Occipital lobe injury and cortical visual outcomes after neonatal hypoglycemia.

OBJECTIVES: Hypoglycemia is a significant problem in neonates, and a pattern of parietooccipital diffusion restriction on MRI scans has been reported. The purpose of this study was to determine whether hypoglycemic injury, as indicated by diffusion restriction in the occipital lobes, correlated with visual evoked potentials and long-term cortical visual dysfunction.
METHODS: A cohort of 45 neonates from 2000-2005 with diffusion-weighted MRI studies after hypoglycemia was studied retrospectively. Perinatal history and follow-up data were analyzed, and results were correlated with diffusion-weighted imaging findings.The presence of occipital diffusion restriction was assessed qualitatively, and the mean apparent diffusion coefficients of mesial occipital lobes were calculated.
RESULTS: Among 25 patients who underwent diffusion-weighted imaging within 6 days after the onset of hypoglycemia, restricted diffusion in the occipital lobes was found in 8 (50%) of 16 term infants but not in preterm infants. For the remaining 20 patients, who had diffusion-weighted imaging performed >6 days after the initial onset of hypoglycemia, occipital diffusion restriction was not seen, even if hypoglycemia was ongoing. Restricted diffusion was associated with abnormal visual evoked potentials detected within 1 week after birth. Cortical visual deficits were seen in a significant proportion of patients with recurrent hypoglycemia and were correlated significantly with low mesial occipital apparent diffusion coefficient values.
CONCLUSIONS: Diffusion-weighted imaging studies performed within 6 days after initial hypoglycemia were sensitive in term but not preterm neonates. Diffusion restriction, with low apparent diffusion coefficient values, in the mesial occipital poles may indicate the prognosis for visual outcomes in acute settings after neonatal hypoglycemia.