Children will be enrolled on the study into one of three strata (patient groups): strata 1 includes children who do not have any symptoms associated with their PNF and MRI scans over the past year may or may not show tumor growth, strata 2 includes children who have symptoms associated with the PNF but MRI scans over the past year have not shown growth and strata 3 includes children who have shown an increase in the size of the PNF on MRI scans over the past year, with or without any symptoms.