title: Assessing the functional status of the motor system in brain tumor patients using transcranial magnetic stimulation.
abstract: BACKGROUND
  Transcranial magnetic stimulation (TMS) is being used in the pre-operative diagnostics of patients with tumors in or near the motor cortex. Although the main purpose of TMS in such patients is to map the functional areas of the motor cortex in spatial relation to the tumor, TMS also provides some numerical neurophysiological measurements of the functional status of the patient's motor system. The aim of this paper is to provide reference values for these neurophysiological measurements from a large and varied clinical sample.
  
  
  METHODS
  TMS was used in the pre-operative work-up of patients with various types of tumors in or near the motor cortex during a 3-year period. Data was collected prospectively in 100 patients, yet this is a post hoc report.
  
  
  RESULTS
  Patient characteristics had no influence on the neurophysiological parameters. The response latency time was almost never different in the tumorous versus healthy hemisphere, so clinicians should be suspicious if they find interhemispheric differences for latency. A high interhemispheric ratio of resting motor threshold (RMT) or a low interhemispheric ratio of motor evoked potential (MEP) amplitude appear to suggest immanent deterioration of the patient's motor status.
  
  
  CONCLUSIONS
  In addition to topographic cortical mapping, TMS also serves as a neurophysiological assessment of the functional status of the patient's motor system. The results presented here provide clinicians with a set of reference values to contextualize findings in their own tumor patients. Further research is still needed to better understand the full clinical relevance of these neurophysiological parameters.
authors.affiliation: Department of Neurosurgery, Charité University Hospital Berlin, Berlin, Germany. thomas.picht@charite.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Picht
authors.forename: Valerie
authors.initials: V
authors.lastname: Strack
authors.forename: Juliane
authors.initials: J
authors.lastname: Schulz
authors.forename: Anna
authors.initials: A
authors.lastname: Zdunczyk
authors.forename: Dietmar
authors.initials: D
authors.lastname: Frey
authors.forename: Sein
authors.initials: S
authors.lastname: Schmidt
authors.forename: Peter
authors.initials: P
authors.lastname: Vajkoczy
mesh_terms: D000368:Aged; D001931:Brain Mapping / Q000379:methods; D001932:Brain Neoplasms / Q000175:diagnosis / Q000503:physiopathology*; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D011930:Reaction Time / Q000502:physiology; D050781:Transcranial Magnetic Stimulation / Q000379:methods*