Follow-Up of Optic Pathway Gliomas in Children with Neurofibromatosis Type 1

Abstract

Optic pathway gliomas (OPG) are found in about 15% of patients with neurofibromatosis Type 1 (NF-1). The natural history of OPG is not yet well documented. Treatment in cases with growing tumors is still controversial. Twenty-one patients with NF-1 and OPG, diagnosed over a 20-year period, and followed neuroradiologically and ophthalmologically for at least two years, were reevaluated. The diagnosis of OPG was made at a mean age of 7.1 years (range 0-14.5 years); six children were asymptomatic, 15 were symptomatic. The mean follow-up was 9.0 years (2.0-18.5 years). In eight initially operated or biopsied patients (three optic nerve and five chiasmal gliomas) tumor re-growth was found in one patient without progression on subsequent follow-up. Improvement of visual acuity occurred in one child after operation of a large suprasellar tumor and deterioration in one patient after biopsy of a chiasmal glioma. The neuroradiological follow-up of the 13 not-operated and not-radiated patients (four optic nerve and nine chiasmal gliomas) was stable in 10, progressive in three, resulting in visual loss in one patient. In 11 children (52%) a second tumor outside the optic pathway was found at a mean age of 4.0 years after the diagnosis of an OPG. Until now they are mostly asymptomatic. Second site tumors were operated in two children because of rapid tumor growth, one child died of a brainstem tumor.

OPG are a frequent complication in children with NF-1, appearing within the first decade. No definite correlation between the size of tumor and the visual function could be shown. Deterioration of visual function correlated more or less with growth of OPG but stable vision did not exclude it. OPG, once detected, are often stable over years and only exceptionally lead to blindness after the diagnosis. Therefore our present attitude is a "wait and see" policy in patients with stable vision, with follow-up of noninvasive investigations (MRI and VEP) at initially yearly intervals. In case of visual deterioration we would consider treatment with carboplatin. We are concerned about the large proportion of additional cerebral tumors in our series. They may be responsible for a deleterious prognosis in some patients with NF-1 and OPG.

Abbreviations
NF-1: neurofibromatosis type 1
OPG: optic pathway glioma
UBO: unidentified bright object
CT: computed tomography
MRI: magnetic resonance imaging
VEP: visual evoked potentials

Key words

MRI - Neurofibromatosis - Optic pathway glioma - Brain tumor