Fig. 4. Hippocampal, gray matter, and lateral ventricular volume change as a function of severity group and surgery. A graphical display is used to present the effects of severity group and surgery in a single bar graph. (A ) Setting the normal hippocampal volume mean equal to 100, hippocampal volume measures for subjects with mild cognitive impairment (MCI) averaged 91.94% (± 1.82% SE; n = 62) of normal (100%; ± 1.30% SE; n = 68) at baseline; and MCI-AD subjects were 77.68% (± 2.27% SE, n = 34) of normal at baseline. MCI-AD subjects are MCI subjects who transitioned to Alzheimer disease during participation in the Alzheimer's Disease Neuroimaging Initiative. The average change in hippocampal volume atrophy for the surgical patients during the first interval was 2.86% (± 0.82%; n = 41) of the average normal hippocampal volume. The background atrophy (nonsurgical control patients) was 0.73% (± 0.32%; n = 123). (B ) For the gray matter volume an atrophy versus  normal (NL; 100 ± 0.95%) was seen of 3.52 ± 0.82% and 5.2 ± 1.03% from NL to MCI and NL to MCI-AD, respectively. The percent change for the first interval for surgery subjects was 1.39 ± 0.43% and for nonsurgical controls 0.25 ± 0.25%. (C ) For the lateral ventricular volume an expansion versus  NL (100 ± 6.83%) was seen of 15.87 ± 8.91% and 28.54 ± 9.28% from NL to MCI and NL to MCI-AD, respectively. The percent change for the first interval for surgery subjects was 5.33 ± 0.85% and for nonsurgical controls 2.93 ± 0.41%. AD = Alzheimer disease; BSL = baseline; DX = direct expansion; MCI = mild cognitive impairment; NL = normal.