Age at Hypoxia and the Pattern of Neuropathology in Children with Developmental Amnesia

Morphometric analysis of structural MRI of the children who suffered hypoxic events perinatally has demonstrated bilateral reduction in grey matter density in the putamen, hippocampus and thalamus (2). The purpose of this study was to determine the differences and commonalities in the pattern of neuropathology between the group of children whose pathology was incurred early in life and the children whose pathology was incurred later in childhood. Methods The early group consisted of six children who suffered hypoxic episodes aged < 1 year. The late group consisted of four children who suffered hypoxic episodes between the ages of 6 and 14. Two control groups were chosen, age-matched to the early group and the late group respectively. All subjects were scanned on a 1.5T Siemens Vision system, using a T1-weighted MPRAGE sequence. The 3D data sets were analysed in SPM99 (Wellcome Department of Cognitive Neurology, London, UK). Each scan was normalised and then segmented as described in Ashburner et al. (1997) (3). The images were smoothed with an isotropic Gaussian kernel. This renders the voxel values equal to the amount of grey matter per unit volume under the smoothing kernel. Two smoothing kernels were used, 4mm and 8mm, in order to sensitise the analysis to the spatial scale of the expected neuropathology (hippocampus and putamen respectively).