Juvenile pilocytic astrocytoma (JPA; optic nerve glioma) is a well known and important optic nerve and brain tumor of childhood (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20). It represents 2% to 5% of brain tumors in children and accounts for about 1% to 2% of all orbital tumors (2,3,4,8). In the authors’ series of biopsy-proven cases, there were 4 cases among 645 biopsied orbital lesions (2). In the authors’ subsequent review of biopsy-proven childhood orbital tumors, it accounted for 5 of 250 biopsies (2%) (3). In the authors’ more recent clinical series of 1,264 consecutive space-occupying orbital lesions, the 48 JPAs accounted for 46% of the 105 optic nerve lesions and for 4% of all orbital lesions (4).

JPA has a definite association with neurofibromatosis type 1 (NF1) (1,19,20). Although figures vary from series to series, we believe that .50% of patients with JPA of the optic nerve have evidence of NF1. It is generally believed that JPA associated with NF1 is less aggressive and can regress (19). In contrast sporadic JPA has an earlier onset and more severe clinical course than the nonsporadic type associated with NF1 (8). JPA of the optic nerve has also been seen in association with von Hippel-Lindau syndrome, but may be coincidental (11). There is a definite predilection for females (13).

Some JPAs of the optic nerve are asymptomatic and are discovered on routine orbital magnetic resonance imaging (MRI) screening in a patient with NF1. Usually, however, JPA is diagnosed in the first or second decade of life when the child presents with progressive visual loss and axial proptosis. It occasionally becomes clinically apparent in adulthood (6). Because there is a high incidence of NF1 associated with this tumor, the affected patient should be evaluated for cutaneous pigmented macules (café-au-lait spots), iris Lisch nodules, and other stigmata of NF1. In the early stages, fundus examination may show a swollen optic disc; later it may become pale with the appearance of a retinochoroidal shunt vessel on the margin of the disc (1). The chronic disc edema can rarely induce a choroidal neovascular membrane in the posterior pole of the eye (18).

JPA located more posteriorly in the intracranial portion of optic nerve, chiasm, or hypothalamus often produces visual loss, strabismus, or nystagmus. Proptosis is not generally present unless the lesion extends anteriorly into the orbit. JPA of the optic nerve can occasionally undergo spontaneous regression, in both sporadic cases and those associated with NF1 (12,17).

Computed tomography (CT) and MRI of optic nerve JPA typically shows an ovoid mass corresponding to an enlarged optic nerve. A characteristic kink in the midportion of the tumor is often present. Extension into the optic foramen to the chiasm and brain is common and is best seen with gadolinium-enhanced MRI. The extent of the tumor, as determined by MRI findings, can help to predict visual loss, with postchiasmal lesions causing greatest visual impairment.

Gross pathology shows an optic nerve mass that is typically surrounded by the dura mater. Histopathologically, JPA has typical histopathologic characteristics (1,3). It is composed of a benign proliferation of pilocytic (hairlike) astrocytes, sometimes with areas of mucinous degeneration and hemorrhage. More round cells are often present. The astrocytic cell processes sometimes have eosinophilic, cylindrical swellings, called Rosenthal fibers (1,3).

The management of JPA of the optic nerve is complex and controversial. Because the lesion is benign, we generally prefer to be as conservative as possible. Biopsy is rarely necessary today, because the diagnosis can usually be established based on the characteristic radiographic findings. Asymptomatic lesions are often followed initially without treatment and many remain stable for long periods of time (9). Serial examinations should be done for pupillary reaction, visual acuity, visual fields, and color vision of both eyes. Most tumors confined to the orbit remain relatively stable, but slow growth can occasionally occur. If the patient is blind and has unacceptable proptosis of the affected eye, then complete removal of the mass by lateral orbitotomy is warranted. For those that extend to the orbital apex or more posteriorly, a neurosurgical approach is necessary. It is usually not necessary to remove the blind eye in such cases. Progressive lesions that involve the chiasm and brain are sometimes fatal and may require radiotherapy. The role of chemotherapy is uncertain, but results from early studies have been encouraging. When the tumor is initially confined to the optic nerve, the mortality is ,5%. When the hypothalamus is involved, mortality rises to .50% (9).

Juvenile pilocytic astrocytoma of the optic nerve has typical clinical and computed tomography features. When it is confined to the orbit and produces a blind eye with progressive irreversible proptosis, the tumor can be removed by a lateral orbitotomy. A clinicopathologic correlation is shown.

Juvenile pilocytic astrocytoma of optic nerve can be diagnosed with either computed tomography or magnetic resonance imaging because of its typical imaging features. However, MRI with gadolinium enhancement and fat suppression is the best method for determining whether there is subtle extension of the tumor into the optic canal and chiasmal area. Two examples of MRI are shown.

Juvenile pilocytic astrocytoma of the optic nerve has characteristic features with magnetic resonance imaging. When the proptosis is more advanced, the proptosis converts from an axial direction to a down-and-out direction, conforming to the contour of the bony orbit. Two related cases are illustrated.

The most common fundus changes with juvenile pilocytic astrocytoma of the optic nerve are a swollen optic disc followed by a retinochoroidal shunt vessel and pallor of the optic disc. The venous stasis secondary to optic disc involvement can prompt development of a juxtapapillary choroidal neovascular membrane.

Shields JA, Shields CL, De Potter, et al. Choroidal neovascular membrane as a presenting feature of optic nerve glioma. Retina 1997;17:349-350.

The benign pilocytic astrocytoma usually has its clinical onset in childhood. There is also a rare malignant form of optic nerve astrocytoma that occurs in adulthood and that is not usually associated with neurofibromatosis (1,2,3,4,5,6,7,8,9,10,11,12,13). Its clinical features, histopathology, and clinical course are very different from the juvenile pilocytic astrocytoma. Fewer than 50 cases have been published (13). Although it is generally considered to be rare, it is possible that many such cases have gone unreported because the patients usually die rapidly with a “brain tumor” and the precise diagnosis may not always be established.