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.