Cent Eur Neurosurg 2005; 66(3): 105-111
DOI: 10.1055/s-2005-836605
Original Article

© Georg Thieme Verlag Stuttgart · New York

Motor Evoked Potentials Following Highly Frequent Transcranial Magnetoelectrical Motor Cortex Stimulation: Normal Data and Potential Modulation by Stimulation-Dependent Inhibitory and Activating Mechanisms

Motorisch evozierte Potenziale nach hochfrequenter repetitiver transkranieller Magnetstimulation des Motorkortex: Normwerte und Potenzialmodulation durch stimulationsassoziierte Inhibition und FazilitierungV. Rohde1 , M. Neubert1 , P. Reinacher1 , M. Weinzierl1 , I. Kreitschmann-Andermahr1 , J. M. Gilsbach1
  • 1Neurochirurgische Klinik, Medizinische Fakultät, Universität Aachen, Germany
Further Information

Publication History

Publication Date:
22 August 2005 (online)


Objective: To determine the normal values (latency, amplitude) of motor evoked potentials (MEP) of the abductor pollicis brevis (APB) and tibialis anterior (TA) muscle after high-frequency repetitive transcranial magnetic stimulation of the motor cortex (rTCMS), and to evaluate stimulation-dependent MEP modulations. Patients and Methods: 29 healthy volunteers underwent rTCMS with 2 and 4 stimuli. The interstimulus interval (ISI) was 2, 3, and 4 ms respectively, which corresponded to frequencies between 250 and 500 stimuli/s. The evoked potentials of the relaxed and voluntarily contracted APB and TA were registered. Results: Depending on the frequency and number of stimuli, the mean corticomuscular latency to the relaxed APB varied between 22.2 and 22.9 ms, and to the relaxed TA between 30.4 and 32.0 ms. The intra- and interindividual variability of the amplitudes was substantial. Voluntary contraction of the target muscle always led to a decrease in latency and increase in amplitude (p < 0.05). Conclusion: The high variability of the amplitudes does not allow the computation of meaningful normal values. The latencies after rTCMS are close to those of normal data after single TCMS, which indicates that in awake humans identical cortical and spinal structures are similarly activated. The discrete variations of latency and amplitude after changing the frequency and stimulus number suggest that inhibitory and excitatory mechanisms on the cortical and/or spinal level modulate the muscle response.


Zielsetzung: Erstellung von Normwerten (Latenz, Amplitude) motorisch evozierter Potentiale (MEP) des M. abductor pollicis brevis (APB) und M. tibialis anterior (TA) nach hochfrequenter transkranieller Magnetstimulation des Motorkortex (rTKMS), und Erfassung stimulationsabhängiger Potenzialmodulationen. Patienten und Methoden: Bei 29 wachen Probanden wurde der Motorkortex transkraniell mit 2 und 4 magnetischen Stimuli bei einem Interstimulusintervall (ISI) von 2, 3 und 4 ms (entsprechend einer Frequenz von 250, 333, 500 Stimuli/s) gereizt. Latenz und Amplitude der MEP des relaxierten und vorinnervierten APB und TA wurden registriert. Ergebnisse: Die mittlere kortikomuskuläre Latenz zum relaxierten APB betrug, je nach Stimuluszahl und Frequenz, 22,2 bis 22,9 ms, zum relaxierten TA 30,4 bis 32,0 ms. Die Amplituden zeigten eine große intra- und interindividuelle Variabilität. Vorinnervation führte immer zu einer Latenzreduktion und Amplitudenzunahme (p < 0,05). Schlussfolgerungen: Wegen der hohen Variabilität ist die Festlegung normwertiger Amplituden nicht indiziert. Die Latenzen nach rTKMS gleichen den bekannten Normwerten nach magnetischem Einzelreiz. Wahrscheinlich werden trotz Reizrepetition beim wachen Probanden identische kortikale und spinale Strukturen in vergleichbarer Art aktiviert. Die Änderungen von Latenz und Amplitude in Abhängigkeit von Stimuluszahl und -frequenz lassen kortikale und/oder spinale Inhibitions- und Fazilitierungsmechanismen vermuten.


  • 1 Barker A T, Freeston I L, Jalinous R, Merton P A, Morton H B. Magnetic stimulation of the human brain.  J Physiol. 1985;  369 3
  • 2 Barker A T, Freeston I L, Jalinous R, Jarratt J A. Clinical evaluation of conduction time measurements in central motor pathways using magnetic stimulation of the human brain.  Lancet. 1986;  7 1325-1326
  • 3 Barker A T, Freeston I L, Jalinous R, Jarratt J A. Magnetic stimulation of the human brain and peripheral nervous system. An introduction and the results of an initial clinical evaluation.  Neurosurgery. 1987;  20 100-109
  • 4 Beradelli A, Inghilleri M, Rothwell J C, Romeo S, Currà A, Gilio F, Modugno N, Manfredi M. Facilitation of muscle evoked responses after repetitive cortical stimulation in man.  Exp Brain Res. 1998;  122 79-84
  • 5 Calancie B, Nordin M, Wallin U, Hagbarth K E. Motor-unit responses in human wrist flexor and extensor muscles to transcranial cortical stimulation.  J Neurophysiol. 1987;  58 1168-1185
  • 6 Classen J, Benecke R. Inhibitory phenomena in individual motor units induced by transcranial magnetic stimulation.  Electroencephal Clin Neurophysiol. 1995;  97 264-274
  • 7 Claus D, Mills K R, Murray N MF. The influence of vibration on the excitability of alpha motoneurons.  Electroencephal Clin Neurophysiol. 1988;  69 431-436
  • 8 Claus D, Mills K R, Murray N MF. Facilitation of muscle responses to magnetic brain stimulation by mechanical stimuli in man.  Exp Brain Res. 1988;  71 273-278
  • 9 Claus D. Die transkranielle motorische Stimulation. Gustav Fischer Verlag, Stuttgart, New York 1989
  • 10 Day B L, Thompson P hD, Dick J P, Nakashima K, Marsden C D. Different sites of action of electrical and magnetic stimulation of the human brain.  Neuroscience Letters. 1987;  75 101-106
  • 11 Di Lazzaro V, Restuccia D, Oliviero A, Profice P, Ferrara L, Insola A, Mazzone P, Tonali P, Rothwell J C. Magnetic transcranial stimulation at intensities below active motor threshold activates intracortical inhibitory circuits.  Exp Brain Res. 1998;  119 265-268
  • 12 Edgley S A, Eyre J A, Lemon R N, Miller S. Excitation of the corticospinal tract by electromagnetic and electrical stimulation of the scalp in macaque monkey.  J Physiol. 1990;  425 301-320
  • 13 Fujiki M, Isono M, Hori S, Ueno S. Corticospinal direct response to transcranial magnetic stimulation in humans.  Electroencephal Clin Neurophysiol. 1996;  101 48-57
  • 14 Gugino L D, Aglio L S, Potts G, Grimson W EL, Shenton M E, Kikinis R, Alexander E, Gonzalez A A, Romero R, Ettinger G J, Cote W A, Leventon M E, Black P M. Perioperative use of transcranial magnetic stimulation.  Techniques in Neurosurgery. 2001;  7 33-51
  • 15 Hess C W, Mills K R, Murray N MF. Magnetic stimulation of the human brain. Facilitation of motor responses by voluntary contraction of ipsilateral and contralateral muscles with additional observations on an amputee.  Neurosci Letters. 1986;  71 235-240
  • 16 Hess C W, Mills K R, Murray N MF. Responses in small hand muscles from magnetic stimulation of the human brain.  J Physiol. 1987;  388 397-419
  • 17 Hess C W. Die mittels Kortexreizung motorisch evozierten Potentiale. In: Stöhr M, Dichgans J, Büttner UW, Hess CW, Altenmüller E (eds). Evozierte Potentiale. Springer, Berlin 1996; 589-654
  • 18 Inghilleri M, Berardelli A, Cruccu G, Priori A, Manfredi M. Motor potentials evoked by paired cortical stimuli.  Electroencephal Clin Neurophysiol. 1990;  77 382-389
  • 19 Jennum P, Winkel H, Fuglsang-Frederiksen A. Repetitive magnetic stimulation and motor evoked potentials.  Electroencephal Clin Neurophysiol. 1995;  97 96-101
  • 20 Jennum P, Winkel H, Fuglsang-Frederiksen A. Paired transcranial magnetic stimulations and motor evoked potentials.  Electromyogr Clin Neurophysiol. 1996;  36 341-348
  • 21 Katayama Y, Tsubokawaq T, Maejina S, Mirayama T, Yamamoto T. Corticospinal direct responses in humans. Identification of the motor cortex during intracranial surgery under general anaesthesia.  J Neurol Neurosurg Psychiatry. 1988;  51 50-59
  • 22 Kujirai T, Caramia M D, Rothwell J C, Day B L, Thompson P D, Ferbert A, Wroe S, Asselman P, Marsden C D. Corticocortical inhibition in human motor cortex.  J Physiol. 1993;  471 501-519
  • 23 Meyer B U, Benecke R, Dressler D, Haug B, Conrad B. Fraktionierte Bestimmung zentraler motorischer Leitungszeiten mittels Reizung von Kortex, spinalen Bahnen und Spinalnervenwurzeln. Möglichkeiten und Grenzen.  Z EEG-EMG. 1988;  19 234-240
  • 24 McCaffrey M, Erickson J P. Modulation of cat motor evoked potential by prior cerebellar or somatosensory stimulation.  Neurosurgery. 1987;  20 193-194
  • 25 Nakamura H, Kitagawa H, Kawaguchi Y, Tsuji H. Intracortical facilitation and inhibition after transcranial magnetic stimulation in conscious humans.  J Physiol. 1997;  498 817-823
  • 26 Nielsen J F. Repetitive magnetic stimulation of cerebral cortex in normal subjects.  J Clin Neurophysiol. 1996;  13 69-76
  • 27 Pascual-Leone A, Valls-Solé J, Wassermann E M, Hallett M. Responses to rapid-rate transcranial magnetic stimulation of the human cortex.  Brain. 1994;  117 847-858
  • 28 Pechstein U, Cedzich C, Nadstawek J, Schramm J. Transcranial high-frequency repetitive electrical stimulation for recording myogenic motor evoked potentials with the patient under general anesthesia.  Neurosurgery. 1996;  39 335-344
  • 29 Rodi Z, Deletis V, Morota N, Vodusek D B. Motor evoked potentials during brain surgery.  Pflügers Arch Eur J Physiol. 1996;  431 (Suppl) R 291-R 292
  • 30 Rohde V, Mayfrank M, Weinzierl M, Krings T, Gilsbach J M. Focussed high frequency repetitive transcranial magnetic stimulation for localization of the unexposed primary motor cortex during brain tumour surgery.  J Neurol Neurosurg Psychiatry. 2003;  74 1283-1287
  • 31 Rohde V, Krombach G A, Baumert J H, Kreitschmann-Andermahr I, Weinzierl M, Gilsbach J M. Measurement of motor evoked potentials following repetitive magnetic motor cortex stimulation during isoflurane or propofol anaesthesia.  Br J Anaesth. 2003;  91 487-492
  • 32 Schäfer M, Biesecker J C, Schulze-Bonhage A, Ferbert A. Transcranial magnetic double stimulation: influence of the intensity of the conditioning stimulus.  Electroencephal Clin Neurophysiol. 1997;  105 462-469
  • 33 Scheufler K M, Zentner J. Total intravenous anesthesia for intraoperative monitoring of the motor pathways. An integral view combining clinical and experimental data.  J Neurosurg. 2002;  96 571-579
  • 34 Tokimura H, Ridding M C, Tokimura Y, Amassian V E, Rothwell J C. Short latency facilitation between pairs of threshold magnetic stimuli applied to human motor cortex.  Electroencephal Clin Neurophysiol. 1996;  101 263-272
  • 35 Ugawa Y, Rothwell J C, Day B L, Thompson P D, Marsden C D. Percutaneous electrical stimulation of the corticospinal pathways at the level of the pyramidal decussation in man.  Ann Neurol. 1991;  29 418-427
  • 36 Valls-Solé J, Pascual-Leone A, Wassermann E M, Hallett M. Human motor evoked responses to paired transcranial stimulation.  Electroencephal Clin Neurophysiol. 1992;  85 355-364
  • 37 Ziemann U, Rothwell J C, Ridding M C. Interaction between intracortical inhibition and facilitation in human motor cortex.  J Physiol. 1996;  496 873-881
  • 38 Ziemann U, Tergau F, Wassermann E M, Wischer S, Hildebrandt J, Paulus W. Demonstration of facilatory I wave interaction in the human motor cortex by paired transcranial magnetic stimulation.  J Physiol. 1998;  511 181-190
  • 39 Ziemann U, Tergau F, Wischer S, Hildebrandt J, Paulus W. Pharmacological control of facilitory I-wave interaction in human motor cortex. A paired transcranial magnetic stimulation study.  Electroencephal Clin Neurophysiol. 1998;  109 321-330

Prof. Dr. V. Rohde

Neurochirurgische Klinik · Medizinische Fakultät · Universität Aachen

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52057 Aachen · Germany

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Email: vrohde@ukaachen.de