Data from: Thalamic volume is reduced in cervical and laryngeal dystonias

Background: Dystonia, a debilitating movement disorder characterized by abnormal fixed positions and/or twisting postures, is associated with dysfunction of motor control networks. While gross brain lesions can produce secondary dystonias, advanced neuroimaging techniques have been required to identify network abnormalities in primary dystonias. Prior neuroimaging studies have provided valuable insights into the pathophysiology of dystonia, but few directly assessed the gross volume of motor control regions, and to our knowledge, none identified abnormalities common to multiple types of idiopathic focal dystonia.

Methods: We used two gross volumetric segmentation techniques and one voxelwise volumetric technique (voxel based morphometry, VBM) to compare regional volume between matched healthy controls and patients with idiopathic primary focal dystonia (cervical, n = 17, laryngeal, n = 7). We used (1) automated gross volume measures of eight motor control regions using the FreeSurfer analysis package; (2) blinded, anatomist-supervised manual segmentation of the whole thalamus (also gross volume); and (3) voxel based morphometry, which measures local T1-weighted signal intensity and estimates gray matter density or volume at the level of single voxels, for both whole-brain and thalamus.

Results: Using both automated and manual gross volumetry, we found a significant volume decrease only in the thalamus in two focal dystonias. Decreases in whole-thalamic volume were independent of head and brain size, laterality of symptoms, and duration. VBM measures did not differ between dystonia and control groups in any motor control region.

Conclusions: Reduced thalamic gross volume, detected in two independent analyses, suggests a common anatomical abnormality in cervical dystonia and spasmodic dysphonia. Defining the structural underpinnings of dystonia may require such complementary approaches.

研究背景：肌张力障碍（Dystonia）是一种使人衰弱的运动障碍性疾病，以异常固定姿势和/或扭转姿势为特征，与运动控制网络功能障碍相关。尽管脑大体病变可引发继发性肌张力障碍，但原发性肌张力障碍的网络异常仍需借助先进神经成像技术（neuroimaging techniques）才能识别。既往神经成像研究虽为肌张力障碍的病理生理学研究提供了重要见解，但极少有研究直接评估运动控制脑区的大体体积，且据我们所知，尚无研究明确多种特发性局灶性肌张力障碍共有的异常特征。
研究方法：本研究采用两种大体体积分割技术与一种体素水平体积分析技术——基于体素的形态测量学（voxel based morphometry, VBM），对比特发性原发性局灶性肌张力障碍患者（颈段肌张力障碍17例、喉段肌张力障碍7例）与匹配健康对照的脑区体积差异。具体方法包括：（1）借助FreeSurfer分析软件包，对8个运动控制脑区进行自动化大体体积测量；（2）由解剖学家监督的盲法手动分割全丘脑（同样为大体体积测量）；（3）基于体素的形态测量学分析，该技术可测量局部T1加权信号强度（T1-weighted signal intensity），并在单个体素水平估计灰质密度或体积，涵盖全脑与丘脑两个分析维度。
研究结果：通过自动化与手动大体体积测量两种方法，本研究仅在两类局灶性肌张力障碍患者的丘脑发现了显著的体积降低。全丘脑体积减小与头围、脑体积、症状偏侧性及病程均无关联。基于体素的形态测量学分析显示，肌张力障碍患者与健康对照在任意运动控制脑区的测量结果均无显著差异。
研究结论：两项独立分析均检测到丘脑大体体积减小，提示颈段肌张力障碍与痉挛性发音障碍（spasmodic dysphonia）存在共有的解剖学异常。明确肌张力障碍的结构基础，或许需要采用这类互补的研究方法。