Patients Undergoing Tumor Surgery Research Articles

"Non-Eloquent" brain regions predict neuropsychological outcome in tumor patients undergoing awake craniotomy.

Supratotal resection of primary brain tumors is being advocated especially when involving "non-eloquent" tissue. However, there is extensive neuropsychological data implicating functions critical to higher cognition in areas considered "non-eloquent" by most surgeons. The goal of the study was to determine pre-surgical brain regions that would be predictive of cognitive outcome at 4-6 months post-surgery. Cortical reconstruction and volumetric segmentation were performed with the FreeSurfer-v6.0 image analysis suite. Linear regression models were used to regress cortical volumes from both hemispheres, against the total cognitive z-score to determine the relationship between brain structure and broad cognitive functioning while controlling for age, sex, and total segmented brain volume. We identified 62 consecutive patients who underwent planned awake resections of primary (n = 55, 88%) and metastatic at the University of New Mexico Hospital between 2015 and 2019. Of those, 42 (23 males, 25 left hemispheric lesions) had complete pre and post-op neuropsychological data available and were included in this study. Overall, total neuropsychological functioning was somewhat worse (p = 0.09) at post-operative neuropsychological outcome (Mean = -.20) than at baseline (Mean = .00). Patients with radiation following resection (n = 32) performed marginally worse (p = .036). We found that several discrete brain volumes obtained pre-surgery predicted neuropsychological outcome post-resection. For the total sample, these volumes included: left fusiform, right lateral orbital frontal, right post central, and right paracentral regions. Regardless of lesion lateralization, volumes within the right frontal lobe, and specifically right orbitofrontal cortex, predicted neuropsychological difference scores. The current study highlights the gaps in our current understanding of brain eloquence. We hypothesize that the volume of tissue within the right lateral orbital frontal lobe represents important cognitive reserve capacity in patients undergoing tumor surgery. Our data also cautions the neurosurgeon when considering supratotal resections of tumors that do not extend into areas considered "non-eloquent" by current standards.

Pineal anlage tumor: clinical and diagnostic features, and rationales for treatment

PurposeTo provide a treatment-focused review and develop basic treatment guidelines for patients diagnosed with pineal anlage tumor (PAT).MethodsProspectively collected data of three patients with pineal anlage tumor from Germany was combined with clinical details and treatment information from 17 published cases.ResultsOverall, 20 cases of PAT were identified (3 not previously reported German cases, 17 cases from published reports). Age at diagnosis ranged from 0.3 to 35.0 (median: 3.2 ± 7.8) years. All but three cases were diagnosed before the age of three years. For three cases, metastatic disease at initial staging was described. All patients underwent tumor surgery (gross-total resection: 9, subtotal resection/biopsy: 9, extent of resection unknown: 2). 15/20 patients were alive at last follow-up. Median follow-up for 10/15 surviving patients with available follow-up and treatment data was 2.4 years (0.3–6.5). Relapse was reported for 3 patients within 0.8 years after diagnosis. Five patients died, 3 after relapse and 2 from early postoperative complications. Two-year-progression-free- and -overall survival were 65.2 ± 12.7% and 49.2 ± 18.2%, respectively. All 4 patients who received intensive chemotherapy including high-dose chemotherapy combined with radiotherapy (2 focal, 2 craniospinal [CSI]) had no recurrence. Focal radiotherapy- and CSI-free survival rates in 13 evaluable patients were 46.2% (6/13) and 61.5% (8/13), respectively.ConclusionPAT is an aggressive disease mostly affecting young children. Therefore, adjuvant therapy using intensive chemotherapy and considering radiotherapy appears to comprise an appropriate treatment strategy. Reporting further cases is crucial to evaluate distinct treatment strategies.

Enhanced recovery and same-day discharge after brain tumor surgery under general anesthesia: initial experience with Hospital-at-Home-based postoperative follow-up.

The objective of this study was to describe the outcomes of outpatient oncological neurosurgery (OON) in a European clinical setting and to compare them with the conventional inpatient protocol. Patients who had undergone OON (either tumor removal or biopsy) at the authors' center since 2019 were analyzed. A matched cohort of patients was selected from patients undergoing tumor surgery in the same period. Collected data included patient demographics, postoperative progress, specific location of the target lesion, and the procedure performed. There were 18 patients in the case group and 59 patients in the control group. The outpatient surgeries had a same-day discharge rate of 89%, and all ambulatory patients successfully completed the Enhanced Recovery After Surgery program within 6.24 hours of the procedure. All ambulatory patients underwent Hospital-at-Home postoperative follow-up for an average of 4.12 days. Radiological complications were present in 11% of the case group and 8% of the control group. Postoperative neurological deficit occurred in 6% of the same-day discharge group and 3% of the control group. Among the patients in the control group, 3% suffered from postoperative seizures, whereas no seizures were observed in the case group. These differences were not statistically significant. General anesthesia-related complications were not observed in any of the patients. The authors' findings demonstrate that Enhanced Recovery After Surgery protocols and same-day discharge craniotomy for tumor resection and image-guided biopsy under general anesthesia, when patients are carefully selected, can be safely performed with excellent outcomes in a European clinical setting. The OON program proved to be a viable alternative to conventional hospitalization, showing comparable safety records and offering advantages in terms of patient recovery.

Effect of Inhalation Anesthetics on Tumor Metastasis.

Many factors affect the prognosis of patients undergoing tumor surgery, and anesthesia is one of the potential influencing factors. In general anesthesia, inhalation anesthesia is widely used in the clinic because of its strong curative effect and high controllability. However, the effect of inhalation anesthetics on the tumor is still controversial. More and more research has proved that inhalation anesthetics can intervene in local recurrence and distant metastasis of tumor by acting on tumor biological behavior, immune response, and gene regulation. In this paper, we reviewed the research progress of diverse inhalation anesthetics promoting or inhibiting cancer in the critical events of tumor recurrence and metastasis, and compared the effects of inhalation anesthetics on patients' prognosis in clinical studies, to provide theoretical reference for anesthesia management of patients undergoing tumor surgery.

Effect of Dexmedetomidine on Perioperative Stress Response and Immune Function in Patients With Tumors

Objective:This study aims to investigate the effect of dexmedetomidine on perioperative stress response and immune function in patients with tumors.Methods:Sixty patients who underwent selective radical gastrectomy for cancer were randomly divided into 3 groups: remifentanil group (group R), dexmedetomidine group (group D), and sufentanil group (group S). Remifentanil, dexmedetomidine, and sufentanil were used as general anesthetics. Endotracheal intubation and mechanical ventilation were performed after the spontaneous respiration disappeared. Then, the data were recorded, and blood samples were collected at all time points.Results:The heart rate significantly increased (P < 0.05) at T1 in group S, and both heart rate and mean arterial pressure significantly increased (P < 0.05) in group R when compared to group D. The heart rate significantly increased (P < 0.05) at T2 in group S and group R. Furthermore, the heart rate significantly increased (P < 0.05) at T3 and T4 in group S and group R. Intra-group comparison: The heart rate at T1–T4 and mean arterial pressure at T1–T4 significantly increased (P < 0.05) in group S, and the heart rate at T1 and T4, and mean arterial pressure at T2–T4 significantly increased (P < 0.05) in group R when compared to T0. The serum IL-6, IFN-γ, and β-EP significantly increased (P < 0.05) at T0’ in group S and group R when compared to group D. Blood glucose, and serum IL-10, IFN-γ, and β-EP significantly increased (P < 0.05), while IL-18 significantly decreased (P < 0.05) at T1’ in group S and group R.Conclusion:Continuous infusion of dexmedetomidine in combination with the inhalation of sevoflurane is superior to sevoflurane + remifentanil or sufentanil in patients undergoing tumor surgery.

Surgical complication and postoperative pulmonary function in patients undergoing tumor surgery with thoracic wall resection.

Postoperative complications of thoracic wall resection include respiratory complications, skin necrosis and infection. The aim of the present study was to examine postoperative complications in patients who required combined thoracic wall resection during the surgical removal of a tumor. The present study included 68 patients; there were 50 patients with lung tumors and 18 patients with musculoskeletal tumors. The clinical factors associated with complications were compared between the two groups. Preoperative and postoperative pulmonary function tests were performed to examine the residual pulmonary function in 16 patients. Thoracic cage reconstruction was performed in 46 patients. Postoperative complications occurred in 30 (44.1%) patients, and one patient died from postoperative pneumonitis. Compared with the pulmonary function preoperative test results, the postoperative results revealed a decrease in the mean vital capacity percentage and an increase in the mean forced expiratory volume within 1 sec as a percent of the forced vital capacity. In patients with lung tumors, pneumonectomy can result in an increased rate of complications following thoracic wall resection. Residual pulmonary function is affected by impaired thoracic cage expansion and removal of the lung. However, the results of the present study demonstrated that these complications can be somewhat stabilized by thoracic wall reconstruction.

Therapeutic effect of ginkgo biloba extract on postoperative delirium in aged patients

Objective: To observe whether Ginkgo biloba extract (EGb761) can improve postoperative delirium in elderly patients. Methods: Eighty elderly patients undergoing tumor surgery at Zhejiang Cancer Hospital and complicated with postoperative delirium(POD) between June 2013 and July 2016 were randomly divided into treatment group (group A) and control group (group B) according to the random number table method. Patients in group A received ginkgo biloba extract (EGb761) drops oral treatment (3 times/d, 80 mg each time) in addition to oxygen inhalation and appeasement treatment. Patients in group B underwent routine oxygen inhalation and appeasement treatment. POD assessment was performed twice between the hours of 8: 00 am and 8: 00 pm daily after the diagnosis of POD. Observed indicators include sex ratio, age, body mass index (BMI), educated level, type of surgery, anesthesia method, duration of surgery, intraoperative mean arterial blood pressure, intraoperative blood loss, type of POD, visual analogue scale (VAS) scores when diagnosis of POD, the onset time of POD, initial RASS scores, duration of POD. Results: A total of 80 patients with POD were enrolled, 23 patients were excluded for did not cooperate with the tests of POD or refused to participate in the study. Finally, 57 elderly patients completed the study, 29 patients in the medication group (A group) and 28 patients in the control group (B group). There was no significant difference in sex ratio, age, BMI, education level, operation type, anesthesia method, operation duration, intraoperative mean arterial pressure, intraoperative blood loss, POD type and VAS score (all P>0.05). There was no significant difference between the two groups in POD onset time and initial RASS score (all P>0.05). The duration of POD in group A and group B was 16 (16)h and 48 (35) h respectively, the difference was statistically significant (U=161.500, P<0.001). Conclusion: Ginkgo biloba extract (EGb761) can shorten the course of POD in elderly patients.

Intraoperative subdural low-noise EEG recording of the high frequency oscillation in the somatosensory evoked potential

ObjectiveThe detectability of high frequency oscillations (HFO, >200Hz) in the intraoperative ECoG is restricted by their low signal-to-noise ratio (SNR). Using the somatosensory evoked HFO, we quantify how HFO detectability can benefit from a custom-made low-noise amplifier (LNA). MethodsIn 9 patients undergoing tumor surgery in the central region, subdural strip electrodes were placed for intraoperative neurophysiological monitoring. We recorded the somatosensory evoked potential (SEP) simultaneously by custom-made LNA and by a commercial device (CD). We varied the stimulation rate between 1.3 and 12.7Hz to tune the SNR of the N20 component and the evoked HFO and quantified HFO detectability at the single trial level. In three patients we compared Propofol® and Sevoflurane® anesthesia. ResultsIn the average, amplitude decreased in both in N20 and evoked HFO amplitude with increasing stimulation rate (p<0.05). We detected a higher percentage of single trial evoked HFO with the LNA (p<0.001) for recordings with low impedance (<5kΩ). Average amplitudes were indistinguishable between anesthesia compounds. ConclusionLow-noise amplification improves the detection of the evoked HFO in recordings with subdural electrodes with low impedance. SignificanceLow-noise EEG might critically improve the detectability of interictal spontaneous HFO in subdural and possibly in scalp recordings.

Serum metabolism during breast cancer treatment.

e23043 Serum metabolism during breast cancer treatment Background: Breast cancer treatment may include surgery, systemic therapy and radiation, often involving side-effects. Many patients experience weight gain during treatment, which is associated with decreased survival rates1. The purpose of this study was to describe serum metabolic alterations in breast cancer patients undergoing treatment, and relate these alterations to weight gain during treatment. Methods: This pilot study includes 60 breast cancer patients, aged 35-75 years, with histologically verified stage I/II disease. All patients underwent tumor surgery, and were treated according to national guidelines. Samples were collected before and 6 months after surgery, and analyzed by MR spectroscopy (MRS) and mass spectrometry (MS). 170 metabolites and 105 lipoprotein subfractions were quantified by combined MRS and MS analyses. Results: Multilevel PLS-DA showed significant alterations in serum metabolite profiles post-treatment, both in patients receiving (n = 35) and not receiving (n = 25) chemotherapy (classification accuracy: 86.7% and 77.0%, resp., p &lt; 0.001). Lipoprotein profiles were also significantly altered in both groups (p &lt; 0.001). Chemotherapy recipients had decreased levels of citrate, ornithine, and methionine after treatment, while non-recipients had increased levels of glutamate, alanine, proline and two biogenic amines, and decreased levels of acylcarnitines. 17/52 patients (32.7%) gained weight (≥ 1.5 kg) during treatment. Weight gain was predicted from pre-treatment samples with accuracy 67.0% (p = 0.020). Weight gain patients had lower levels of three acylcarnitines and 20 phosphocholines, and higher levels of lysine and isoleucine, suggesting aberrant lipid and amino acid metabolism. Weight gain was also reflected in the post-treatment samples (accuracy 66.8%, p = 0.015), with weight gain patients having higher levels of five acylcarnitines, and lower levels of glycine, isoleucine and valine. Conclusions: This study indicates that treatment induces changes in serum metabolite levels. Patients gaining weight had significantly different metabolite profiles than those not gaining weight both before and after treatment. 1. Chan et al, Ann Oncol 25: 1901-14, 2014.

Adjuvant regimens with trastuzumab administered for small HER2-positive breast cancer in routine clinical practice.

Trastuzumab has proven to improve the prognosis of HER2-positive breast cancer, but the information available about its administration for small tumors is still limited. Therefore, we assessed the use of adjuvant regimens with trastuzumab for the treatment of small HER2-positive breast cancer in routine clinical practice. This observational study was conducted in patients with HER2-positive breast adenocarcinoma ≤1.5cm who received trastuzumab-based adjuvant treatment in clinical practice. Clinical/histopathological data were retrieved from patients' medical charts. A total of 101 evaluable patients were enrolled (median age [range], 56.7 [49.0-64.8] years; ECOG 0, 98.0%; ductal carcinoma, 88.1%; lymph nodes N0, 79.2%). Only five (5.0%) patients received neoadjuvant treatment, while all patients underwent tumor surgery. Adjuvant trastuzumab was administered at a mean (±SD) dose of 5.9±1.5mg/kg/cycle, and mostly in a three-weekly schedule (89 [89.0%] patients). The most frequent adjuvant therapy used with trastuzumab was chemotherapy (87 [86.1%] patients), followed by radiotherapy (63 [62.4%] patients) and hormone therapy (52 [51.5%] patients). Chemotherapy regimens mainly included doxorubicin, cyclophosphamide and paclitaxel/docetaxel (n=30), docetaxel and cyclophosphamide (n=15), docetaxel and carboplatin (n=13). Hormone therapy mainly included letrozole (n=17) and tamoxifen (n=17). Nine (8.9%) patients reported trastuzumab-related adverse events; only one allergic reaction reached grade 3 toxicity. This study shows that trastuzumab-based adjuvant treatment of small HER2-positive breast cancer is mostly based on chemotherapy-mainly paclitaxel/docetaxel. Adjuvant administration of trastuzumab for small HER2-positive breast cancer seems to be similar to that used for larger tumors.

SM-04 * PROPHYLACTIC ANTIEPILEPTIC DRUGS DO NOT REDUCE SEIZURE RATES IN SURGICAL BRAIN TUMOR PATIENTS

Though no clear evidence supports seizure prophylaxis in patients with cerebral tumors, prophylactic use of anti-epileptic drugs (AEDs) for patients undergoing tumor surgery is common practice. A retrospective chart review was performed of 609 consecutive patients from 2010-2013 who underwent surgery for brain neoplasms at the University of Florida. Patients who did not present with seizures preoperatively were divided into supratentorial and infratentorial groups. There were 357 patients with supratentorial tumors with 297 (83.2%) receiving AEDs post-operatively and 60 (16.8%) not receiving AEDs. From surgery to last follow-up, one patient (2%) in the non-AED group had a seizure and 15 (6.2%) in the AED group had seizures (p = 0.487). There were 129 patients with infratentorial tumors, with 32 (24.8%) receiving AEDs and 97 (75.2%) not receiving AEDs. In the post-operative period, one patient (1.2%) in the non-AED group had a seizure and zero in the AED group had a seizure (p = 1). 16 (5.4%) patients in the supratentorial group and 3 (9.4%) patients in the infratentorial group on AEDs experienced toxicity related to AEDs. At discharge, 254 patients (85.5%) with supratentorial tumors without seizures remained on AEDs. At last follow up, 129 patients (53.8%) with supratentorial tumors remained on AEDs despite no seizures. AEDs do not significantly reduce post-operative seizures in surgical brain tumor patients in this analysis. Additionally, once a patient is prescribed an AED, discontinuation of AED therapy is unlikely, even if the patient remains seizure free.

Back pain in patients with degenerative spine disease and intradural spinal tumor: what to treat? when to treat?

Back pain is common in industrialized countries and one of the most frequent causes of work incapacity. Successful treatment is, therefore, not only important for improving the symptoms and the quality of life of these patients but also for socioeconomic reasons. Back pain is frequently caused by degenerative spine disease. Intradural spinal tumors are rare with an annual incidence of 2-4/1,00,000 and are mostly associated with neurological deficits and radicular and nocturnal pain. Back pain is not commonly described as a concomitant symptom, such that in patients with both a tumor and degenerative spine disease, any back pain is typically attributed to the degeneration rather than the tumor. The aim of the present retrospective investigation was to study and analyze the impact of microsurgery on back/neck pain in patients with intradural spinal tumor in the presence of degenerative spinal disease in adjacent spinal segments. Fifty-eight consecutive patients underwent microsurgical, intradural tumor surgery using a standardized protocol assisted by multimodal intraoperative neuromonitoring. Clinical symptoms, complications and surgery characteristics were documented. Standardized questionnaires were used to measure outcome from the surgeon's and the patient's perspectives (Spine Tango Registry and Core Outcome Measures Index). Follow-up included clinical and neuroradiological examinations 6 weeks, 3 months and 1 year postoperatively. Back/neck pain as a leading symptom and coexisting degenerative spine disease was present in 27/58 (47 %) of the tumor patients, and these comprised to group under study. Patients underwent tumor surgery only, without addressing the degenerative spinal disease. Remission rate after tumor removal was 85 %. There were no major surgical complications. Back/neck pain as the leading symptom was eradicated in 67 % of patients. There were 7 % of patients who required further invasive therapy for their degenerative spinal disease. Intradural spinal tumor surgery improves back/neck pain in patients with coexisting severe degenerative spinal disease. Intradural spinal tumors seem to be the only cause of back/neck pain more often than appreciated. In these patients suffering from both pathologies, there is a higher risk of surgical overtreatment than undertreatment. Therefore, elaborate clinical and radiological examinations should be performed preoperatively and the indication for stabilization/fusion should be discussed carefully in patients foreseen for first time intradural tumor surgery.

Simultaneous Direct Cortical Motor Evoked Potential Monitoring and Subcortical Mapping for Motor Pathway Preservation During Brain Tumor Surgery

The warning-sign hierarchy between quantitative subcortical motor mapping and continuous motor evoked potential monitoring during resection of supratentorial brain tumors: clinical article.Seidel K, Beck J, Steiglitz L, Schucht P, Raabe A.J Neurosurg 2013; 118:287-296. Mapping and monitoring are believed to provide an early warning sign to determine when to stop tumor removal to avoid mechanical damage to the corticospinal tract (CST). The objective of this study was to systematically compare subcortical monopolar stimulation thresholds (1-20 mA) with direct cortical stimulation (DCS)-motor evoked potential (MEP) monitoring signal abnormalities and to correlate both with new postoperative motor deficits. The authors sought to define a mapping threshold and DCS-MEP monitoring signal changes indicating a minimal safe distance from the CST. A consecutive cohort of 100 patients underwent tumor surgery adjacent to the CST while simultaneous subcortical motor mapping and DCS-MEP monitoring were used. Evaluation was performed regarding the lowest subcortical mapping threshold (monopolar stimulation, train of 5 stimuli, interstimulus interval 4.0 milliseconds, pulse duration 500 microseconds) and signal changes in DCS-MEPs (same parameters, 4 contact strip electrode). Motor function was assessed 1 day after the surgery, at discharge, and at 3 months postoperatively. The lowest individual motor thresholds (MTs) were as follows (MT in mA, number of patients): >20 mA, n = 12; 11 to 20 mA, n = 13; 6 to 10 mA, n = 20; 4 to 5 mA, n = 30; and 1 to 3 mA, n = 25. Direct cortical stimulation showed stable signals in 70 patients, unspecific changes in 18, irreversible alterations in 8, and irreversible loss in 4 patients. At 3 months, 5 patients had a postoperative new or worsened motor deficit (lowest mapping MT 20 mA, 13 mA, 6 mA, 3 mA, and 1 mA). In all 5 patients, DCS-MEP monitoring alterations were documented (2 sudden irreversible threshold increases and 3 sudden irreversible MEP losses). Of these 5 patients, 2 had vascular ischemic lesions (MT 20 mA, 13 mA) and 3 had mechanical CST damage (MT: 1 mA, 3 mA, and 6 mA; in the latter 2 cases, the resection continued after mapping and severe DCS-MEP alterations occurred thereafter). In 80% of patients with a mapping MT of 1 to 3 mA and in 75% of patients with a mapping MT of 1 mA, DCS-MEPs were stable or showed unspecific reversible changes, and none had a permanent motor worsening at 3 months. In contrast, 25% of patients with irreversible DCS-MEP changes and 75% of patients with irreversible DCS-MEP loss had permanent motor deficits. Mapping should primarily guide tumor resection adjacent to the CST. Direct cortical stimulation-motor evoked potential is a useful predictor of deficits, but its value as a warning sign is limited because signal alterations were reversible in only approximately 60% of the present cases and irreversibility is a post hoc definition. The true safe mapping MT is lower than previously thought. The authors postulate a mapping MT of 1 mA or less where irreversible DCS-MEP changes and motor deficits regularly occur. Therefore, they recommend stopping tumor resection at an MT of 2 mA at the latest. The limited spatial and temporal coverage of contemporary mapping may increase error and may contribute to false, higher MTs.

Inaccuracies in additive manufactured medical skull models caused by the DICOM to STL conversion process

IntroductionThe process of fabricating physical medical skull models requires many steps, each of which is a potential source of geometric error. The aim of this study was to demonstrate inaccuracies and differences caused by DICOM to STL conversion in additively manufactured medical skull models. Material and methodsThree different institutes were requested to perform an automatic reconstruction from an identical DICOM data set of a patients undergoing tumour surgery into an STL file format using their software of preference. The acquired digitized STL data sets were assessed and compared and subsequently used to fabricate physical medical skull models. The three fabricated skull models were then scanned, and differences in the model geometries were assessed using established CAD inspection software methods. ResultsA large variation was noted in size and anatomical geometries of the three physical skull models fabricated from an identical (or “a single”) DICOM data set. ConclusionsA medical skull model of the same individual can vary markedly depending on the DICOM to STL conversion software and the technical parameters used. Clinicians should be aware of this inaccuracy in certain applications.

Updated Clinical Considerations for Dental Implant Therapy in Irradiated Head and Neck Cancer Patients

An increasing number of reports indicate successful use of dental implants (DI) during oral rehabilitation for head and neck cancer patients undergoing tumor surgery and radiation therapy. Implant-supported dentures are a viable option when patients cannot use conventional dentures due to adverse effects of radiation therapy, including oral dryness or fragile mucosa, in addition to compromised anatomy; however, negative effects of radiation, including osteoradionecrosis, are well documented in the literature, and early loss of implants in irradiated bone has been reported. There is currently no consensus concerning DI safety or clinical guidelines for their use in irradiated head and neck cancer patients. It is important for health care professionals to be aware of the multidimensional risk factors for these patients when planning oral rehabilitation with DIs, and to provide optimal treatment options and maximize the overall treatment outcome. This paper reviews and updates the impact of radiotherapy on DI survival and discusses clinical considerations for DI therapy in irradiated head and neck cancer patients.

The warning-sign hierarchy between quantitative subcortical motor mapping and continuous motor evoked potential monitoring during resection of supratentorial brain tumors

Mapping and monitoring are believed to provide an early warning sign to determine when to stop tumor removal to avoid mechanical damage to the corticospinal tract (CST). The objective of this study was to systematically compare subcortical monopolar stimulation thresholds (1-20 mA) with direct cortical stimulation (DCS)-motor evoked potential (MEP) monitoring signal abnormalities and to correlate both with new postoperative motor deficits. The authors sought to define a mapping threshold and DCS-MEP monitoring signal changes indicating a minimal safe distance from the CST. A consecutive cohort of 100 patients underwent tumor surgery adjacent to the CST while simultaneous subcortical motor mapping and DCS-MEP monitoring was used. Evaluation was done regarding the lowest subcortical mapping threshold (monopolar stimulation, train of 5 stimuli, interstimulus interval 4.0 msec, pulse duration 500 μsec) and signal changes in DCS-MEPs (same parameters, 4 contact strip electrode). Motor function was assessed 1 day after surgery, at discharge, and at 3 months postoperatively. The lowest individual motor thresholds (MTs) were as follows (MT in mA, number of patients): > 20 mA, n = 12; 11-20 mA, n = 13; 6-10 mA, n = 20; 4-5 mA, n = 30; and 1-3 mA, n = 25. Direct cortical stimulation showed stable signals in 70 patients, unspecific changes in 18, irreversible alterations in 8, and irreversible loss in 4 patients. At 3 months, 5 patients had a postoperative new or worsened motor deficit (lowest mapping MT 20 mA, 13 mA, 6 mA, 3 mA, and 1 mA). In all 5 patients DCS-MEP monitoring alterations were documented (2 sudden irreversible threshold increases and 3 sudden irreversible MEP losses). Of these 5 patients, 2 had vascular ischemic lesions (MT 20 mA, 13 mA) and 3 had mechanical CST damage (MT 1 mA, 3 mA, and 6 mA; in the latter 2 cases the resection continued after mapping and severe DCS-MEP alterations occurred thereafter). In 80% of patients with a mapping MT of 1-3 mA and in 75% of patients with a mapping MT of 1 mA, DCS-MEPs were stable or showed unspecific reversible changes, and none had a permanent motor worsening at 3 months. In contrast, 25% of patients with irreversible DCS-MEP changes and 75% of patients with irreversible DCS-MEP loss had permanent motor deficits. Mapping should primarily guide tumor resection adjacent to the CST. DCS-MEP is a useful predictor of deficits, but its value as a warning sign is limited because signal alterations were reversible in only approximately 60% of the present cases and irreversibility is a post hoc definition. The true safe mapping MT is lower than previously thought. The authors postulate a mapping MT of 1 mA or less where irreversible DCS-MEP changes and motor deficits regularly occur. Therefore, they recommend stopping tumor resection at an MT of 2 mA at the latest. The limited spatial and temporal coverage of contemporary mapping may increase error and may contribute to false, higher MTs.

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

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. To evaluate the safety of low threshold motor evoked potential mapping for tumor resection close to the primary motor cortex. 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. 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. These preliminary data demonstrate that a monopolar HF-TOF threshold > 3 mA was not associated with a significant new motor deficit.