SURVEY OF OPHTHALMOLOGY

VOLUME 37 * NUMBER 3. NOVEMBER-DECEMBER

1992

MAJOR REVIEW

Optic Nerve Sheath Meningiomas JONATHAN

J. DUTTON,

M.D.,

PH.D.

Duke University Eye Center, Durham, North Carolina

Abstract. Meningiomas are benign neoplastic lesions arising from meningothelial cells of the meninges. Primary orbital meningiomas, originating in the optic nerve sheath, represent l-2% of all meningiomas, and are the second most common optic nerve tumor after gliomas. They primarily affect middle-aged adults. Patients typically present with visual loss, frequently associated with optic atrophy and often with optociliary shunt vessels. The lesion is usually unilateral, but is bilateral in about 5% of cases. Meningiomas show characteristic indolent growth over years, progressing inexorably to blindness in the affected eye. Management should be conservative in most cases. In very rare situations, surgery has improved visual prognosis. In most patients, however, surgery offers no benefit, and should be reserved for those with blindness or severe proptosis, or when extension toward the optic canal is documented. Although preliminary results of radiotherapy are encouraging, very few patients have been treated using this modality, and the long-term advantage for vision remains unproven. Even when untreated, the prognosis for life is excellent, with an overall tumor-related mortality of 0%. (Sure Ophthalmol 37:167-183, 1992)

Key words. meningioma orbital tumor

9 optic nerve tumor

??

optic sheath meningioma

??

lowed for long periods of time without treatment, so the efficacy of the various treatment modalities in most cases remains uncertain. For the present review as much of the published literature as possible was examined. Many of these reports give statistical data on age, sex, symptoms, and response to treatment as percentages of their patient population. Because of small sample sizes, such values vary widely. Where these data allowed, patients were grouped into larger series in order to minimize sampling errors. Patients were excluded if specific data on symptoms, clinical findings, age, sex, or results of therapy were lacking. Only those patients for whom precise data were available are considered. Therefore, the number of cases grouped here for each described parameter varies. For each parameter discussed below, the to-

Meningiomas are common benign neoplasms that may arise in the orbital optic nerve sheath, where they account for one-third of all primary optic nerve tumors. Despite a large literature, there is still considerable controversy regarding the natural history of these tumors and their appropriate management. Evaluation of published reports has been difficult because most studies are based on intracranial meningiomas, and fail to distinguish these from primary orbital lesions. Where data on optic sheath tumors are given, reported results are based on very small patient series short follow-up periods, and there are inconsistencies in presentation of findings that make direct comparisons difficult. Statistical sampling errors resulting from small series account for most of the large variations in reported results. Furthermore, few patients have been fol-

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tal number of patients reported in the literature examined for that finding, and utilized in our evaluation is given. The frequencies of occurrence for any particular finding (e.g., optooiliary shunt vessels) are noted as a percentage of that total number of patients. Because data are based on many individual reports, these numbers should be viewed with caution. Nevertheless, they are consistent with previous studies, and in most cases lie well within the reported ranges of variation. Values given here have the advantage of reducing some of the sampling errors, since they are based on larger numbers of patients.

I. Historical Background In 1755, Spry (quoted by Scarpa”*) described a young woman with decreased vision in one eye associated with an afferent pupillary defect and orbital pain. She was treated with bleeding, purges, and division of the temporal artery, to no avail. At surgery, a large optic nerve tumor was found, which from Spry’s description was probably an optic sheath meningioma. In 1816, Scarpa”’ characterized tumors of the optic nerve, most of which were childhood optic gliomas. However, some of his patients were adults in whom one optic nerve was surrounded externally by a thickened, firm mass. According to Scarpa’s original descriptions, these were probably cases of optic sheath meningiomas. Scarpa treated his patients with surgical excision, but noted a high rate of orbital recurrence. In 1835, Jean Cruveilhier” was the first to recognize meningiomas as a pathologic entity, although confusion with other optic nerve tumors persisted until Hudson’s” classification in 19 12 clearly separated optic gliomas from sheath meningiomas. Byers” counted 102 cases of optic nerve tumors from the 19th century literature, but most of these were optic gliomas. By 1928, Mayer’* collected 40 cases of orbital meningiomas, but no distinction was made between primary optic nerve tumors and secondary meningiomas extending from intracranial sites. Verhoep2* felt that no case up to that time had been proven to arise primarily in the orbit, but concluded a priori that there was no reason why meningiomas should not arise from the optic nerve sheath. The first unequivocal cases of primary optic nerve sheath meningiomas were described by Coston” and Friedenwald.45 Up to the present day, about 498 cases of orbital meningiomas have been described. Meningiomas in general are the second most

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common brain neoplasms after gliomas, representing 15-20% of all intracranial tumors in adults4~2s~3s and 2% of intracranial tumors in children.20 They may have considerable effect on visual function.5g’136 Most meningiomas that involve the orbit represent extensions from intracranial sites.‘96 However, as noted above, primary optic sheath lesions are now well documented. Among 1723 meningiomas for which the site of origin could be determined, primary optic nerve sheath lesions were found in 22 patients ( 1.3%).‘g~2392~g3~‘36 Although usually considered quite rare, optic sheath meningiomas may be more common than has usually been recognized, and may be confused clinically with anterior optic gliomas.‘j4 Wright et a114’identified 50 optic sheath meningiomas among 3000 orbital tumors (1.7%) seen at Moorefields Eye Hospital up to 1989.

II. Epidemiology and Location A. AGE AT PRESENTATION Hudson” felt that optic sheath meningiomas occurred primarily in young individuals, with 25% in the first decade and 50% in the first two decades of life. Karp et al,“” in a review of 25 patients recorded at the AFIP, supported that view, with 40% of their patients less than 20 years of age and 24% less than 10 years old. Craig and Gogelalg recognized that optic meningiomas occurred primarily in middle-aged adults, a notion that has been confirmed in numerous studies since thatnme 2~16~493,64~107~113 CmfingmdWGght'7 suggested that confusion between meningiomas and arachnoid proliferation associated with optic gliomas in young patients may have accounted for the discrepancies in age range reported in different studies. However, Karp et al’s series66 was based on histologically confirmed specimens, and the sample apparently resulted from the AFIP’s biased referral pattern. From the 256 patients with optic sheath meningiomas for whom data were available, the mean age at presentation was 40.8 years (range, 2.5 to 78). Only 4% of these patients were less than 20 years of age,15,19,57,64,107,113.123,139 and the youngest patient reported was only 2.5 years old.‘jg The mean age was 42.5 years (range, 2.5 to 73) for females and 36.1 years (range, 10 to 78) for males. Wilson”‘j suggested that patients with bilateral meningiomas tended to be younger, generally in the first decades of life. Of the 15 bilateral cases for which age data were given, the mean age was 34.2 years (range, 13 to 70), with a median of 33.0 years. However, these data refer

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OPTIC NERVE SHEATH MENINGIOMAS TABLE Epidemiologic

1

Characteristics and Location of Optic Sheath Mening-iomas Mean

Age (256 pts)* Females Males All patients Sex (356 pts) Laterality (498 pts):

Side affected (2 13 pts):

Range

42.5 yrs 36.1 yrs 40.8 yrs

2.5-73 lo-78 2.5-78

Female: 217 (61%)

yrs yrs yrs

Male: 139 (39%)

Unilateral: 475(95%)

Bilateral: 23(5%)

Right: 111(52%)

Left: 102(48%)

Sites of origin for meningiomas involving the orbit (5000 pts) Secondary tumors, intracranial origin: 4502(90%) Primary tumors, orbital origin: 498( 10%) Ectopic: 21(4%) Optic sheath: 477(96%) Orbital optic nerve: 438(92%) Optic canal: 40(8%) *Number of patients indicates number for which each parameter

to the age at which visual loss occurred in the second eye. In five cases where adequate history is known, the onset of visual loss in the first eye began on average 18.2 years (range, 2 to 27) before the second eye was affected.52*58~75~‘Thus, “6 the mean age for initial onset of symptoms among these five patients with bilateral optic sheath meningiomas was 12.8 years. Although the numbers are exceedingly small, these data do suggest an earlier age for initial onset of the disease in bilateral cases. B. SEX DISTRIBUTION It has long been recognized that meningiomas occur more frequently among females. In Craig and Gogela’s 1949 series,lg 76% of patients were female. Sex data has been provided in the literature for 356 patients (Table l), and although the ratio has tended to equalize, overall there appears to be a slight female predominance of 6 1% versus 39% for ma1es.2~4g~62~6g~113,‘40 C. LATERALITY A slight predilection for the right optic nerve has been reported in several studies, ranging from 55% to 71%.58,1’“,113Karp et a16’jfound no difference in laterality, except among a small sample of females less than 20 years of age, where 8 of 9 cases (89%) involved the right orbit. Other studies have not confirmed these findings. 64~114~140 Among 213 cases of optic sheath meningiomas where laterality data were given, 111 (52%) occurred in the right optic nerve, 102 (48%) occurred in the left nerve (Table 1). Of the 477 cases of sheath meningiomas de-

was reported.

scribed in the literature, 23 (5%) were bilateral. Ofthese 23 cases, 15 (65%) represented canalicular meningiomas. 19.26.30.52.58.100.104.1261n contrast, among the 454 unilateral sheath meningiomas described, only 26 (5.7%) involved the optic canal. The implications of this for possible spread from one optic nerve to the other is discussed below.

D. SITES OF ORIGIN In his original descriptions, Scarpa”* clearly recognized that the optic nerve was affected by meningiomas, but was unable to determine that the nerve sheath was the site of origin. Other early authors felt that such tumors could arise along the nerve. 32,54,g4Cushing and Eisenhart2’ believed, on histopathologic evidence, that the optic nerve could be a site of origin, although no confirmed case could be established. The first unequivocal primary optic nerve meningioma was reported by Friedenwald,45 and the first large series was presented by Craig and Gogela.lg Since that time it has become well accepted that meningiomas indeed arise from optic nerve arachnoid tissue.12’ Approximately 90% of meningiomas involving the orbit derive from intracranial sites,1g’136primarily from the olfactory groove and sphenoid ridge. However, based on a much smaller series of patients, Blodi and Brailey’ found 13 out of 20 (65%) meningiomas involving the orbit to arise from the intraorbital optic nerve. Sibony113 found that 18 of 22 (81%) optic nerve lesions were situated at the orbital apex.

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In 40 out of the 477 cases (8%) of optic sheath meningiomas reported, the tumors were confined to the optic canal. 19,21,25,30,31,39,52,57,58,65,68,77,78, 89,103,104,106,‘21,121a,122,125,126,130,133,137,142

Although

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DUTI’ON TABLE 2

ClinicalSignsand Symptoms of Optic Shath Meningioma No. Pts.

these

could be considered as either intracranial or orbital lesions, they are included here with primary orbital meningiomas arising from the optic nerve sheath. These tumors have a higher incidence of bilaterality than those at other sites, with 62% being unilateral and 38% bilateral. This tendency for canalicular meningiomas to occur bilaterally was already noted by Craig and Gogela,lg but its significance remains unclear. In 1923, Benedict5 described removal of a meningioma from the orbit that appeared to arise from an orbital site ectopic to the optic nerve. However, its base was firmly attached to the superior orbital fissure, and it possibly arose from the sphenoid ridge. Wiegmann134 reported an encapsulated meningioma within the extraconal space that was clearly separate from the optic nerve. Among the 498 cases of primary orbital meningiomas reported, in 2 1 patients (4%) the tumor was presumed to be of ectopic (nonoptic sheath) origin. 5,19,24,74,80,110,124,134 Rootman’ mentioned one ectopic lesion among 23 primary orbital meningiomas (4%). It has been suggested that such tumors may arise from ectopic arachnoid cells within the orbital interstitial tissues or along orbital nerves.24 However, Craig and Gogelal were unable to identify any arachnoid clusters within the orbit, nor any meningeal tissue associated with orbital nerves, except the optic nerve. They suggested that these isolated meningiomas arise from arachnoid tufts that grow through the dura of the optic nerve. Tan and Lim124 felt that their specimen, located in the medial orbit, arose from the sheath of the ethmoidal nerve. Spencer’“’ argued that no example had been proven of primary meningioma in the orbit separate from the optic nerve sheath. He felt that other lesions, such as fibroxanthomas arising from fibrous and angiomatous mesodermal elements, could be mistaken histologically for meningiomas. Likewise, Karp et a1’j6noted the histologic similarity between hemangiopericytomas and fibrous histiocytomas, and what have been classified as angioblastic or fibroblastic meningiomas. However, more recently Shuangshoti”’ suggested that ectopic meningiomas may arise directly from orbital mesenchymal cells. Although the existence of true ectopic orbital meningiomas remains open to question, it is likely they do occur, though rarely. Hudson” was the first to mention the intraoc-

Condition Decreased vision* Decreased visual field Decreased color vision Proptosis Disc atrophy Disc swelling Decreased motility Optociliary shunts

No. Pts. with Data Available Affected (%) 380

365(96)

135

112(83) 33(73) 142(59) 87(49) 1OO(48) 121(47) 71(30)

2:: 177 208 258 238

*20/20-20/40(45%); 20/50-20/400(31%); CF-NLP (24%). Duration of symptoms (119 pts): Mean = 41.9 mos. Range = 1 mo-17 yrs. (1-12 mos (32%); l-5 yrs (46%); over 5 yrs (22%)

ular invasion of sheath meningiomas. Of 477 cases, 18 patients (3.8%) have been described with focal tumor invasion of the optic disc, sclera, choroid and retina ‘8.33,56,60,66,83,9’,92,99,” 1,129Cibis et all5 r;ported

a 13-year-old child with a white elevated subretinal mass that proved to be a sheath meningioma extending from the globe to the chiasm. Optic nerve tumors may enter the globe along penetrating shunt vessels, posterior ciliary arteries, or the central retinal vessels.‘j’ Meningioma cells have been demonstrated within the vascular lumina of ciliary arteries and of the central retinal vessels.10,42*56 E. ASSOCIATION WITH NEUROFIBROMATOSIS The incidence of neurofibromatosis (NF) in the general population is 0.03-0.05%.50 A higher incidence in patients with intracranial meningiomas has long been recognized,73 and a similar relationship has been accepted for optic sheath meningiomas. I20 The true incidence of NF among patients with sheath meningiomas is difficult to ascertain, since most studies fail to mention its occurrence. It is unclear whether NF was absent in these cases or simply not recognized. In the seven studies that specifically examined for NF, there were 12 affected patients among 142 (9%) with sheath meningiomas.3~15*64~66~123*12g,140 Even if it is assumed that all the other reported cases did not have NF, the incidence of association is still more than 2%, considerably higher than in the general population. The fact that both optic gliomas and meningiomas occur more frequently in patients with NF, together with the fact that both tumors can present with similar

clinical symptoms and sometimes conflicting radiologic findings, may lead to considerable diagnostic confusion. Some children believed to have optic gliomas may in fact harbor meningiomas instead. The therapeutic implications of this are discussed below.

III. Clinical Signs and Symptoms (Table 2) In patients with optic sheath meningiomas, the common findings of visual impairment, proptosis, disc swelling, and optic atrophy have been known for over a century.1g~5s*‘20However, Walsh (mentioned by Spencer”‘) was the first to recognize a triad of findings which together have been considered pathognomonic for the disease, namely visual loss, optic atrophy, and optociliary shunt vessels. Frisen et a146later formalized this concept. Although this combination has recently been shown to be a nonspecific finding in some cases of optic nerve compression,87a nevertheless, this triad strongly suggests the diagnosis of sheath meningioma. However, the simultaneous occurrence of all three findings in any individual is uncommon. A. VISUAL ACUITY AND FIELDS The most frequent presenting symptom of optic nerve sheath meningioma is loss of visual acuity, which was seen in 365 of 380 reported cases vision is (96%). 2~16~48~62~64~69~107~113~123~139~140 Initially, generally only mildly impaired. Among 12 1 patients where more specific data are available, 54 (45%) presented with acuities of 20/20 to 20/40, 38 (31%) with 20/60 to 20/400, and only 29 (24%) with counting fingers or worse. Wright et a1141 had 16 of 50 patients (32%) with vision of 20/60 or better at presentation, and 22 of 50 (44%) with hand motions or worse, of which 12 (24%) were NLP. Alper’ reported 23 of 55 patients (42%) already blind at initial examination. Visual loss is typically gradual. Among 119 patients, the mean duration of symptoms prior to presentation was 41.9 months (range = 1 month to 17 years).16*58, 62~66~‘13~13g~‘ Of40these, 38 patients (32%) had symptoms for one year or less, and 26 patients (22%) for five years or more. Transient obscurations of vision may be the presenting symptom in some patients.‘z1a~136Wright et a114’reported 7 of 50 patients (14%) with obscurations. Among these seven patients, the visual disturbance was gaze evoked in three (43%), postural in two (28.5%), and spontaneous in two (28.5%). Decreased color vision is usually an early finding. Color vision testing was specifically mentioned in

Fig. 1. A 38-year-old woman with an optic sheath meningioma of the left optic nerve presenting with visual loss and minimal proptosis.

only 45 patients, but among these a deficit was noted in 33 (73~o).38~68~69~81rl13~122~137 In bilateral cases, visual loss typically begins in one eye only. Among the five patients for whom data are given, the time interval separating visual dysfunction in the two eyes has been reported as from 2 to 27 years.52,58,75,126 Visual field defects were documented in 112 of 135 patients (83%) where such data were reported, and presumably defects would have been present on detailed testing in all patients with visual loss. Among the 112 reported field defects, peripheral constriction was seen in 39 cases (35%), central, centrocecal, and paracentral scotomas were noted in 32 patients (29%), altitudinal defects in 18 (16%), and increased size of the 69,107,112,113,123,136 but com_ blind spot in 15 (13%), pressive optic neuropathy may be associated with any type of field defect. The incidence of generalized constriction appears to be higher with canalicular tumors.“‘j B. EXTERNAL

CHANGES

Proptosis was found on initial examination in 142 of 241 patients (59%). In most cases it follows the onset of visual loss, although occasionally it may be the first sign noticed by the patient. Generally, proptosis is mild to moderate [(2 to 5 mm) Fig. 11. It is slowly progressive and rarely may reach 10 mm or more. Proptosis is seen less frequently in patients with canalicular lesions, since they typically present with visual loss while the tumor is still very small. Wright et a113’suggested that mild proptosis early in tumor growth results from straightening of the normally sinusoidal shape of the optic nerve by the relatively stiff tumor.

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Fig. 2. Fundus of a patient with an optic sheath meningioma showing marked disc edema.

Fig. 3. Fundus photograph showing an optic sheath meningioma with disc pallor and optociliary shunt vessels (arrow).

Limitation of ocular motility is a variable finding. Among 258 patients for whom data were given, decreased motility was seen in 12 1 cases (47%) at the time of presentation. In most patients this results from mechanical restriction of extraocular muscle function due to a stiffening of the optic nerve sheath, although cranial nerve palsy may be responsible in about 5% of patients.13” The degree of restriction is often greatest in attempted upgaze.* Orbital pain and generalized headache have been reported in up to 50% of some series.‘g~123 Wright et a1r4’reported pain in only two out of 50 (4%) of their patients. Most studies make no mention of this complaint and its true incidence remains unclear. We have seen several cases of apical meningiomas associated with pain, presumably from compression of sensory nerves.

mann in 1893 in a g-year-old child with chronic optic nerve compression from an optic nerve tumor.‘04 He believed that these vessels represented dilated collateral channels between the retinal veins and the choroid, resulting from compression of the central retinal vein. Elschnig4’ demonstrated that these represented shunts between the retinal and choroidal circulation by observing them in an enucleated eye. Such vessels may be seen with chronic disc swelling from many causes, and have also been noted with disc drusen and arachnoid cysts of the optic nerve.3g The association between optic sheath meningiomas and optociliary shunt vessels was first noted by Walsh (mentioned in Spencer’*‘). Using fluorescein angiography, Frisen et a146 demonstrated flow of blood from the retinal veins through these shunts to the choroidal circulation in a patient with optic nerve compression from meningioma. Schatz et allosa histologically traced such shunts as collaterals from the retinal to the choroidal venous circulation passing around or through Bruch’s membrane. Imes et al”’ photographically traced the evolution of optociliary shunt vessels over 8.5 years in a woman with an optic sheath meningioma. They demonstrated that chronic disc swelling and congestion of the central retinal vein preceded the first appearance of shunts by l-2 years. As early atrophy became visible, the shunts enlarged and proliferated (Fig. 3), only to regress as atrophy became complete. The development of shunts results from compression of the optic nerve, obstructing flow in the central retinal vein. Dilatation of regressed, but vestigial, retinociliary anastomoses

C. FUNDUSCOPIC

APPEARANCE

On funduscopic examination, chronic disc swelling may be seen as an early finding. It was reported in 100 of 208 patients (48%) with optic sheath meningiomas (Fig. 2). Disc swelling is seen less frequently with tumors confined to the canal.“‘j Optic atrophy, which may be subtle, is a somewhat later finding, but it was already noted at the time of presentation in 87 of 177 patients (49%) where data were given. Some degree of both edema and atrophy may be seen together. Overall, 98% of patients will show one or the other of these two findings.*,'6,48,49,58,64,6",'13,140 The incidence and degree of atrophy increases as optic nerve compression progresses.5z,66~75,1l3 Optociliary veins were first described by Salz-

OPTIC NERVE SHEATH MENINGIOMAS

Fig. 4. Contrasted axial CT scan of a right optic sheath meningioma showing thickening of the optic sheaths. Tram-tracking is visible as a slight central lucency representing the optic nerve (arrow) surrounded by the enhancing tumor.

Fig. 5. Axial CT scan of an optic sheath meningioma with a globular configuration and areas of calcification (arrow).

in earlier embryonic developmentso” present reestablishes flow of retinal venous blood to the vortex veins.61 Although the presence of optociliary shunt vessels is considered to be useful in the diagnosis of sheath meningiomas, they are seen relatively infrequently. Among 238 patients for whom such data were reported, shunt vessels were seen in only 71 cases (30%). Because shunts tend to appear some years after symptoms begin and may involute as optic atrophy is complete, their true incidence may be significantly higher. Sibony et al”’ described the presence of nonspecific refractile bodies on the optic disc associated with the chronic stage of disc swelling in 7 of 13 cases of optic sheath meningiomas. Although such bodies have been noted with other causes of chronic papilledema, these authors felt that the incidence with sheath meningiomas was higher than for other etiologies. These bodies tend to cluster at the temporal disc margin and are best seen on red-free stereophotographs. Their appearance coincides with or precedes the initial decrease in vision. As optic atrophy develops, refractile bodies disappear.

ally at the optic canal, is rare with primary orbital meningiomas, 78 but has been reported on CT in 11 out of 47 patients (23%) reported by Clark et al,“j Gabibov et aL4s and Daniels et al.” Calcification is an important finding that, when present, helps differentiate optic sheath meningiomas from optic nerve gliomas within the orbit. However, this finding is rarely mentioned. Jakobiec et alM noted fine calcifications in 10 of 47 patients (21%), and Sarkies’O” noted it in 12 of 22 cases (55%). Wright et a1i41 reported calcification on CT in 10 out of 47 (21%) optic sheath meningiomas. With longstanding tumors, remolding and enlargement of the bony orbital contour may be seen.35s138Brandt et al” demonstrated the value of contrast orbitography in imaging small meningiomas of the optic nerve, but the technique is invasive and carries the risk of orbital hemorrhage. Computerized tomography has revolutionized the diagnosis of optic nerve tumors. Of 150 patients reported utilizing this modality, 97% demonstrated the tumor on initial examination, and Ed_ 99% on follow-up studies. 16,29,48,62,79,107,112,1~3 cept for lesions confined to the optic canal, CT demonstrates enlargement of the orbital optic nerve in the vast majority of cases. Among 150 patients for whom data are given, the most common pattern was diffuse tubular enlargement (Fig. 4), which was seen in 96 cases (64%).“gV48,63*64, 7g,112,113 Commonly, there may be some anterior or posterior expansion.64 A globular shape, due to tumor growth outside the dural sheath (Fig. 5), was reported in 38 of the 150 patients (25%). The meningioma assumed a fusiform shape on CT in 15 patients (10%). It is mainly these latter

IV.

Radiographic Findings

Before the advent of computerized tomography, radiographic studies proved to be inconsistent and unreliable in the diagnosis of optic nerve meningiomas. Plain orbital radiographs and polytomography through the optic canals demonstrated enlargement of the optic foramen in only 11 of 37 cases (30%). 16,56*62,*5,113 Even with can&c_ ular tumors, plain radiographs are frequently negative.‘*’ Hyperostosis of adjacent bone, usu-

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Fig. 6. Gadolinium-enhanced axial MRI scan (TR 600, TE 20) of an optic sheath meningioma utilizing a fatsuppression technique. The meningioma is hyperintense to normal optic nerve. The central lucency (arwithin the row) represents the optic nerve surrounding tumor.

Fig. 7. B-scan echograph of an optic sheath meningioma showing a solid widening of the optic nerve shadow. The arrow points to the optic disc. (Reprinted from Frazier Byrne S43 with permission of the author and publisher.)

cases that may be confused with optic gliomas. Jakobiec et a164 and Dutton35 reported one patient with a 14-year history of enlarging meningioma that on CT completely replaced all orbital soft tissue and eroded through the lateral orbital wall into the temporalis fossa. Tram-tracking, a radiographic sign in which the denser and thickened optic nerve sheath outlines a central lucency representing the residual optic nerve, is a characteristic finding suggestive of sheath meningioma (Fig. 4). However, it may be seen with other causes of diffuse sheath thickening such as inflammatory perioptic pseudotumor.“j Jakobiec et a164 found tram-tracking in 11 of 47 (23%) meningiomas, and Daniels et al*’ noted it in all of his three patients. On coronal views, the thickened sheath appears as a dense ring around the more radiolucent central optic nerve. Contrast studies generally show moderate to marked enhancement. Magnetic resonance imaging has only recently been used to evaluate optic nerve lesions.‘,z8~‘43 This modality offers excellent tissue differentiation and contrast enhancement based on variations in fat content and subtle differences in hydration, thus allowing excellent visualization of the nerve. The intracanalicular segment, not easily imaged on CT, is seen on MRI because of negligible resonant signal intensity from adjacent cortical bone on partial saturation images. With intraorbital optic nerve meningiomas, MRI shows a thickening of the nerve, and isointense or slightly hyperintense signal intensity compared to normal nerve, on both the Tl and T2

weighted sequences. Standard MRI has been considered inferior to contrasted CT for intracranial meningiomas because they are isomagnetic to normal brain.‘44 However, the introduction of paramagnetic contrast agents has greatly improved MRI differentiation of intracranial meningiomas and other tumors. GadoliniumDTPA contains the strongly paramagnetic gado’ chelated to diethylenetriaminopenlinium+’ ion taacetic acid (DTPA) to reduce its toxicity. Its selective presence in some tissues alters their proton relaxation times and increases signal intensity, and thus contrast. Gd-DTPA Tl-weighted MRI images show marked enhancement of intracanalicular and intracranial meningiomas not clearly seen on routine MRI studies or on CT.14’ However, in the orbit the surface of the enhancing tumor blends with the high-signal orbital fat which may obscure the interface. Hyperostosis of bone adjacent to meningiomas does not appear as hypointense on MRI as might be expected from bone, but rather is isointense to brain and enhances with Gd-DTPA, suggesting infiltration of tumor. Fat suppression MRI techniques eliminate the chemical-shift misregistration usually seen perpendicular to the frequency-encoding axis at the fat-water interface and which obscures the surface of the optic nerve. This technique improves tissue contrast of orbital structures,‘15 and more accurately represents the true anatomic borders of the optic nerve, both in the orbit and in the optic canal. 124aWhen used with contrast administration, fat-suppression Tl-weighted imaging

Fig. 8. A-scan echograph of an optic sheath meningioma. The nerve is widened, with medium-high internal reflectivity and irregular acoustic structure. “S” marks the surface spikes of the optic sheath. (Reprinted from Frazier Byrne S43 with permission of the au-

Fig. 9. Histologic section of an optic sheath meningioma revealing spindle cells arranged in a concentric x 25). whorl formation. (Original magnification (Courtesy of Alan Proia, M.D.)

thor and publisher.)

gives superior delineation of tumor surface adjacent to orbital fat (Fig. 6), and demonstrates the tram-tracking sign characteristic of meningiomas by enhancing the contrast between the tumor and perineural subarachnoid space.56a,‘24a

V. Echographic Findings On echographic evaluation of sheath meningiomas, the optic nerve characteristically shows marked widening (Fig. 7), with predominantly medium-high reflectivity, and irregular acoustic structure43 (Fig. 8). Internal calcification may be seen, and the absence of cystic degeneration may help distinguish these lesions from optic nerve gliomas.“’ In 15 meningiomas studied by Gans et a1,4g87% had optic nerves more than twice the diameter of a normal control group. The anterior optic nerve measured 5.3 mm (4.2-7.8 mm) compared to a normal value of 2.5 mm (2.2-2.9 mm). Posteriorly, the nerve measured 6.3 mm (3.9-8.7 mm), with a normal of 2.6 mm (2.3-3.3 mm). The 30 degree test, in which optic nerve diameter is measured in primary position and again at 30 degrees of eccentric gaze, was usually negative, suggesting an homogeneous, solid infiltration of the nerve, rather than increased subarachnoid fluid.

VI. Histopathology Meningiomas arise from meningothelial cells found at specific locations along the meninges. Larger collections of these cells (known as pac-

chionian bodies or arachnoid granulations) project into the intracranial dural sinuses and veins and show a relationship to the origin of meningiomas. rzoSmaller collections, termed arachnoid villi, are located at other sites along the sphenoid ridge, planum sphenoidale, tuberculum sellae, and olfactory groove, and are uniformly present along the canalicular and intraorbital portions of the optic nerves. Optic sheath meningiomas are believed to arise from the meningothelial “cap cells” of these arachnoid villi. Two histologic patterns are seen in meningiomas of the optic nerve, both already well described by Schott in 1877.“’ In the meningothelial or syncytial pattern, polygonal cells are arranged in sheets separated by vascular trabeculae. Mitoses are uncommon. In the transitional pattern, spindle or oval cells are arranged in a concentric whorl formation (Fig. 9). Psammoma bodies are more common here than in the meningothelial pattern. These develop from hyalinization and deposition of calcium salts in the degenerated centers of whorls, and are responsible for the calcifications noted on plain X-ray series. Other histologic types, such as the angioblastic and fibroblastic patterns, are associated with intracranial meningiomas, and are usually seen in the orbit only in secondary or ectopic orbital meningiomas. ’ Both may metastasize. Rootman”’ mentioned recent immunohistochemical evidence for the meningothelial origin of an angioblastic meningioma from the optic nerve sheath. Meningiomas are true neoplasms. They spread in the subarachnoid space and are usually “encapsulated” by the intact arachnoid and dura (Fig. 10). Meningiomas have a tendency to ex-

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a single lesion connected by subtle attenuated tumor extension, or “metastases.” Trobe et a1126 demonstrated tumor along the tuberculum sellae in a case of “bilateral canalicular meningiomas.” Growth of meningiomas is typically indolent over many months to years. It may be initiated or accelerated by pregnancy.g2~138 As the tumor grows within the subarachnoid space, it commonly encircles the optic nerve. Compression results in obstruction to axonal transport, disc swelling, optociliary shunt vessels, and eventually to demyelination. 6,53,67Invasion of the nerve with widening of septa may simulate the appearance of an optic glioma.g~“6,g7Continued compression and obliteration of the pial blood supply to the nerve leads to optic atrophy.

Fig. 10. Histologic section of an optic sheath menin-

gioma (arrow) showing tumor between the optic nerve (right) and the overlying dural sheath (left). (Original magnification x 10). Courtesy of Alan Proia, M.D.

VII. Treatment (Table 3) The most appropriate therapy for optic sheath meningiomas remains a matter of controversy. For well over a century surgical removal was the mainstay of therapy, ever since Scarpa”’ reported his successful results in several cases. Excision was originally through an anterior orbital approach, which did not allow complete removal of deeper orbital tumors. With the lateral orbitotomy introduced by Kronlein in 1888,” and modified by others, surgery on the optic nerve became more successful.‘3 However, posterior orbital lesions still could not be reached. In his review of 1901, Byers’* stated that the greatest danger in managing these tumors was not orbital recurrenceper se, but the risk of intracranial extension from residual tumor at the apex. He and others considered radical surgery necessary to prevent such occurrence.‘2’55,g8 Dandy*‘j**’ felt that complete surgical excision was essential to prevent posterior extension and death. Durante in 1887” was apparently the first to use a frontal craniotomy for the removal of a meningioma involving the orbit. Later modifications by Dandy*‘jT” and Gushing and Eisenhart23 allowed complete extirpation of optic sheath meningiomas up to the chiasm.

tend along all paths of least resistance, frequently invading the optic nerve along its septae and around the spaces surrounding the central retinal vessels.‘05 Tumor cells may invade through the dura and into surrounding orbital tissues.64,76,82,138 When adjacent to bone, tumor frequently extends into the haversian canal system, where it incites hyperostosis and bone proliferation.’ Optic sheath meningiomas may extend posteriorly through the optic canal to the middle cranial fossa. Although they may invade along the intracranial optic nerve to the chiasm, meningiomas do not appear to invade the brain.g2s ‘20~‘30Optic nerve meningiomas, even with chiasmal extension, have not been associated with increased intracranial pressure or pituitary-hypothalamic dysfimction.‘36 Meningiomas may arise at multiple sites simulThey can involve both optic taneously. 52*57,58*go~19’ nerves, or one nerve and an intracranial site such as the sphenoid ridge. At surgery, meningiomas may not be apparent to visual inspection, despite positive biopsy. 76 It is unclear whether cases of multiple tumors represent truly separate lesions,

TABLE

3

Results of Various Management Approaches to Optic Sheath Meningiomas

Management (No. of Pts.) Observation (64) Surgical excision (148) Radiotherapy (11)

Recurrence

Mortality

25% -

0% 0% 0%

Improved Vision 0%

Stable

Decreased

14% 1% 9%

86% 94% 18%

Vision

Vision

OPTIC NERVE SHEATH MENINGIOMAS Most orbital meningiomas have been treated surgically. When located in the anterior or midorbit, surgery through a lateral orbitotomy allows adequate visualization for complete excision (Fig. 11). However, most optic sheath meningiomas are located at or near the orbital apex and will require a combined approach - orbitotomy for biopsy and confirmation of diagnosis, followed by craniotomy for excision. Canalicular lesions must be approached via a craniotomy. When tumors are very large and infiltrative, orbital exenteration may be necessary. It has long been recognized that surgery for meningiomas is associated with a high rate of local recurrence. Such data are not readily available for primary orbital meningiomas. However, of 248 intracranial meningiomas treated surgically, recurrence was seen in 84 (34%), and 47 patients (19%) eventually died from their disease. 4,86,132In 135 of these patients the excision was initially considered to be complete, and among these, recurrence was seen in only three patients (2%), and none died from their disease.4s132Jaaskelainen et a163 followed 657 patients after total resection of intracranial meningiomas and found a rising recurrence rate with time; 3% at 5 years, 15% at 15 years, and 21% at 25 years after surgery. Among another 113 patients known to have had only subtotal resection followed by radiotherapy, 84 (74%) experienced recurrence, and 46 (41%) died from their tumors.4,132 However, in a later publication on the same group of patients, Wara13’ reported a lo-year survival of only 10%. For primary optic sheath meningiomas, the results of surgical excision have been reported for only 148 patients. Among this group, no patients died from their disease over a follow-up For interval of l-9 years. 2,19,48,58,62,69,81,103,107,125,1%3,139 88 patients for whom data were given, recurrence of tumor was seen in 22 (25%).2,48*66,107Incomplete excision has been associated with diffuse orbital invasion7 and intracranial spread to the chiasm.13’ Kennerdell et a16’felt that any attempt at surgical excision carries an unnecessary risk of such spread. Attempts have been made to decompress the optic nerve by opening the dural sheath. Miller87 reported arresting progressive visual loss by this technique. However, others have been unable to demonstrate any benefit from the procedure.“jz 138,13gWright et a114’ stated that not only did sheath decompression fail to slow the loss of vision, but it was often associated with massive orbital invasion requiring exenteration.

Fig. 11. An optic sheath meningioma as seen at surgery through a lateral orbitotomy incision. The nerve shows a tubular enlargement with dilated surface vessels. The globe (not seen) is at the bottom.

Operative complications following orbital surgery have been reported in 30% of cases.*“07 These include new visual field defects, central retinal artery occlusion, motility disturbance, and phthisis bulbi.2,6g Gabibov et a148 reported 74% ptosis following orbital excision, but most of these resolved over several months. Complications of transcranial surgery have been reported in 84 of 936 cases (9%),‘j3 and included seizures, cerebrospinal fluid leak, and meningitis.g3~107~135 In most cases, excision of orbital meningiomas results in blindness.2~4s~6g~g7~‘38~13g Most such tumors lie near the orbital apex and share their blood supply with the pia mater. Attempted excision results in interruption of pial vessels and ischemic injury to the optic nerve.‘37 Of 120 patients with primary optic sheath meningiomas treated with surgery alone, 94 (78%) showed postoperative loss of vision to the NLP level, and in another 19 (16%) vision declined.2~48,62~6g,‘07~1 13, 13’Seven cases of visual improvement or stability have been reported after removal of a meningioma

from

the

optic

~~~~~~2~16~38~62~8~~~2~119~125~138~139

With the exception of a canalicular meningioma removed by Torma,125 all have been small tumors located close to the globe and without significant neural invasion. McReynolds (quoted in Byers13) was one of the first to use radiotherapy in the management of a meningioma involving the orbit. His patient was treated with radium, but later died of unknown causes. Little information is available on the use of this modality for primary optic sheath meningiomas, and most of our knowledge on this treatment modality must be inferred from reports on intracranial meningiomas. For the latter lesions,

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a number of reports have considered radiotherapy to be ineffective.37~44,47.‘02.“6Fukui, for example, treated five patients with up to 6000 cGy and found progressive disease in all cases over a follow-up of 7-8 years.47 However, several other studies suggest that, in appropriate doses, radiotherapy may delay the recurrence of partially resected tumors.4’8”4’41,6*,70,95,152,14I Among 1 1 1 in_ tracranial lesions treated with partial excision plus 3000-5500 cGy, and followed for up to 10 years, tumor recurrence was seen in 37 patients (33%), and 24 patients (22%) died from their disThese results are better than for parease. 4,g5~131 tial excision alone, but not nearly as good as for total surgical resection. In 3 of 19 treated cases (16%), there was CT evidence of tumor regression.‘* Valentine’*’ treated 29 intracranial meningiomas with single high dose irradiation using a sterotactic procedure (radiosurgery). Tumor growth was arrested or reversed in 23 patients (79%). In 24 reported cases where an intracranial meningioma affected the visual pathways, but did not extend into the orbit, nine (38%) showed improvement in visual acuity following radiotherapy, and in 14 patients (58%) visual field improved.47,72 Complications from radiotherapy were reported in 3 of 19 patients (16%) treated by Kupersmith et a1,72and included a new visual field defect, central retinal artery occlusion, and encephalopathy. Only a few patients with primary optic sheath meningioma have been treated with radiotherapy. Smith et a1118~1’greported a patient whose vision improved from hand motions to 20/70 following such treatment. After two years vision again deteriorated. Nevertheless, it was their impression that radiotherapy could slow the rate of visual deterioration. 11*Mondon et al” treated an optic sheath meningioma with 5500 cGy and noted improvement in both visual acuity and visual field that was maintained for two years. CT examination did not, however, show any change in tumor size. Ito et a16* also noted improved vision in two similar patients treated with radiotherapy. Kennerdell et al”’ reported the results of radiotherapy (5500 cGy) in six patients with sheath meningiomas. Improvement in visual acuity from 20/40 - CF to 20/20 - 20/60 and in visual field was documented in five of the six (83%), with 30 to 84 months follow-up. Sarkies”’ found no improvement in two patients with bilateral optic sheath meningiomas treated with radiotherapy. All together, among the 12 reported patients with sheath meningiomas treated by ir-

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radiation, visual acuity improved in nine (75%), remained stable in one (8%), and declined in two ( 17%).6”~6g~‘07~1’ The g follow-up interval was 2-6 years. Sixty-four patients have been reported with sheath meningiomas followed conservatively without any treatment. Among these, 55 patients (86%) showed progressive visual loss, and the other nine (14%) remained stable over the follow-up interval of l-7 years. Visual field deterioration was documented in 35 patients (55%), and in 29 (45%) it was said to remain stable. However, with more precise testing, progressive field loss would have been seen in all patients with visual loss. No patient in this group is known to have died of their disease.

VIII. Prognosis In patients with optic sheath meningiomas, the prognosis for life is excellent. Among 228 patients for which data are available, 46 (20%) showed extension to the optic canal, or intracranially to the chiasm at the time of presentation recur_ or at surgery. 16~29~48~58~79~107~119,123 Orbital rences following incomplete excision are frequently associated with intracranial spread.2*1’3, ‘~3’Nevertheless, the only mortalities reported are six patients in Alper’s’ series from the AFIP, all mentioned in an earlier publication by Karp et a1.66Of the six deaths, four resulted from operative complications; three on attempted excision of secondary posterior fossa or olfactory groove tumors, and one during repeat surgery for recurrence. The other two patients died from secondary olfactory groove meningiomas 23 and 24 years after surgery for their optic sheath lesions. Thus, the overall tumor-related mortality rate for optic sheath meningiomas is 0% over a followup interval of 4-l 1 years. The prognosis for vision is poor.51 Without treatment, visual loss progresses slowly but inexorably to blindness in the affected eye. Surgery offers no benefit, and in most cases accelerates the process. In only rare and exceptional cases can a small, anteriorly situated tumor be removed from the optic nerve with preservation or improvement of vision. Radiotherapy appears to be beneficial in stabilizing or improving visual symptoms associated with some intracranial meningiomas, and in delaying the onset of recurrence. Its efficacy in the primary management of optic sheath lesions remains unclear because of the very small number of patients treated. However, preliminary data reporting visual improvement following radiotherapy are encouraging.

179 It has been stated that optic sheath meningiomas in children exhibit a more aggressive course.2@‘~12g~130~138~140 Five of six deaths reported by Alper” occurred in patients less than 2 1 years old. However, as mentioned above, all five deaths resulted from operative complications or secondary causes. The tumor-related mortality rate among young patients is no greater than among older individuals (0%). In Alper’s* series, recurrences were seen in five out of 12 patients (42%) under 2 1 years of age, three of these (25%) with intracranial extension. Recurrences were seen in four out of 12 patients (33%) between 21 and 35 years of age, in two out of 13 patients (15%) between 36 and 50 years of age, and in none of six patients older than 51 years of age. Wright et al”’ reported an 1 l-year-old child with a unilateral sheath meningioma in whom partial excision was followed by aggressive recurrence involving the chiasm and opposite optic nerve. Wright et a114’reported four out of six patients (67%) less than 20 years of age to have intracranial extension at presentation, but similar findings were noted in only nine of 20 patients (45%) between 20 and 40 years of age, and in four of 24 patients (17%) over 40. Among the 30 patients under 2 1 years of age specifically discussed in the literature, six (20%) were described with significant recurrence. This compares with an overall postsurgical recurrence for optic sheath meningiomas of 31%. Although the data presented by Alper* and Wright et a114’ are suggestive of a more aggressive behavior for sheath meningiomas in some young patients, especially with regard to early intracranial extension, there is no evidence that this has any significant effect on prognosis for life or vision in the contralateral eye.

IX.

Conclusions: Rationale for Management

It appears that for meningiomas confined to the intraorbital optic nerve, and where some vision remains, observation without surgery is apThe 3g only possible exceppropriate. 2*6g~130~138~‘ tions are small tumors immediately behind the globe, or in cases of young children, where biopsy for diagnosis may be indicated.“’ All orbital tumors should be followed with serial CT, or ideally gadolinium-enhanced, fat-suppression MRI examinations for possible posterior extension. In patients over 40 years of age, no therapy is indicated in the absence of posterior progression, although radiotherapy may improve or stabilize vision for some time. However, once blindness

supervenes, surgical extirpation may be necessary for relief of disfiguring proptosis, orbital pain, or intraocular complications. In patients less than 30 years of age, the risk of eventual intracranial extension may be more significant, and radiographic evaluation alone may not reliably rule out posterior spread. Wright et a114’ now advocate early complete excision of the tumor and optic nerve via a craniotomy for this group of young patients. However, with the possible exception of the child described by Wright et a1,13’the prognosis for vision in the opposite eye, as well as for life, has not been shown to be worse among young patients, even after intracranial extension. Such aggressive surgical intervention for tumors confined to the orbit, especially when good vision remains, may be unnecessary. For sheath meningiomas that threaten intracranial extension, or that already extend to the intracanalicular or intracranial portions of the optic nerve, the decision regarding treatment is more complex. Since mortality from intracranial extension has not been reported, the only rationale for treatment would be the perceived risk of spread from one orbit to the contralateral optic nerve. There are no confirmed instances of such spread. There have been 40 reported cases of canalicular meningiomas. Among these, 26 were unilateral, and in five cases (19%) already showed intracranial extension at the time of presentation. Of the 40 canalicular tumors, 15 (38%) were bilateral. The onset of symptoms in the two eyes was separated by 2 to 27 years.1g*58~1”“~126 Liano75 presented a case of an optic nerve meningioma with extension to the planum sphenoidale, and Trobe et a1126demonstrated bilateral canalicular meningiomas interconnected by tumor across the planum. It could not be determined whether the tumor arose in the planum with extension to both canals, or spread from one canal to the other. Rootman”’ also discussed a patient with bilateral canalicular meningiomas and surgical evidence of tumor extension across the planum sphenoidale. He felt that tumor did spread from one optic nerve to the other. However, Hart et a15* obtained multiple intracranial biopsies between bilateral canalicular meningiomas and all were histologically negative. From CT studies on eight patients with bilateral optic sheath meningiomas, Lewis et al 74aconcluded that bilateral tumors most likely originate from the forward extension of a single intracranial meningeal focus. In the majority of reported bilateral cases, there is no histologic information regarding possible

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extension from one side to the other. Among 381 cases of primary optic sheath meningiomas for which data are available, at least 60 (15%) have been described with intracranial extension at the time of presentation. Wright et a114’reported 17 of 50 patients (34%) with intracranial involvement, and Sarkies”’ noted this in 11 of 22 patients (50%). Wright et a114’described a young female with a unilateral meningioma extending intracranially and medially onto the jugum sphenoidale. An 1 l-year-old child reported by Wright et a1,13’enucleated for a left optic meningioma, was found three years later to have middle cranial fossa extension with involvement of the chiasm and opposite optic nerve. Over the next four years the tumor progressed into the right orbit resulting in blindness. However, the authors could not rule out an origin from the sphenoid with bilateral optic nerve extension. The actual risk of tumor spread, if any, from one optic nerve to the other remains unknown. Based on the higher incidence of bilaterality with canalicular tumors, and on unilateral tumors with progressive posterior extension, this risk may be real, and could be as high as 2-4%. In patients less than 30 years of age, with a higher incidence of intracranial spread, this risk may be even greater. It is reasonable, therefore, to follow all patients with high resolution CT or preferably MRI scans for posterior extension of optic sheath meningiomas. It must be stressed, however, that no radiologic technique can detect microscopic spread, and false-negative studies must be expected. For tumors that clearly extend toward the optic canal, with or without significant visual loss, excision via a combined transorbital and transcranial approach should be considered, especially if vision is already compromised. Radiotherapy does not appear to be as effective as complete surgical excision in controlling tumor recurrence, at least for intracranial lesions. However, in patients over 40 years of age, where the risk of intracranial spread appears to be less, radiotherapy may play a role in slowing tumor progression and improving vision.

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56a.Hendrix LE, Kneeland JB, Haughton VM, et al: MR imaging of optic nerve lesions: Value of gadopenetate dimeglumine and fat-suppression technique. AJNR Zl: 749754, 1990 57. Hirst LW, Miller NR, Allen GS: Sphenoid pneumosinus dilitans with bilateral optic nerve meningiomas. J Neurosurg 51:402407, 1979 58. Hollenhorst RW Jr, Hollenhorst RW Sr, MacCarty CS: Visual prognosis of optic nerve sheath meningiomas producing shunt vessels on the optic disc. Mayo Clin Proc 53:84-92, 1978 59. Huber A: Eye Signs and Symptoms in Brain Tumors. St Louis, CV Mosbv. 1976, ed 3. PP 199-273 60. Hudson AC: Primary tumors’df the optic nerve. R Ophthalmol Hosp Rep 18:317-439, 1912 61. Imes RK, Schatz H, Hoyt WF, et al: Evolution of optociliary veins in optic nerve sheath meningioma. Arch Ophthalmol 103:5&-60, 1985 62. To M, IshizawaA. Mivaoka M. et al: Intraorbital meningiomas. Surgical’ management and role of radiation therapy. Surg Neural 29:448453, 1988 63. Jaaskeliinen J, Hahia M, Serva A: Atypical and anaplastic meningiomas: radiology, surgery, radiotherapy, and outcome. Surg Neural 25:233-242, 1986 64. Jakobiec FA, Depot MJ, Kennerdell JS, et al: Combined clinical and computed tomographic diagnosis of orbital glioma and meningioma. Ophthalmology 91:137-155, 1984 65. Tames BP, Smith IL: Bilateral optic nerve sheath meningiomas presenting as the chiasmal syndrome, in Neuro-ophthalmoloev Update. New York. Masson Pub1 USA, 1’977, pp l%l’s3 66. Karp LA, Zimmerman LE, Borit A, et al: Primary intraorbital meningiomas. Arch Ophthalmol 91:24-28, 1974 67. Kayan A, Earl CJ: Compressive lesions of the optic nerves and chiasm. Brain 98:1328, 1975 68. Kennerdell JS, Maroon JC: Intracanalicular meningioma with chronic optic disc edema. Ann Ophthalmol 7:507-512, 1975 69. Kennerdell JS, Maroon JC, Malton M, et al: The management of optic sheath meningiomas. Am J Ophthalmol 106:450-457, 1988 70. King DL, Chang CH, Pool JL: Radiotherapy in management of meningiomas. Acta Radio1 (Ther) 5:26-33, 1966 71. Kronlein RU: Zur Pathologie und operativen Behandlung der Dermoidcysten der Orbita. Beitr z klin Chir 4:149-163, 1888 72. Kupersmith MJ, Warren FA, Newell J, et al: Irradiation of meningiomas of the intracranial anterior visual pathway. Ann Neural 21:131-137, 1987 73. Lapresle 1, Netskv MG, Zimmerman HM: The pathology of meningiomas. Am J Path01 28:757-767, i952 74. Levkoeva E: Psammoma orbitae. Zentralbl f ges Ophthalmol25:225, 1931 74a.Lewis T, Kingsley D, Moseley I: Do bilateral optic nerve sheath menmgibmas exist? Br J Neurosurg- 5:12-18, 1991 75. Liano H, Garcia-Ahx C, Lousa M, et al: Bilateral optic nerve meningioma. Eur Neurol21:102-106, 1982 76. Lindenburg RD, Walsh FB, Sacks JG: Neuropathology of zFi7p Atlas. Philadelphia, Lea & Febiger, 1973, pp 77. Little HL, Chambers JW, Walsh FB: Unilateral intracranial optic nerve involvement. Arch Ophthalmol 73: 331-337;1965 78. Lloyd GAS: The radiology of primary orbital meningiomas. Br I Radio1 44:405-411, 1971 79. Lloyd GAS: Primary orbital meningioma: a review of 4 1 patients investigated radiologically. Clin Radio1 33: 181187, 1982 80. MacMichael IM, Cullen JF: Primary intraorbital men-

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Outline I. Historical background Epidemiology and location A: Age at presentation B. Sex distribution C. Laterality D. Sites of origin E. Association with neurofibromatosis III. Clinical signs and symptoms A. Visual acuity and fields B. External changes C. Funduscopic appearance IV. Radiographic findings V. Echographic findings VI. Histopathology VII. Treatment VIII. Prognosis IX. Conclusions: Rationale for management II.

Reprint address: Jonathan Dutton, M.D., Duke University Eye Center, Box 3802, Durham, NC 27710.