Table (E)T-2a Mean (sd) brain volumes (uncorrected and corrected for TIV) and mean TIV at baseline and 6 months, and change over 6 months from these measures and the BBSI
Baseline / 6 months / Difference (loss over 6 months)HD / Control / HD / Control / HD / Control / p value
Brain volume (cm3) / Uncorrected / 1043 (94) / 1124 (59) / 1023 (90) / 1119 (60) / 20 (8) / 5 (7) / 0.0005
Log-correcteda / 1040 (46) / 1132 (40) / 1021 (46) / 1126 (40) / 20 (7) / 6 (3) / <0.0001
Proportion of TIVb / 0.75 (0.04) / 0.82 (0.03) / 0.74 (0.04) / 0.82 (0.03) / 0.007 (0.006) / -0.003 (0.003) / 0.0011
BBSI (cm3) / 6.16 (5.02) / 1.47 (2.98) / 0.0375
TIV (cm3) / 1393 (144) / 1370 (81) / 1377 (135) / 1359 (82)
BBSI = brain boundary shift integral
TIV = total intracranial volume
a) Volumes are standardised for head size assuming a linear relationship between log transformed values and log TIV, see text for details
b) Volumes are represented as a proportion of TIV (volume/TIV); unlike log correction, this method does not rely on the provision of normative data from the control group
Table (E)T-2b Rates of atrophy over 6 months calculated from the measurements in Table (E)T-2a, with differences adjusted for age
Crude / p value / Adjusted / p value
Atrophy ratea (%/6months) calculated from: / uncorrected vols / 1.92 (0.69) / 0.44 (0.64) / 1.48 / 0.0001 / 1.53 / <0.001
log-corrected vols / 1.91 (0.71) / 0.58 (0.22) / 1.33 / 0.0001 / 1.35 / <0.001
vol as proportion of TIV / 0.92 (0.85) / -0.38 (0.37) / 1.30 / 0.0001 / 1.29 / 0.003
BBSI / 0.55 (0.44) / 0.13 (0.27) / 0.42 / 0.036 / 0.44 / 0.042
TIV = total intracranial volume
BBSI = brain boundary shift integral
a Loss over 6 months has been presented as percentage of baseline brain volume