Validity of large-deformation high dimensional brain mapping of the basal ganglia in adults with Tourette syndrome

Abstract

The basal ganglia and thalamus may play a critical role for behavioral inhibition mediated by prefrontal, parietal, temporal, and cingulate cortices. The cortico-basal ganglia-thalamo-cortical loop with projections from frontal cortex to striatum, then to globus pallidus or to substantia nigra pars reticulata, to thalamus and back to cortex, provides the anatomical substrate for this function. In-vivo neuroimaging studies have reported reduced volumes in the thalamus and basal ganglia in individuals with Tourette Syndrome (TS) when compared with healthy controls. However, patterns of neuroanatomical shape that may be associated with these volume differences have not yet been consistently characterized. Tools are being developed at a rapid pace within the emerging field of computational anatomy that allow for the precise analysis of neuroanatomical shape derived from magnetic resonance (MR) images, and give us the ability to characterize subtle abnormalities of brain structures that were previously undetectable. In this study, T1-weighted MR scans were collected in 15 neuroleptic-naïve adults with TS or chronic motor tics and 15 healthy, tic-free adult subjects matched for age, gender and handedness. We demonstrated the validity and reliability of large-deformation high dimensional brain mapping (HDBM-LD) as a tool to characterize the basal ganglia (caudate, globus pallidus and putamen) and thalamus. We found no significant volume or shape differences in any of the structures in this small sample of subjects.

Fig. 1

The template surfaces of the basal ganglia structures and thalamus embedded in the template MR scan. The thalamus, caudate nucleus, putamen, globus pallidus and nucleus accumbens were manually segmented in the template MR scan. Shown here are the triangulated surfaces superimposed on each segmentation and the cross-section outlines in the template MR scan.

Fig. 2

Landmarks for mapping of the basal ganglia structures and thalamus. The most anterior boundary of the caudate nucleus and the most posterior boundary of the thalamus were identified by landmarks and a line (blue) connecting these points created an anterior/posterior axis. The region between the two points was then divided into five equally distanced slices along this axis and in each slice five landmarks surrounding the structures of interest were placed at predetermined places. Panel a shows the first slice, and panel b shows the second slice. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Surface deformations of adult TS subjects compared with healthy controls. Left column: surface-normal component maps, magnitude and direction of deformations are displayed as color on the mean control surfaces, with cooler colors indicating inward deformations and warmer colors indicating outward deformations. Right column: statistical significance of the deformations, via Wilcoxon’s signed rank test, inward in purple (P<0.05), outward in red (P<0.05), and non-significant deformations (P>0.05), are shown in green. Top row: view from above. Second row: the surfaces are shown from a perspective slightly above and to the right of a midline plane, showing the top side of the structures. We note that immediately medial to the medial wall of the caudate nucleus and the anterior wall of the thalamus is the lateral ventricle. The blue colors here together with the red colors at the anterior wall of the caudate, the lateral wall of the putamen and the posterior wall of the thalamus suggest an outward movement of these structures. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)