Continuous Dynamic Mapping to Identify the Corticospinal Tract in Motor Eloquent Brain Tumors: An Update

Abstract Objective We recently developed a new subcortical mapping technique based on the concept of stimulating the tissue at the site of and synchronously with resection. Our hypothesis was that instead of performing resection and mapping sequentially, a synchronized resection and mapping could potentially improve deficit rates. Methods We report our 5-year series of patients who prospectively underwent tumor surgery adjacent to the corticospinal tract (CST) (defined as < 1 cm using diffusion tension imaging and fiber tracking) with simultaneous subcortical short train cathodal monopolar mapping, equipped with a new acoustic motor evoked potential (MEP) alarm. Continuous (temporal coverage) and dynamic (spatial coverage) mapping was realized technically by integrating the mapping probe at the tip of a new suction device. Motor function was assessed using the Medical Research Council scale (from M1 to M5) 1 day after surgery, at discharge, and at 3 months. Results Technically, the method was successful in all 182 cases. The lowest individual motor thresholds reached during resection were > 10 mA, n = 56; 6–10 mA, n = 31; 4–5 mA, n = 37; and 1–3 mA, n = 58. At 3 months, six patients (3%) had a persisting postoperative motor deficit that was caused by direct mechanical injury in three of these patients (1.7%). Conclusions Continuous dynamic mapping was found to be a feasible and ergonomic technique for localizing the exact site of the CST and distance to the motor fibers. This new technique may improve the safety of motor eloquent tumor surgery.

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Continuous dynamic mapping of the corticospinal tract during surgery of motor eloquent brain tumors: evaluation of a new method

Journal of Neurosurgery ◽

10.3171/2014.1.jns13909 ◽

2014 ◽

Vol 120 (5) ◽

pp. 1015-1024 ◽

Cited By ~ 56

Author(s):

Andreas Raabe ◽

Jürgen Beck ◽

Philippe Schucht ◽

Kathleen Seidel

Keyword(s):

Corticospinal Tract ◽

Diffusion Tensor ◽

Motor Evoked Potential ◽

Motor Deficit ◽

Mapping Technique ◽

Tumor Surgery ◽

Motor Mapping ◽

Dynamic Mapping ◽

Spatial Coverage ◽

Continuous Dynamic

Object The authors developed a new mapping technique to overcome the temporal and spatial limitations of classic subcortical mapping of the corticospinal tract (CST). The feasibility and safety of continuous (0.4–2 Hz) and dynamic (at the site of and synchronized with tissue resection) subcortical motor mapping was evaluated. Methods The authors prospectively studied 69 patients who underwent tumor surgery adjacent to the CST (< 1 cm using diffusion tensor imaging and fiber tracking) with simultaneous subcortical monopolar motor mapping (short train, interstimulus interval 4 msec, pulse duration 500 μsec) and a new acoustic motor evoked potential alarm. Continuous (temporal coverage) and dynamic (spatial coverage) mapping was technically realized by integrating the mapping probe at the tip of a new suction device, with the concept that this device will be in contact with the tissue where the resection is performed. Motor function was assessed 1 day after surgery, at discharge, and at 3 months. Results All procedures were technically successful. There was a 1:1 correlation of motor thresholds for stimulation sites simultaneously mapped with the new suction mapping device and the classic fingerstick probe (24 patients, 74 stimulation points; r2 = 0.98, p < 0.001). The lowest individual motor thresholds were as follows: > 20 mA, 7 patients; 11–20 mA, 13 patients; 6–10 mA, 8 patients; 4–5 mA, 17 patients; and 1–3 mA, 24 patients. At 3 months, 2 patients (3%) had a persistent postoperative motor deficit, both of which were caused by a vascular injury. No patient had a permanent motor deficit caused by a mechanical injury of the CST. Conclusions Continuous dynamic mapping was found to be a feasible and ergonomic technique for localizing the exact site of the CST and distance to the motor fibers. The acoustic feedback and the ability to stimulate the tissue continuously and exactly at the site of tissue removal improves the accuracy of mapping, especially at low (< 5 mA) stimulation intensities. This new technique may increase the safety of motor eloquent tumor surgery.

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Continuous Dynamic Mapping of the Corticospinal Tract in Motor Eloquent Tumor Surgery: Our Experience and Evaluation of the Method

Acta Medica Academica ◽

10.5644/ama2006-124.308 ◽

2021 ◽

Vol 49 (1, 2, 3) ◽

pp. 63

Author(s):

Andrej Porčnik ◽

Jure Pešak ◽

Tilen Žele ◽

Blaž Koritnik ◽

Zoran Rodi ◽

...

Keyword(s):

Corticospinal Tract ◽

Cortical Stimulation ◽

Gross Total Resection ◽

Motor Deficit ◽

Total Resection ◽

Direct Cortical Stimulation ◽

Dynamic Mapping ◽

Combined Use ◽

Eloquent Tumor ◽

Continuous Dynamic

Objective. The aim of this article is to present our experience with continuous dynamic mapping (CDM) of the corticospinal tract (CST) when removing tumors in motor eloquent regions.Methods. We studied 44 patients with a brain tumor adjacent to the CST where CDM was used. The mapping probe was integrated at the tip of the suction device. Thresholds for eliciting MEPs were recorded. In all patients, along with CDM, MEPs to direct cortical stimulation were also monitored throughout the operation. Motor function was assessed preoperatively, after the procedure and on discharge.Results. In the series, there were 37 patients with gliomas, six with brain metastasis, and one with cavernoma. The threshold to elicit MEPs in CDM was >20 mA in 17 cases, 16–20 mA in six cases, 11–15 mA in six cases, 6–10 mA in nine cases and 2–5 mA in six cases. MEPs to direct cortical stimulation were preserved in all patients. In three cases a new temporary motor deficit was noted. No new permanent motor deficit occurred. Gross total resection was reached in 57% of cases.Conclusions. From our experience, the combined use of CDM and MEPs to direct cortical stimulation improves the safety of surgery in the proximity of the CST, and at the same time offers the possibility of higher rates of gross total resection.

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Long-term motor deficit in brain tumour surgery with preserved intra-operative motor-evoked potentials

Brain Communications ◽

10.1093/braincomms/fcaa226 ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Davide Giampiccolo ◽

Cristiano Parisi ◽

Pietro Meneghelli ◽

Vincenzo Tramontano ◽

Federica Basaldella ◽

...

Keyword(s):

Evoked Potentials ◽

Brain Tumour ◽

Evoked Potential ◽

Corticospinal Tract ◽

Motor Evoked Potentials ◽

Motor Evoked Potential ◽

Motor Deficit ◽

Motor Deficits ◽

Brain Tumour Surgery

Abstract Muscle motor-evoked potentials are commonly monitored during brain tumour surgery in motor areas, as these are assumed to reflect the integrity of descending motor pathways, including the corticospinal tract. However, while the loss of muscle motor-evoked potentials at the end of surgery is associated with long-term motor deficits (muscle motor-evoked potential-related deficits), there is increasing evidence that motor deficit can occur despite no change in muscle motor-evoked potentials (muscle motor-evoked potential-unrelated deficits), particularly after surgery of non-primary regions involved in motor control. In this study, we aimed to investigate the incidence of muscle motor-evoked potential-unrelated deficits and to identify the associated brain regions. We retrospectively reviewed 125 consecutive patients who underwent surgery for peri-Rolandic lesions using intra-operative neurophysiological monitoring. Intraoperative changes in muscle motor-evoked potentials were correlated with motor outcome, assessed by the Medical Research Council scale. We performed voxel–lesion–symptom mapping to identify which resected regions were associated with short- and long-term muscle motor-evoked potential-associated motor deficits. Muscle motor-evoked potentials reductions significantly predicted long-term motor deficits. However, in more than half of the patients who experienced long-term deficits (12/22 patients), no muscle motor-evoked potential reduction was reported during surgery. Lesion analysis showed that muscle motor-evoked potential-related long-term motor deficits were associated with direct or ischaemic damage to the corticospinal tract, whereas muscle motor-evoked potential-unrelated deficits occurred when supplementary motor areas were resected in conjunction with dorsal premotor regions and the anterior cingulate. Our results indicate that long-term motor deficits unrelated to the corticospinal tract can occur more often than currently reported. As these deficits cannot be predicted by muscle motor-evoked potentials, a combination of awake and/or novel asleep techniques other than muscle motor-evoked potentials monitoring should be implemented.

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Neurophysiologic Mapping of Thalamocortical Tract in Asleep Craniotomies: Promising Results From an Early Experience

Operative Neurosurgery ◽

10.1093/ons/opaa330 ◽

2020 ◽

Author(s):

Mirela V Simon ◽

Daniel K Lee ◽

Bryan D Choi ◽

Pratik A Talati ◽

Jimmy C Yang ◽

...

Keyword(s):

General Anesthesia ◽

Corticospinal Tract ◽

Sensory Function ◽

Motor Deficit ◽

Motor Deficits ◽

Central Sulcus ◽

Postcentral Gyrus ◽

Subcortical Stimulation ◽

Subcortical Mapping

Abstract BACKGROUND Subcortical mapping of the corticospinal tract has been extensively used during craniotomies under general anesthesia to achieve maximal resection while avoiding postoperative motor deficits. To our knowledge, similar methods to map the thalamocortical tract (TCT) have not yet been developed. OBJECTIVE To describe a neurophysiologic technique for TCT identification in 2 patients who underwent resection of frontoparietal lesions. METHODS The central sulcus (CS) was identified using the somatosensory evoked potentials (SSEP) phase reversal technique. Furthermore, monitoring of the cortical postcentral N20 and precentral P22 potentials was performed during resection. Subcortical electrical stimulation in the resection cavity was done using the multipulse train (case #1) and Penfield (case #2) techniques. RESULTS Subcortical stimulation within the postcentral gyrus (case #1) and in depth of the CS (case #2), resulted in a sudden drop in amplitudes in N20 (case #1) and P22 (case #2), respectively. In both patients, the potentials promptly recovered once the stimulation was stopped. These results led to redirection of the surgical plane with avoidance of damage of thalamocortical input to the primary somatosensory (case #1) and motor regions (case #2). At the end of the resection, there were no significant changes in the median SSEP. Both patients had no new long-term postoperative sensory or motor deficit. CONCLUSION This method allows identification of TCT in craniotomies under general anesthesia. Such input is essential not only for preservation of sensory function but also for feedback modulation of motor activity.

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Intraoperative Motor Evoked Potential Alteration in Intracranial Tumor Surgery and Its Relation to Signal Alteration in Postoperative Magnetic Resonance Imaging

Neurosurgery ◽

10.1227/01.neu.0000371973.46234.46 ◽

2010 ◽

Vol 67 (2) ◽

pp. 302-313 ◽

Cited By ~ 67

Author(s):

Andrea Szelényi ◽

Elke Hattingen ◽

Stefan Weidauer ◽

Volker Seifert ◽

Ulf Ziemann

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Motor Cortex ◽

Evoked Potential ◽

Corticospinal Tract ◽

Motor Evoked Potential ◽

Motor Deficit ◽

Warning Sign ◽

Precentral Gyrus ◽

Resonance Imaging

Abstract OBJECTIVE To determine the degree to which the pattern of intraoperative isolated, unilateral alteration of motor evoked potential (MEP) in intracranial surgery was related to motor outcome and location of new postoperative signal alterations on magnetic resonance imaging (MRI). METHODS In 29 patients (age, 42.8 ± 18.2 years; 15 female patients; 25 supratentorial, 4 infratentorial procedures), intraoperative MEP alterations in isolation (without significant alteration in other evoked potential modalities) were classified as deterioration (> 50% amplitude decrease and/or motor threshold increase) or loss, respectively, or reversible and irreversible. Postoperative MRI was described for the location and type of new signal alteration. RESULTS New motor deficit was present in all 5 patients with irreversible MEP loss, in 7 of 10 patients with irreversible MEP deterioration, in 1 of 6 patients with reversible MEP loss, and in 0 of 8 patients with reversible MEP deterioration. Irreversible compared with reversible MEP alteration was significantly more often correlated with postoperative motor deficit (P < .0001). In 20 patients, 22 new signal alterations affected 29 various locations (precentral gyrus, n = 5; corticospinal tract, n = 19). Irreversible MEP alteration was more often associated with postoperative new signal alteration in MRI compared with reversible MEP alteration (P = .02). MEP loss was significantly more often associated with subcortically located new signal alteration (P = .006). MEP deterioration was significantly more often followed by new signal alterations located in the precentral gyrus (P = .04). CONCLUSION MEP loss bears a higher risk than MEP deterioration for postoperative motor deficit resulting from subcortical postoperative MR changes in the corticospinal tract. In contrast, MEP deterioration points to motor cortex lesion. Thus, even MEP deterioration should be considered a warning sign if surgery close to the motor cortex is performed.

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