• optic nerve sheath meningioma;
  • stereotactic fractionated radiation therapy;
  • visual fields;
  • visual acuity


  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions


Radiotherapy (RT) has occasionally been practiced in the treatment of optic nerve sheath meningioma (ONSM). Recently, stereotactic fractionated RT (SFRT) has been introduced as a tool with better precision for RT delivery. A comprehensive review was undertaken to provide more insight into this matter.


A literature search was performed to identify reports dealing with both clinical aspects (diagnosis) and treatment in ONSM, focusing on RT in primary (p)ONSM. In particular, major emphasis was placed on the role of SFRT in pONSM.


SFRT was capable of achieving excellent local tumor control, with improved/stable functional capacity in ≥80%, accompanied with very low toxicity in meticulously planned RT. This holds true for the majority of patients with progressive functional loss and probably the vast majority of those with some degree of functional loss at presentation. Those blind at presentation benefit from postoperative RT, whereas those with only minimal functional loss at presentation must be carefully selected for the best treatment, because a wait-and-see policy will inevitably lead to serious dysfunction or even blindness.


SFRT should be considered the treatment of choice for the majority of patients with pONSM. Every effort should be made to further investigate the remaining questions in this disease, such as optimal timing for the patients with no or slight vision loss at presentation. Cancer 2007; 110:714–22. © 2007 American Cancer Society.

Optic nerve sheath meningioma (ONSM) is a rare tumor. It originates from the cap cells of the arachnoid and is separated into a primary and a secondary form. Primary ONSM arise from the sheath of the intraorbital or, less commonly, the intracanalicular portions of the optic nerve. Secondary ONSM arise intracranially, usually from the sphenoid ridge or tuberculum sellae and subsequently invade the optic canal and orbit. Although these tumors are frequently referred to as 1 entity, because of differing clinical characteristics, treatment, and outcome, all of which may have implications for future strategies, they will not be discussed together here. This article focuses on primary (p)ONSM, in which both intraorbital and intracanalicular ONSM are placed. The aim is to summarize pretreatment and treatment characteristics of pONSM, putting special emphasis on recent achievements with the use of high-precision external beam radiation therapy (RT).

Search Strategy and Selection Criteria

  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions

To identify appropriate references to be selected for this review, we searched PubMed, with the search restricted to articles reported in English. “Gray literature” was not searched. For the initial (ie, Pre-treatment) part, we selected primarily large reviews and original articles dealing with those topics (eg, clinical findings, imaging). Additional references were obtained using reference lists from these articles, including books and book chapters dealing with scholarly written pretreatment aspects of this disease. We primarily focused on journals with high impact in each of these fields (eg, ophthalmology, neuro-ophthalmology, neurosurgery, radiology) by merging the search terms “optic nerve tumor,” “optic nerve sheath meningioma,” “meningioma” with the given subject term, eg, “visual field.” In the Treatment section, we selected series with the highest impact in clinical journals covering the fields of ophthalmology, neuro-ophthalmology, neurosurgery, and radiation oncology. Additional references were obtained from the reference lists of available articles, fulfilling the above-mentioned criteria. In all cases, the search terms were merged with, for each appropriate section, “observation,” “surgery,” and “surgery and postoperative radiotherapy.” In particular, these search terms were merged with “radiation therapy,” “radiotherapy,” “stereotactic radiotherapy,” or “stereotactic fractionated radiotherapy.” We used the largest and the most recent reports from searches using the latter search terms (ie, those related to stereotactic radiotherapy or stereotactic fractionated radiotherapy) to construct Table 1.

Table 1. Recent Studies on the Use of High-Precision RT in Optic Nerve Sheath Meningioma
AuthorsYearNRT characteristicsVisual outcomeFollow-upToxicity/Comments
  • RT indicates radiation therapy; ONSM, optic nerve sheath meningioma; CF, conventional fractionation; SFRT, stereotactic fractionated radiation therapy; RON, radiation-induced optic neuritis.

  • *

    A total of 64 patients with ONSM were in this report.

Narayan et al.20031454–55.8 Gy, CF2 (14.2%) decreased,9–81 mo5 (35.5%) toxicity, including
    9 (63.9%) stable,51.8 mo2 (14.2%) iritis,
    5 (35.5%) improved vision(median)1 (7.1%) dry eye,
    (three or more lines) 1 (7.1%) retinopathy, and
      1 (7.1%) orbital pain
Turbin et al.200218*40–55 Gy, CF,nonsignificant decrease100 mo6 (33%) toxicity, including
    conventional multiport in visual acuity;(median) 4 retinopathy,
   or conformal RT44.4% showed at  1 persistent iritis, and
    least two lines of improvement  1 temporal lobe atrophy
Liu et al.2002545–54 Gy, CF, SFRT4 (80%) improvement andrange 12–84 moNo RON
     1 (20%) stable(median 24 mo)No RT-necrosis
Andrews et al.20023050.4 Gy, CF, SFRTin 20/22 (92%) functioning eyes2–71 mo4 (13%) toxicity, including
    preservation of vision; in 42%(median 22 mo) 2 visual loss,
     improvement  1 optic neuritis, and
       1 transient orbital pain
Pitz57/Becker5920021554 Gy, CF, SFRT100% improved or stablerange 12–71 moNo RON
     visual fields and visual acuity(median 35.5 mo)No RT-necrosis
Baumert et al.20042245–54 Gy, CF, SFRT16 (73%) improvedrange 1–68 mo1 (5%) optic neuropathy
    5 (22%) stable(median, 20 mo) and vitreous hemorrhage
Richards et al.2005443–45 Gy, CF, SFRT100% improved/stable visual acuityrange, 2–4 yrs cerebral punctuate small
    75% improvement in visual fields(median, 2 yrs) vessel fallout in RT field
Landert et al.2005750.4–54 Gy, CF, SFRT85% improvement in visual acuityrange, 8–40 mo1 (14%) acute eye lid edema
    86% improved/stable visual fields(mean, 23 mo) 
Sitathanee et al.2006651.6–59.1 Gy, CF, SFRT80% improved visual acuityrange, 7–66 mo1 (16%) vitreous hemmorhage
    66% improved visual fields(median, 34 mo) (in uncontrolled diabetes)
    83% improved proptosis  no other toxicities

Pretreatment Aspects

  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions

pONSM represent approximately 96% of all intraorbital and approximately 1% to 2% of all intracranial meningiomas,1 being the second most common optic nerve tumor, after gliomas.1–4 They represent only 10% of all ONSM, the remaining 90% being classified as secondary ONSM. The vast majority of pONSM (92%) arise intraorbitally, whereas only 8% arise from the intracanalicular part of the optic nerve sheath (ONS).1 Most of these tumors are unilateral, with 5% presenting bilaterally. ONSM typically affect middle-aged women. There is no strong evidence for a predilection for left or right laterality.1 Four percent of all pONSM are considered ectopic, ie, arising from ectopic arachnoid cells within the orbital tissues.5–7 These ectopic, extradural meningiomas do not have a connection to the ONS and do not originate intracranially.

The triad of visual impairment, optic atrophy, and optocilliary shunt vessels has for a long time been considered highly suggestive for ONSM. However, it is not pathognomonic, but rather a typical sign of optic nerve dysfunction resulting from various etiologies, such as compressive, ischemic, or inflammatory ones. The most frequent presenting symptom of ONSM is painless loss of visual acuity, an early and reliable symptom. In bilateral ONSM, visual loss is accentuated unilaterally. The vast majority of patients suffer from an impaired pupillary light reaction on the affected side, a so-called relative afferent pupillary deficit. Any type of visual field defect may occur.3, 8–12 Decreased color vision is also usually an early symptom. Transient loss of vision, so-called obscuration, usually only lasts for seconds and is usually related to change of body position (ie, rising) or to eye movements.11 Of external changes, the most frequently observed is a mild proptosis, which follows the onset of visual loss. This is less seen in patients with canalicular ONSM. Decreased motility (mostly in up gaze) is seen in approximately half of the patients.13, 14 Orbital pain and headaches have been reported less frequently than other symptoms.7, 10, 15

On funduscopic examination, a pathologic appearance of the optic disc is revealed in virtually every case.2, 3, 13, 15–18 This may consist of disc swelling, various degrees of optic atrophy, or both. Intracanalicular ONSM tends to initially present with an atrophic disc.11 Another important finding represents optocilliary shunt vessels, noted in approximately one-third of cases. Finally, the presence of nonspecific refractile bodies on the optic disc was noted and was associated with the chronic stage of disc swelling.12

Computed tomography (CT) revolutionized the diagnosis of ONSM in the 1980s. It easily demonstrates eventual calcification of the ON and hyperostosis associated with ONSM. CT scans are best obtained before and after contrast administration using thin sections (1.5–3.0 mm). The most common pattern described was diffuse tubular enlargement and, less frequently, globular or fusiform.2, 3, 12, 19 Tram-tracking, a radiographic sign in which the denser and thickened ONS outlines a central lucency representing the residual ON, is a characteristic finding suggestive of ONSM. It may also, however, be seen in other diffuse sheath thickening such as those found in inflammatory perioptic pseudotumor, ON lymphomas, and optic neuritis.20–22 In ONSM, the meningioma surrounds the ON and the caliber of ON is attenuated within the surrounding tumor. This is in contrast to ON gliomas, where the ON itself is expanded.

The imaging modality that today has gained the most widespread use in the diagnostic approach to ONSM is magnetic resonance imaging (MRI). Gadolinium-enhanced, fat-suppression T-1 weighted pulse sequenced MRI using fine-cut axial and coronal images has been established as the optimal MRI approach. MRI is particularly helpful in detecting intracanalicular or intracranial extensions of pONSM, which on CT scan may be “silent.” The en plaque ONSM, a variant of ONSM where the tumor spreads along the ON as a thin layer, is often only diagnosed as enhanced fat-suppression T1-weighted images. With the use of MRI it is nowadays easier to differentiate ONSM from sarcoidosis,23 optic neuritis,24–28 schwannoma, hemangiopericytoma, hemangioma, hemangioblastoma, metastasis, and glioma.29–32 Ancillary tests such as 111-In-Octeotride scintigraphy33 or 3D ultrasound coronal C-scan imaging34 hold promise for future studies, as recently shown.

The World Health Organization (WHO) classification from 199335 identifies 3 grades (I, benign; II, atypical; III/IV, malignant) of malignancy and further discussion indicates that the recurrence potential is the most predictable aspect of various histologic types.36 For these 3 types the recurrence rates were 6.9%, 34.6%, and 72.7%, respectively. When growth types of meningiomas are taken into account, again 3 types are identified: meningothelial, fibroblastic, and transitional. It has been recently recognized that more detailed emphasis on cellular arrangement adds little to the expected behavior of the tumor.37


  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions

The major finding directing treatment in the last several decades is the duality of the natural course of the disease: whereas the prognosis for life is excellent, with virtually no patients dying of this disease, the prognosis for function is extremely poor, with the majority of treatment options resulting in blindness of treated patients. The latter include observation, surgery, surgery and postoperative RT, and RT alone. Although some drugs/agents may have a modest effect on other meningiomas, they have no proven effect on ONSMs.38–40

Observation has its premises in slow tumor growth, with sometimes durable periods of stable vision or extremely slow vision impairment, and in poor functional results obtained, regardless of the type of surgical intervention. This, indeed, may be a useful approach in cases when there is a slow deterioration of vision, as well as when ONSM is situated near the orbital apex. The behavior of the tumor, however, is absolutely unpredictable. One must rely on strict follow-up, because the tempo of deterioration sometimes surprises the ophthalmologist, and at the time of subsequent follow-up examination leads to recognition of severe functional deficits or blindness. Therefore, the crucial question is: what amount of functional impairment should lead to treatment? Kennerdell et al.8 suggested that when visual acuity is progressively lost below the level of 20/40 or the visual field is constricting, treatment must be initiated. However, it is likely that strict follow-up should also include imaging (MRI) because these 2 combined aspects could provide a better framework for appropriate and timely decisions on the institution of treatment. There are suggestions of reassessment of patients on a 3 to 6-month schedule, with serial neuro-ophthalmologic and visual field examination with MRI being used at 3-month intervals.41

A comparison of this treatment approach with others is unequivocally associated with serious flaws. Patients submitted to mere observation are likely to represent a subgroup exhibiting either minimal or no functional impairment. With such a good prognosis in this group of patients, an observation-only approach may lead to retention of acuity and visual fields in some of the patients, and in some this was so for many years.42 However, with prolonged follow-up about 85% of patients experienced vision decline.1, 8, 43

The 2 major problems with this approach are: 1) the jeopardy of affecting the contralateral (unaffected) eye, particularly in cases of intracanalicular ONSM, with an incidence of such an event being 38% in 1 series1 and 2) the longer the course of pretreatment growth of primary ONM and consequent visual disturbance, the less are the chances for posttreatment (particularly post-RT) visual improvements.

Under the term Surgery, biopsy, optic nerve sheath fenestration, tumor removal, and ON and tumor resection are considered. Biopsy was used in the past, but was hazardous, leading to functional impairment. It is not considered necessary nowadays, because the characteristic clinical picture, funduscopic findings, and imaging are used to provide clinical diagnosis of ONSM. ONS fenestration was aimed at decompressing the ON by opening the dural sheath. Whereas some44 found it successful in arresting progressive visual loss, others found it unsuccessful,4, 45 and some even observed its deleterious effect on outcome, which resulted from subsequent massive orbital invasion that necessitated exenteration.15 Therefore, this method is largely abandoned nowadays. Tumor removal (excision) is a frequently practiced treatment approach in ONSM. An initial anterior orbital approach was found inadequate because it did not allow complete removal of deeper orbital tumors, especially those at the orbital apex. More successful was the lateral orbital approach, particularly for tumors located in the anterior or midorbit, but the problem of adequate treatment of apical orbital ONSM largely remained.46 An intracranial approach (frontal craniotomy)47 and its modifications48, 49 enabled complete extirpation of ONSM up to the chiasm. This approach, coupled with orbitotomy for biopsy, was largely standard practice in the past decades. In a summary of the literature with a total of 148 patients,1 the mortality was zero, the rate of operative complication was 30%,2, 8, 9, 13, 50 and the recurrence rate was 25%.2, 9, 13, 51 This confirms previous observations that incomplete excision was associated with diffuse orbital invasion52 and intracranial spread to the chiasm.44 Importantly, vision was improved in only 5% of the patients; in 1% it was found to be stable, whereas 94% of patients experienced decreased vision. In most cases blindness occurred due to the interruption of pial vessels and ischemic injury to the optic nerve, because tumors and the optic nerve share a blood supply. Of the aforementioned 94% impairment of vision, 78% of patients experienced no light perception and in 16% patients' vision declined. In the rare cases with improved vision, tumors were unequivocally situated anteriorly, close to the globe, without significant neural invasion, and were quite small.4, 13, 14, 28, 41, 53, 54 These data, coupled with those showing the effectiveness of RT slowly, but definitely, challenged surgery as the treatment of choice in primary ONSM.37, 42, 55–60 It is likely that this would remain largely confined to continuously progressing, large, uni- or bilateral tumors in nonfunctioning eyes so as to prevent major intracranial spread, preferably by en bloc excision.

Surgery and postoperative RT has mostly been practiced in cases of pONSM extending to the intracranial sites with clearly documented visual impairment. Complete resection is the goal, but could be switched to a subtotal resection if no clear resection planes were identified around the optic nerve to minimize visual loss, if possible at all. In such cases postoperative RT was frequently administered.8, 43, 61 Improved vision ranged from 33% to 44%, stable vision ranged from 25% to 67%, whereas decreased vision ranged from 0% to 31%. However, the combination of less aggressive surgery and postoperative RT did not lead to a substantially lower incidence of postoperative complications when compared with surgery alone.43 Coupled with the most recent data on the effectiveness of RT alone, these data warrant reevaluation of this approach to identify a subgroup of patients that may benefit from it. Likely candidates would include larger tumors in which there is still useful vision. Limiting surgery and offering postoperative RT may provide preservation of vision and tumor growth arrest.

The history of RT alone in ONSM starts with the report of Byers,46 who credited McReynolds with the first use of this treatment modality. However, it was Smith et al.28 who were the first to clearly document the effectiveness of RT in pONSM. In early reports RT doses of, mostly, around 5500 cGy were used, reporting favorable outcomes.6, 8 When Dutton1 in 1992 summarized the data from the literature in a total of 12 treated pONSM patients, visual acuity improved in 75%, remained stable in 8%, and declined in 17% after follow-up periods of 2–6 years. The major factors preventing the wider application of RT in pONSM were that the effectiveness of RT alone in ONSM has only been documented in a few patients, the belief that meningiomas are radio-resistant,62, 63 and the fear of excessive toxicity. With time, however, RT-induced toxicity was largely demystified. It was observed that brain necrosis is extremely unusual after 54 Gy given in 1.8-Gy daily fractions, being 0.2% in an analysis that included 1388 patients.64 The risk of injury to the optic pathways also depends on the single and total RT doses. Without previous surgical damage to the pathways, with the single dose of <2.0 Gy and the total dose ranging from 45 to 50 Gy, this risk was below 2%.64, 65 If the total dose increases to 54 Gy, the risk of optic neuropathy rises to roughly 5%.66, 67 However, in the study on head and neck cancer67 with a dose of <59 Gy no injury was observed in 106 optic nerves. With ≥60 Gy, the 15-year actuarial risk of developing optic neuropathy was 47% with fraction sizes of ≥1.9 Gy, but was only 11% with fraction sizes <1.9 Gy.

The 1990s were a time of wide application of more precise, computer-driven RT technologies. The use of 3D treatment planning enabled more precision in planning and treatment. The aim of these techniques was to conform RT dose to the shape of the tumor and, therefore, diminish the dose to the surrounding healthy tissue, thus decreasing the risk of RT-induced toxicity. Initial attempts to better conform the RT dose included special head rotation68 in 3 patients in 1992. Lee et al.69 first documented improved vision after the use of 3D conformal radiation therapy (3D-CRT) in ONSM using conventionally fractionated doses totaling 50.40 Gy. Several reports of interesting cases followed, using different techniques such as stereotactic fractionated radiosurgery,70 intensity-modulated RT (IMRT),71 stereotactic fractionated RT (SFRT),72 or 3D-CRT73, 74 with stable or improved visual function at follow-up times of up to 2 years. In none of these reports was RT-induced optic pathway toxicity observed. This opened up a new era of RT in pONSM. As with earlier reports, RT rarely caused significant tumor shrinkage on imaging,65–70 a frequent reason for surgeons not to recommend RT in cases of rapid visual decline but to recommend surgery to immediately alleviate pressure to visual pathways.75, 76 However, it must be clearly stated that improvement in visual function can occur even during the course of RT,77 as well as later on in the follow-up period, in neither case dependent on tumor shrinkage, but rather RT-induced edema decrease and “decompression” of the functional nerve structures.

The year 2002 was the year of RT in pONSM, with 4 studies/5 reports that included precise data on treatment planning and delivery of RT as well as longer follow-up. Importantly, toxicity of RT was much lower than in earlier studies using conventionally planned RT. The characteristics of these studies and the outcome are given in Table 1, including the most recent multi-institutional study by Baumert et al.,78 and smaller studies of Richards et al.,79 Landert et al.,80 a report of a case by Paridaens et al.,81 and the most recent report by Sitathanee et al.,82 all published later on. Liu et al.,58 Becker et al.,59 as well as Pitz et al.57 and Baumert et al.78 reported on pONSM exclusively/separately. Turbin et al.43 provided the longest follow-up, reporting on 18 pONSM of a total of 64 ONSM patients, without specifying the details on the outcome for pONSM. Instead, the results were separately provided for patients treated with RT alone and those treated with observation, surgery, and surgery with postoperative RT. The former were the only ones not experiencing significant deterioration of vision, with 44.4% of them experiencing at least 2 lines of improved visual function. This figure could have been significantly higher if the authors had provided the comparison of visual acuity before RT and not at the time of diagnosis and at the last follow-up. There was a 33% incidence of RT-induced toxicity, but it was left unexplained which patients actually experienced toxicity regarding RT dose and treatment planning, as it remained unknown what was actually the RT dose patients treated with RT-only received. Also, theoretical concerns that RT in diabetic ONSM patients may lead to more frequent vascular complications43 are not substantiated by any data. Of particular importance is that all other treatment options led to a significant decrease in visual function. Two German studies dealt with a group of patients suffering from primary as well as from secondary ONSM treated by an identical standardized SFRT protocol. Detailed ophthalmologic data of the pONSM patients of these 2 studies have been given in Pitz et al.57 In none of their patients was any decline in visual function noted. Excluding those eyes already being blind at the initiation of treatment, the rate of improvement of either visual acuity or visual field was 58%. There was a tendency for improvement in those patients suffering from rather mild or no decline in visual acuity but visual field defect. In comparison, the response rate of patients exhibiting a more pronounced impairment of visual function was smaller. This led the authors to conclude that an early initiation of RT is advisable. In the study of Andrews et al.,33 although there was a 92% rate of improved or stable vision, there was 13% toxicity. It was left unexplained which patients experienced toxicity, particularly important because there were 9 of 30 patients with intraorbital ONSM and 1 in whom ONSM extended intracanalicularly, all other ONSM being more extensive. The recent study of Narayan et al.74 reported 5 (35.5%) patients suffering from late toxicity. Their case of radiation-induced retinopathy may be attributed to a rather anterior location of the tumor. Other side effects were dry eye, orbital pain (in a patient suffering form migraine), and iritis, which responded well to local steroid therapy. In contrast, the other studies dealing with pONSM providing clearly documented treatment parameters57–59 showed excellent treatment outcome (improved or stable vision in 100% of patients in both studies) and no toxicity to optic pathways were observed. The follow-up in these studies ranged from 1–7 years (mean, 3 years; median, 2 years),58 and 1–6 years (median, 35.5 months).59 This is likely adequate follow-up for the detection of RT-induced toxicity on optic pathways. The recent study of Baumert et al.78 reported on 22 patients with pONSM treated with SFRT in 4 European institutions. This study reconfirmed that SFRT offers excellent results (95% improved and stable visual outcome) observed after a median of 20 months (range, 1–68 months). Only 1 (5%) patient developed radiation retinopathy, thus providing an overall/ultimate success rate of 91%.

In 4 of the most recent and small studies, a total of 12 patients were presented.79–82 Richards et al.79 confirmed these finding in their small series of 4 patients treated similarly. Slightly lower total prescribed (43.40–45.00 Gy) and daily (1.67 Gy) doses were used. In all cases visual acuity improved at the last assessment, whereas visual fields improved in 65% of patients. No significant toxicity was observed. Landert et al.80 reported on 7 eyes treated with SFRT as compared with 6 untreated eyes. Doses of 50.4 to 54.0 Gy were used. In treated eyes, visual acuity improved in 86%, whereas visual fields improved in 57% of patients, remained stable in 29% patients, and worsened in only 14% of patients. These results were significantly better than corresponding figures of untreated eyes (visual acuity: worsening, 67%; visual fields: worsening, 50%). No complications of the treatment were documented. A report of a case from the Netherlands81 reconfirmed worldwide experience with SFRT, being an effective and safe treatment method in ONSM. Finally, a report from Thailand82 showed that even higher (range, 51.6–59.1 Gy; median, 55.7 Gy) doses can be safely and effectively given in this patient population.

What all these studies have provided is that with the highly sophisticated RT used in recent years the results with 50–54 Gy, conventionally fractionated (mostly using 1.8 Gy per fraction), using the target volume typically expanding 3–5 mm from the known tumor margins, at least 80% of visual improvement or stability can be obtained after a follow-up of several years. These results could have been better if cases with pretreatment mild or moderate visual loss were represented more, because patients with marked improvement after SFRT are likely those having visual acuities ranging from 20/40 to 20/30, which may allow a greater potential for good treatment results, as reiterated recently by Richards et al.,79 Landert et al.,80 and Sitathanee et al.82 Nevertheless, the results of SFRT were accompanied with extremely low toxicity, which, in cases without significant extension outside the orbit, is negligible. Toxicity in 2 studies33, 43 could be attributed rather to undisclosed predisposing factors and more extensive tumors in which planning was rather difficult, and accompanied with dose inhomogeneities leading to its occurrence. Also, a recent report83 of a case with radiation retinopathy occurring 2 years after SFRT (optic nerve dose, 54 Gy in 30 daily fractions; optic nerve head dose, 48–54 Gy; posterior retina dose, 27.8–48 Gy) for pONSM located intraorbitally and intracanalicularly did not provide additional information on this matter. Neither pretreatment factors that may have contributed to its occurrence nor the exact incidence of such findings among the other, presumably existing, cases of pONSM treated with either conventional RT or SFRT have been provided. Therefore, it remains unexplained why such patients developed retinopathy while still receiving 27–48 Gy to the posterior retina. This has serious implications, so as not to jeopardize the treatment success of SFRT, which effectively combined biological (fractionation; 50–54 Gy in daily fractions of 1.8 Gy) and technological (stereotactic treatment planning, daily reproducibility of high precision, and high conformation of the dose to the desired treatment volume) aspects of treatment. This dose/fractionation was shown to produce no toxicity to optic nerve/chiasm when IMRT was used to treat irregularly shaped intracranial meningiomas other than that of the optic nerve sheath.84


  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions

RT has been practiced in the treatment of ONSM for decades, and the very recent reports confirm its effectiveness in patients with ONSM.33, 43, 57, 59, 74, 78, 85 However, only recently has excellent functional outcome matched with very low toxicity been enabled by modern RT techniques. This holds even truer as RT candidates represent an unfavorable group of patients suffering from “clinically active” disease, characterized by progressive vision impairment. The recent results suggest consideration of RT in the treatment of pONSM early in the course of the disease, possibly earlier than up to now has been the case. Whereas surgery remains reserved for cases of large tumors causing blindness and preventing spread to intracranial sites, the only other treatment approach to be considered is observation. Observation is still practiced worldwide in expectation that some pONSM will grow slowly, and hence will lead to slow impairment of vision. At present, however, there are no tests allowing a precise prediction of growth velocity of an individual tumor. Furthermore, there is a lack of clinical correlation between progression in imaging and progression in functional impairment. Moreover, virtually all cases managed by observation end up in serious dysfunction or even blindness. This calls for a clinical assessment of ONSM patients combining both ophthalmologic examination and imaging (as each of these performed separately might miss signs of progression). As soon as either diagnostic tool shows progression, RT should be administered.

Taking into account the effectiveness of high-precision RT, the recent data call for a change of the practice worldwide. Although prospective randomized trials investigating this issue are highly desirable, the rarity of this condition will probably prevent their being undertaken in the near future. Therefore, evidence coming from available studies has to be considered, especially because RT seems the only treatment modality allowing stabilizing or even improvement of vision in patients with pONSM. Although several institutions are practicing this approach, there is no standard treatment approach worldwide. Hopefully, joint efforts of specialized centers capable of monitoring the disease and performing sophisticated RT will lead to a standardized protocol. Every effort should be made to spread awareness of these changes in treatment approach.


  1. Top of page
  2. Abstract
  3. Search Strategy and Selection Criteria
  4. Pretreatment Aspects
  5. Treatment
  6. Conclusions
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