No abstract

Although age-related regional volume loss is apparent and widespread in nondemented individuals, mild cognitive impairment is associated with a unique pattern of structural vulnerability reflected in differential volume loss in specific regions. Early identification of patterns of abnormality is of fundamental importance for detecting disease onset and tracking progression.

BACKGROUND Congenital scoliosis is a common type of vertebral malformation. Genetic susceptibility has been implicated in congenital scoliosis. METHODS We evaluated 161 Han Chinese persons with sporadic congenital scoliosis, 166 Han Chinese controls, and 2 pedigrees, family members of which had a 16p11.2 deletion, using comparative genomic hybridization, quantitative polymerase-chain-reaction analysis, and DNA sequencing. We carried out tests of replication using an additional series of 76 Han Chinese persons with congenital scoliosis and a multi-center series of 42 persons with 16p11.2 deletions. RESULTS We identified a total of 17 heterozygous TBX6 null mutations in the 161 persons with sporadic congenital scoliosis (11%); we did not observe any null mutations in TBX6 in 166 controls (P<3.8×10−6). These null alleles include copy-number variants (12 instances of a 16p11.2 deletion affecting TBX6) and single-nucleotide variants (1 nonsense and 4 frame-shift mutations). However, the discordant intrafamilial phenotypes of 16p11.2 deletion carriers suggest that heterozygous TBX6 null mutation is insufficient to cause congenital scoliosis. We went on to identify a common TBX6 haplotype as the second risk allele in all 17 carriers of TBX6 null mutations (P<1.1×10−6). Replication studies involving additional persons with congenital scoliosis who carried a deletion affecting TBX6 confirmed this compound inheritance model. In vitro functional assays suggested that the risk haplotype is a hypomorphic allele. Hemivertebrae are characteristic of TBX6-associated congenital scoliosis. CONCLUSIONS Compound inheritance of a rare null mutation and a hypomorphic allele of TBX6 accounted for up to 11% of congenital scoliosis cases in the series that we analyzed.

Objective: To investigate whether longitudinal declines in cognition are associated with higher fibrillar amyloid-beta (A␤) deposition in vivo in individuals without dementia. Method: [11 C]PiB images were obtained to measure fibrillar A␤ burden in 57 participants without dementia from the Baltimore Longitudinal Study of Aging. Participants (33 men, 24 women) had a mean (SD) age of 78.7 (6.2) years. Six participants (4 men, 2 women) had mild cognitive impairment defined as Clinical Dementia Rating ϭ 0.5. To measure [11 C]PiB retention, distribution volume ratios (DVR) for 15 regions of interest were estimated by fitting a simplified reference tissue model to the measured time activity curves. Mixed effects regression was used to predict cognitive trajectories over time using data before and including time of PiB (mean follow-up 10.8 years), with mean cortical DVR, age at baseline, sex, and education as independent predictors. Voxel-based analysis identified local associations. Results: [11 C]PiB retention was higher in older individuals. Greater declines over time in mental status and verbal learning and memory, but not visual memory, were associated significantly with higher PiB retention. Voxel-based analysis showed significant associations in frontal and lateral temporal regions. Conclusions:Higher A␤ deposition is associated with greater longitudinal decline in mental status and verbal memory in the preceding years. The differential association for verbal but not visual memory may reflect the greater reliance of verbal word list learning on prefrontal regions, which show early A␤ deposition. Prospective imaging may help distinguish between individuals with evolving neuropathology who develop accelerated cognitive decline vs those with normal aging. Postmortem studies of associations between amyloid-beta (A␤) burden and antemortem cognition yield conflicting findings. 1,2 We found that longitudinal cognitive trajectories were similar between cognitively normal individuals with and without Alzheimer disease (AD) neuropathology and that both groups differed from individuals with mild cognitive impairment (MCI) or AD, who showed marked cognitive decline. 3Radiotracers for in vivo imaging of fibrillar A␤ burden allow prospective investigation of relationships between cognitive performance and A␤. Consistent with postmortem studies, 20% to 30% of clinically normal individuals show A␤ deposition on imaging.4,5 Across the spectrum of cognitive function, lower memory correlates cross-sectionally with higher [ 11 C]PiB. 6,7 The only study investigating longitudinal changes in cognition in relation to A␤ e-Pub ahead of print on February 10, 2010, at www.neurology.org.

Knowledge of risk factors for greater procedural pain intensity identified in this study may help clinicians select interventions that are needed to minimize procedural pain. Clinical trial registered with www.clinicaltrials.gov (NCT 01070082).