The motor-evoked potential threshold evaluated by tractography and electrical stimulation

2009 ◽  
Vol 111 (4) ◽  
pp. 785-795 ◽  
Author(s):  
Kyousuke Kamada ◽  
Tomoki Todo ◽  
Takahiro Ota ◽  
Kenji Ino ◽  
Yoshitaka Masutani ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Stimulus Intensity ◽  
Evoked Potential ◽  
Diffusion Tensor ◽  
Motor Evoked Potential ◽  
Motor Area ◽  
Brain Functions ◽  
The Neural Networks ◽  
Hand Motor Area ◽  
Fiber Stimulation

Object To validate the corticospinal tract (CST) illustrated by diffusion tensor imaging, the authors used tractography-integrated neuronavigation and direct fiber stimulation with monopolar electric currents. Methods Forty patients with brain lesions adjacent to the CST were studied. During the operation, the motor responses (motor evoked potential [MEP]) elicited at the hand by the cortical stimulation to the hand motor area were continuously monitored, maintaining the consistent stimulus intensity (mean 15.1 ± 2.21 mA). During lesion resection, direct fiber stimulation was applied to elicit MEP (referred to as fiber MEP) to identify the CST functionally. The threshold intensity for the fiber MEP was determined by searching for the best stimulus point and changing the stimulus intensity. The minimum distance between the resection border and illustrated CST was measured on postoperative isotropic images. Results Direct fiber stimulation demonstrated that tractography accurately reflected anatomical CST functioning. There were strong correlations between stimulus intensity for the fiber MEP and the distance between the CST and the stimulus points. The results indicate that the minimum stimulus intensity of 20, 15, 10, and 5 mA had stimulus points ~ 16, 13.2, 9.6, and 4.8 mm from the CST, respectively. The convergent calculation formulated 1.8 mA as the electrical threshold of the CST for the fiber MEP, which was much smaller than that of the hand motor area. Conclusions The investigators found that diffusion tensor imaging–based tractography is a reliable way to map the white matter connections in the entire brain in clinical and basic neuroscience applications. By combining these techniques, investigating the cortical-subcortical connections in the human CNS could contribute to elucidating the neural networks of the human brain and shed light on higher brain functions.

scholarly journals Prediction of recovery from supplementary motor area syndrome after brain tumor surgery: preoperative diffusion tensor tractography analysis and postoperative neurological clinical course

2018 ◽  
Vol 44 (6) ◽  
pp. E3 ◽  
Author(s):  
Kazunori Oda ◽  
Fumio Yamaguchi ◽  
Hiroyuki Enomoto ◽  
Tadashi Higuchi ◽  
Akio Morita
Keyword(s):  
Diffusion Tensor Imaging ◽  
Corpus Callosum ◽  
Supplementary Motor Area ◽  
Diffusion Tensor ◽  
Motor Area ◽  
Primary Motor Area ◽  
Sma Syndrome ◽  
Interhemispheric Connectivity ◽  
Recovery Group ◽  
Diffusion Tensor Imaging Tractography

OBJECTIVEPrevious studies have suggested a correlation between interhemispheric sensorimotor networks and recovery from supplementary motor area (SMA) syndrome. In the present study, the authors examined the hypothesis that interhemispheric connectivity of the primary motor cortex in one hemisphere with the contralateral SMA may be important in the recovery from SMA syndrome. Further, they posited that motor cortical fiber connectivity with the SMA is related to the severity of SMA syndrome.METHODSPatients referred to the authors’ neurological surgery department were retrospectively analyzed for this study. All patients with tumors involving the unilateral SMA region, without involvement of the primary motor area, and diagnosed with SMA syndrome in the postoperative period were eligible for inclusion. Preoperative diffusion tensor imaging tractography (DTT) was used to examine the number of fiber tracts (NFidx) connecting the contralateral SMA to the ipsilateral primary motor area via the corpus callosum. Complete neurological examination had been performed in all patients in the pre- and postoperative periods. All patients were divided into two groups: those who recovered from SMA syndrome in ≤ 7 days (early recovery group) and those who recovered in ≥ 8 days (late recovery group). Differences between the two groups were assessed using the Student t-test and the chi-square test.RESULTSEleven patients (10 men, 1 woman) were included in the study. All patients showed transient postoperative motor deficits because of SMA syndrome. Tractography data revealed NFidx from the contralateral SMA to the ipsilateral primary motor area via the corpus callosum. The mean tumor volume (early 27.87 vs late 50.91 cm3, p = 0.028) and mean NFidx (early 8923.16 vs late 4726.4, p = 0.002) were significantly different between the two groups. Fisher exact test showed a significant difference in the days of recovery from SMA syndrome between patients with an NFidx > 8000 and those with an NFidx < 8000.CONCLUSIONSDiffusion tensor imaging tractography may be useful for predicting the speed of recovery from SMA syndrome. To the authors’ knowledge, this is the first DTT study to identify interhemispheric connectivity of the SMA in patients with brain tumors.

scholarly journals Novel use of Diffusion Tensor Imaging to Delineate the Rat Basolateral Amygdala

2018 ◽  
Author(s):  
Andre Obenaus ◽  
Eli Kinney-Lang ◽  
Amandine Jullienne ◽  
Elizabeth Haddad ◽  
Duke Shereen ◽  
...  
Keyword(s):  
Diffusion Tensor Imaging ◽  
Basolateral Amygdala ◽  
Diffusion Tensor ◽  
Brain Regions ◽  
The Novel ◽  
Brain Functions ◽  
Novel Approach ◽  
Basolateral Nucleus ◽  
Adaptive Processes ◽  
Summary Statement

AbstractThe amygdaloid complex, including the basolateral nucleus (BLA) contributes crucially to emotional and cognitive brain functions, and is thus a major target of research in both humans and rodents. However, delineating structural amygdala plasticity in both normal and disease-related contexts using neuroimaging has been hampered by the difficulty of unequivocally identifying the boundaries of the BLA. This challenge is a result of poor contrast between BLA and the surrounding gray matter, including other amygdala nuclei. Here we describe a novel DTI approach to enhance contrast, enabling optimal identification of BLA in rodent brain from MR images. We employed this methodology together with a slice-shifting approach to measure BLA volume. We then validated the results by direct comparison to both histological and cellular-identity (parvalbumin)-based conventional techniques for defining BLA in the same brains used for MRI. We also confirmed the BLA region using DTI based tractography. The novel approach used here enables accurate and reliable delineation of BLA. Because this nucleus is involved in, and is changed by, developmental, degenerative and adaptive processes, the instruments provided here should be highly useful to a broad range of neuroimaging studies. Finally, the principles used here are readily applicable to numerous brain regions and across species.Summary StatementUse of MRI directionally encoded diffusion tensor imaging (DTI) can delineate the basolateral amygdala (BLA) and volumes derived from DTI were found to match those obtained using histological methods. Our approach can be used to identify the BLA.

scholarly journals Utility and the Limit of Motor Evoked Potential Monitoring for Preventing Complications in Surgery for Cerebral Arteriovenous Malformation

2010 ◽  
Vol 67 (3) ◽  
pp. ons222-ons228 ◽  
Author(s):  
Tsuyoshi Ichikawa ◽  
Kyouichi Suzuki ◽  
Tatsuya Sasaki ◽  
Masato Matsumoto ◽  
Jun Sakuma ◽  
...  
Keyword(s):  
Blood Flow ◽  
Arteriovenous Malformation ◽  
Evoked Potential ◽  
Corticospinal Tract ◽  
Motor Evoked Potential ◽  
Internal Capsule ◽  
Motor Area ◽  
Precentral Gyrus ◽  
Venous Infarction ◽  
Direct Injury

Abstract OBJECTIVE: To evaluate the usefulness of motor evoked potential (MEP) monitoring and mapping in arteriovenous malformation surgery. METHODS: Intraoperative MEP monitoring was performed in 21 patients whose AVMs were located near the motor area or fed by arteries related to the corticospinal tract to detect blood flow insufficiency and/or direct injury to the corticospinal tract and/or to map the motor area. RESULTS: In 4 of 16 patients monitored for blood flow insufficiency, the MEP changed intraoperatively. In 2 patients, the changes were attributable to temporary occlusion of the feeding artery (anterior choroidal or lenticulostriate artery): 1 patient had a venous infarction around the internal capsule caused by thrombosis of the draining vein and the other bled intraoperatively from the nidus. In 17 patients, the MEP was monitored to rule out direct injury. In 1 patient, the MEP changed on coagulation of fragile vessels around the nidus in the precentral gyrus; it recovered after coagulation was discontinued. In 1 of 5 patients with MEP changes, the MEP did not recover; permanent hemiparesis developed in this patient because of venous infarction. In 1 of 11 patients subjected to MEP mapping of the motor area, we found translocation to the postcentral sulcus. CONCLUSION: In arteriovenous malformation surgery, MEP monitoring facilitates the detection of blood flow insufficiency and/or direct injury of the corticospinal tract and mapping of the motor area. It contributes to reducing the incidence of postoperative motor paresis.

scholarly journals Intraoperative subcortical motor evoked potential stimulation: how close is the corticospinal tract?

2015 ◽  
Vol 123 (3) ◽  
pp. 711-720 ◽  
Author(s):  
Ehab Shiban ◽  
Sandro M. Krieg ◽  
Bernhard Haller ◽  
Niels Buchmann ◽  
Thomas Obermueller ◽  
...  
Keyword(s):  
Evoked Potential ◽  
Corticospinal Tract ◽  
Diffusion Tensor ◽  
Motor Evoked Potential ◽  
Motor Deficits ◽  
Subtotal Resection ◽  
Stimulation Intensity ◽  
Postoperative Mri ◽  
Subcortical Stimulation ◽  
Measured Distance

OBJECT Subcortical stimulation is a method used to evaluate the distance from the stimulation site to the corticospinal tract (CST) and to decide whether the resection of an adjacent lesion should be terminated to prevent damage to the CST. However, the correlation between stimulation intensity and distance to the CST has not yet been clearly assessed. The objective of this study was to investigate the appropriate correlation between the subcortical stimulation pattern and the distance to the CST. METHODS Monopolar subcortical motor evoked potential (MEP) mapping was performed in addition to continuous MEP monitoring in 37 consecutive patients with lesions located in motor-eloquent locations. The proximity of the resection cavity to the CST was identified by subcortical MEP mapping. At the end of resection, the point at which an MEP response was still measurable with minimal subcortical MEP intensity was marked with a titanium clip. At this location, different stimulation paradigms were executed with cathodal or anodal stimulation at 0.3-, 0.5-, and 0.7-msec pulse durations. Postoperatively, the distance between the CST as defined by postoperative diffusion tensor imaging fiber tracking and the titanium clip was measured. The correlation between this distance and the subcortical MEP electrical charge was calculated. RESULTS Subcortical MEP mapping was successful in all patients. There were no new permanent motor deficits. Transient new postoperative motor deficits were observed in 14% (5/36) of cases. Gross-total resection was achieved in 75% (27/36) and subtotal resection (> 80% of tumor mass) in 25% (9/36) of cases. Stimulation intensity with various pulse durations as well as current intensity was plotted against the measured distance between the CST and the titanium clip on postoperative MRI using diffusion-weighted imaging fiberitracking tractography. Correlational and regression analyses showed a nonlinear correlation between stimulation intensity and the distance to the CST. Cathodal stimulation appeared better suited for subcortical stimulation. CONCLUSIONS Subcortical MEP mapping is an excellent intraoperative method to determine the distance to the CST during resection of motor-eloquent lesions and is highly capable of further reducing the risk of a new neurological deficit.

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