INTRODUCTION — Optic pathway gliomas (OPGs; also referred to as optic gliomas) are low-grade astrocytic tumors that occur in the optic nerve, chiasm, or both. They occur sporadically and in patients with neurofibromatosis type 1 (NF1). Although often indolent, OPGs can cause clinical symptoms due to mass effect and visual loss.
The classification, diagnosis, natural history, and management of OPGs will be reviewed here. Diagnosis and management of NF1 are reviewed separately. (See "Neurofibromatosis type 1 (NF1): Pathogenesis, clinical features, and diagnosis" and "Neurofibromatosis type 1 (NF1): Management and prognosis".)
EPIDEMIOLOGY — OPGs account for approximately 2 percent of cerebral gliomas. They are typically slow-growing neoplasms that occur mainly in children, with 90 percent diagnosed before the age of 20 and 75 percent before the age of 10 .
CLASSIFICATION — OPGs are classified by anatomic location and by whether or not they are associated with neurofibromatosis type 1 (NF1; von Recklinghausen disease).
Location — Low-grade gliomas may involve the anterior visual pathway (optic nerves or more anteriorly) in 25 to 35 percent of cases or the posterior visual pathway (chiasm and postchiasmal extension).
Anterior visual pathway — Anterior tumors can be subdivided into orbital, intracanalicular, and intracranial prechiasmal lesions . These tumors occur most frequently in prepubescent children, and most are classified as pilocytic astrocytomas . (See "Classification and pathologic diagnosis of gliomas, glioneuronal tumors, and neuronal tumors".)
The tumor may appear as either an infiltrative lesion or one that is sharply demarcated from the normal optic nerve. Invasion of the leptomeninges or a dense fibroblastic reaction is frequently seen. As the tumor progresses, it compresses the optic nerve. As a result, the optic nerve becomes demyelinated and optic atrophy develops.
Posterior visual pathway — Posterior tumors may arise in the optic chiasm, hypothalamus, or anterior third ventricle . Chiasmal and hypothalamic lesions present at a mean age of approximately three years. Histologically, these are typically pilocytic astrocytomas. Occasionally, gangliogliomas occur [4-6].
Association with neurofibromatosis — OPGs are the most common central nervous system tumors associated with NF1. If all children underwent screening, estimates indicate that OPGs would be found in 15 percent of those with NF1 [7,8]. NF1 tumors more commonly involve the anterior visual pathway, while tumors in NF1-negative children are more frequent in the posterior visual pathway .
The natural history and clinical presentation of OPGs in patients with NF1, along with the potential role of screening, are discussed separately. (See "Neurofibromatosis type 1 (NF1): Pathogenesis, clinical features, and diagnosis", section on 'Optic pathway gliomas'.)
However, most evidence supports their designation as true, slow-growing neoplasms:
●OPGs are virtually identical histologically to pilocytic astrocytomas seen elsewhere in the nervous system . Sporadic pilocytic astrocytomas often have a tandem duplication of chromosome 7q34 and associated BRAF-KIAA fusion gene, which is relevant for targeted therapy [12,13]. (See "Uncommon brain tumors", section on 'Pilocytic astrocytoma' and 'Role of targeted therapies' below.)
●Their clinical behavior may be aggressive; this is never observed with hamartomas.
●Allelic chromosomal loss occurs in some pilocytic astrocytomas, suggesting that they are clonal lesions arising from inactivation of a tumor suppressor gene. As an example, loss of chromosome 17q (the location of the neurofibromatosis type 1 [NF1] gene) is demonstrable in some cases, even in patients without NF1 or NF2-related schwannomatosis (NF2), suggesting some link between this gene and tumor development .
●BRAF duplications have been identified in approximately 70 percent of cases .
●OPGs in patients with NF1 exhibit a characteristic loss of neurofibromin (which functions as a negative growth regulator for astrocytes) and increased Ras activation [16,17].
CLINICAL PRESENTATION — The signs and symptoms of OPGs usually develop over a course of months to years and depend upon the location of the tumor.
Orbital tumors most often present with proptosis; less frequent findings are strabismus and symptoms similar or identical to spasmus nutans (pendular or dysconjugate nystagmus, torticollis, and head-bobbing) [18-20]. Unilateral visual impairment is a relatively uncommon presenting symptom, possibly due to the young age of these patients at presentation. Funduscopic examination may show edema of the optic disc and/or pallor due to atrophy.
Chiasmal and hypothalamic gliomas often present as large masses even though they are typically well differentiated and low grade (most often pilocytic) [2,10,21]. In patients with chiasmal lesions, the chief complaint is usually impaired vision. Obstructive hydrocephalus also may be noted at presentation [10,22]. The diencephalic syndrome, manifested by progressive emaciation and failure to thrive in an apparently alert, cheerful infant, can be seen with hypothalamic gliomas . (See "Poor weight gain in children older than two years in resource-abundant settings", section on 'Increased needs'.)
Endocrinopathies due to hypothalamic extension are present in 10 to 20 percent of patients with OPGs. The most frequent is precocious puberty due to involvement of the hypothalamic-pituitary-gonadal axis; this occurs in up to 39 percent of children with neurofibromatosis type 1 (NF1) and chiasmal OPGs . Thus, all children with chiasmal tumors should be screened for endocrine abnormalities.
The primary presenting symptoms tend to be different in patients with and without NF1. While patients with sporadic OPG are more likely to present with signs of increased intracranial pressure and hydrocephalus, those with NF1-associated OPGs are more likely to present with precocious puberty .
DIAGNOSIS — The diagnosis of OPG should be considered in any child presenting with unexplained visual loss, monocular or asymmetric nystagmus, a diencephalic syndrome, or optic atrophy.
The diagnosis is best made by contrast-enhanced magnetic resonance imaging (MRI), which allows visualization of the entire course of the optic nerve and optic pathway. MRI also delineates hypothalamic involvement more clearly than computed tomography (CT). In patients with established tumors who are being followed serially, noncontrast MRI provides similar accuracy in terms of tumor size assessments compared with contrast-enhanced MRI .
Three typical patterns are seen on neuroimaging studies [27-29]:
●Tubular thickening, tortuosity, or both of the optic nerve (image 1)
●Suprasellar tumor with contiguous chiasmal or optic nerve involvement (image 2)
●Suprasellar tumor with optic tract involvement (image 3)
The differential diagnosis of masses in the region of the hypothalamus includes craniopharyngioma, glioma, germinoma, teratoma, lymphoma, Langerhans cell histiocytosis, and neurosarcoidosis. Cyst formation is unusual in optic gliomas but may be seen with cases exhibiting extension into the hypothalamic region. The presence of a cyst and calcification within a suprasellar mass is more suggestive but not diagnostic of adamantinomatous craniopharyngioma . (See "Causes, presentation, and evaluation of sellar masses" and "Craniopharyngioma".)
Suprasellar masses without apparent optic nerve extension or optic tract involvement are less likely to be OPGs, and biopsy may be required for diagnosis. Although some experts advocate biopsy of any lesion in the suprasellar region, we recommend that a biopsy be obtained if the lesion does not appear vascular and there is no apparent primary tumor from which the lesion could have metastasized.
When performed, biopsies provide an opportunity for molecular studies that may alter management and prognostic understanding in the future. In a study of 72 patients with non-NF1 optic pathway glioma in which a biopsy sample for molecular profiling was available, those patients with unfavorable clinical course (as defined by progression after radiation therapy, multiple systemic therapies, metastasis, or fatal disease) had clear differences in clinical presentation and molecular alterations, pathway activation, and/or expression . Most notably, the presence of KIAA1549-BRAF fusion was associated with more aggressive disease.
CLINICAL COURSE AND PROGNOSIS — The clinical behavior of OPGs is unpredictable . Spontaneous regression, malignant degeneration, and metastatic dissemination through ventriculoperitoneal shunts have all been reported. In children, the variable clinical course is more a function of location than specific histology [21,33]. In adults, by contrast, OPGs tend to be histologically anaplastic, displaying aggressive clinical behavior [34-36].
●Children with intracranial and intraorbital tumors of the optic nerve have a comparatively better prognosis, with a median survival of more than 15 years . Approximately 5 percent of optic nerve gliomas invade the optic chiasm; locally invasive recurrence can also develop following complete intraorbital excision.
●The outcome for patients with chiasmal and postchiasmal gliomas is usually less favorable . However, some children with chiasmal gliomas may survive for long periods without treatment [10,38], and cases of spontaneous regression have been reported, all in patients with neurofibromatosis type 1 (NF1) [39-41].
●Patients with OPGs associated with NF1 tend to have a better prognosis, at least in part due to the predominance of anterior lesions. However, compared with patients without NF1, those with NF1 have approximately twice the recurrence rate following complete excision of an intraorbital glioma, but a similar prognosis following radiation of a chiasmal glioma [8,42,43]. Risk factors for recurrent/refractory OPG in children with NF1 include young age (<24 months at time of initial treatment), posterior tumor location, and familial inheritance .
Even with prolonged survival, however, many patients have significant long-term visual impairment [37,45-47]. In a retrospective study of 59 children with sporadic OPGs (median age at diagnosis 2.5 years), 45 percent of patients had 20/40 vision or worse in their best eye at a median follow-up of 5.2 years, including 15 patients (25 percent) with severe bilateral vision loss .
Although the prognosis for survival may be better in NF1 patients with OPGs, significant visual impairment is frequent, and it is unclear whether treatment with either chemotherapy or radiation improves the prognosis for retaining vision in these children [47,48]. Risk factors for vision loss in these patients include posterior tumor location, optic disc abnormalities, and abnormal visual acuity at the time of initial treatment .
In contrast to children, the clinical course of an OPG in an adult resembles the behavior of the tumor's histology, which is more commonly a malignant glioma. In adults, malignant OPGs can result in rapidly progressive visual loss, and middle-aged or older adults may present with the rapid onset of blindness [49-52]. Tumor invasion into adjacent brain may then become apparent, leading to death within a few months of presentation . Standard radiotherapy and/or chemotherapy of these lesions typically leads to disappointing results .
TREATMENT — Optimal management of OPGs is controversial. Treatment decisions should take into account the patient's age, the presence or absence of neurofibromatosis type 1 (NF1), and the location of the tumor. A multidisciplinary approach is strongly recommended, with close consultations with the ophthalmologist, radiation oncologist, pediatric oncologist, neuroradiologist, and neurosurgeon.
If possible, a period of observation should precede treatment initiation in young patients and those with NF1. Tumor size and visual function should be closely monitored both clinically and by serial brain magnetic resonance imaging (MRI); an untoward change in either clinical status or size on imaging may signal the need for active treatment [32,55]. Adults should be managed aggressively, as dictated by pathology.
Optic nerve tumors — Observation without specific treatment is appropriate for tumors that exclusively involve the optic nerve until there is evidence of either extension into the optic canal or progressive visual compromise. In patients with symptoms due to visual loss or abnormal eye movements, serial neuro-ophthalmologic examinations and MRI scans can be used to assess tumor progression.
A minority of children with isolated intraorbital gliomas and NF1 will experience tumor progression within 5 to 10 years [7,8,27,42,45,56,57]. Chemotherapy is usually the first choice in this situation. If there is progression associated with proptosis and a significant cosmetic problem, and there is poor or no vision in that eye, then surgery should be considered; however, surgery invariably results in complete loss of vision in the involved eye. Radiation therapy (RT) is generally deferred in children with NF1 due to an increased risk of secondary malignancy and other sequelae.
In a child without NF1, RT may be considered if there is progressive visual loss or radiographic progression after a trial of chemotherapy. Radiation may prove useful to save, and at times improve, vision in an eye that has not lost vision . Upon further evidence of progression, amputation of the nerve within the orbit may be considered. It has been recommended that resection be performed flush with the chiasm to prevent centripetal extension . However, there are few data supporting this concept.
Posterior tumors — Noninvasive imaging studies may not be able to differentiate OPGs from other lesions that may require different therapy (eg, craniopharyngiomas, germinomas) . For this reason, a pathologic diagnosis should be established in all cases of pediatric diencephalic tumors except for those patients with NF1, in whom the diagnosis of an OPG is virtually certain. Biopsy of small lesions should be carried out carefully, so that remaining vision is not jeopardized [60,61].
Following diagnosis, patients can be managed with observation, tumor resection, radiotherapy, chemotherapy, and/or targeted therapy. Although these treatments may improve tumor-related symptoms, there is no evidence that any routine intervention enhances long-term survival.
Surgery — Tumor resection and/or ventricular shunting is indicated when an OPG is causing obstructive hydrocephalus. However, the role of radical resection in other settings is controversial.
Traditionally, patients with OPGs have been treated nonsurgically or with conservative surgical approaches due to the morbidity and the uncertain influence of surgical treatment on outcome. A retrospective series examined conservative surgical strategies in 33 patients with OPGs who would have been considered eligible for radical surgery in many centers today, but who were treated with no surgery, with conservative surgery (<50 percent resection), or with biopsy alone, followed by adjuvant therapy with radiation (29 patients) and/or chemotherapy (18 patients) . After a mean follow-up of 11 years, only five of these conservatively treated patients had died (three of tumor progression, one of acute shunt malfunction, and one of intercurrent infection). Twenty-three surviving patients had functional vision in at least one eye, 12 required no endocrine replacement, and 16 were capable of meeting standard academic requirements.
There may, however, be benefits to radical resection other than prolongation of survival. These include a delay in the time to disease progression in older children and a delay in the need for RT in younger children [62,63].
●In a study of 45 patients with extensive gliomas of the chiasm and third ventricle, 77 percent experienced stabilization or improvement in visual function after radical resection. The surgical mortality was 6 percent .
●In another series of 16 children with chiasmal or hypothalamic tumors treated with radical resection, three infants died of progressive disease. However, 11 of the other 13 were alive without disease progression 4 to 54 months following radical resection; six did not receive adjuvant chemotherapy or radiation .
Chemotherapy — Despite the benign histologic appearance of many OPGs, chemotherapy results in surprisingly high response rates. For this reason, chemotherapy is often preferred as initial treatment rather than radiation, especially in children less than age five years, for whom there is a high likelihood of deleterious effects on cognitive function with other treatment modalities [45,64-68]. The use of chemotherapy can often postpone the need for radiation, a delay that may reduce neurocognitive morbidity without compromising survival [45,69-72]. Targeted therapy is also being studied in this setting. (See 'Role of targeted therapies' below.)
The efficacy of this approach in deferring RT was illustrated in a multicenter study of 85 children with progressive OPGs (median age 33 months) who received alternating combinations of chemotherapy every three weeks (procarbazine/carboplatin, etoposide/cisplatin, and vincristine/cyclophosphamide) . This chemotherapy-first approach was successful in avoiding the use of RT in children in 75 and 61 percent of children at three and five years, respectively. The median interval between the start of therapy and the need for radiation in the 25 children in whom it was delivered was 35 months. Delaying radiation did not jeopardize outcomes; the 89 percent overall survival rate at five years is comparable to that achieved with initial irradiation, and visual outcomes were not dissimilar.
Between 40 and 60 percent of patients eventually progress after chemotherapy and require further therapy [45,69,70]. Patients who have OPGs in the setting of NF1 often have indolent disease, and fewer require subsequent therapy.
Various combination chemotherapy regimens have been used to treat these tumors. Combinations of vincristine and actinomycin D, vincristine and carboplatin, cisplatin or carboplatin plus etoposide, or a nitrosourea-based combination regimen are most frequently used [64-66,69,73,74]. The following describes the range of findings.
●In one study, 78 children with newly diagnosed, progressive low-grade gliomas, including 58 with diencephalic tumors, were treated with carboplatin and vincristine . Forty-four (56 percent) patients had an objective response to treatment, and the progression-free survival rate at three years was 68 percent. The three-year progression-free survival rate was higher in children five years or younger at the time of treatment (74 versus 39 percent in older children).
●In a second series, 34 children ranging in age from 4 months to 16 years old (median 45 months) with unresectable low-grade glioma (29 of which were located in the optic pathway) received 10 monthly courses of cisplatin and etoposide . Twenty-four (70 percent) achieved an objective response, while the remainder had stable disease; no patient required elective radiotherapy. The three-year progression-free survival rate for the 31 previously untreated patients was 78 percent and was significantly higher in children older than 12 months (87 versus 33 percent).
Role of targeted therapies — Therapies targeting the MAPK pathway have an emerging role in treatment of OPGs, since BRAF alterations occur in a high percentage of tumors with pilocytic astrocytoma histology. When to use targeted therapy is controversial, with some advocating its use as a first-line option and others favoring use after treatment failure with more studied therapies (chemotherapy and/or RT) . Clinical trial participation is encouraged.
MAPK pathway inhibitors with evidence of activity in OPGs include trametinib and selumetinib (MEK1/MEK2 inhibitors) and vemurafenib (a BRAF inhibitor) [79,80]. Among these options, MEK1/MEK2 inhibition is generally preferred to BRAF inhibition as it avoids paradoxical activation of the MAPK pathway that can occur with direct BRAF inhibitors.
Based on available data, it is unknown whether favorable early responses to MEK1/MEK2 inhibitor therapy in OPG will be durable. Nevertheless, for now, targeted therapy for both NF1-related and NF1-unrelated OPG is a promising treatment for progressive tumors that may delay or avoid use of RT or alkylating therapy, both of which are associated with significant toxicities in this setting.
●Selumetinib – Selumetinib, which is approved by the US Food and Drug Administration for NF1-associated plexiform neurofibromas, is active in both NF1-associated and sporadic OPGs. Supporting evidence includes results of a phase II Pediatric Brain Tumor Consortium trial of selumetinib 25 mg/m2/dose orally twice daily for up to 26 months in children with recurrent/progressive low-grade gliomas, in which patients with OPG were primarily enrolled in two different strata:
•Patients with NF1 – Strata 3 enrolled 25 patients with NF1-associated recurrent/progressive low-grade glioma, including 13 OPGs . No BRAF alterations were detected in three patients for whom tissue was available. Ten of 25 patients (40 percent) achieved a sustained complete or partial response, with a median time to partial response of 3.6 months. The two-year progression-free survival was 96 percent. In 10 evaluable patients with OPG, visual acuity improved (20 percent) or was stable (80 percent). The most common grade 3/4 toxicities were creatine phosphokinase (CPK) elevation (10 percent) and maculopapular rash (10 percent). Eight patients required a dose reduction due to adverse effects.
•Patients without NF1 – Strata 4 enrolled 25 patients with recurrent/progressive sporadic (non-NF1) OPG or hypothalamic low-grade glioma . Among six patients for whom BRAF testing was performed, three were positive for a BRAF-KIAA gene fusion; all six were negative for BRAF V600E point mutation. In the entire strata, two-year progression-free survival was 74 percent; partial response and stable disease were observed in 24 and 56 percent of patients, respectively. The median time to response was 19.7 months, and response did not depend on BRAF status. Visual acuity improved in 4 of 19 evaluable patients (21 percent) and remained stable in 13 (68 percent). Grade 3/4 toxicities were uncommon and mostly consisted of CPK elevation, emesis, or hyponatremia.
Based on these results, non-BRAF V600E OPGs are included as an eligible tumor in ongoing randomized trials of selumetinib versus carboplatin/vincristine in newly diagnosed or previously untreated pediatric low-grade glioma in patients with and without NF1 (NCT03871257 and NCT04166409).
●Angiogenesis inhibitors – There are now a number of reports that have noted qualitative improvement in vision after bevacizumab-based treatment in children with OPGs [83-86], even without radiographic progression . Although the numbers are small, these reports suggest that improvement is significant enough to consider its use, either alone or in conjunction with other therapies, in all patients with OPG and failing vision.
●Immune modulators – Immune modulators such as lenalidomide are being explored in pediatric patients who have progressed on standard therapies. In a phase II study of high-dose and low-dose lenalidomide in 74 children with pilocytic astrocytoma or OPG, there were four partial responses in each arm, and low-dose therapy was better tolerated .
Radiotherapy — For patients with progressive chiasmal OPGs with or without NF1, 5- and 10-year progression-free survival is better in patients who receive radiation. Despite this, the survival rate after 20 years is equivalent to that in patients who have not received radiation. There is also no clear evidence that earlier intervention for chiasmal OPGs changes prognosis [7,24].
Nevertheless, external beam radiation therapy (45 to 54 Gy) has been used in patients with progressive tumor to diminish tumor bulk, decrease recurrence rates, prolong recurrence-free survival, reverse the diencephalic syndrome, and improve vision [1,2,22,88-92].
●RT can arrest progressive visual and neurologic impairment, although the maximal effect can take years to be observed. In one retrospective study of 42 OPG patients with median age of 6.6 years (range 1.25 to 19 years), 29 patients were irradiated for progressive disease . A decrease in tumor size at 24 and 60 months was observed in 18 and 46 percent of patients, respectively, with a median time to response of 62 months . Stabilization of or improvement in vision occurred in 81 percent. The 10-year freedom from progression and overall survival rates were 89 and 100 percent, respectively.
●Two separate series evaluated patients with glioma of the optic chiasm or optic nerve who were treated with radiation. After 10 to 13 years of follow-up, the 5-, 10-, and 15-year overall actuarial survival rates were 94 to 96, 81 to 90, and 74 to 90 percent, respectively [92,93]. Fifty-five percent of the patients in one series had a radiation-induced complication, most often involving the pituitary gland .
●A contemporary study using fractionated proton therapy to a median of 50.4 Gy (relative biologic effectiveness [RBE]) in 38 pediatric patients achieved 100 percent blindness-free survival if radiation therapy was given early, as defined by initial diagnosis or first salvage therapy . All patients were treated with proton therapy by rationale of reduced collateral normal tissue radiation exposure as compared with photon-based radiation therapy.
The long-term sequelae of RT may be functionally devastating (especially in young children) despite the benefit of disease stabilization and objective tumor shrinkage in the majority of irradiated patients. Significant cognitive and endocrine deficits are most prominent following irradiation in infants . These radiation-induced complications have led to the use of chemotherapy as the initial treatment, so that RT can be deferred as long as possible [56,95]. (See "Overview of the management of central nervous system tumors in children", section on 'Long-term morbidity' and 'Chemotherapy' above.)
Occlusive vascular disease, angiographically similar to moyamoya disease, and usually presenting with ischemic stroke, can also occur following radiation for a chiasmal tumor, particularly in patients with NF1 [95-98]. (See "Moyamoya disease and moyamoya syndrome: Etiology, clinical features, and diagnosis".)
In one retrospective study of 47 patients treated for optic glioma, moyamoya disease developed in 5 of 28 patients treated with radiation (including three of five patients with NF1) compared with none of 19 who did not receive radiation . A second series documented occlusive vasculopathy in 13 of 69 children with OPGs, at a median of 36 months after radiation treatment . In addition to radiation therapy itself, a major risk factor was NF1.
In addition, malignant gliomas can develop in previously irradiated fields [61,99,100]. The use of RT in patients with NF1 is of particular concern because of the development of second primary tumors . In an observational series of 58 patients, 9 of 18 patients (50 percent) developed one or more additional nervous system tumors, and five of these died as a result of the second tumor. By contrast, 8 of 40 patients (20 percent) who were not irradiated for their OPGs developed second nervous system tumors, and no deaths were observed. A more contemporary study reported a threefold increased risk of second nervous system tumors in patients who received RT compared with those who did not .
Newer RT techniques (eg, proton beam irradiation and stereotactic radiotherapy) may provide adequate tumor control while reducing collateral radiation exposure to other tissues, contributing to decreasing treatment-related morbidity . Further experience is needed with proton beam therapy to know whether this approach improves long-term outcomes.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Primary brain tumors" and "Society guideline links: Neurofibromatosis type 1".)
SUMMARY AND RECOMMENDATIONS
●Approach – The optimal management of patients with optic pathway gliomas (OPGs) is uncertain. There are no randomized clinical trials to guide clinical decision-making, and current approaches are based upon observational studies. Our approach is based on tumor location, patient age, and whether or not the patient has neurofibromatosis type 1 (NF1). (See 'Treatment' above.)
●Anterior pathway lesions
•In such patients, lesions should be monitored for progression with serial magnetic resonance imaging (MRI) scans and careful neuro-ophthalmologic examinations.
•Active treatment is indicated when there is evidence of progression or lesions cause unsightly proptosis or significant visual loss. Chemotherapy is usually the first choice in this situation. Radiation therapy (RT) may be considered if there is progressive visual loss after a trial of chemotherapy. If progression is associated with proptosis and a significant cosmetic problem and there is no vision in that eye, surgery should be considered. However, surgery typically results in complete loss of vision in the involved eye.
●Chiasmal and hypothalamic tumors
•Patients with NF1 – For patients without significant visual field deficits, we suggest initial observation because of the relatively favorable prognosis in NF1 patients (Grade 2C). Surgery may be required if symptoms of obstructive hydrocephalus are present. (See 'Posterior tumors' above and 'Surgery' above.)
In children who subsequently have evidence of progression or have significant visual deficits, we suggest chemotherapy (Grade 2C). Targeted therapy with a MEK1/MEK2 inhibitor is an alternative to chemotherapy, and clinical trial participation is encouraged. Surgery may be indicated if it is judged that appropriate resection can relieve pressure on the optic apparatus and thereby improve vision. However, surgical morbidity in this location should not be underestimated. RT should be deferred as long as possible to minimize the effects on the developing central nervous system. (See 'Posterior tumors' above.)
•Patients without NF1 – In patients without NF1, a biopsy is typically required to determine whether the OPG is a grade 1 pilocytic astrocytoma or another type of tumor. (See 'Posterior tumors' above.)
For patients with a pilocytic astrocytoma who are symptomatic, chemotherapy is preferred as initial treatment in children less than 10 years of age. For older patients, either chemotherapy or RT may be used. MAPK pathway inhibition is an evolving option for tumors with BRAF alterations, and clinical trial participation is encouraged. (See 'Role of targeted therapies' above.)
For children with other histologic tumor types, the treatment depends on the type of tumor.
●Adults – Adult patients with malignant OPG should be treated as high-grade astrocytomas. (See "Clinical presentation, diagnosis, and initial surgical management of high-grade gliomas" and "Radiation therapy for high-grade gliomas" and "Initial treatment and prognosis of IDH-wildtype glioblastoma in adults".)
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