Neuroimaging essentials in essential tremor: A systematic review

Abstract

BackgroundEssential tremor is regarded to be a disease of the central nervous system. Neuroimaging is a rapidly growing field with potential benefits to both diagnostics and research. The exact role of imaging techniques with respect to essential tremor in research and clinical practice is not clear. A systematic review of the different imaging techniques in essential tremor is lacking in the literature.MethodsWe performed a systematic literature search combining the terms essential tremor and familial tremor with the following keywords: imaging, MRI, VBM, DWI, fMRI, PET and SPECT, both in abbreviated form as well as in full form. We summarize and discuss the quality and the external validity of each study and place the results in the context of existing knowledge regarding the pathophysiology of essential tremor.ResultsA total of 48 neuroimaging studies met our search criteria, roughly divided into 19 structural and 29 functional and metabolic studies. The quality of the studies varied, especially concerning inclusion criteria. Functional imaging studies indicated cerebellar hyperactivity during rest and during tremor. The studies also pointed to the involvement of the thalamus, the inferior olive and the red nucleus. Structural studies showed less consistent results.Discussion and conclusionNeuroimaging techniques in essential tremor give insight into the pathophysiology of essential tremor indicating the involvement of the cerebellum as the most consistent finding. GABAergic dysfunction might be a major premise in the pathophysiological hypotheses. Inconsistencies between studies can be partly explained by the inclusion of heterogeneous patient groups. Improvement of scientific research requires more stringent inclusion criteria and application of advanced analysis techniques. Also, the use of multimodal neuroimaging techniques is a promising development in movement disorders research. Currently, the role of imaging techniques in essential tremor in daily clinical practice is limited.

A preliminary study of the neuroanatomical correlates of primary writing tremor: role of cerebellum

“…In a DTI study in WC, FA values were reported to be increased bilaterally in the white matter of the posterior limb of the internal capsule and adjacent structures in the patients compared to the controls. Abnormalities in DTI indices of the cerebellar peduncles and red nucleus have been reported in patients with ET [26]. Comparing our results with those reported in WC and ET, it appears that PWT is a separate entity with a different pathophysiology.…”

“…VBM has also been used to understand the pattern of gray matter changes in patients with ET [11][12][13]. Sharifi et al [26] in a latest review on neuroimaging in ET have highlighted six VBM studies in ET giving different results with predominant atrophy in some parts of cerebellum and cerebrum. The anterior lobe of the cerebellum has been reported to be atrophied in patients with ET [11], which is similar to our finding in patients with PWT.…”

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

“…The complexity of ET‐related pathology was supported by findings of cerebellar abnormalities and widespread brain neuro‐degeneration (Louis, 2014b, 2014c). The cerebello‐thalamo‐cortical network (Sharifi, Nederveen, Booij, & van Rootselaar, 2014) (cerebello‐thalamo‐cortical [CTC], also known as “tremor network”) has been proposed to play a substantial role in ET. In CTC network, the inferior olive nuclei project, via climbing fibers, to Purkinje cells in the contralateral cerebellar cortex, which send GABAergic inhibitory projections to the dentate and other deep cerebellar nuclei that in turn project to cortical brain areas via thalamic projections and to the red nucleus (Sharifi et al., 2014).…”

Evaluation of Thalamus Area In Essential Tremor Patients With Proton Magnetik Resonance Spectroscopy

“…There are few proton MRS studies on the cerebellum and thalamus regions, which are thought to be mainly affected in the pathophysiology of ET (20). Louise et al (7) compared the cerebellar cortex, white matter, vermis, thalamus and basal ganglia of 16 ET patients and 11 healthy subjects using H-1 MRS examination and they found that the mean cerebellar cortex total creatine (tCR) NAA/tCR values of patients with ET were significantly lower than the control group.…”