Abstract
Sleep disturbances, especially poor quality of sleep (QoS), are common among essential tremor (ET) patients and may have adverse effects on their quality of life, but the etiology driving the poor QoS in these individuals remains inadequately understood. Few data are available on the neuroimaging alterations of ET with poor QoS. Thirty-eight ET patients with poor QoS (SleET), 48 ET patients with normal QoS (NorET), and 80 healthy controls (HCs) participated in this study. All subjects underwent a 3.0-T magnetic resonance imaging (MRI) scan for resting-state functional MRI data collection. Then, the whole-brain functional connectome was constructed by thresholding the partial correlation matrices of 116 brain regions. Graph theory and network-based statistical analyses were performed. We used a non-parametric permutation test for group comparisons of topological metrics. Partial correlation analyses between the topographical features and clinical characteristics were conducted. The SleET and NorET groups exhibited decreased clustering coefficients, global efficiency, and local efficiency and increased the characteristic path length. Both of these groups also showed reduced nodal degree and nodal efficiency in the left superior dorsolateral frontal gyrus, superior frontal medial gyrus (SFGmed), posterior cingulate gyrus (PCG), lingual gyrus, superior occipital gyrus, right middle occipital gyrus, and right fusiform gyrus. The SleET group additionally presented reduced nodal degrees and nodal efficiency in the right SFGmed relative to the NorET and HC groups, and nodal efficiency in the right SFGmed was negatively correlated with the Pittsburgh Sleep Quality Index score. The observed impaired topographical organizations of functional brain networks within the central executive network (CEN), default mode network (DMN), and visual network serve to further our knowledge of the complex interactions between tremor and sleep, adding to our understanding of the underlying neural mechanisms of ET with poor QoS.
Highlights
Essential tremor (ET) is a common movement disorder characterized by postural or kinetic tremor of the bilateral upper limbs, with a worldwide prevalence of approximately 1% (Haubenberger et al, 2018)
In a recent metaanalysis of sleep disturbances in ET (Jimenez-Jimenez et al, 2020), the results from nine studies using the Pittsburg Sleep Quality Index (PSQI) to assess quality of sleep (QoS) revealed higher PSQI scores and a greater frequency of poor QoS in ET patients compared to healthy controls
Patients in the SleET group were older at disease onset (p = 0.013), presented with a head tremor (p = 0.024) and tremor at rest (p = 0.028) in greater numbers, and had higher total Tremor Rating Scale (TRS) (p = 0.012) and TRSB domain (p = 0.006) scores compared to the normal ET patients (NorET) group
Summary
Essential tremor (ET) is a common movement disorder characterized by postural or kinetic tremor of the bilateral upper limbs, with a worldwide prevalence of approximately 1% (Haubenberger et al, 2018). Functional Connectome of ET’s QoS have demonstrated that sleep disturbances, including poor quality of sleep (QoS), insomnia, rapid eye movement (REM) sleep behavior disorder (RBD), restless legs syndrome, and excessive daytime somnolence, may occur frequently in ET patients (Ondo and Lai, 2006; Gerbin et al, 2012; Sengul et al, 2014; Rohl et al, 2016; Barbosa et al, 2017). In a recent metaanalysis of sleep disturbances in ET (Jimenez-Jimenez et al, 2020), the results from nine studies using the Pittsburg Sleep Quality Index (PSQI) to assess QoS revealed higher PSQI scores and a greater frequency of poor QoS (based on the percentage of ET patients with a PSQI score ≥ 5 points) in ET patients compared to healthy controls. Little evidence is available concerning the possible pathophysiology changes of sleep disturbances in ET, especially in ET patients with poor QoS
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