Can screening for optic nerve gliomas in patients with neurofibromatosis type I be performed with visual-evoked potential testing?

Background: Screening for optic nerve gliomas (ONGs) in children with neurofibromatosis type 1 (NF1) is problematic. Visual acuity (VA) can be unreliable in children. Magnetic resonance imaging is the most sensitive test for ONG, but it is expensive. This study was designed to determine whether visual-evoked potential testing (VEP) is a sensitive and cost-effective screening test for ONG in NF1 in children. Methods: We undertook a retrospective review of patients with NF1 at a tertiary care eye center that were born between 1983 and 2003. VA was considered abnormal if 20/40 or worse or more than 2 lines difference between eyes. VEP was abnormal if the P100 was >108 ms (ms) or the interocular difference was greater than 5.0 ms. Results: Of 297 patients found with NF1, 144 were children and 30 had VEP and MRI. Of those, 14 had ONG and 16 did not. The average P100 of the VEP was 110.5 ms in patients with ONG compared with 103.1 ms ( p = 0.004) in those without ONG. VEP was 86% sensitive and 75% specific in detecting ONG. VA was 50% sensitive and 50% specific. Six patients with ONG had normal vision and abnormal VEP. Two subjects had initial abnormal VEP but normal MRI and showed ONG on follow-up imaging. One subject with ONG had a normal VEP initially but subsequent VEP was abnormal. Conclusion: Using serial VEPs, the sensitivity is 93%. Cost of VEP and MRI is $150 and $1750, respectively. VEP is a sensitive and cost-effective screening test for ONG in NF1. VEP may assist in earlier diagnoses of ONG, especially in children with equivocal or difficult ophthalmic examinations.