Fornix-Fimbria DWI Hyperintensity on Magnetic Resonance Imaging in Children

Purpose: The fornix-fimbria complex is part of the Papez circuit which is mainly involved in emotions and memory. While reviewing brain MRI studies of young children, we noted DWI hyperintensity in this region in some patients. The aim of this study was to evaluate diffusion-weighted-imaging signal hyperintensity in the fornix-fimbria complex in young children aged 0-2 years of age.

Methods: Brain MRI studies of 646 children aged 0-2 years of age (mean 10 months) were retrospectively evaluated for DWI signal changes in the fimbria-fornix complex. Medical charts were evaluated for age, gender, and clinical status. We measured the ADC values of the fimbria and fornix and compared them to those of children without signal changes. The unpaired two-tailed Student’s t-test was used for statistical analysis. P values < .05 were considered statistically significant.

Results: Fornix-fimbria complex DWI signal hyperintensity was noted in 39 (6%) of the 646 children (mean age of 9.4 months). The mean ADC value for those 39 children was significantly lower than that of the children with normal DWI (p<.001). Most children (51.2%) had an otherwise normal MRI scan. When detected, the most common abnormality was parenchymal volume loss (12.8%). The most common indication for imaging was seizures (30.7%).

Conclusion: Fornix-fimbria complex DWI hyperintensity was detected in 6% of children aged 0-2 years. Seizures were the most common indication, accounting for approximately 30%. Most MRI scans were otherwise normal. The etiology is not entirely clear, possibly reflecting a transient phenomenon.