Diffusion Tensor Imaging in Patients With Essential Tremor

Abstract

BACKGROUND AND PURPOSE:The traditional paradigm has regarded essential tremor (ET) as a benign disorder. However, recent clinical, neuroimaging, and neuropathologic studies suggest that ET may be a progressive neurologic disorder. Based on clinicopathologic findings that cerebellum and its outflow are the key structures in ET and degeneration of gray matter in cerebellum is followed by consequent wallerian degeneration of white matter (WM) fibers, the aim of the present study was to investigate changes in anisotropy in patients with ET.

White matter measures correlate with essential tremor severity—A pilot diffusion tensor imaging study

“…Importantly, areas that correlate with objective tremor measures extend to the midbrain, specifically areas around the cerebral peduncles and red nucleus thus including the WM within dentate‐rubro‐olivary pathway (Guillain‐Mollaret triangle), which is considered a tremorgenic loop (Murdoch, Shah, & Jampana, 2016). These findings are consistent with previous studies showing abnormalities in DTI parameters directly within red nucleus (Jia et al., 2011), in retrorubral WM (Shin, Han, Kim, & Lee, 2008) and the Guillain‐Mollaret triangle (Nicoletti et al., 2010) in ET patients. However, no correlation with tremor clinical parameters was reported in these studies (Jia et al., 2011; Nicoletti et al., 2010; Shin et al., 2008).…”

“…These findings are consistent with previous studies showing abnormalities in DTI parameters directly within red nucleus (Jia et al., 2011), in retrorubral WM (Shin, Han, Kim, & Lee, 2008) and the Guillain‐Mollaret triangle (Nicoletti et al., 2010) in ET patients. However, no correlation with tremor clinical parameters was reported in these studies (Jia et al., 2011; Nicoletti et al., 2010; Shin et al., 2008). Our data show a unique correlation of CST changes exclusively with combined TremScore but not with frequency or FTM scale.…”

“…At this point, we might only speculate about relationships between tremor symptoms and WM clusters located in UF, ILF, and IFOF. All these bundles are involved in memory retrieval, reward processing, emotional regulation, impulsive responding, semantic language processing, attention, and reversal learning (Mandonnet, Nouet, Gatignol, Capelle, & Duffau, 2007; Martino & De Lucas, 2014; Olson, Von Der Heide, Alm, & Vyas, 2015), although orbitofrontal WM, part of both UF and ILF, was associated with the FTM score (Klein et al., 2011) and showed affected in previous ET study (Shin et al., 2008). Also, atrophy in frontal and temporal gray matter regions, which are interconnected by UF, was found related to the FTM scale (Bagepally et al., 2012) and an improvement of WM integrity within the ILF and IFOF was consistently reported among longitudinal DTI studies evaluating effects of physical training (Huang, Lu, Song, & Wang, 2015; Scholz et al., 2009), implying their involvement in motor functions.…”

Functional Anatomy of Essential Tremor: Lessons from Neuroimaging

“…41 Based on reduced fractional anisotropy in the pons, cerebellum, and midbrain and extensive WM damage in the frontal cortex and temporoparietal regions in patients with ET, others proposed that an abnormality in the cerebellothalamocorticocerebellar loop is responsible for the tremor. 46 Similarly, compromised WM has been reported in frontoparietal regions, cerebral hemispheres, the thalamus, and brain stem. 42 In summary, with the exception of 1 study, 43 most DTI research in ET demonstrated that widespread disintegrity of cerebral and cerebellar fiber tracts is common and likely underlies tremor generation.…”

“…42 In summary, with the exception of 1 study, 43 most DTI research in ET demonstrated that widespread disintegrity of cerebral and cerebellar fiber tracts is common and likely underlies tremor generation. [40][41][42]46 Although it is known that DTI measures are indicators for WM integrity, the exact nature underlying these pathologic processes is unknown. Whether demyelination, myelin injury, neuronal loss, or other processes underlie abnormal DTI values in patients with ET remains to be ascertained.…”