Andrea Szelényi1, Julia Wölfle2, Igor Fischer2, Hans-Jakob Steiger2, Michael Sabel2. 1. Department of Neurosurgery, Hospital of the Ludwig Maximilians University Munich (LMU), Munich, Germany. Electronic address: andrea.szelenyi@med.uni-muenchen.de. 2. Department of Neurosurgery, University Hospital Duesseldorf, Medical Faculty, Heinrich-Heine-University, Duesseldorf, Germany.
Abstract
BACKGROUND: 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. NEW METHODS: 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). RESULTS AND COMPARISON WITH EXISTING METHODS: 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. CONCLUSION: 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.
BACKGROUND: 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. NEW METHODS: 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). RESULTS AND COMPARISON WITH EXISTING METHODS: 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. CONCLUSION: 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.