MRI and clinical differences between optic pathway tumours in children with and without neurofibromatosis.

The purpose of this study was to evaluate the value of MRI in studying optic pathway tumours associated with neurofibromatosis, and to look for potentially helpful criteria for the management of such lesions. This retrospective study included 14 children with neurofibromatosis type 1 (NF-1) as well as a lesion of the optic pathway. Clinical data and MRI findings were analysed with regard to location, structure and course of the tumours, and were compared with 13 optic pathway tumours in patients without NF-1. The median age of onset was 4.1 years. 11 patients with NF-1 were asymptomatic. In the NF-1 group, the optic nerves were involved in 10 cases without a cystic component at the time of diagnosis. In the non-NF-1 group, the tumour was located in the chiasma in 11 cases; 12 cases had a cystic component. 10 of the NF-1 group had no tumour progression over an average follow-up of 3.2 years without treatment. These findings suggest that optic astrocytomas in association with NF-1 are distinct lesions from isolated optic gliomas. In NF-1, most such tumours show only slight progression, and may correspond to perineural gliomatosis rather than a true pilocytic astrocytoma. Among NF-1 patients, initial MRI provides no prognostic criteria in children who subsequently show tumour progression. Nevertheless, MRI can be useful in establishing the diagnosis of NF-1 and can serve as a baseline study.