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Low-Threshold Monopolar Motor Mapping for Resection of Primary Motor Cortex Tumors
Journal article

Low-Threshold Monopolar Motor Mapping for Resection of Primary Motor Cortex Tumors

  • Seidel, Kathleen Department of Neurosurgery, Inselspital, Bern University Hospital, Bern, Switzerland
  • Beck, Jürgen Department of Neurosurgery, Inselspital, Bern University Hospital, Bern, Switzerland
  • Stieglitz, Lennart Department of Neurosurgery, Inselspital, Bern University Hospital, Bern, Switzerland
  • Schucht, Philippe Department of Neurosurgery, Inselspital, Bern University Hospital, Bern, Switzerland
  • Raabe, Andreas Department of Neurosurgery, Inselspital, Bern University Hospital, Bern, Switzerland
  • 2012-1-4
Published in:
  • Operative Neurosurgery. - Oxford University Press (OUP). - 2012, vol. 71, no. suppl_1, p. ons104-ons115
English Abstract

BACKGROUND:
Microsurgery within eloquent cortex is a controversial approach because of the high risk of permanent neurological deficit. Few data exist showing the relationship between the mapping stimulation intensity required for eliciting a muscle motor evoked potential and the distance to the motor neurons; furthermore, the motor threshold at which no deficit occurs remains to be defined.


OBJECTIVE:
To evaluate the safety of low threshold motor evoked potential mapping for tumor resection close to the primary motor cortex.


METHODS:
Fourteen patients undergoing tumor surgery were included. Motor threshold was defined as the stimulation intensity that elicited motor evoked potentials from target muscles (amplitude > 30 μV). Monopolar high-frequency motor mapping with train-of-5 stimuli (HF-TOF; pulse duration = 500 microseconds; interstimulus interval = 4.0 milliseconds; frequency = 250 Hz) was used to determine motor response--negative sites where incision and dissection could be performed. At sites negative to 3-mA HF-TOF stimulation, the tumor was resected.


RESULTS:
HF-TOF mapping localized the motor neurons within the precentral gyrus by using variable, low-stimulation intensities. The lowest motor thresholds after final resection ranged from 3 to 6 mA, indicating close proximity of motor neurons. Postoperatively, 12 patients had no new motor deficit, 1 patient had a minor new temporary deficit (M4+, National Institutes of Health Stroke Scale 1), and another patient had a minor new permanent deficit (M4+, National Institutes of Health Stroke Scale 2). Thirteen patients had complete or gross total resection.


CONCLUSION:
These preliminary data demonstrate that a monopolar HF-TOF threshold > 3 mA was not associated with a significant new motor deficit.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/6411
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