title: Neuroimaging essentials in essential tremor: a systematic review.
abstract: BACKGROUND
  Essential 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  A 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.
  
  
  CONCLUSIONS
  Neuroimaging 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.
authors: Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands ; Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands.
authors: Sarvi
authors: S
authors: Sharifi
authors: Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands ; Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands.
authors: Aart J
authors: AJ
authors: Nederveen
authors: Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands ; Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors: Jan
authors: J
authors: Booij
authors: Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands ; Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands.
authors: Anne-Fleur
authors: AF
authors: van Rootselaar
mesh_terms: D001921:Brain / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D020329:Essential Tremor / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D059906:Neuroimaging / Q000379:methods*
keywords: DWI, diffusion weighted imaging; Essential tremor; MRI; MRI, magnetic resonance imaging; Neuroimaging; PET, positron emission tomography; Pathophysiology; Review; SPECT, single-photon emission computed tomography; Scintigraphy; VBM, voxel-based morphometry; fMRI, functional magnetic resonance imaging