Longitudinal Assessment of Childhood Optic Gliomas: Relationship Between Flicker VEP and MRI Findings

Abstract

Purpose: : To evaluate longitudinally the relationship between functional and morphologic findings in childhood optic gliomas (OG) by comparing flicker VEP (FVEP) with brain magnetic resonance imaging (MRI) changes.

Methods: : Fourteen children (median age 3 yrs, range: 2–7) suffering from OGs involving chiasm and retro–chiasmatic visual pathways underwent serial FVEP and MRI examinations over a median follow–up time of 38 months (range 12–76). FVEPs were monocularly recorded in response to 8 Hz sine–wave flicker stimuli presented in a mini–Ganzfeld according to a published technique.¹ MRI examinations were performed according to standard procedures. Longitudinal results of both tests were examined in a blind fashion by independent evaluators. FVEPs were judged to be improved, stable or worsened if changes in the amplitude and/or phase of the fundamental response component exceeded the limits of test–retest variability (±90^th percentile) established in the same patients. MRI results were judged to show regression, stabilization or progression of OG based on its changes in size (≥ 20%) or extension. Two to seven pairs (< one month apart) of FVEP/MRI examinations per patient (median: 4, range 2–7) were collected. Agreement between test changes over time were evaluated by K–statistics.

Results: : Based on a total of 38 pairs of longitudinal FVEP/MRI examinations, both tests agreeed in showing worsening (progression), stabilization and improvement (regression) in 5, 10 and 15 cases, respectively. In 3 cases, FVEPs showed a worsening and MRI a stabilization, while in 5 cases FVEPs showed an improvement and MRI a stabilization. Agreement between FVEP and MRI changes was 78.9% (95% CI: ± 37%, K = 0.67, p < 0.001).

Conclusions: : The results indicate that changes over time in FVEPs, an objective and non–invasive test of visual function, can accurately predict associated changes in OG size and extension as assessed by MRI, and suggest that the latter changes may have a significant impact on optic pathway activity during developmental age. ¹Trisciuzzi et al. Clin. Neurophysiol. 115(1): 217–226

Keywords: visual impairment: neuro-ophthalmological disease • tumors • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials