title: Comparison of a special designed high intensity coil to a standard round coil-TMS-setting.
abstract: Routine diagnostic Transcranial Magnetic Stimulation (TMS) is performed with a round coil (RC) for cranial and spinal root stimulation, being less successful for motor evoked potentials (MEP) of lower limb muscles. MEP elicited with a special configured flat figure-of-eight coil designed for high intensity stimulation (HI-coil) were compared to RC with regard to handling, efficiency, and physiological properties of MEP.
  
  
  
  MEP elicited with HI-coil and 9-cm diameter RC for cortical, spinal and peripheral stimulation (PES) were compared for Motor threshold (MT), latencies and amplitudes of bilateral Abductor pollicis brevis (APB) and Abductor hallucis muscles (AH).
  
  
  
  MT for HI-coil were significantly lower for cortical and spinal root stimulation compared to RC (APB: 37% vs. 48%; AH: 58% vs. 72%). MEP-latencies elicited with HI-coil and RC were without significant difference. AH-MEP amplitudes were significantly larger for HI-coil cortical (705±980μV vs. 370±280μV) and root stimulation (260±210μV vs. 151±100μV). Amplitudes elicited by PES compared to HI-coil were always significantly larger.
  
  
  
  Results for cortical and spinal root stimulation with regards to latencies and amplitudes for APB were equivalent between HI-coil and RC. PES was superior in achieving supramaximal stimulation in terms of amplitudes. The use of the HI-coil might be advantageous for MEP of lower extremity muscles with emphasis on pathologic conditions requiring higher stimulation intensities.
authors.affiliation: Department of Neurosurgery, Hospital of the Ludwig Maximilians University Munich (LMU), Munich, Germany. Electronic address: andrea.szelenyi@med.uni-muenchen.de.
authors.forename: Andrea
authors.initials: A
authors.lastname: Szelényi
authors.affiliation: Department of Neurosurgery, University Hospital Duesseldorf, Medical Faculty, Heinrich-Heine-University, Duesseldorf, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Wölfle
authors.affiliation: Department of Neurosurgery, University Hospital Duesseldorf, Medical Faculty, Heinrich-Heine-University, Duesseldorf, Germany.
authors.forename: Igor
authors.initials: I
authors.lastname: Fischer
authors.affiliation: Department of Neurosurgery, University Hospital Duesseldorf, Medical Faculty, Heinrich-Heine-University, Duesseldorf, Germany.
authors.forename: Hans-Jakob
authors.initials: HJ
authors.lastname: Steiger
authors.affiliation: Department of Neurosurgery, University Hospital Duesseldorf, Medical Faculty, Heinrich-Heine-University, Duesseldorf, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Sabel
mesh_terms: D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology; D002574:Cervical Vertebrae; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D007866:Leg / Q000502:physiology; D008159:Lumbar Vertebrae; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology; D013126:Spinal Nerve Roots / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation*; D014953:Wrist / Q000502:physiology; D055815:Young Adult
keywords: Flat figure-of-eight coil (HI coil); Motor evoked potentials; Round coil; Transcranial magnetic stimulation