Tag: Motor evoked potential

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Application of intraoperative motor evoked potential monitoring during giant internal carotid artery aneurysm surgery using prolonged temporary occlusion

Application of intraoperative motor evoked potential monitoring during giant internal carotid artery aneurysm surgery using prolonged temporary occlusion

Acta Neurochir (2015) 157:1833–1840

Clipping and bypass surgery are common therapeutic options for the management of giant internal carotid artery (ICA) aneurysms. However, potential ischemic risks may be exaggerated by prolonged temporary occlusion (PTO) during the surgery. Monitoring motor-evoked potentials (MEPs) is a sensitive technique for detecting potential ischemia intraoperatively. This preliminary study was designed to evaluate the effectiveness of applying MEP monitoring during giant ICA aneurysm surgery using PTO.

Methods From July 2009 to July 2012, 11 patients with giant ICA aneurysms who could not pass the preoperative hemodynamic evaluations were enrolled in this study. MEP monitoring was utilized intraoperatively in all cases. Clipping was performed if there were no significant MEP changes under PTO. A variant extracranial-to-intracranial (EC-IC) bypass was performed if there was reproducible loss of MEP signals after PTO or unclippable anatomic features.

Results Five patients underwent clipping alone and six underwent bypass. There were no significant differences in baseline clinical data between the two groups. The overall percentage of patients with good outcomes (Glasgow Outcome Score≥4) improved from 72.7 % (8/11) postoperatively to 90.9 % (10/11) after 26.0±9.5 months of follow-up. There were no significant differences between the clipping and bypass groups regarding short- and long-term outcomes (p=0.545 and p=1.000).

Conclusions MEP monitoring is useful for evaluating the safety of PTO, surgical strategy, and outcomes of giant ICA aneurysm surgery. Direct clipping during safe PTO under intraoperative MEP monitoring is applicable for giant ICA aneurysms. Its use achieved favorable outcomes by indicating the need for bypass surgery.

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Surgical results of tumor resection using tractography-integrated navigation-guided fence-post catheter techniques and motor-evoked potentials for preservation of motor function in patients with glioblastomas near the pyramidal tracts

Surgical results of tumor resection using tractography-integrated

Neurosurg Rev (2015) 38:293–307

The current optimal surgery for glioblastomas (GBMs) near the pyramidal tract (PT) is to remove as much tumor as possible and to preserve motor function. The purpose of this study is to investigate the usefulness of tractography integrated navigation-guided fence-post catheter techniques and motor-evoked potentials (MEPs) for preserving postoperative motor function after GBM surgery.

We retrospectively examined 49 patients who underwent resection for GBM near the PT. Diffusion tensor (DT) imaging-based tractography of the PT was performed preoperatively and integrated into the navigation system. When possible, silicon catheters were used as “fence-posts” and were inserted along the tumor boundaries, avoiding the PT, before tumor removal using the navigation system (fence-post catheter techniques). Cortical and subcortical MEPs were also monitored during resection of the tumor. Fence-post catheter techniques using a tractography integrated navigation system were used in 45 of 49 patients.

This technique enabled placement of the catheters, avoided the motor pathways, and allowed easier resection of the tumors. Tumors near the PT were resected using subcortical and cortical MEPs. The amplitudes of cortical MEPs after tumor removal were maintained at over 33 % of those obtained before resection.

Thirty-six patients showed obvious responses of subcortical MEPs at ≤20 mA. The degree of resection was gross total in 21 patients, subtotal in 21, and partial in seven. One month after surgery, only one patient showed worsened motor function.

Therefore, fence-post catheter techniques using a tractography-integrated navigation system and MEPs may contribute to preserving motor function after surgery for GBMs that are near the PT.

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Continuous dynamic mapping of the corticospinal tract during surgery of motor eloquent brain tumors

Continuous dynamic subcortical mapping

J Neurosurg 120:1015–1024, 2014

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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Cervical decompression and reconstruction without intraoperative neurophysiological monitoring

J Neurosurg Spine 16:107–113, 2012. DOI: 10.3171/2011.10.SPINE11199

The primary goal of this study was to review the immediate postoperative neurological function in patients surgically treated for symptomatic cervical spine disease without intraoperative neurophysiological monitoring. The secondary goal was to assess the economic impact of intraoperative monitoring (IOM) in this patient population.

Methods. This study is a retrospective review of 720 consecutively treated patients who underwent cervical spine procedures. The patients were identified and the data were collected by individuals who were not involved in their care.

Results. A total of 1534 cervical spine levels were treated in 720 patients using anterior, posterior, and combined (360°) approaches. Myelopathy was present preoperatively in 308 patients. There were 185 patients with increased signal intensity within the spinal cord on preoperative T2-weighted MR images, of whom 43 patients had no clinical evidence of myelopathy. Three patients (0.4%) exhibited a new neurological deficit postoperatively. Of these patients, 1 had a preoperative diagnosis of radiculopathy, while the other 2 were treated for myelopathy. The new postoperative deficits completely resolved in all 3 patients and did not require additional treatment. The Current Procedural Terminology (CPT) codes for IOM during cervical decompression include 95925 and 95926 for somatosensory evoked potential monitoring of the upper and lower extremities, respectively, as well as 95928 and 95929 for motor evoked potential monitoring of the upper and lower extremities. In addition to the charge for the baseline [monitoring] study, patients are charged hourly for ongoing electrophysiology testing and monitoring using the CPT code 95920. Based on these codes and assuming an average of 4 hours of monitoring time per surgical case, the savings realized in this group of patients was estimated to be $1,024,754.

Conclusions. With the continuing increase in health care costs, it is our responsibility as providers to minimize expenses when possible. This should be accomplished without compromising the quality of care to patients. This study demonstrates that decompression and reconstruction for symptomatic cervical spine disease without IOM may reduce the cost of treatment without adversely impacting patient safety.

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Motor-evoked potentials (MEP) during brainstem surgery to preserve corticospinal function

Acta Neurochir (2011) 153:1753–1759. DOI 10.1007/s00701-011-1065-7

Brainstem surgery bears a risk of damage to the corticospinal tract (CST). Motor-evoked potentials (MEPs) are used intraoperatively to monitor CST function in order to detect CST damage at a reversible stage and thus impede permanent neurological deficits. While the method of MEP is generally accepted, warning criteria in the context of brainstem surgery still have to be agreed on.

Method We analyzed 104 consecutive patients who underwent microsurgical resection of lesions affecting the brainstem. Motor grade was documented prior to surgery, early postoperatively and at discharge. A baseline MEP stimulation intensity threshold was defined and intraoperative testing aimed to keep MEP response amplitude constant. MEPs were considered deteriorated and the surgical team was notified whenever the threshold was elevated by ≥20 mA or MEP response fell under 50%.

Findings On the first postoperative day, 18 patients experienced new paresis that resolved by discharge in 11. MEPs deteriorated in 39 patients, and 16 of these showed new postoperative paresis, indicating a 41% risk of new paresis. In the remaining 2/18 patients, intraoperative MEPs were stable, although new paresis appeared postoperatively. In one of these patients, intraoperative hemorrhage caused postoperative swelling, and the new motor deficit persisted until discharge. Of all 104 patients, 7 deteriorated in motor grade at discharge, 92 remained unchanged, and 5 patients have improved.

Conclusions Adjustment of surgical strategy contributed to good motor outcome in 33/39 patients. MEP monitoring may help significantly to prevent motor deficits during demanding neurosurgical procedures on the brainstem.

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

Neurosurgery 67[ONS Suppl 1]:ons222-ons228, 2010 DOI: 10.1227/01.NEU.0000374696.84827.22

OBJECTIVE: To evaluate the usefulness of motor evoked potential (MEP) monitoring andmapping 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.

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