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Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
Brain. Author manuscript; available in PMC Feb 1, 2009.
Published in final edited form as:
PMCID: PMC2376833
NIHMSID: NIHMS44897

Focal white matter changes in spasmodic dysphonia: a combined DTI and neuropathological study

Abstract

Spasmodic dysphonia (SD) is a neurological disorder characterized by involuntary spasms in the laryngeal muscles during speech production. Although clinical symptoms of SD are well characterized, the pathophysiology of this voice disorder is unknown. We describe here, for the first time to our knowledge, disorder-specific brain abnormalities in SD patients as determined by a combined approach of diffusion tensor imaging (DTI) and postmortem histopathology. We used DTI to identify brain changes in SD and to target those brain regions for neuropathological examination. DTI showed rightsided decrease of fractional anisotropy in the genu of the internal capsule and bilateral increase of overall water diffusivity in the white matter along the corticobulbar/corticospinal tract in 20 SD patients compared to 20 healthy subjects. In addition, water diffusivity was bilaterally increased in the lentiform nucleus, ventral thalamus, and cerebellar white and gray matter in SD patients. These brain changes were substantiated with focal histopathological abnormalities presented as a loss of axonal density and myelin content in the right genu of the internal capsule and clusters of mineral depositions containing calcium, phosphorus and iron in the parenchyma and vessel walls of the posterior limb of the internal capsule, putamen, globus pallidus, and cerebellum in the postmortem brain tissue from one SD patient compared to three controls. The specificity of these brain abnormalities is confirmed by their localization limited only to the corticobulbar/corticospinal tract and its main input/output structures. We also found positive correlation between the diffusivity changes and clinical symptoms of SD (r = 0.509, p = 0.037). These brain abnormalities may alter the central control of voluntary voice production and, therefore, may underlie the pathophysiology of SD.

Keywords: laryngeal dystonia, corticobulbar tract, basal ganglia, neuroimaging, neuropathology
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