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. 2005 Jan 25;64(2):282-9.
doi: 10.1212/01.WNL.0000149638.45635.FF.

Reduced medial temporal lobe N-acetylaspartate in cognitively impaired but nondemented patients

L L Chao  1 , N Schuff, J H Kramer, A T Du, A A Capizzano, J O'Neill, O M Wolkowitz, W J Jagust, H C Chui, B L Miller, K Yaffe, M W Weiner
Affiliations

Reduced medial temporal lobe N-acetylaspartate in cognitively impaired but nondemented patients

L L Chao et al. Neurology. .

Abstract

Background: N-acetylaspartate (NAA) in the medial temporal lobe (MTL) and parietal lobe gray matter (GM) is diminished in Alzheimer disease (AD). Because NAA is considered a marker of neuronal integrity, reduced medial temporal and parietal lobe NAA could be an early indication of dementia-related pathology in elderly individuals.

Objectives: 1) To determine whether cognitively impaired but nondemented (CIND) elderly individuals exhibit a similar pattern of reduced medial temporal and parietal lobe NAA as AD patients. 2) To compare regional NAA patterns, hippocampal and neocortical gray matter (GM) volumes in CIND patients who remained cognitively stable and those who became demented over 3.6 years of follow-up. 3) To examine the relationship between memory performance, medial temporal lobe NAA, and hippocampal volume.

Methods: Seventeen CIND, 24 AD, and 24 cognitively normal subjects were studied using MRSI and MRI.

Results: Relative to controls, CIND patients had reduced MTL NAA (19 to 21%, p = 0.005), hippocampal (11 to 14%, p < or = 0.04), and neocortical GM (5%, p = 0.05) volumes. CIND patients who later became demented had less MTL NAA (26%, p = 0.01), hippocampal (17 to 23%, p < or = 0.05), and neocortical GM (13%, p = 0.02) volumes than controls, but there were no significant differences between stable CIND patients and controls. MTL NAA in combination with hippocampal volume improved discrimination of CIND and controls over hippocampal volume alone. In AD and CIND patients, decreased MTL NAA correlated significantly with impaired memory performance.

Conclusion: Reduced medial temporal lobe N-acetylaspartate, together with reduced hippocampal and neocortical gray matter volumes, may be early indications of dementia-related pathology in subjects at high risk for developing dementia.

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Figures

Figure
Figure
Examples of N-acetylaspartate (NAA) images and representative proton spectra obtained from the medial temporal lobe (MTL) region, including the hippocampus and entorhinal cortex (location indicated by a circle in the MRI and NAA images) in a healthy control (HC), a cognitively impaired but nondemented (CIND) patient, and a patient with Alzheimer disease (AD). The indicated size for the voxel in the figure approximates the nominal spatial resolution of the MRSI. Also shown are the corresponding axial MR images for anatomic reference of the low-resolution NAA images. Note that MRI and NAA images have different fields of view. Reduction of NAA in the CIND and AD patients with respect to the healthy control subject becomes apparent when the NAA peak intensity in each spectrum is compared with creatine (Cr).
See this image and copyright information in PMC

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