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P211: MEP threshold evaluated by deterministic tractography and subcortical stimulation
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
disturbance in LSS and compare these to those observed in healthy control subjects. Furthermore, we aimed to characterize the effects of therapeutic interventions using the parameter identification approach. Methods: 11 LSS patients were evaluated pre and post surgery and were compared to 15 age-matched healthy subjects. Postural control was assessed using external disturbances (tilting platform). We then calculated transfer functions between input (platform tilt) and output (body lean) and identified abnormal postural control mechanisms using a model-based approach. Results: Amplitude, velocity and frequency range of LSS patients’ spontaneous sway is larger than that of healthy control subjects signaling larger “internal noise” of the system. Characteristic features of patients’ transfer functions indicate abnormalities of postural control mechanisms. In particular, velocity feedback and sensor weighting seems to be affected. Surgery mainly influenced spontaneous sway, whereas transfer functions were less affected. Conclusion: Postural control deficits in LSS patients are characterized by larger internal noise, altered velocity feedback control, and altered sensor fusion. The effects of spinal surgery and physiotherapy on velocity feedback and sensor fusion showed a clear tendency towards the values identified in healthy subjects. Surprisingly, these therapeutic effects clearly correlated with clinical measures of balance and gait stability. Measures of internal noise were significantly affected by therapeutic interventions. However, these measures poorly correlated with clinical scales of stability. We conclude that model-based parameters of postural control extracted from transfer functions of patients’ reactions allow for a precise picture of the individual postural control deficit. Parameters related to spontaneous sway, i.e. internal noise represent a more global, and less specific picture of abnormal postural control.
S103
was applied to elicit MEP (fiber-MEP) to functionally identify CST. The threshold intensity for the fiber-MEP was determined by searching for the best stimulus point and changing stimulus intensity. The minimum distance between the resection border and illustrated CST was measured on postoperative isotropic images. Results: Direct fiber stimulation demonstrated that CST-tractography accurately reflected anatomical CST functioning. There were strong correlations between stimulus intensity for the fiber-MEP and the distance between CST and the stimulus points. The results indicate that the minimum stimulus intensity of 20, 15, 10 and 5mA had stimulus points of approximately 16, 13.2, 9.6 and 4.8 mm far from CST, respectively. The convergent calculation formulated 1.8mA, which was much smaller than that of the hand motor area. Interpretation: DTI-based tractography is a reliable way to map the white matter connections in the entire brain. By combining these techniques, investigating the cortico-subcortical connections in the human central nervous system could contribute to elucidating the neural networks of the human brain and shed light on higher brain functions.
P210 Preoperative functional mapping for rolandic brain tumor surgery C. Terranova, R. Maggio, V. Rizzo, F. Angileri, A. Conti, A. Germano’, P. Girlanda, F. Tomasello, A. Quartarone University of Messina, Neuroscience, messina, Italy Question: The resection of tumors within or close to eloquent motor areas is usually guided by the compromise between the maximal allowed resection and preservation of neurological functions. Navigated transcranial magnetic stimulation (nTMS) is an emerging technology that can be used for preoperative mapping of the motor cortex. In the present study we report the experience gained during the first year of systematic use of nTMS. Methods: We performed pre-surgical mapping by using nTMS in 17 patients with lesions in or close to the precentral gyrus. The study was conducted on consecutive patients scheduled for surgical treatment. Preoperative mapping was performed with the eXimia navigated brain stimulation system. Results: nTMS allowed to exactly localize the motor cortex in 88.2% of cases. In 70.6% it provided the surgeon with new unexpected information about functional anatomy of the motor area, influencing the pre-operative planning. Moreover, in 29.4% these functional information had a clear impact on surgery, making necessary a change of surgical strategy to avoid damage to the motor cortex. Conclusions: nTMS has a large benefit in the treatment of rolandic brain tumors. It adds important information about spatial relationship between functional motor cortex and the tumor and reduces surgical-related postoperative motor deficits.
Figure 1. (A) Postoperative image demonstrating the resection cavity (arrowhead) and ischemic lesions by surgical manipulation as high intense areas. (B) Isotropic image, (C) Volume calculation by segmentation of the resection cavity and CST. (D) Threedimensional measurement of the minimum distance between the resection cavity and CST.
P211 MEP threshold evaluated by deterministic tractography and subcortical stimulation K. Kamada 1 , N. Kunii 2 , K. Kawai 2 , N. Saito 2 1 Asahikawa AMedical University, Neurosurgery, Asahikawa, Japan; 2 The University of Tokyo, Neurosurgery, Tokyo, Japan Objective: To validate the corticospinal tract (CST) illustrated by diffusion tensor imaging (DTI), we used CST-tractography integrated neuronavigation and direct fiber stimulation with monopolar electric currents. Methods: Forty patients with brain lesions adjacent to CST were studied. During the operation, the motor responses (motor evoked potential; MEP) at the hand by the cortical stimulation to the hand motor area were continuously monitored. During lesion resection, direct fiber stimulation
Figure 2. Scatter plot between the stimulus intensity of direct fiber stimulation and the distance between CST and the stimulus points on the postoperative isotopic images. Note that the minimum stimulus intensity with 20, 15, 10 and 5mA indicated that the stimulus point was approximately 16.0, 13.2, 9.6 and 4.8mm far from CST, respectively.
Reference: [1] Kamada K, Todo T, Ota T, et al. J Neurosurg 2009 Oct;111(4):785-95.
disturbance in LSS and compare these to those observed in healthy control subjects. Furthermore, we aimed to characterize the effects of therapeutic interventions using the parameter identification approach. Methods: 11 LSS patients were evaluated pre and post surgery and were compared to 15 age-matched healthy subjects. Postural control was assessed using external disturbances (tilting platform). We then calculated transfer functions between input (platform tilt) and output (body lean) and identified abnormal postural control mechanisms using a model-based approach. Results: Amplitude, velocity and frequency range of LSS patients’ spontaneous sway is larger than that of healthy control subjects signaling larger “internal noise” of the system. Characteristic features of patients’ transfer functions indicate abnormalities of postural control mechanisms. In particular, velocity feedback and sensor weighting seems to be affected. Surgery mainly influenced spontaneous sway, whereas transfer functions were less affected. Conclusion: Postural control deficits in LSS patients are characterized by larger internal noise, altered velocity feedback control, and altered sensor fusion. The effects of spinal surgery and physiotherapy on velocity feedback and sensor fusion showed a clear tendency towards the values identified in healthy subjects. Surprisingly, these therapeutic effects clearly correlated with clinical measures of balance and gait stability. Measures of internal noise were significantly affected by therapeutic interventions. However, these measures poorly correlated with clinical scales of stability. We conclude that model-based parameters of postural control extracted from transfer functions of patients’ reactions allow for a precise picture of the individual postural control deficit. Parameters related to spontaneous sway, i.e. internal noise represent a more global, and less specific picture of abnormal postural control.
S103
was applied to elicit MEP (fiber-MEP) to functionally identify CST. The threshold intensity for the fiber-MEP was determined by searching for the best stimulus point and changing stimulus intensity. The minimum distance between the resection border and illustrated CST was measured on postoperative isotropic images. Results: Direct fiber stimulation demonstrated that CST-tractography accurately reflected anatomical CST functioning. There were strong correlations between stimulus intensity for the fiber-MEP and the distance between CST and the stimulus points. The results indicate that the minimum stimulus intensity of 20, 15, 10 and 5mA had stimulus points of approximately 16, 13.2, 9.6 and 4.8 mm far from CST, respectively. The convergent calculation formulated 1.8mA, which was much smaller than that of the hand motor area. Interpretation: DTI-based tractography is a reliable way to map the white matter connections in the entire brain. By combining these techniques, investigating the cortico-subcortical connections in the human central nervous system could contribute to elucidating the neural networks of the human brain and shed light on higher brain functions.
P210 Preoperative functional mapping for rolandic brain tumor surgery C. Terranova, R. Maggio, V. Rizzo, F. Angileri, A. Conti, A. Germano’, P. Girlanda, F. Tomasello, A. Quartarone University of Messina, Neuroscience, messina, Italy Question: The resection of tumors within or close to eloquent motor areas is usually guided by the compromise between the maximal allowed resection and preservation of neurological functions. Navigated transcranial magnetic stimulation (nTMS) is an emerging technology that can be used for preoperative mapping of the motor cortex. In the present study we report the experience gained during the first year of systematic use of nTMS. Methods: We performed pre-surgical mapping by using nTMS in 17 patients with lesions in or close to the precentral gyrus. The study was conducted on consecutive patients scheduled for surgical treatment. Preoperative mapping was performed with the eXimia navigated brain stimulation system. Results: nTMS allowed to exactly localize the motor cortex in 88.2% of cases. In 70.6% it provided the surgeon with new unexpected information about functional anatomy of the motor area, influencing the pre-operative planning. Moreover, in 29.4% these functional information had a clear impact on surgery, making necessary a change of surgical strategy to avoid damage to the motor cortex. Conclusions: nTMS has a large benefit in the treatment of rolandic brain tumors. It adds important information about spatial relationship between functional motor cortex and the tumor and reduces surgical-related postoperative motor deficits.
Figure 1. (A) Postoperative image demonstrating the resection cavity (arrowhead) and ischemic lesions by surgical manipulation as high intense areas. (B) Isotropic image, (C) Volume calculation by segmentation of the resection cavity and CST. (D) Threedimensional measurement of the minimum distance between the resection cavity and CST.
P211 MEP threshold evaluated by deterministic tractography and subcortical stimulation K. Kamada 1 , N. Kunii 2 , K. Kawai 2 , N. Saito 2 1 Asahikawa AMedical University, Neurosurgery, Asahikawa, Japan; 2 The University of Tokyo, Neurosurgery, Tokyo, Japan Objective: To validate the corticospinal tract (CST) illustrated by diffusion tensor imaging (DTI), we used CST-tractography integrated neuronavigation and direct fiber stimulation with monopolar electric currents. Methods: Forty patients with brain lesions adjacent to CST were studied. During the operation, the motor responses (motor evoked potential; MEP) at the hand by the cortical stimulation to the hand motor area were continuously monitored. During lesion resection, direct fiber stimulation
Figure 2. Scatter plot between the stimulus intensity of direct fiber stimulation and the distance between CST and the stimulus points on the postoperative isotopic images. Note that the minimum stimulus intensity with 20, 15, 10 and 5mA indicated that the stimulus point was approximately 16.0, 13.2, 9.6 and 4.8mm far from CST, respectively.
Reference: [1] Kamada K, Todo T, Ota T, et al. J Neurosurg 2009 Oct;111(4):785-95.