Visual pathway glioma: an erratic tumour with therapeutic dilemmas

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Abstract
OBJECTIVE Our experience in children with visual pathway glioma (VPG) was reviewed to delineate its clinical characteristics. DESIGN The charts and imaging studies of 21 children with VPG who were followed up in our centre during the last 12 years were reviewed and summarised. RESULTS VPG accounted for 13.1% of all brain tumours treated during this period. Sixty two per cent of the children with VPG had neurofibromatosis type 1 (NF-1). Among these, more than 60% were detected as part of routine work up. In some cases decreasing visual function preceded the appearance of the VPG on imaging studies. Tumour growth rate was markedly unpredictable. All treatment modalities employed led to tumour shrinkage and stabilisation for a variable period, but none was successful in totally eradicating the tumour. Complications were less severe after chemotherapy compared with radiotherapy. Three children died, none with NF-1, with a globular hypothalamic/chiasmatic tumour and accompanying electrolyte abnormalities. CONCLUSIONS NF-1 is a favourable prognostic marker for VPG. Whenever possible a period of observation is necessary before treatment is initiated, during which time tumour size and visual function should be closely followed up; an untoward change in either of these is an indication for the start of treatment, preferably chemotherapy first. The combination of a globular hypothalamic/chiasmatic glioma and electrolyte abnormalities in a child without NF-1 are related to a poor prognosis. The growth rate of VPG is unpredictable and erratic, especially in children with NF-1 Follow up needs both MRI of brain and visual function studies (funduscopic examination, visual fields and acuity, if possible) Only symptomatic or growing tumours need treatment Although both chemotherapy and radiotherapy should decrease or stabilise tumour growth, chemotherapy, with less side effects, should be used initially Tumour progression is treated with chemotherapy, surgery, or radiotherapy Patients without NF-1 who have globular tumours and electrolyte abnormalities may have a poor prognosis