Morphological Abnormalities in the Basal Ganglia of Dystonia Patients

Abstract

<b><i>Objective:</i></b> The pathophysiology of dystonia is poorly understood. As opposed to secondary forms of dystonia, primary dystonia has long been believed to lack any neuroanatomical substrate. During trajectory planning for DBS, however, conspicuous T2-hyperinstensive signal alterations (SA) were registered within the target region, even in young patients, where ischemia is rare. <b><i>Methods:</i></b> Fifty MRIs of primary dystonia patients scheduled for DBS were analyzed. Total basal ganglia (BG) volumes, as well as proportionate SA volumes, were measured and compared to 50 age-matched control patients. <b><i>Results:</i></b> There was a 10-fold preponderance of percentaged SA within the globus pallidus (GP) in dystonia patients. The greatest disparity was in young patients <25 years. Also, total BG volume differences were observed with larger GP and markedly smaller putamen and caudate in the dystonia group. <b><i>Conclusions:</i></b> BG morphology in primary dystonia differed from a control population. Volume reductions of the putamen and caudate may reflect functional degeneration, while volume increases of the GP may indicate overactivity. T2-hyperintensive SA in the GP of young primary dystonia patients, where microvascular lesions are highly unlikely, are striking. Their pathogenic role remains unclear.

Structural magnetic resonance imaging in dystonia: A systematic review of methodological approaches and findings

“…A stronger magnetic field (measured in tesla, T) provides higher signal to noise ratio, enabling higher image resolution; however, stronger fields are limited by faster signal loss, exacerbation of inhomogeneities within the field (which can distort the measured signal) and potential tissue heating due to differing radiofrequency requirements. The studies identified used either 1.5 T ( n = 16) [9–24] or 3 T ( n = 57) strength.…”

“…Amongst the volumetric studies, spatial resolution is important, with smaller voxel sizes reducing partial volume effects and enhancing delineation of anatomical borders, resulting in more accurate volumetric measures. Specifically, amongst the volumetric studies, the majority had dimensions of ≤1 mm 3 ( n = 27), with the rest having a maximum dimension of 1–1.5 mm ( n = 7) [17, 22, 24–28], 1.5–2 mm ( n = 1) [16] or not stated ( n = 4) [14, 29–31].…”

“…Imaging data analysis, particularly using whole brain approaches, can involve multiple comparisons over thousands of voxels, increasing the risk of type I errors. Commonly employed multiple comparison correction approaches identified in this review included the Bonferroni correction ( n = 14) [16, 26, 29, 36, 37, 42, 43, 49, 51, 59, 62, 64, 68, 71], false discovery rate correction ( n = 13) [11, 14, 17, 20, 22, 34, 40, 41, 50, 72, 77–79] and family wise error based correction ( n = 19) [15, 21, 23, 27, 28, 31–33, 46, 54, 55, 58, 66, 67, 69–71, 75, 80, 81]. Several studies also analysed voxels as a cluster in the ROI, reducing the potential impact of multiple comparisons, either by setting cluster‐extent thresholds with p values within certain limits ( p < 0.025 to p < 0.001, n = 12) [9, 10, 15, 25, 29–31, 33, 44, 60, 61, 67, 70, 73, 74, 76, 79], or by using threshold‐free cluster enhancement ( n = 6) [14, 32, 33, 52, 58].…”

“…Seventy‐two of the human studies compared the dystonia cohort with an unaffected control group, matched for age and gender, with the remaining paper comparing genotypic and phenotypic dystonia subgroups [31] (Tables 2–4). There was substantial variation in cohort size, with ≤10 ( n = 10) [24, 32, 34, 38, 40, 43, 49, 64, 65, 68], 10–20 ( n = 25) [9, 10, 12, 14, 18–20, 29, 30, 35–37, 41, 42, 46–48, 50, 51, 56, 60, 67, 69, 75, 80], 20–30 ( n = 15) [11, 15, 21, 26, 28, 33, 52, 57, 62, 70, 71, 74, 76, 79, 81] and >30 ( n = 23) [13, 16, 17, 22, 23, 25, 27, 31, 39, 44, 45, 53–55, 58, 59, 61, 63, 66, 72, 73, 77, 78] participants.…”

“…MTR is the difference between an acquisition with and without this off-resonance pulse. (n = 1) [16] or not stated (n = 4) [14,[29][30][31].…”