BOLD FMRI IN INFANTS AND YOUNG CHILDREN WITH SUSPECTED VISUAL IMPAIRMENT

Objectives: Accurate visual function assessment in infants and young children is usually difficult. fMRI with passive visual stimulation is non-invasive, and does not require patient cooperation. Thus, may provide new information for visual functional assessment.

Methods: Subjects: 42 patients mean aged 1 year old (12±7 months, 36m:6f) with clinical suspected abnormal visual function received blood oxygenation level-dependent functional MRI (BOLD fMRI) examination. All the subjects were sedated with Chloral Hydrate. Patient history includes HIE, PVL, hydrocephalus, kernicterus, and Cerebral palsy. Paradigm: fMRI study was block-designed. An alternation of darkness and flash served as visual stimulation. Each condition last 30 seconds. There were totally four cycles and the fMRI scan lasted 4 minutes. Image acquisition and analysis: T2* WI functional images were acquired with a single-shot echo-planar pulse sequence by a 2-T Elscint/GE MR scanner with TR/TE/Flip=3000ms/45ms/90o, FOV=373mm×212mm, Matrix=128×72. T1-weight, 3D structural images were acquired with TR/ TE/ Flip=25ms/6ms/28o, FOV=220mm×220mm, Matrix=220×220, THK=2.0mm. Statistical Parametric Mapping software (SPM99) was used to analysis the fMRI images. Brain activation areas were considered when cluster size >10 and p value <0.005.

Results: Of the total 42 children, 8 patients showed no response to the visual stimuli in the visual cortex, neither in occipital lobe nor in any other brain area. 11 patients showed positive BOLD signal in visual cortex (6 were laterally, 5 were bilaterally). 23 children showed negative BOLD signal in visual cortex (12 were laterally, 11 were bilaterally). Both positive and negative BOLD signal varied in activation size and intensity, mostly related to the brain damage. In 2 children after stem cell implantation, the BOLD signal enlarged significantly.

Conclusion: As a non-invasive method, BOLD fMRI may provide subjective evident in infants and young children for testing their visual function. The signal behavior (cortex activation type and size) may be used to assess brain maturity and/or damage, as well as to evaluate therapy effect.