation had not been firmly established and that, at least in theory, radiation could cause visual pathway damage that might not otherwise occur. They were told that the usual course in untreated patients was one of progressive visual loss, possibly eventuating in blindness, but when or whether this might occur could not be predicted. Patients were also warned that there was a risk of the tumor extending toward the brain and that serial clinical and radiological testing was imperative to evaluate the extent of the tumor. The patients were told that the preference was to observe rather than treat. In every case the patient was encouraged to seek the opinion of other neuro-ophthalmologists, which several did, and several also conferred with a radiation oncologist. Each of the patients agreed to be treated initially by observation alone, reserving the future right to implement intervention.
The patient demographic and clinical data are summarized in Table 1 and Table 2. Six tumors involved the left side, and six patients were men. The mean age at diagnosis was 50 years (range, 26-74 years) with 6.2 years of follow-up (range, 2-18 years). The mean follow-up from the time of the first symptom was 10.2 years (range 3-28 years). Five patients maintained stable visual function or improved. Only 4 individuals had an initial visual acuity (VA) of 20/200 or worse. Three patients had a VA of hand motions or no light perception with progression of visual field deficits in 3 to 10 years, but 1 patient had a VA of 20/300 that was unchanged 18 years later. Three of 11 patients with good acuity (≥20/30) at diagnosis had marked loss of VA (20/100 to light perception) and visual field in 4 to 15 years, excluding patient 14. Six patients (with follow-up of 5-20 years) retained a VA of 20/30 or better; 3 of them showed slight improvement. The 3 patients with improvement in VA also had corresponding improvement in visual field. Two of 3 patients who retained good acuity had slight progression of visual field deficit. Venous collaterals were present in 2 patients at diagnosis and in 6 at last follow-up. Optic nerve pallor was seen in 7 patients at diagnosis and in 10 at last follow-up.
Patient 1 was followed up expectantly for 8 years during which time his vision declined from 20/15 to no light perception. At that time computed tomographic scanning for the first time showed the tumor adjacent to the intracranial opening of the optic canal, and he underwent surgical resection. Patient 14 was followed up expectantly for 7 years during which time her VA declined gradually from 20/20 to 20/30. At that point magnetic resonance imaging showed that there was tumor at the cranial end of the optic canal, and a neurosurgeon recommended tumor resection. The tumor was resected leaving the patient blind in that eye. In both cases microscopic examination of the excised lesion showed that it was a benign meningioma arising from the optic nerve sheath.
Optic nerve sheath meningiomas do not cause death; visual loss is the feared consequence. In 1988, Kennerdell et al1 published their observations on 39 patients with primary ONSM. Eighteen of the patients were followed up without intervention. They were selected because their tumor was confined to the orbit, and they either had good vision or very poor vision when initially evaluated. In the 6 patients who had a VA of 20/200 or worse at the outset, VA generally declined under observation. The other 12 whose VA ranged from 20/20 to 20/200 are probably those who are most comparable to our patients. Five patients had a VA of 20/20 to 20/40 that remained essentially unchanged after intervals of 3 to 5 years. The others had severe visual loss over intervals ranging from 4 to 13 years. No patient improved under observation. In a meta-analysis by Dutton2 of published cases, there were 64 patients who were observed without intervention. Vision remained stable in only 14% of cases, but without having more details, it is impossible to determine the significance of this statistic. A recently published uncontrolled retrospective study described the outcome in an agglomeration of 64 cases treated in various ways at 4 institutions.3 The patients included 13 who were observed only, 12 who underwent surgery, 18 who underwent radiation, and 16 who underwent both surgery and radiation. The authors did not describe how or why patients were assigned to one form of treatment or another, and no individual patient-specific details are provided. However, the clinical findings at initial examination and the duration of follow-up were similar in all of the subgroups. In any case 11 of 13 observed patients had a decline in VA during a mean follow-up period of 10.8 years.
Our series includes only 4 individuals with an initial VA of 20/200 or worse. Six of our patients (with follow-up of 5-20 years) retained a VA of 20/30 or better, with 3 of them showing slight improvement in VA and visual field. The mean duration of follow-up in the 5 patients in which VA remained the same or improved (patients 4, 6, 8, 12, and 13) was 9.4 years (range, 6-18 years), which is longer than that for the group as a whole. Thus, it seems unlikely that the good outcome was an artifact resulting from inadequate follow-up. Not surprisingly, patients with marked loss of vision at diagnosis do poorly. Of the patients who initially have good VA, perhaps half will retain good VA and visual fields, some of them for many years. We found no means of predicting which patients will have a decline or when a decline might occur.
It can be argued that the cause for our patients' neuro-ophthalmological and neuroradiological abnormalities was erroneous. Since the diagnosis of ONSM is presumptive without a tissue diagnosis, it is possible that some of the patients who remained stable or improved had a different diagnosis such as sarcoid or glioma. All of these patients however had excellent neuroimaging results, many of them undergoing repeated scans, which were strongly suggestive of the diagnosis of ONSM. Our approach also conforms to the current standard of care of reaching the diagnosis of ONSM based on appropriate clinical details supported by high quality neuroimaging without pathologic confirmation.3
Three of the 16 patients had slight improvement, a phenomenon that has been observed in other meningiomas4 and also in gliomas of the anterior visual pathway.5 To the best of our knowledge, the only other reference to improvement in an ONSM was reported by Turbin et al3 concerning their 2 patients with biopsy-proven ONSM who did not undergo radiation and still improved. Presumably the biopsy could not be credited with the improvement. If these 2 series were combined, this would yield a spontaneous recovery rate of 5 of 29 eyes, or 17%. Spontaneous improvement is obviously exceptional but not rare and must be considered when assessing treatment.
Some patients with ONSM who undergo radiation may have sustained improvement for many years,4- 8 and many experts advocate radiation for this tumor.9 Turbin et al3 showed that their patients who underwent radiation alone had the best visual outcome and recommended " . . . that fractionated external beam radiation (5000-5500 cGy) be considered as initial treatment in adults in selected cases of ONSM when preservation of visual function is a reasonable therapeutic goal."3(p890) Among the patients reported by Turbin and coauthors, complications from radiation occurred in one third of those treated with radiation only and in others who underwent both radiation and surgery. This is a high incidence, but the period covered in that study makes it likely that some of those patients had been treated by obsolete techniques. With the increasingly sophisticated methods of delivering radiation to the optic nerve, the current complication rate is apt to be low but not negligible.
Based on our experience and the published cases, it seems reasonable to radiate patients with ONSM who have poor VA at initial examination. In patients who have good VA, one could monitor their visual function without intervention. If all patients with good VA were radiated at the time of diagnosis, a sizable proportion would be placed unnecessarily at risk. However, once visual function begins to decline, it would be appropriate to refer the patient to a radiation oncologist who has the technology that is requisite to deliver carefully focused radiation to the tumor.
Submitted for publication June 7, 2001; final revision received June 25, 2002; accepted July 11, 2002.
Corresponding author: Robert A. Egan, MD, Casey Eye Institute, 3375 SW Terwilliger Blvd, Portland, OR 97201 (e-mail: firstname.lastname@example.org).