Regional hypometabolism related to language disturbance in Alzheimer's disease

Profiling spontaneous speech decline in Alzheimer's disease: a longitudinal study

OBJECTIVE

This study aims to document the nature and progression of spontaneous speech impairment suffered by patients with Alzheimer's disease (AD) over a 12-month period, using both cross-sectional and prospective longitudinal design.

METHODS

Thirty one mild-moderate AD patients and 30 controls matched for age and socio-cultural background completed a simple and complex oral description task at baseline. The AD patients then underwent follow-up assessments at 6 and 12 months.

RESULTS

Cross-sectional comparisons indicated that mild-moderate AD patients produced more word-finding delays (WFDs) and empty and indefinite phrases, while producing fewer pictorial themes, repairing fewer errors, responding to fewer WFDs, produce shorter and less complex phrases and produce speech with less intonational contour than controls. However, the two groups could not be distinguished on the basis of phonological paraphasias. Longitudinal follow-up, however, suggested that phonological processing deteriorates over time, where the prevalence of phonological errors increased over 12 months. Discussion Consistent with findings from neuropsychological, neuropathological and neuroimaging studies, the language deterioration shown by the AD patients shows a pattern of impairment dominated by semantic errors, which is later joined by a disruption in the phonological aspects of speech.

Comparison of the diagnostic performance of FDG-PET and VBM-MRI in very mild Alzheimer’s disease

PURPOSE

The aim of this study was to compare the diagnostic performance of( 18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and voxel-based morphometry (VBM) on magnetic resonance imaging (MRI) in the same group of patients with very mild Alzheimer's disease (AD).

METHODS

Thirty patients with very mild AD (age 67.0+/-5.8 years; MMSE score 25.5+/-1.2, range 24-28), 32 patients with mild AD (age 67.0+/-4.5 years, MMSE score 22.1+/-0.8, range 21-23) and 60 age- and sex-matched normal volunteers underwent both FDG-PET and three-dimensional spoiled gradient echo MRI. Statistical parametric mapping was used to conduct voxel by voxel analysis and Z score mapping. First, the region of interest (ROI) maps of significant reductions in glucose metabolism and grey matter density in the mild AD patients were defined. Secondly, analysis of receiver operating characteristic (ROC) curves for Z scores in the ROI maps discriminating very mild AD patients and normal controls was performed.

RESULTS

In mild AD patients, FDG-PET indicated significant reductions in glucose metabolism in the bilateral posterior cingulate gyri and the right parietotemporal area, while VBM analysis showed a significant decrease in grey matter volume density in the bilateral amygdala/hippocampus complex, compared with the normal control group. ROC analysis showed that in very mild AD patients the accuracy of FDG-PET diagnosis was 89% and that of VBM-MRI diagnosis was 83%. The accuracy of the combination of FDG-PET and VBM-MRI diagnosis was 94%.

CONCLUSION

In very mild AD, both FDG-PET and VBM-MRI had high accuracy for diagnosis, but FDG-PET showed slightly higher accuracy than VBM-MRI. Combination of the two techniques will yield a higher diagnostic accuracy in very mild AD by making full use of functional and morphological images.

The evolution of dysgraphia in Alzheimer’s disease

Evidence from recent studies suggests that writing may be an aspect of cognition capable of identifying impairments specific to patients with Alzheimer's Disease (AD). The precise nature and progression of the writing disorder, however, remains unclear. The current study assessed the central and peripheral aspects of writing among a sample of minimal, mild and moderate AD patients and a group of healthy elderly controls on a narrative description task. Comparisons of the two groups indicated that AD patients suffer from a primary impairment at the semantic level. Even those in the minimal stages of the disease could be differentiated from controls on measures of word finding and information conveyed. This semantic impairment was coupled with a secondary milder impairment in phonological processing. The prevalence of phonological errors increased, but no shift in error type (plausible/implausible) was identified as the disease progressed. In addition to the central impairments, patients evinced damage at the peripheral level. In the more severe stages, patients experienced more problems with letter formation and stroke placement and tended to rely upon the more simplistic writing form of print. The writing impairment in AD is multi-componential in nature and follows the pattern of cortical deterioration reported in the brains of AD patients.

A metabolic imaging severity rating scale for the assessment of cognitive impairment

PURPOSE

This study was designed to validate a simple scoring system for evaluating fluorodeoxyglucose (FDG) positron emission tomographic (PET) scans that can be used routinely in patients undergoing the clinical assessment of cognitive impairment.

METHODS

The FDG-PET scans of 106 patients with cognitive impairment (65 with Alzheimer disease, 16 with frontal lobe dementia, and 25 atypical cases) were acquired using the PENN-PET scanner 40 minutes after the intravenous administration of 8 mCi FDG. Metabolic activity in various anatomic structures of the brain was scored using the following qualitative scale: 4 = normal; 3 = mildly decreased; 2 = moderately decreased; 1 = severely decreased; and 0 = no activity. Regions of interest were also placed over these regions to obtain a quantitative value. Two distinct scores were obtained. Values for visual and sensorimotor cortices, thalami, basal ganglia, and cerebellum comprised score I. Score II consisted of the values for the frontal, temporal, and parietal cortices. The qualitative metabolic imaging severity rating scale (MISRS) was compared with a quantitative MISRS (obtained from the region-of-interest analysis of the same structures). The MISRS was then compared with the results from the Mini-Mental Status Examination (MMSE) and the Dementia Severity Rating Score (DSRS).

RESULTS

In all patients, the qualitative MISRS scores correlated significantly with the quantitative MISRS (r = 0.73, P < 0.0001). In all patients with cognitive impairment, the qualitative and quantitative MISRS scores correlated significantly with the DSRS and the MMSE (P < 0.001). In patients with Alzheimer disease, the qualitative and quantitative MISRS significantly correlated with the DSRS and MMSE.

CONCLUSION

A simple and practical rating scale can be used to assess the severity of cognitive impairment in patients with different types of dementing illnesses.

Nature of personal semantic memory: evidence from Alzheimer's disease

Personal semantic memory is factual knowledge about a person's own past. Although personal semantic memory is assumed to have features of both semantic memory and episodic memory, the relationship to episodic memory and to semantic memory have not been well documented. In patients with Alzheimer's disease, episodic memory, semantic memory, and personal semantic memory are all defective. In this study, the hypothesis that defective personal semantic memory is related to both semantic and episodic memory dysfunction was tested in patients with Alzheimer's disease. Functions of episodic, semantic, and personal semantic memory were examined by using the Wechsler Memory Scale-Revised (WMS-R), subtests of the WAIS-R (Information, Vocabulary, Comprehension and Similarities), and the Family Line Test (FLT) in 62 patients who met the NINCDS/ADRDA criteria for probable Alzheimer's disease. Specific effects of episodic and semantic memory on personal semantic memory were examined by using multiple linear regression analysis with the total score of the FLT as the dependent variable and the WMS-R Delayed Recall weighted sum score and the WAIS-R Semantic Memory score (a composite of standardized scores of the four subtests) as the independent variables. Personal semantic memory function was significantly correlated with both the episodic and semantic memory functions, after controlling age, sex, educational attainment, and severity of dementia. This result supports the hypotheses that personal semantic memory has features of both episodic and semantic memory, and that semantic memory is transformed from episodic memory.

Neuronal substrates for semantic memory: a positron emission tomography study in Alzheimer's disease

We examined 57 patients with mild Alzheimer's disease by using three kinds of verbal semantic memory tests (category fluency, confrontation naming and generation of verbal definition) and correlated each score with regional cerebral glucose metabolism determined by (18)F-fluorodeoxyglucose and positron emission tomography. The scores of all three verbal semantic memory tests correlated significantly with regional cerebral glucose metabolism in the left inferior temporal gyrus, even after controlling for the effects of age, sex and educational attainment. In contrast, the scores of the word recall test did not correlate significantly with regional cerebral glucose metaboliosm in the left inferior temporal gyrus, neither before nor after controlling for these confounders. Our results suggested that the left inferior temporal lobe contributes to verbal semantic memory.

Features of regional cerebral glucose metabolism abnormality in corticobasal degeneration

We studied regional cerebral glucose metabolism in 15 patients with a clinical diagnosis of corticobasal degeneration (CBD), 15 patients with probable Alzheimer's disease (AD), and 15 healthy controls for 19 brain regions. Asymmetry in regional glucose metabolism was found in the central and frontal cortices in patients with CBD as compared with either the normal controls or the patients with AD. Regional glucose metabolism in CBD patients was significantly lower in the paracentral and superior parietal areas and thalamus than in patients with AD. Relative glucose metabolism in patients with CBD was significantly higher in the posterior cingulate, medial temporal and basal frontal areas, and significantly lower in the paracentral and superior parietal areas than in those with AD. These features of regional glucose metabolic abnormality in CBD may correspond to neurological and cognitive disturbances peculiar to CBD.

Specific temporoparietal gyral atrophy reflects the pattern of language dissolution in Alzheimer's disease

The aim of this study was to determine the topography and degree of atrophy in speech and language-associated cortical gyri in Alzheimer's disease. The post-mortem brains of 10 patients with pathologically confirmed Alzheimer's disease and 21 neurological and neuropathological controls were sectioned in serial 3 mm coronal slices and grey and white matter volumes were determined for specific cortical gyri. All Alzheimer's disease patients had prospectively documented impairments in verbal and semantic memory with concomitant global decline. The cortical regions of interest included the planum temporale, Heschl's gyri, the anterior superior temporal gyri, the middle and inferior temporal gyri, area 37 at the inferior temporoparietal junction, areas 40 and 39 (supramarginal and angular gyri) and Broca's frontal regions. Although most patients had end-stage disease, the language-associated cortical regions were affected to different degrees, with some regions free of atrophy. These included Broca's regions in the frontal lobe and Heschl's gyri on the superior surface of the temporal lobe. In contrast, the inferior temporal and temporoparietal gyri (area 37) were severely reduced in volume. The phonological processing regions in the superior temporal gyri (the planum temporale) were also atrophic in all Alzheimer's disease patients while the anterior superior temporal gyri were only atrophic in female patients. Such atrophy may underlie the more severe language impairments previously described in females with Alzheimer's disease. The present study is the first to analyse the volumes of language-associated gyri in post-mortem patients with confirmed Alzheimer's disease. The results show that atrophy is not global but site-specific. Atrophied gyri appear to reflect a specific network of language and semantic memory dissolution seen in the clinical features of patients with Alzheimer's disease. Females showed greater atrophy than males in the anterior superior temporal gyri.