Structural grey matter changes in the substantia innominata in Alzheimer's disease and dementia with Lewy bodies: a DARTEL-VBM study

Abstract

Objectives: Several cholinergic nuclei, and in particular the nucleus basalis of Meynert, are localised to the substantia innominata in the basal forebrain. These nuclei provide major cholinergic innervation to the cerebral cortex and hippocampus, and have an essential role in cognitive function. The aim of this study was to investigate volumetric grey matter (GM) changes in the substantia innominata from structural T1 images in Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and healthy older participants using voxel-based morphometry.

Methods: Participants (41 DLB, 47 AD and 39 controls) underwent 3 T T1 magnetic resonance imaging and cognitive assessments. Voxel-based morphometry analysis used SPM8 with a substantia innominata brain mask to define the subspace for voxel GM analyses. Group differences, and selected behavioural and clinical correlates, were assessed.

Results: Compared with that in controls, bilateral GM loss in the substantia innominata was apparent in both AD and DLB. Relative to controls, significant bilateral GM loss in the substantia innominata was observed in DLB and AD. In DLB, significant associations were also observed between substantia innominata GM volume loss, and the levels of cognitive impairment and severity of cognitive fluctuations.

Conclusions: Relative to that controls, atrophy of the substantia innominata was apparent in DLB and AD, and is associated with specific clinical manifestations in DLB. © 2016 The Authors. International Journal of Geriatric Psychiatry Published by John Wiley & Sons Ltd.

Keywords: Alzheimer's disease; DARTEL-VBM; dementia with Lewy bodies; magnetic resonance imaging; substantia innominata.

Figure 1

Generation of left (green) and right (red) substantia innominata brain masks on a magnetic resonance imaging T1 brain template for voxel grey matter analyses. Masks were derived from four contiguous coronal sections (anterior → posterior) starting at the level of the hemispheric crossing of the anterior commissure (A), ending at the level at which the anterior commissure fully emerges from the temporal lobe (D). Red and green regions show the segmentations containing the substantia innominata. Blue arrows depict the location of the anterior commissure. R, right; L, left. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 2

Significant grey matter loss of the substantia innominata in Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) compared with controls. Results are superimposed on a magnetic resonance imaging T1 brain template image and displayed neurologically (left is left) in the coronal (A, C) and axial (B, D) views. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 3

Association between substantia innominata grey matter volume and mini‐mental state examination (MMSE) in dementia with Lewy bodies. Graph shows the relationship at the most significant voxel (red arrow). Results are superimposed on a magnetic resonance imaging T1 brain template image and displayed neurologically (left is left) in the coronal (B) and axial (C) views. [Colour figure can be viewed at wileyonlinelibrary.com]

Figure 4

Association between substantia innominata grey matter volume and fluctuation score in dementia with Lewy bodies. The graph shows the relationship at the most significant voxel (red arrow). Results are superimposed on a magnetic resonance imaging T1 brain template image and displayed neurologically (left is left) in the coronal (B) and axial (C) views. [Colour figure can be viewed at wileyonlinelibrary.com]