Determination of medial temporal lobe atrophy in early Alzheimer's disease with computed tomography

Is there any role for computed tomography measurements of medial temporal lobe atrophy in dementia? A review of the literature and case series from a memory clinic

Neuroimaging in dementia has focused on documenting any burden of vascular disease or excluding any reversible intracranial pathology. We review the use of computed tomography to examine for medial temporal lobe atrophy in dementia and compare this with a case series of such measurements from our memory clinic. Measures of medial temporal lobe atrophy were used to separate patients with Alzheimer's disease from those with normal cognition, mood disorders or other forms of early dementia.

Accuracy of CT scan measurements of the medial temporal lobe in routine dementia diagnostics

BACKGROUND

Atrophy of the medial part of the temporal lobe is seen in Alzheimer's disease (AD). We studied the usefulness of CT scan measurements of the medial temporal lobe (MTL) in elderly with suspected dementia.

METHODS

MTL measurements were done with callipers by three raters, blinded to the diagnosis and to each other, on scans from 110 subjects with suspected dementia from a memory clinic in Oslo, Norway and 36 participants included in the OPTIMA study, Oxford, England.

RESULTS

The correlation between the MTL and the Mini-Mental State Examination (MMSE) was very low, and there was a marked overlap between Alzheimer and cognitively unimpaired subjects. The inter-rater reliability was lower on the Norwegian than on the OPTIMA scans (R = 0.48 vs R = 0.68), but this was partly explained by larger MTL readings (4.5 mm after adjustment for age, gender and MMSE sumscore) on the OPTIMA scans as the reliability was confounded by MTL width and was higher at larger MTLs. A wider scan width (3 mm vs 2 mm in the OPTIMA scans) can also contribute to differences in reliability.

CONCLUSIONS

The published threshold values regarding the CT scan MTL measurements for the diagnosis of AD may be invalid when applied by other radiology departments without a local standardisation and validation.

Neuroimaging predictors of dementia in stroke patients

The risk of dementia is increased in stroke patients. Dementia syndromes associated with cerebrovascular diseases were commonly recognized as an immediate consequence of stroke. However, more and more data suggest that degenerative pathology and white matter changes (WMC) may play a role in the development of dementia in stroke patients. The aim of this paper was to review the literature concerning the neuroimaging predictors of dementia in stroke patients. From the literature data, it appears that although vascular lesions alone may lead to dementia, in stroke patients, no clear association between stroke location and size has yet been identified, even if the role of the left hemisphere has been suggested. The influence of silent infarcts remains undetermined while more and more data suggest that global cerebral atrophy and WMC are predictive factors of post-stroke dementia (PSD). The influence of medial temporal lobe atrophy on the risk of PSD has until now never been evaluated.

Temporal lobe-oriented CT scanning and dementia in Down's syndrome

BACKGROUND

Although individuals with Down's syndrome (DS) are uniquely at risk of developing Alzheimer's disease, the diagnosis of dementia in DS is problematic because of the difficulty in detecting cognitive decline in individuals with pre-existing learning disability.

AIM

To determine if dementia in DS is associated with Medial Temporal Lobe (MTL) atrophy as measured by temporal lobe-oriented CT scanning.

METHOD

Ten individuals with DS who were experiencing functional decline had CT scans with temporal lobe-oriented views. All individuals were assessed for the presence of dementia according to modified DSM-IIIR criteria. The minimal thickness of the MTL, corrected for age-related atrophy was measured using a computer calipers at the level of the mid-brainstem by a radiologist blind to the dementia diagnosis.

RESULTS

All six individuals who met modified DSM-IIIR criteria for dementia showed significant MTL atrophy.

CONCLUSIONS

The utility of temporal lobe-oriented CT scanning as an adjunct to the diagnosis of dementia in DS appears promising and warrants further study.

CT measurement of medial temporal lobe atrophy in Alzheimer's disease, vascular dementia, depression and paraphrenia

OBJECTIVE

Measurement of medial temporal lobe atrophy (MTL) by computerised tomography (CT) may be a useful adjunct to the diagnosis of AD. The aim of this study was to assess the sensitivity, specificity, predictive values and diagnostic accuracy of CT measurement of MTL thickness for patients with probable AD, compared with a 'diseased' control group, and to correlate the measure with neuropsychological test scores.

DESIGN

Cross-sectional.

METHODS

One hundred subjects were prospectively recruited: 60 with probable AD (mean age 73.7 years, mean Mini-Mental State Examination [MMSE] 19.6), 17 with probable vascular dementia (VaD) (mean age 77.9 years, mean MMSE 20.9), 14 with depression (mean age 73.2 years, mean MMSE 25.7) and nine with paraphrenia (mean age 74 years, mean MMSE 25.4). Axial and temporal lobe-oriented CT brain was performed and the minimum MTL thickness was measured electronically.

RESULTS

The mean minimum MTL thickness was significantly smaller in AD subjects compared to VaD (p<0.0001) and psychiatric subjects (p<0.0001). For the clinical diagnosis of probable AD, the sensitivity of the measure was 0.75, specificity 0.9, and diagnostic accuracy 0.81. For the mildest cases of AD (CDR 0.5), the sensitivity of the measure was 0.61, specificity 0.91, and diagnostic accuracy 0.81. No significant correlations with neuropsychological test scores were found.

CONCLUSIONS

Temporal lobe-oriented CT imaging is a non-invasive test with good discrimination for AD. Potential uses of this technique include as an aid to diagnosis and possibly as a means of monitoring disease progression.

Medial temporal lobe atrophy in stroke patients: relation to pre-existing dementia

OBJECTIVE

The links between stroke and Alzheimer's disease seem to be closer than expected by chance. In a previous study it was shown that up to 16% of patients admitted for stroke had pre-existing dementia. Medial temporal lobe atrophy (MTLA) is strongly associated with Alzheimer's disease. The aim of this study was to determine the prevalence of MTLA and its relation with pre-existing dementia.

METHOD

The study was conducted on 170 consecutive stroke patients (87 women; median age 75 years; 152 infarcts), who underwent non-contrast CT with temporal lobe oriented 2 mm contiguous slices at admission. A cut off point of 11.5 mm was used to differentiate patients with and without MTLA. Pre-existing dementia was assessed using the informant questionnaire on cognitive decline in the elderly (IQCODE) with a cut off score of 104.

RESULTS

Ninety four patients (55.3%) had MTLA, of whom 23 (24.5%) had pre-existing dementia; of 76 patients without MTLA, only four (5.3%) had pre-existing dementia (p=0.0007). The logistic regression analysis with MTLA as dependent variable found the following independent variables: increasing age (p<0.05), and global cerebral atrophy scores (p<0.01). The IQCODE scores just reached significance (p=0.05).

CONCLUSION

Stroke patients with MTLA are more likely to have pre-existing dementia; this suggests that Alzheimer's disease might contribute to the dementia syndrome. A longitudinal follow up is now necessary to determine whether stroke patients with MTLA and without pre-existing dementia are at increased risk of Alzheimer's disease over subsequent years.

Association between medial temporal lobe atrophy on CT and parietotemporal uptake decrease on SPECT in Alzheimer's disease

OBJECTIVES

Alzheimer's disease is the most frequent cause of degenerative dementia. Despite the available diagnostic criteria, improvement of diagnosic accuracy is still required. The aim of this prospective study was to assess in a large population of patients referred to a memory clinic the diagnostic value of the combination of medial temporal lobe atrophy on temporal oriented CT and decreased temporoparietal uptake on HMPAO single photon emission tomography (SPECT).

METHODS

The study was conducted in 125 patients aged 51-93: 64 with probable Alzheimer's disease (Mean (SD) mini mental state examination (MMSE)=18.34 (6.93)), duration of disease=6.48 (2.93) years, 13 possible Alzheimer's disease (MMSE=21.58 (5.48), duration of disease=6.08 (2.56)), 48 patients with miscellaneous memory disorders (MMSE=21.98 (6.10), duration the disease = 6.85 (3.91)).

RESULTS

For the diagnosis of probable Alzheimer's disease, the sensitivity of this association was 0.56, the specificity 0.93, the positive predictive value 0.95, and the negative predictive value 0.45. The diagnosic accuracy was 0.68. Both medial temporal atrophy and parietotemporal decrease in uptake were present in four of 13 patients with possible Alzheimer's disease and 11 of 48 with miscellaneous memory disorders. The association was absent in 27 of 29 patients with frontotemporal dementia. In mild stages (MMSE>18; n = 32), the sensitivity of the association was 0.34, the specificity 0.93, the positive predictive value 0.85, and the negative predictive value 0.57. The diagnosic accuracy was 0.53.

CONCLUSION

This association, although not sensitive, helps to select patients with high probability of Alzheimer's disease at an early stage which can be of interest for clinical and research purposes.

Sundowning syndrome in demented patients without neuroleptic therapy

Characterisation of sundowning syndrome, defined as 'an exacerbation of symptoms indicating increased arousal or impairment in late afternoon, evening or at night, among elderly demented individuals', is complicated by neuroleptic therapy and frequent failure to specify the nature of the associated dementia. Screening by a memory disorders unit of an institutionalized population of 30 neuroleptic-free demented patients revealed 8 sundowners, with diagnoses of probable Alzheimer's disease (n = 5), frontal lobe dementia (n = 1), Lewy body disease (n = 1), and sequelae of herpes encephalitis (n = 1). Sundowners did not differ from non-sundowners in age, Mini Mental State score, degree of temporal and spatial disorientation or perceptual delusion. Sundowning was related to restlessness (P < 0.0001), sleep disorder (P < 0.003) and a history of hypotension lipothymia (P < 0.08). These results provide further evidence for a chronobiological explanation of sundowning syndrome.