title: Thalamic connectivity in patients with essential tremor treated with MR imaging-guided focused ultrasound: in vivo fiber tracking by using diffusion-tensor MR imaging.
abstract: OBJECTIVE
  To use diffusion-tensor (DT) magnetic resonance (MR) imaging in patients with essential tremor who were treated with transcranial MR imaging-guided focused ultrasound lesion inducement to identify the structural connectivity of the ventralis intermedius nucleus of the thalamus and determine how DT imaging changes correlated with tremor changes after lesion inducement.
  
  
  METHODS
  With institutional review board approval, and with prospective informed consent, 15 patients with medication-refractory essential tremor were enrolled in a HIPAA-compliant pilot study and were treated with transcranial MR imaging-guided focused ultrasound surgery targeting the ventralis intermedius nucleus of the thalamus contralateral to their dominant hand. Fourteen patients were ultimately included. DT MR imaging studies at 3.0 T were performed preoperatively and 24 hours, 1 week, 1 month, and 3 months after the procedure. Fractional anisotropy (FA) maps were calculated from the DT imaging data sets for all time points in all patients. Voxels where FA consistently decreased over time were identified, and FA change in these voxels was correlated with clinical changes in tremor over the same period by using Pearson correlation.
  
  
  RESULTS
  Ipsilateral brain structures that showed prespecified negative correlation values of FA over time of -0.5 or less included the pre- and postcentral subcortical white matter in the hand knob area; the region of the corticospinal tract in the centrum semiovale, in the posterior limb of the internal capsule, and in the cerebral peduncle; the thalamus; the region of the red nucleus; the location of the central tegmental tract; and the region of the inferior olive. The contralateral middle cerebellar peduncle and bilateral portions of the superior vermis also showed persistent decrease in FA over time. There was strong correlation between decrease in FA and clinical improvement in hand tremor 3 months after lesion inducement (P < .001).
  
  
  CONCLUSIONS
  DT MR imaging after MR imaging-guided focused ultrasound thalamotomy depicts changes in specific brain structures. The magnitude of the DT imaging changes after thalamic lesion inducement correlates with the degree of clinical improvement in essential tremor.
authors.affiliation: From the Department of Radiology, Neuroradiology Division (M.W., N.T., T.J.D.), Department of Neurosurgery (D.S.H., N.K., W.J.E.), and Department of Neurology (B.B.S.), University of Virginia, 1215 Lee St, New Hospital, 1st Floor, Room 1011, Charlottesville, VA 22908-0170; and Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland (M.W.).
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
authors.forename: Diane S
authors.initials: DS
authors.lastname: Huss
authors.forename: Binit B
authors.initials: BB
authors.lastname: Shah
authors.forename: Nicholas
authors.initials: N
authors.lastname: Tustison
authors.forename: T Jason
authors.initials: TJ
authors.lastname: Druzgal
authors.forename: Neal
authors.initials: N
authors.lastname: Kassell
authors.forename: W Jeff
authors.initials: WJ
authors.lastname: Elias
mesh_terms: D000368:Aged; D001931:Brain Mapping; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D020329:Essential Tremor / Q000473:pathology* / Q000601:surgery*; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D010865:Pilot Projects; D011446:Prospective Studies; D013788:Thalamus / Q000473:pathology*; D016896:Treatment Outcome; D059708:Ultrasonic Surgical Procedures / Q000379:methods*