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In multiple sclerosis (MS) patients, trigeminal neuralgia (TN) represents a challenging syndrome to treat, often refractory to medical therapy and percutaneous techniques. Despite the frequent lack of a neurovascular conflict, the trigeminal nerve's axons are often damaged, with the myelin sheath permanently degenerated, thus explaining the difficulty in treating TN in MS. The authors illustrate trigeminal interfascicular neurolysis (the combing technique) to control refractory recurrent TN in MS: the nerve is longitudinally divided along its fibers from the root entry zone, determining good pain relief. The video can be found here: https://youtu.be/o1XksPW5fMY., Competing Interests: Disclosures Dr. Acerbi reports personal fees from Carl Zeiss Meditec outside the submitted work., (© 2020 The Authors.)

OBJECTIVE The best management of veins encountered during the neurosurgical approach is still a matter of debate. Even if venous sacrifice were to lead to devastating consequences, under certain circumstances, it might prove to be desirable, enlarging the surgical field or increasing the extent of resection in tumor surgery. In this study, the authors present a large series of patients with vascular or oncological entities, in which they used indocyanine green videoangiography (ICG-VA) with FLOW 800 analysis to study the patient-specific venous flow characteristics and the management workflow in cases in which a venous sacrifice was necessary. METHODS Between May 2011 and December 2017, 1972 patients were admitted to the authors' division for tumor and/or neurovascular surgery. They retrospectively reviewed all cases in which ICG-VA and FLOW 800 were used intraoperatively with a specific target in the venous angiographic phase or for the management of venous sacrifice, and whose surgical videos and FLOW 800 analysis were available. RESULTS A total of 296 ICG-VA and FLOW 800 studies were performed intraoperatively. In all cases, the venous structures were clearly identifiable and were described according to the flow direction and speed. The authors therefore defined different patterns of presentation: arterialized veins, thrombosed veins, fast-draining veins with anterograde flow, slow-draining veins with anterograde flow, and slow-draining veins with retrograde flow. In 16 cases we also performed a temporary clipping test to predict the effect of the venous sacrifice by the identification of potential collateral circulation. CONCLUSIONS ICG-VA and FLOW 800 analysis can provide complete and real-time intraoperative information regarding patient-specific venous drainage pattern and can guide the decision-making process regarding venous sacrifice, with a possible impact on reduction of surgical complications.

OBJECTIVE Indocyanine green videoangiography (ICG-VA) is an intraoperative technique used to highlight vessels in neurovascular surgery. Its application in the study of the vascular pathophysiology in CNS tumors and its role in their surgical management are still rather limited. A recent innovation of ICG-VA (i.e., the FLOW 800 algorithm integrated in the surgical microscope) allows a semiquantitative evaluation of cerebral blood flow. The aim of this study was to evaluate for the first time the systematic application of ICG-VA and FLOW 800 analysis during surgical removal of CNS tumors. METHODS Between May 2011 and December 2017, all cases in which ICG-VA and FLOW 800 analysis were used at least one time before, during, or after the tumor resection, and in which surgical videos were available, were retrospectively reviewed. Results of the histological analysis were analyzed together with the intraoperative ICG-VA with FLOW 800 in order to investigate the tumor-related videoangiographic features. RESULTS Seventy-one patients who underwent surgery for cerebral and spinal tumors were intraoperatively analyzed using ICG-VA with FLOW 800, either before or after tumor resection, for a total of 93 videoangiographic studies. The histological diagnosis was meningioma in 25 cases, glioma in 14, metastasis in 7, pineal region tumor in 5, hemangioblastoma in 4, chordoma in 3, and other histological types in 13 cases. The authors identified 4 possible applications of ICG-VA and FLOW 800 in CNS tumor surgery: extradural surveys allowed exploration of sinus patency and the course of veins before dural opening; preresection surveys helped in identifying pathological vascularization (arteriovenous fistulas and neo-angiogenesis) and regional venous outflow, and in performing temporary venous clipping tests, when necessary; postresection surveys were conducted to evaluate arterial and venous patency and parenchymal perfusion after tumor removal; and a premyelotomy survey was conducted in intramedullary tumors to highlight the posterior median sulcus. CONCLUSIONS The authors found ICG-VA with FLOW 800 to be a useful method to monitor blood flow in the exposed vessels and parenchyma during microsurgical removal of CNS tumors in selected cases. In particular, a preresection survey provides useful information about pathophysiological changes of brain vasculature related to the tumor and aids in the individuation of helpful landmarks for the surgical approach, and the postresection survey helps to prevent potential complications associated with the resection (such as local hypoperfusion or venous infarction).

OBJECT The Milan Complexity Scale-a new practical grading scale designed to estimate the risk of neurological clinical worsening after performing surgery for tumor removal-is presented. METHODS A retrospective study was conducted on all elective consecutive surgical procedures for tumor resection between January 2012 and December 2014 at the Second Division of Neurosurgery at Fondazione IRCCS Istituto Neurologico Carlo Besta of Milan. A prospective database dedicated to reporting complications and all clinical and radiological data was retrospectively reviewed. The Karnofsky Performance Scale (KPS) was used to classify each patient's health status. Complications were divided into major and minor and recorded based on etiology and required treatment. A logistic regression model was used to identify possible predictors of clinical worsening after surgery in terms of changes between the preoperative and discharge KPS scores. Statistically significant predictors were rated based on their odds ratios in order to build an ad hoc complexity scale. For each patient, a corresponding total score was calculated, and ANOVA was performed to compare the mean total scores between the improved/unchanged and worsened patients. Relative risk (RR) and chi-square statistics were employed to provide the risk of worsening after surgery for each total score. RESULTS The case series was composed of 746 patients (53.2% female; mean age 51.3 ± 17.1). The most common tumors were meningiomas (28.6%) and glioblastomas (24.1%). The mortality rate was 0.94%, the major complication rate was 9.1%, and the minor complication rate was 32.6%. Of 746 patients, 523 (70.1%) patients improved or remained unchanged, and 223 (29.9%) patients worsened. The following factors were found to be statistically significant predictors of the change in KPS scores: tumor size larger than 4 cm, cranial nerve manipulation, major brain vessel manipulation, posterior fossa location, and eloquent area involvement (Nagelkerke R(2) = 0.286). A grading scale was obtained with scores ranging between 0 and 8. Worsened patients showed mean total scores that were significantly higher than the improved/unchanged scores (3.24 ± 1.55 vs 1.47 ± 1.58; p < 0.001). Finally, a grid was developed to show the risk of worsening after surgery for each total score: scores higher than 3 are suggestive of worse clinical outcome. CONCLUSIONS Through the evaluation of the 5 aforementioned parameters-the Big Five-the Milan Complexity Scale enables neurosurgeons to estimate the risk of a negative clinical course after brain tumor surgery and share these data with the patient. Furthermore, the Milan Complexity Scale could be used for research and educational purposes and better health system management.

Object: Surgery of brainstem lesions is increasingly performed despite the fact that surgical indications and techniques continue to be debated. The deep pons, in particular, continues to be a critical area in which the specific risks related to different surgical strategies continue to be examined. With the intention of bringing new knowledge into this important arena, the authors systematically examined the results of brainstem surgeries that have been performed through the lateral infratrigeminal transpontine window., Methods: Between 1990 and 2013, 29 consecutive patients underwent surgery through this window for either biopsy sampling or for removal of a deep pontine lesion. All of this work was performed at the Department of Neurosurgery of the Istituto Nazionale Neurologico "Carlo Besta", in Milan, Italy. A retrospective analysis of the findings was conducted with the intention of bringing further clarity to this important surgical strategy., Results: The lateral infratrigeminal transpontine window was exposed through 4 different approaches: 1) classic retrosigmoid (15 cases), 2) minimally invasive keyhole retrosigmoid (10 cases), 3) translabyrinthine (1 case), and 4) combined petrosal (3 cases). No deaths occurred during the entire clinical study. The surgical complications that were observed included hydrocephalus (2 cases) and CSF leakage (1 case). In 6 (20.7%) of 29 patients the authors encountered new neurological deficits during the immediate postoperative period. All 6 of these patients had undergone lesion removal. In only 2 of these 6 patients were permanent sequelae observed at 3 months follow-up. These findings show that 93% of the patients studied did not report any permanent worsening of their neurological condition after this surgical intervention., Conclusions: This retrospective study supports the idea that the lateral infratrigeminal transpontine window is both a low-risk and safe corridor for either biopsy sampling or for removal of deep pontine lesions.

Object: Fluorescein, a dye that is widely used as a fluorescent tracer, accumulates in cerebral areas where the blood-brain barrier is damaged. This quality makes it an ideal dye for the intraoperative visualization of high-grade gliomas (HGGs). The authors report their experience with a new fluorescein-guided technique for the resection of HGGs using a dedicated filter on the surgical microscope., Methods: The authors initiated a prospective Phase II trial (FLUOGLIO) in September 2011 with the objective of evaluating the safety of fluorescein-guided surgery for HGGs and obtaining preliminary evidence regarding its efficacy for this purpose. To be eligible for participation in the study, a patient had to have suspected HGG amenable to complete resection of the contrast-enhancing area. The present report is based on the analysis of the short- and long-term results in 20 consecutive patients with HGGs (age range 45-74 years), enrolled in the study since September 2011. In all cases fluorescein (5-10 mg/kg) was injected intravenously after intubation. Tumor resection was performed with microsurgical technique and fluorescence visualization by means of BLUE 400 or YELLOW 560 filters on a Pentero microscope., Results: The median preoperative tumor volume was 30.3 cm(3) (range 2.4-87.8 cm(3)). There were no adverse reactions related to fluorescein administration. Complete removal of contrast-enhanced tumor was achieved in 80% of the patients. The median duration of follow-up was 10 months. The 6-months progression-free survival rate was 71.4% and the median survival was 11 months., Conclusions: Analysis of these 20 cases suggested that fluorescein-guided technique with a dedicated filter on the surgical microscope is safe and allows a high rate of complete resection of contrast-enhanced tumor as determined on early postoperative MRI. Clinical trial registration no.: 2011-002527-18 (EudraCT).

Object: Incident reporting systems are universally recognized as important tools for quality improvement in all complex adaptive systems, including the operating room. Nevertheless, introducing a safety culture among neurosurgeons is a slow process, and few studies are available in the literature regarding the implementation of an incident reporting system within a neurosurgical department. The authors describe the institution of an aviation model of incident reporting and investigation in neurosurgery, focusing on the method they have used and presenting some preliminary results., Methods: In 2010, the Inpatient Safety On-Board project was developed through cooperation between a team of human factor and safety specialists with aviation backgrounds (DgSky team) and the general manager of the Fondazione Istituto Neurologico Carlo Besta. In 2011, after specific training in safety culture, the authors implemented an aviation-derived prototype of incident reporting within the Department of Neurosurgery. They then developed an experimental protocol to track, analyze, and categorize any near misses that happened in the operating room. This project officially started in January 2012, when a dedicated team of assessors was established. All members of the neurosurgical department were asked to report near misses on a voluntary, confidential, and protected form (Patient Incident Reporting System form, Besta Safety Management Programme). Reports were entered into an online database and analyzed by a dedicated team of assessors with the help of a facilitator, and an aviation-derived root cause analysis was performed., Results: Since January 2012, 14 near misses were analyzed and classified. The near-miss contributing factors were mainly related to human factors (9 of 14 cases), technology (1 of 14 cases), organizational factors (3 of 14 cases), or procedural factors (1 of 14 cases)., Conclusions: Implementing an incident reporting system is quite demanding; the process should involve all of the people who work within the environment under study. Persistence and strong commitment are required to enact the culture change essential in shifting from a paradigm of infallible operators to the philosophy of errare humanum est. For this paradigm shift to be successful, contributions from aviation and human factor experts are critical.

Object: The authors report on the use of stereoelectroencephalography (stereo-EEG) in the presurgical electroclinical evaluation of infants and very young children with focal drug-resistant epilepsy., Methods: Fifteen patients (9 girls and 6 boys, mean age 34.1 ± 7.3 months, range 21-45 months), potentially candidates to receive surgical treatment for their focal drug-resistant epilepsy, were evaluated using stereo-EEG recording for a detailed definition of the epileptogenic zone. Stereoelectroencephalography was indicated because neuroradiological (brain MRI) and video-EEG data failed to adequately localize the epileptogenic zone. Stereotactic placement of multicontact intracerebral electrodes was preceded by the acquisition of all pertinent anatomical information from structural and functional MRI and from brain angiography, enabling the accurate targeting of desired structures through avascular trajectories. Stereoelectroencephalography monitoring attempted to record habitual seizures; electrical stimulations were performed to induce seizures and for the functional mapping of eloquent areas. Stereoelectroencephalography-guided microsurgery, when indicated, pointed to removal of the epileptogenic zone and seizure control., Results: Brain MRI revealed an anatomical lesion in 13 patients (lobar in 2 cases, multilobar or hemispheric in 11 cases) and was unremarkable in 2 patients. One patient underwent 2 stereo-EEG studies. The arrangement of the intracerebral electrodes was unilateral in all but 1 case. One patient died the day following electrode placement due to massive brain edema and profound hyponatremia of undetermined cause. In 8 cases intracerebral electrical stimulations allowed mapping of functionally critical areas; in 3 other cases that received purposeful placement of electrodes in presumably eloquent areas, no functional response was obtained. Of the 14 patients who completed stereo-EEG monitoring, 1 was excluded from surgery for multifocality of seizures and 13 underwent operations. Postoperatively, 2 patients exhibited an anticipated, permanent motor deficit, 3 experienced a transient motor deficit, and 2 experienced transient worsening of a preexisting motor deficit. Three patients developed a permanent homonymous hemianopia after posterior resections. Histological analysis revealed cortical malformations in 10 cases. Of the 10 patients with a postoperative follow-up of at least 12 months, 6 (60%) were seizure-free (Engel Class Ia), 2 (20%) experienced a significant reduction of seizures (Engel Class II), and 2 (20%) were unchanged (Engel Class IV)., Conclusions: The present study indicates that stereo-EEG plays a prominent role in the presurgical evaluation of focal epilepsies also in the first years of life and that it may offer a surgical option in particularly complex cases that would have scarcely benefitted from further medical treatment. Results of stereo-EEG-guided resective surgery were excellent, with 80% of patients exhibiting a substantial improvement in seizures. In consideration of the potentially life-threatening risks of major intracranial surgery in this specific age group, the authors recommend reserving stereo-EEG evaluations for infants with realistic chances of benefiting from surgery.

Object: Hemangiopericytomas are rare tumors that behave aggressively with a high rate of local recurrence and distant metastases. With the aim of determining the outcome and response to various treatment modalities, a series of 39 patients who underwent microsurgical resection for primary meningeal hemangiopericytoma over a 24-year period is presented., Methods: Patients with hemangiopericytoma were identified from histopathology records and their medical records were analyzed retrospectively by 2 independent reviewers to collect data on surgical treatment, adjuvant therapy, postoperative course, local or distant recurrence, and follow-up., Results: Of the 39 patients, 19 were male and 20 were female. Mean patient age was 44.1 years. Thirty-four tumors were intracranial and 5 were spinal. The mean follow-up period was 123 months. Twenty-eight patients developed local recurrence. The recurrence rate at 1, 5, and 15 years was 3.5%, 46%, and 92%, respectively. Extraneural metastasis occurred in 8 patients (26%) at an average of 123 months after initial surgery. Recurrences and metastases were treated by surgical excision, external beam radiation therapy (EBRT), chemotherapy, and/or stereotactic radiosurgery. Adjuvant EBRT following initial surgery was found to extend the disease-free interval from 154 months to 254 months, although it did not prevent the development of metastasis. In those patients with EBRT and complete resection, the mean recurrence-free interval was found to be 126.3 months longer (p = 0.04) and overall survival 126 months longer than without EBRT. Furthermore, adjusting for resection, patients undergoing EBRT had 0.33 times increased risk of recurrence compared with those who did not (p = 0.03). A majority of patients remained able to live independently despite revision surgery for recurrence., Conclusions: The mean follow-up of this patient series represents the longest follow-up duration published to date and demonstrates extended survival in a significant number of patients with hemangiopericytoma. Gross-total resection followed by adjuvant EBRT provides patients with the highest probability of an increased recurrence-free interval and overall survival. Prolonged survival justifies long-term follow-up and aggressive treatment of initial, recurrent, and metastatic disease.