Predicting memory performance in normal ageing using different measures of hippocampal size.

A number of different methods have been employed to correct hippocampal volumes for individual variation in head size. Researchers have previously used qualitative visual inspection to gauge hippocampal atrophy. The purpose of this study was to determine the best measure(s) of hippocampal size for predicting memory functioning in 102 community-dwelling individuals over 80 years of age. Hippocampal size was estimated using magnetic resonance imaging (MRI) volumetry and qualitative visual assessment. Right and left hippocampal volumes were adjusted by three different estimates of head size: total intracranial volume (TICV), whole-brain volume including ventricles (WB+V) and a more refined measure of whole-brain volume with ventricles extracted (WB). We compared the relative efficacy of these three volumetric adjustment methods and visual ratings of hippocampal size in predicting memory performance using linear regression. All four measures of hippocampal size were significant predictors of memory performance. TICV-adjusted volumes performed most poorly in accounting for variance in memory scores. Hippocampal volumes adjusted by either measure of whole-brain volume performed equally well, although qualitative visual ratings of the hippocampus were at least as effective as the volumetric measures in predicting memory performance in community-dwelling individuals in the ninth or tenth decade of life.

Comparing white matter lesions on T2 and FLAIR MRI in the Sydney Older Persons Study.

There is suggestion that magnetic resonance imaging (MRI) fluid-attenuated inversion recovery (FLAIR) sequence may be more accurate than T2 images in detecting white matter lesions (WML) in older people. Comparative ratings of these two image sequences have not been directly investigated in very old individuals to date. We compared the ratings of periventricular and deep WML on these two sequences in a sample of 111 community dwellers (mean age 85.5 years) using semiquantitative methods. Periventricular WML were as commonly detected on T2 as on FLAIR but were more severely rated on the latter sequence. No such bias was observed for the deep WML. With one exception, correlations between the two sets of measures were significant at the P < 0.001 level (range: 0.34-0.75). Intrarater reliability coefficients were moderate to excellent for most ratings. These results suggest that ratings performed on T2-weighted images to detect WML in very old individuals are very comparable with those performed on FLAIR images although FLAIR may allow a finer grading of periventricular lesions. Absence of FLAIR does not preclude the identification of WML in this population. These findings have clinical and epidemiological relevance where the acquisition of supplementary MRI data may not always be possible.

Hippocampal size and memory function in the ninth and tenth decades of life: the Sydney Older Persons Study.

OBJECTIVES: The purpose of this study was to define magnetic resonance imaging (MRI) correlates of normal brain ageing, with the specific objective of investigating whether the size of the hippocampus is selectively correlated with age related memory performance in non-demented individuals in their ninth and tenth decades of life. METHODS: Hippocampal size was estimated using MRI based volumetry and qualitative visual assessment in 102 community dwelling individuals aged between 81 and 94 years. Participants were evaluated on a variety of clinical and experimental instruments, including a comprehensive neuropsychological test battery. All participants underwent neurological examination, an extensive medical history was obtained, and an informant confirmed details of each participant's functional ability. RESULTS: Both visual and volumetric hippocampal measures were identified as robust predictors of memory performance, even when the influence of age related illnesses and sociodemographic variables was accounted for. When the sample was reduced to include the most cognitively healthy participants who were rated by an informant as showing no evidence of cognitive decline, the left hippocampal measures remained significant predictors of delayed retention of verbal material. CONCLUSIONS: These findings suggest that hippocampal volumes are selectively correlated with memory functioning in both normal and successful ageing.

Traumatic brain injury as a risk factor for Alzheimer's disease: a review.

Accumulating epidemiological evidence implicates traumatic brain injury as a pathogenic agent in the development of Alzheimer's disease (AD). Considering the increase in the prevalence of both traumatic brain injury and AD in recent times, the possibility that brain trauma may provoke the early development of AD has important implications for health service planning, preventative efforts, and medico-legal compensation settlements. This paper evaluates the plausibility of the proposed link between traumatic brain injury and AD, largely by way of exploring a theoretical perspective advanced by Satz (1993) and considering recent contributions from the epidemiological, neuropathological, and biochemical literature that are pertinent to this issue. The literature reviewed provides sufficient support and empirical vindication to give credence to the proposed association between these two neuropsychological entities at the statistical, theoretical, and biological level.