Voxel based morphometry in cervical dystonia.

<p>Voxel based morphometry demonstrated reduced gray matter local tissue volume in the posterior cingulate (A and B, blue voxels, shown at two significance thresholds, presented as family-wise uncorrected p-values), but no differences in the thalamus, in cervical dystonia (family-wise error corrected p = 0.9996). When the analysis was restricted to only those voxels in a thalamic mask (to minimize the loss of statistical power by multiple-comparisons correction; C, green voxels), no significant differences in local tissue volume were noted (p = 0.34). Significant voxels (A, B) and thalamic mask (C) overlie the mean gray matter structural image. Note that identical structural scans were used in VBM analyses and segmentation analyses (i.e., scans used in this figure were the same as those used for data in Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155302#pone.0155302.g002" target="_blank">2</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155302#pone.0155302.g003" target="_blank">3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155302#pone.0155302.g005" target="_blank">5</a>). VBM results were corrected using threshold-free cluster enhancement (TFCE). All axial and coronal views are from a single plane, indicated in MNI Talairach coordinates. Color bars at bottom indicate TFCE-corrected p-values for the images above. Abbreviations: pat = patients; ctrl = controls. R = Right hemisphere; L = Left hemisphere.</p

Demographic information and gross volumetric negative-control contrasts.

<p>Demographic and volumetric negative-control measures for each experimental group demonstrate high group similarity. Within each experimental group (cervical dystonia–CD; spasmodic dysphonia–SD), controls were matched to patients for gender, handedness, and age +/- five years (A). Each volumetric negative-control measure is expressed as the percentage of mean control volume (<i>e</i>.<i>g</i>., estimated total intracranial volume (eTIV) for CD patients is 2% larger for patients than for matched controls). No large-scale volumetric measures differed between patients and controls (A, p-values uncorrected). The reduction of thalamic volume in patients maintained significance following normalization for all volumetric negative-control measures (B).</p

Regional automated and manual gross volume measures.

<p>A reduction in thalamic volume, not seen in other regions involved in the control of movement, was seen in both cervical dystonia and spasmodic dysphonia. Total volume (i.e., number of voxels in left plus right hemispheres) is shown for each region of interest (mean ± standard error of the mean). Given the large differences in volume between brain regions, the axis has been adjusted to focus on each cluster of values. Breaks in the y-axis are indicated by hashed horizontal bars. All p-values corrected for multiple comparisons (Bonferroni corrected significance threshold, p = 0.00625); * p≤0.0060; ** p = 0.00020. Abbreviation: BA6 = Brodmann Area 6; Thal auto = automated thalamic segmentation.</p

Relationship of clinical measures to gross thalamic volume in CD patients.

<p>The relationship between individual gross thalamic volume (manually segmented, in mm³) and clinical measures suggests that reduced gross thalamic volume is a risk factor for dystonia, and is not a secondary effect of dystonia symptoms. Data are shown for all variables, even if excluded from regression models, so raw data for CD and SD can be viewed and compared. Both CD patients and controls (A) showed declining volume with age. Patient:control gross thalamic volume showed a qualitative divergence with age between CD and controls, but the divergence was not statistically significant. (B) There was no relationship between volume and age in the SD cohort (for either SD or controls), presumably reflecting the smaller age range in this cohort. Likewise, there was no divergence of slopes with age between SD and controls. Age at CD onset (C) appeared to correlate with gross thalamic volume, but this was likely driven by the relationship between age at scan and age of onset; age at SD onset (D) was not correlated with volume. Gross thalamic volume did not correlate significantly with duration for either CD (E); this relationship was not evaluated statistically for SD due to collinearity with other variables, but the positive slope suggests no indication of a decline in volume with increasing duration (F). Thalamic volume also did not correlate with severity of dystonia for either CD or SD in the multiple regression model, as measured by the Tsui scale for CD (G) or the voice-related quality of life score for SD (H), although the SD relationship to severity showed a trend toward significance (V-RQOL, p = 0.056), and appeared significant when evaluated post hoc as a single variable (p = 0.012). The asymmetry of muscles affected with cervical dystonia (as gauged by laterality of units of botulinum toxin injected) did not correlate with asymmetries in thalamic volume (I, p = 0.89). Note that for (C) and (D), thalamic volumes for control subjects are plotted vs. the age at onset for the matched patient, as control subjects do not have an age at onset. Volume for control subjects is included in C and D as a reference only (designated by Ω), to illustrate that patient:control differences persist (and in fact are more robust) when demographics (including age) are matched: with the exception of a single CD/control dyad, every patient showed lower volume than his/her matched control.</p

Relative regional gross volume measures in focal dystonia.

<p>Relative gross thalamic volume, normalized to matched controls, was less in dystonia patients. Total gross thalamic volume was normalized to the mean value for matched controls, expressed as percent difference ± standard error of the mean for each region of interest. This data is reformatted but otherwise identical to that in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155302#pone.0155302.g002" target="_blank">Fig 2</a>. All p-values corrected for multiple comparisons, (Bonferroni corrected significance threshold, p = 0.00625); * p≤0.0060; ** p = 0.00020. Abbreviations: CD = cervical dystonia; SD = spasmodic dysphonia; BA6 = Brodmann Area 6.</p

Regions of probabilistic diffusion tractography that were significantly different between cervical dystonia patients and controls.

<p>(A) shows reduced tractography from the left AL seed region, and (B) shows elevated tractography from the right pallidal seed region. Arrows point to the region through which we drew ROIs in our previous DTI study, which includes AL fibers. <i>A priori</i> segmented regions are shown as reference points: Pink = red nucleus; White = substantia nigra; Blue = pedunculopontine nucleus. MNI talairach coordinates are indicated for each two dimensional image. Lower images in each panel show three dimensional rendering of clusters; the image for the left AL includes the AL seed region in green, and the patient/control difference is shown in blue. t maps and three dimensional clusters are superimposed on the average FA map for all 24 subjects in the study for anatomical reference, and are thresholded at t = +/−2.07 (the threshold used to identify difference clusters, p<0.05, uncorrected, for df = 22). The color bars indicate the range of t values in each panel, from +/−2.07 to the peak t value for each contrast. Warm tones (red, orange, yellow) indicate regions in which cervical dystonia patients exhibited elevated tractography relative to control subjects. Cool tones (blues) indicate regions in which cervical dystonia patients exhibited reduced tractography relative to control subjects. Three dimensional images are shown in mono-color rather than graded/multi-color to illustrate location rather than significance. LH: left hemisphere; RH: right hemisphere.</p

Clinical characteristics of cervical dystonia patients.

*<p>subjects included in 2006 study using different analyses.</p><p>BFM: Burke Fahn Marsden dystonia rating scale.</p><p>Tsui: Tsui rating scale for cervical dystonia.</p><p>TW: Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) for cervical dyston.</p

Group differences for voxel-wise probabilistic diffusion tractography contrast (12 cervical dystonia patients versus 12 matched controls).

*<p>Met significance criteria (p<0.00011 [p<0.05 corrected, or t = 4.70] for t values, and 291 voxels for cluster threshold).</p><p>Negative t values indicate that tractography measures were reduced in cervical dystonia patients relative to control subjects. Positive t values indicate that tractography measures were elevated in cervical dystonia patients relative to control subjects. Note that all regions included in the cluster are reported; however, only one peak within the cluster was required to reach statistical significance (t>4.12). t values are reported for all regions exhibiting peaks of 3.5 or greater. L = left hemisphere; R = right hemisphere; wm = white matter.</p

Group differences for voxel-wise FA contrast (12 cervical dystonia patients versus 12 matched controls).

*<p>Met significance criteria (p<0.00022, [p<0.05, corrected, or t = 4.42] for t values, and 72 voxels for cluster threshold).</p>†<p>p value was within an order of magnitude of the corrected threshold (a trend).</p><p>Positive t values indicate FA values were elevated in cervical dystonia patients relative to control subjects; negative t values indicate FA values were reduced in cervical dystonia patients relative to control subjects. L = left hemisphere; R = right hemisphere; wm = white matter.</p

Probabilistic diffusion tractography and overlap with <i>a priori</i> areas of evaluation (AOEs) used for the FA and MD contrasts.

<p>(A) Examples of tractography from the left ansa lenticularis (AL) seed region, averaged across control subjects (before contrasts were conducted), thresholded at 500 (samples). Note that tractography bifurcated at the level of the substantia nigra (see axial image). (B) Examples of tractography from the left pallidal seed region, averaged across control subjects (before contrasts were conducted), thresholded at 500. Like AL tractography, pallidal tractography bifurcated at the level of the substantia nigra (see axial image). There were also two projections to the thalamus, one superior and one more ventral (see sagittal image). (C) Intersection of tractography with segmentations of our <i>a priori</i> AOEs, including (in descending order) the ansa lenticularis (green), the substantia nigra (white), the red nucleus (pink), the pedunculopontine nucleus (blue), and the superior cerebellar peduncle (peach). Tractography maps are superimposed on the average FA map for all 24 subjects in the study. (D) Example of type Ib GPi neuron from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0031654#pone.0031654-Parent1" target="_blank">[21]</a>, showing extensive arborization, including to the RN and PPN (reprinted with permission from The Journal of Comparative Neurology). MNI talairach coordinates are indicated for all images. LH: left hemisphere; RH: right hemisphere.</p