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Objective: The safety of single-treatment stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) with radiographic evidence of brainstem compression but without motor deficit is controversial. Data on linear accelerator (linac)-based SRS in this setting are scarce. We address this with an outcomes report from an unselected series of patients with VS with radiographic brainstem compression treated with linac SRS., Methods: We included 139 patients with unilateral VS (any size) with radiographic brainstem compression (all without serious brainstem neurological deficits). The SRS prescription dose was 12.5 Gy (single fraction) using 6MV linac-produced photon beams, delivered with a multiple arc technique. Inclusion criteria required at least 1 year of radiographic follow-up with magnetic resonance imaging. The primary endpoint was freedom from serious brainstem toxicity (≥grade 3 Common Terminology Criteria for Adverse Events v5); the secondary was freedom from enlargement (tumor progression or any requiring intervention). We assessed serious cranial nerve complications, excluding hearing loss, defined as Common Terminology Criteria for Adverse Events v5 grade 3 toxicity., Results: Median magnetic resonance imaging follow-up time was 5 years, and median tumor size was 2.5 cm in greatest axial dimension and 5 ml in volume. The median brainstem D0.03 ml=12.6 Gy and median brainstem V10 Gy=0.4 ml. At 5 years, the actuarial freedom from serious brainstem toxicity was 100%, and freedom from tumor enlargement (requiring surgery and/or due to progression) was 90%. Severe facial nerve damage in patients without tumor enlargement was 0.9%., Conclusion: Linac-based SRS, as delivered in our series for VS with radiographic brainstem compression, is safe and effective., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Data are scarce on the efficacy of a second radiosurgery (SRS) treatment of vestibular schwannoma that has progressed following initial treatment with SRS. We sought to report the outcome of our repeat SRS series with long-term imaging follow-up., Materials and Methods: We retrospectively analyzed 6 patients who met the following criteria: Repeat SRS at our institution between 1995 and 2018; solitary unilateral tumor; no evidence of neurofibromatosis; and magnetic resonance (MR) planning for both SRS treatments. All treatments were delivered with a linear accelerator-based system using head frame immobilization. The prescribed dose to the periphery of the tumor was 12.5 Gy in all initial and repeat SRS treatments, except for one repeat treatment to 10 Gy., Results: Follow-up with MR scan following the second SRS treatment was a median 8.4 years. The tumor control rate (lack of progression) following the second SRS treatment was 83% (5/6). Actuarial 10-year outcomes following repeat SRS were: tumor control, 80%; absolute survival, 80%; and cause-specific survival, 100%. Of the patients with at least minimal hearing retention before initial SRS, none had ipsilateral hearing preservation after initial radiation treatment. Improvement in any pretreatment cranial nerve deficits was not seen. The only permanent grade ≥ 3 toxicity from repeat SRS was a case of infraorbital nerve deficit. No patient developed a stroke, malignant transformation, induced second tumor, or facial nerve deficit., Conclusion: There was excellent overall survival, tumor control, and low morbidity in our series for recurrent vestibular schwannoma submitted to repeat single-fraction SRS, supporting additional studies of this treatment strategy., Competing Interests: Conflict of interest The authors have no conflicts of interest to declare., (© 2022 Greater Poland Cancer Centre.)

Glioma diagnosis is based on histomorphology and grading; however, such classification does not have predictive clinical outcome after glioblastomas have developed. To date, no bona fide biomarkers that significantly translate into a survival benefit to glioblastoma patients have been identified. We previously reported that the IDH mutant G-CIMP-high subtype would be a predecessor to the G-CIMP-low subtype. Here, we performed a comprehensive DNA methylation longitudinal analysis of diffuse gliomas from 77 patients (200 tumors) to enlighten the epigenome-based malignant transformation of initially lower-grade gliomas. Intra-subtype heterogeneity among G-CIMP-high primary tumors allowed us to identify predictive biomarkers for assessing the risk of malignant recurrence at early stages of disease. G-CIMP-low recurrence appeared in 9.5% of all gliomas, and these resembled IDH-wild-type primary glioblastoma. G-CIMP-low recurrence can be characterized by distinct epigenetic changes at candidate functional tissue enhancers with AP-1/SOX binding elements, mesenchymal stem cell-like epigenomic phenotype, and genomic instability. Molecular abnormalities of longitudinal G-CIMP offer possibilities to defy glioblastoma progression., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objectives: To determine the long-term outcome after stereotactic radiosurgery (SRS) for temporal bone paragangliomas., Materials and Methods: We retrospectively reviewed the medical records of 11 patients with temporal bone paragangliomas (10 patients with a glomus jugulare tumor and 1 patient with a glomus tympanicum tumor) treated between January 1997 and July 2012 at the University of Florida with SRS to a median dose of 15 Gy in 1 fraction. Ten previously unirradiated patients received SRS as did 1 patient who received prior fractionated radiotherapy (FRT) and then received salvage SRS for a local recurrence. The major outcome endpoint was local control, meaning no further growth or shrinkage on follow-up computed tomography or magnetic resonance imaging scans., Results: The median follow-up time was 5.3 years. Two patients developed a local recurrence after SRS, including the patient who received salvage SRS after prior FRT. The overall local control rates at 5 and 10 years were both 81%. The cause-specific survival rates at 5 and 10 years were both 88%. The distant metastasis-free survival rates at 5 and 10 years were both 100%. The overall survival rates at 5 and 10 years were both 78%. There were no severe complications., Conclusions: SRS for benign head and neck paragangliomas is a safe and efficacious treatment associated with minimal morbidity. SRS is suitable for patients with skull base tumors <3 cm when FRT is logistically unsuitable. Surgery is reserved for patients in good health whose risk of associated morbidity is low. Observation is a reasonable option for asymptomatic patients with a limited life expectancy.

Stereotactic radiosurgery (SRS) is a procedure that delivers a single large radiation dose to a well-defined target. Here, we describe a frameless SRS technique suitable for intracranial targets in canines. Medical records of dogs diagnosed with a primary intracranial tumour by imaging or histopathology that underwent SRS were retrospectively reviewed. Frameless SRS was used successfully to treat tumours in 51 dogs with a variety of head sizes and shapes. Tumours diagnosed included 38 meningiomas, 4 pituitary tumours, 4 trigeminal nerve tumours, 3 gliomas, 1 histiocytic sarcoma and 1 choroid plexus tumour. Median survival time was 399 days for all tumours and for dogs with meningiomas; cause-specific survival was 493 days for both cohorts. Acute grade III central nervous system toxicity (altered mentation) occurred in two dogs. Frameless SRS resulted in survival times comparable to conventional radiation therapy, but with fewer acute adverse effects and only a single anaesthetic episode required for therapy., (© 2013 John Wiley & Sons Ltd.)

: The reported prevalence rates of arteriovenous malformations (AVMs) in the general population range from 0.001% to 0.50%. The following case describes the initial presentation of hemorrhage from an intracranial AVM in an 18-year-old college football player. It also discusses treatment of the AVM with stereotactic radiosurgery and successful return to football 17 months after radiosurgery (18.5 months after initial presentation). It is the first published description of return to contact sports after stereotactic radiosurgery for intracranial AVM.

Objective: To identify deficiencies leading to readmissions to the University of Florida Neurosurgery Service by using the Institute for Healthcare Improvement STate Action on Avoidable Rehospitalizations Readmissions diagnostic tool and to report the opinions of patients, their families, and health care providers., Methods: A retrospective review of hospital admission and discharge data was conducted. All patients who met eligibility criteria and who were discharged from the neurosurgery service between January 1 and March 31, 2012, and readmitted within 30 days after discharge (n=74; 66 patients; 7 multiple readmissions) were included. A chart review revealed potential precipitating factors. Health care providers, patients, and family members were also interviewed. Median values and frequencies were used to summarize the data., Results: The 30-day readmission rate on the neurosurgery service was 14%. Problems associated with wound care accounted for 24% of readmissions, neurologic conditions accounted for 50%, and other medical conditions accounted for 26%. Patients and providers agreed on the medical diagnoses resulting in readmission, but providers also often named "patient noncompliance" as a factor leading to readmission, whereas patients often thought they either were "sent home too early" or had a "general decline with no improvement.", Conclusions: Systematic patterns and common themes associated with patient readmissions were identified for a neurosurgical service. These findings are now being used to implement changes in discharge planning., (Copyright © 2014 Elsevier Inc. All rights reserved.)

During the last 2 decades, there has been a shift in the U.S. health care system towards improving the quality of health care provided by enhancing patient safety and reducing medical errors. Unfortunately, surgical complications, patient harm events, and malpractice claims remain common in the field of neurosurgery. Many of these events are potentially avoidable. There are an increasing number of publications in the medical literature in which authors address cognitive errors in diagnosis and treatment and strategies for reducing such errors, but these are for the most part absent in the neurosurgical literature. The purpose of this article is to highlight the complexities of medical decision making to a neurosurgical audience, with the hope of providing insight into the biases that lead us towards error and strategies to overcome our innate cognitive deficiencies. To accomplish this goal, we review the current literature on medical errors and just culture, explain the dual process theory of cognition, identify common cognitive errors affecting neurosurgeons in practice, review cognitive debiasing strategies, and finally provide simple methods that can be easily assimilated into neurosurgical practice to improve clinical decision making., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objective: We previously performed a nationwide survey of American neurosurgical residents before the initiation of the 2011 Accreditation Council for Graduate Medical Education regulations, in which more than 70% indicated the proposed changes would negatively impact residency training. We sought to resurvey the resident population as to the actual changes that occurred to their programs after the 2011 standards went into effect., Methods: Surveys were mailed to every neurosurgery training program in the United States and Puerto Rico. Program directors and coordinators were asked to distribute surveys to their residents., Results: A total of 253 neurosurgery residents responded. Reported duty-hour violations were largely unchanged after the 2011 duty-hour changes. Sixty-percent of residents reported that they had underreported duty hours, with nearly 25% of respondents doing so on a weekly or daily basis. Most reported that the 2011 changes had not affected operative caseload, academic productivity, quality of life, or resident fatigue. The majority of residents disagreed or strongly disagreed that the PGY-1 16-hour limitation had a positive impact on first-year resident training (69%) or had improved patient safety (62%). Overall, the majority of respondents reported that the 2011 changes had a negative (35%) or negligible (33%) effect on residency training at their institution., Conclusion: Respondents indicated that the 2011 Accreditation Council for Graduate Medical Education regulations have had a smaller perceived effect on neurosurgical training programs than previously predicted. However, the majority of residents admitted to underreporting duty hours, with a quarter doing so on a regular basis. The 16-hour rule for interns remains unpopular., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Despite the conformity of stereotactic radiosurgery (SRS) treatment, there are concerns about the risk of malignancy., Objective: We compared the number of cancer cases observed after treatment in a group of SRS patients to the number of cancer cases that would be expected in an age- and gender-matched group., Methods: We collected data from the University of Florida SRS database for patients treated for meningiomas, intracranial schwannomas, arteriovenous malformations (AVMs), trigeminal neuralgia, pituitary adenomas, cavernous angiomas, and metastases. We used the Florida Cancer Data System (FCDS) to determine the actual cancer rates for SRS-treated patients, and we compared these to the cancer rates in similar groups of non-SRS-treated patients based on rates available from the SEER (surveillance epidemiology and end results) database., Results: A total of 2,369 patients were analyzed. Of these, 862 were patients with metastases who were analyzed only to ensure the sensitivity of using the FCDS to determine malignancy rates. The results for patients with more than 5 years of follow-up are reported. Without the metastases patients, a total of 627 patients had more than 5 years of follow-up data. Follow-up in patient-years was 1,711 for the meningioma patients, 1,851 for the schwannoma patients, 1,407 for the AVM patients and 338 for patients with a diagnosis of 'other'. The observed cancer rate in the meningioma patients was 3.96% compared to the expected rate of 10% (binomial 95% confidence interval, CI = 1.85-7.94). The observed cancer rate in the schwannoma patients was 4.93% compared to the expected rate of 12.5% (95% CI = 2.61-8.89). The observed cancer rate in the AVM patients was 3.64% compared to the expected rate of 4.43% (95% CI = 1.49-8.10). The observed cancer rate in patients treated for other diagnoses (e.g. pituitary adenoma or trigeminal neuralgia) was 0% compared to the expected rate of 6.36% (95% CI = 0-11.7)., Conclusions: In a large population of SRS-treated patients, there was no increased risk of malignancy compared to the general population., (© 2014 S. Karger AG, Basel.)

Background: Stereotactic radiosurgery is ideal for treating small cerebral arteriovenous malformations (AVMs) that are surgically inaccessible. However, given the inherent delay of AVM obliteration and the potential for radiosurgical failure, detailed evaluation of the neurovascular architecture is necessary to monitor persistence of residual flow. Modern imaging systems such as magnetic resonance imaging (MRI) and angiography allow clinicians to assess transnidus flow after radiosurgical intervention., Objective: To determine the accuracy of an MRI diagnosis of complete thrombosis and to identify variables that affect the precision of MRI assessment., Methods: One hundred twenty patients were reviewed after receiving radiosurgery at the University of Florida from 1990 to 2010. Each patient had an MRI demonstrating AVM obliteration and an angiogram either confirming or denying AVM thrombosis., Results: MRI correctly predicted complete AVM obliteration in 82% of patients. There was a significant correlation between AVM volume and MRI accuracy in 2 separate models. In the first model, logistic regression analysis revealed a significant linear relationship between the natural log of AVM volume and MRI accuracy. The second model showed significant evidence of a cutoff point in MRI accuracy near an AVM volume of 2.80 cm(3), above which MRI agreement with angiography is 90% and below which MRI agreement falls off sharply to remain constant at 70%., Conclusion: MRI is a useful diagnostic system for assessing AVM obliteration, but its accuracy is inherently linked to the nidus volume it is measuring. These results suggest that MRI may be able to take on an increasingly independent role in the evaluation of AVM regression.

Background: Surgical education is moving rapidly to the use of simulation for technical training of residents and maintenance or upgrading of surgical skills in clinical practice. To optimize the learning exercise, it is essential that both visual and haptic cues are presented to best present a real-world experience. Many systems attempt to achieve this goal through a total virtual interface., Objective: To demonstrate that the most critical aspect in optimizing a simulation experience is to provide the visual and haptic cues, allowing the training to fully mimic the real-world environment., Methods: Our approach has been to create a mixed-reality system consisting of a physical and a virtual component. A physical model of the head or spine is created with a 3-dimensional printer using deidentified patient data. The model is linked to a virtual radiographic system or an image guidance platform. A variety of surgical challenges can be presented in which the trainee must use the same anatomic and radiographic references required during actual surgical procedures., Results: Using the aforementioned techniques, we have created simulators for ventriculostomy, percutaneous stereotactic lesion procedure for trigeminal neuralgia, and spinal instrumentation. The design and implementation of these platforms are presented., Conclusion: The system has provided the residents an opportunity to understand and appreciate the complex 3-dimensional anatomy of the 3 neurosurgical procedures simulated. The systems have also provided an opportunity to break procedures down into critical segments, allowing the user to concentrate on specific areas of deficiency.

Stereotactic radiosurgery for intracranial arteriovenous malformations (AVMs) has been performed since the 1970s. When an AVM is treated with radiosurgery, radiation injury to the vascular endothelium induces the proliferation of smooth muscle cells and the elaboration of extracellular collagen, which leads to progressive stenosis and obliteration of the AVM nidus. Obliteration after AVM radiosurgery ranges from 60% to 80%, and relates to the size of the AVM and the prescribed radiation dose. The major drawback of radiosurgical AVM treatment is the risk of bleeding during the latent period (typically 2 years) between treatment and AVM thrombosis., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Object: Ventricular infection after ventriculostomy placement carries a high mortality rate. Responding to ventriculostomy infection rates, a multidisciplinary performance improvement team was formed, a comprehensive protocol for ventriculostomy placement was developed, and the efficacy was evaluated., Methods: A best-practice protocol was developed, including hand hygiene before the procedure; prophylactic antibiotics; sterile gloves changed between preparation, draping, and procedure; hair removal by clipping for dressing adherence; skin preparation using iodine povacrylex (0.7% available iodine) and isopropyl alcohol (74%); full body and head drape; full surgical attire for the surgeon and other bedside providers; and an antimicrobial-impregnated catheter. A checklist of critical components was used to confirm proper insertion and to monitor practice. Procedure-specific infection rates were calculated using the number of infections divided by the number of patients in whom an external ventricular drainage (EVD) device was inserted × 100 (%). Data were reported back to providers and to the committee. Bundle compliance was monitored over a 4-year period., Results: At the authors' institution, 2928 ventriculostomies were performed between the beginning of the fourth quarter of 2006 and the end of the first quarter of 2012. Although the best-evidence bundle was applied to all patients, only 588 (20.1%) were checklist monitored (increasing from 7% to 23% over the study period). The infection rate for the 2 quarters before bundle implementation was 9.2%. During the study period, the rate decreased quarterly to 2.6% and then to 0%. Over a 4-year period, the rate was 1.06% (2007), 0.66% (2008), 0.15% (2009), and 0.34% (2010); it was 0% in 2011 and the first quarter of 2012. The overall EVD infection rate was 0.46% after bundle implementation., Conclusions: Bundle implementation including an antimicrobial-impregnated catheter dramatically decreased EVD-related infections. Training and situational awareness of appropriate practice, assisted by the checklist, plus use of the antibiotic-impregnated catheter resulted in sustained reduction in ventriculitis.

Background: Previous studies suggest that nonurgent pages comprise a substantial portion of the pages received by residents while on duty. We evaluated the number, type, and urgency of pages received and the task being performed at the time of paging by on-call junior neurosurgery residents at a large teaching hospital, with the aim of providing insight into mechanisms that can be developed to improve paging patterns and ultimately reduce physician distractions due to nonurgent communications., Methods: For eight 12-hour call sessions, a medical student shadowed the on-call junior neurosurgery resident and recorded all pages received and the time, paging number and location, priority of the page (nonurgent, urgent, or emergency), and the activity the resident performed when the page was received. During one 5-hour session, a recorder measured the amount of time spent returning pages., Results: During the study period, 439 communications were recorded (mean of 54.9 per 12-hour session; range, 33-75). Communications occurred at a rate of every 13 minutes and ranged from every 34 minutes to every 8.7 minutes. Paging remained frequent even during the hours when on-call residents are most likely to sleep (2-5 am), with an average of 4 communications per hour. The time to return pages ranged from 15 to 174 seconds (mean, 79.7 seconds). Most pages were nonurgent (68.3%) and occurred during patient care activities (65%)., Conclusions: Paging communications were frequent. Most pages were nonurgent and were received during important patient care activities. This suggests that a viable solution must address the work context of the individual being paged and the individual initiating the page to ensure that urgent communications are properly prioritized and attended to.

Implementation of a standard protocol and use of antibiotic-coated ventricular catheters helped reduce EVD-related infections from 9.2% to almost zero at the University of Florida. This project demonstrated the success of creating a task force to identify areas of improvement, implement solutions, and monitor the outcomes.

Background: Despite a high success rate in the stereotactic radiosurgical treatment of intracranial arteriovenous malformations (AVMs) that cannot be safely resected with microsurgery, some patients must be managed after treatment failure., Objective: To provide an update on the use of repeat linear accelerator radiosurgery as a treatment for failed AVM radiosurgery at the University of Florida., Methods: We reviewed 103 patients who underwent repeat radiosurgical treatment for residual AVM at the University of Florida between December 1991 and December 2007. Each of these patients had at least 2 radiosurgical treatments for the same AVM. Patient information, including AVM nidus volume, prescription dose, age, and sex, was collected at the time of initial treatment and again at the time of retreatment. Patients were followed up after treatment with magnetic resonance, computed tomography, and angiographic imaging at standard intervals to determine the status of their AVM. The median follow-up after retreatment was 31 months., Results: Between the first and second treatments, the median AVM nidus volume was decreased by 69% (from a median volume of 12.7 to 4.0 cm), allowing the median prescribed dose to be increased from 1500 cGy on initial treatment to 1750 cGy on retreatment. The final obliteration rate on retreatment was 65.3%. After salvage retreatment, 5 patients (4.9%) experienced radiation-induced complications, and 6 patients (5.8%) experienced posttreatment hemorrhage., Conclusion: Repeat radiosurgery is a safe and effective salvage treatment for AVMs.

Rats generate stereotyped exploratory (5-12 Hz) vibrissa movements when navigating through their environment. Like other rhythmic behaviors, the production of whisking relies on a subcortical pattern generator. However, the relatively large vibrissae representation in motor cortex (vMCx) suggests that cortex also contributes to the control of whisker movements. The goal of this study was to examine the relationship between neuronal activity in vMCx and the kinematics of vibrissae movements. We recorded multiunit activity (MUA) and single units in the rhythmic region of vMCx while measuring vibrissa position in awake, head-restrained rats. The rats were engaged in one of two behavioral tasks where they were rewarded for either 1) producing noncontact whisking epochs that met specified criteria (epochs ≥4 Hz, whisks >5 mm) or 2) whisking to contact an object. There was significant coherence between the frequency of MUA and vibrissae movements during free-air whisking but not when animals were using their vibrissae to contact an object. Spike rate in vMCx was most frequently correlated with the amplitude of vibrissa movements; correlations with movement frequency did not exceed chance levels. These findings suggest that the specific parameter under cortical control may be the amplitude of whisker movements.

Background: Radiographic response of brain metastasis to stereotactic radiosurgery (SRS) over time has not been well characterized. Being able to predict SRS-induced changes in tumor size over time may allow improved counseling of patients and potentially earlier recognition of poor response to SRS., Objective: To quantify the rate of change in size of metastatic brain tumors after treatment with a linear accelerator (LINAC) SRS., Methods: We performed a retrospective analysis of patients with single metastatic brain tumors treated with LINAC SRS at the University of Florida between 1992 and 2009 who had at least one MRI after treatment. A total of 218 patients with 406 follow-up MRI scans were included in the study. Tumor area was calculated by measuring the largest tumor area on axial imaging and using the equation for area of an ellipse. Primary outcome was percent change in tumor size. The contribution of several factors including gender, primary tumor histology, synchronous or asynchronous presentation, prior treatment, primary tumor control, and SRS dose were examined using multivariate analysis., Results: Mean patient age was 58.3 years (range 4-86), and 48.6% of patients were female. Sixty-three percent of patients had primary tumor control and 70.6% had asynchronous presentation of their brain metastases. SRS peripheral dose range was 1,000-2,250 cGy with a median of 1,750 cGy. The mean percent size change was -22.6% with a mean rate of change of -7.0% per month. The median percent change was -49.7% with a median rate of change of -8.8% per month. The median follow-up was 4.8 months (range 0.3-52.5). Female gender and melanoma histology were found to be significant predictors of an increase in tumor size. Lack of previous surgical resection was a significant predictor of a decrease in tumor size after SRS. Other factors tested with multivariate analysis, including age, synchronicity of presentation, dose, dose volume, Karnofsky performance score, and primary tumor control, were not significant in predicting tumor size change after SRS., Conclusion: In this study, brain metastases decreased in size by a median of 50% for a median follow-up of 4.8 months after SRS. The overall rate of decrease was 9% per month after treatment with SRS. Melanoma histology was a predictor of poor tumor control., (Copyright © 2012 S. Karger AG, Basel.)

Background: The Accreditation Council for Graduate Medical Education (ACGME) duty hour standards that began July 2011 will further limit resident duty hours., Objective: To survey neurosurgery residents in the United States on duty hour violations under the current system and the predicted effects on education and patient safety of the new regulations., Methods: Surveys were mailed to every neurosurgery training program in the United States and Puerto Rico. Program directors and coordinators were asked to distribute surveys to their residents., Results: Three hundred seventy-seven neurosurgery residents mailed surveys back to the study center (34% response rate). More than one-third of respondents reported violating the 80-hour rule occasionally or frequently (36%). Thirty-one residents (8%) reported having been involved in a motor vehicle collision or life-threatening event and 20 (6%) reported having made a medical error resulting in patient harm after an extended shift. Eighty-three percent disagreed with the 16-hour proposed regulation for postgraduate year 1. The majority of respondents thought that the new standards will have a negative or strongly negative effect on their residency training (72%)., Conclusion: This national duty hour survey of neurosurgical residents reveals considerable concern over the new ACGME proposed standards. The majority of respondents believe that the new standards will have a negative effect on their residency training. Furthermore, this survey indicates an overwhelming negative attitude toward mandated duty hour regulations among neurosurgical residents. Duty hour violations reported in this survey may be a more honest depiction of true violations than previous surveys and are higher than expected.

Stereotactic radiosurgery is the term coined by Lars Leksell to describe the application of a single, high dose of radiation to a stereotactically defined target volume. In the 1970s, reports began to appear documenting the successful obliteration of arteriovenous malformations (AVMs) with radiosurgery. When an AVM is treated with radiosurgery, a pathologic process appears to be induced that is similar to the response-to-injury model of atherosclerosis. Radiation injury to the vascular endothelium is believed to induce the proliferation of smooth-muscle cells and the elaboration of extracellular collagen, which leads to progressive stenosis and obliteration of the AVM nidus thereby eliminating the risk of hemorrhage. The advantages of radiosurgery - compared to microsurgical and endovascular treatments - are that it is noninvasive, has minimal risk of acute complications, and is performed as an outpatient procedure requiring no recovery time for the patient. The primary disadvantage of radiosurgery is that cure is not immediate. While thrombosis of the lesion is achieved in the majority of cases, it commonly does not occur until two or three years after treatment. During the interval between radiosurgical treatment and AVM thrombosis, the risk of hemorrhage remains. Another potential disadvantage of radiosurgery is possible long term adverse effects of radiation. Finally, radiosurgery has been shown to be less effective for lesions over 10 cc in volume. For these reasons, selection of the optimal treatment for an AVM is a complex decision requiring the input of experts in endovascular, open surgical, and radiosurgical treatment. In the pages below, we will review the world's literature on radiosurgery for AVMs. Topics reviewed will include the following: radiosurgical technique, radiosurgery results (gamma knife radiosurgery, particle beam radiosurgery, linear accelerator radiosurgery), hemorrhage after radiosurgery, radiation induced complications, repeat radiosurgery, and radiosurgery for other types of vascular malformation.

Intracranial hypotension is not an uncommon diagnosis after lumbar puncture or neurosurgery. However, spontaneous intracranial hypotension (SIH) is a poorly understood entity that can present with a wide variety of symptoms/signs ranging from headache to coma. SIH may result from an occult spinal cerebrospinal fluid (CSF) leak. Alternatively, because a CSF leak is not always found, some posit that SIH is caused by venous hypotension that results in increased CSF absorption. The true incidence of SIH is unknown and the diagnosis is frequently missed given the wide range of presenting symptoms and imaging findings that are mistaken for other diagnoses (ie, subdural hematomas, Chiari malformation). Here, based on a comprehensive literature review, we describe the epidemiology, presentation, diagnostic workup and treatment of SIH.

Background and Importance: Disseminated intravascular coagulation is a relatively common complication in patients with trauma, sepsis, obstetric calamities, and certain malignancies. We report a rare case of DIC after embolization and surgery for a large meningioma. We also review the literature on coagulopathy during brain tumor surgery as well as the diagnosis and treatment of this complication., Clinical Presentation: A 62-year-old woman presented with a 3-week history of aphasia, difficulty with handwriting, personality change, and right-sided weakness. Magnetic resonance imaging demonstrated a 6.3 × 5.4-cm multilobe and avidly enhancing mass within the left frontal region. The patient underwent preoperative transcatheter Onyx embolization of the tumor, followed immediately by craniotomy for resection of the tumor. Surgery was complicated by coagulopathy leading to substantial blood loss. The diagnosis of disseminated intravascular coagulation was established by intraoperative thromboelastography, after which the patient was treated with replacement therapy, Amicar, and modest hypotension. One year after surgery, the patient had fully recovered and had no focal neurological deficit., Conclusion: This case report adds to the few reported cases of disseminated intravascular coagulation as a complication of brain tumor surgery. This patient's successful outcome may be attributed to timely recognition of the condition and effective, prompt treatment.

Background: Nonvestibular schwannomas are uncommon tumors of the brain often treated by surgical resection. Surgery may be associated with high morbidity., Objective: We present a series of nonvestibular schwannomas treated with linear accelerator radiosurgery during a 19-year period., Methods: This is a retrospective analysis of patients who underwent treatment of nonvestibular schwannomas at the University of Florida with linear accelerator radiosurgery between August 1989 and February 2008. Forty-nine patients underwent treatment during the study period, and 6 were lost to follow up. The mean age was 51 years (range, 17-82 years), 39% had previous surgical resection, and 67% presented with preradiosurgery cranial nerve deficits. There were 25 trigeminal, 18 jugular foramen, 2 facial, 2 oculomotor, 1 hypoglossal, and 1 high cervical schwannomas. The median tumor volume was 5.3 mL (range, 0.3-24.5 mL), treated with a median dose of 1250 cGy (range, 1000-1500 cGy). Study endpoints were actuarial local tumor control and neurological outcome., Results: Forty-three patients were available for a median follow-up of 37 months (range, 6-210 months). Actuarial local tumor control was 97% at 1 year, 91% at 4.5 years, and 83% at 5 years. There were 4 new cranial nerve deficits (9%) including facial numbness (2 patients), anesthesia dolorosa (1 patient), and facial weakness (1 patient). Thirty-nine percent had documented clinical and/or symptomatic improvement. There were no other morbidity and no mortality with treatment., Conclusion: Radiosurgery for nonvestibular schwannomas offers good actuarial local tumor control and has superior morbidity compared with surgical resection. This is the largest linear accelerator radiosurgical series, and the second largest radiosurgical series reported to date.

Background: In 2004, the Department of Neurosurgery at the University of Florida implemented a major curriculum innovation called the Transition to Practice program. This program was established to prepare residents to more safely transition to the role of independent practitioner., Methods: A qualitative and quantitative evaluation of the program was conducted after its fifth year using online surveys and interviews. Study participants included Transition to Practice graduates, faculty, and current residents., Results: Of the 26 respondents, 89% of faculty and all graduates were very satisfied with the program. Strengths identified included an independent yet mentored broad operative experience, the development of self-confidence, and a real sense of responsibility for patients. Medical billing and coding instruction and career mentoring were areas of the program that required additional attention., Conclusion: Overall, this program is meeting the stated objectives and is well received by the graduates and faculty. Based on the results of this evaluation, curricular changes such as instructions in practice management and implementation of a career-mentoring program have occurred. The Transition to Practice program is a unique curricular response to change that other surgical specialties may find useful in addressing the current-day stresses on graduate medical education.

Objective: Neurosurgical patients have a high risk of hyponatremia and associated complications. We critically evaluated the existing literature to identify the determinants for the development of hyponatremia and which management strategies provided the best outcomes., Methods: A multidisciplinary panel in the areas of neurosurgery, nephrology, critical care medicine, endocrinology, pharmacy, and nursing summarized and classified hyponatremia literature scientific studies published in English from 1950 through 2008. The panel's recommendations were used to create an evaluation and treatment protocol for hyponatremia in neurosurgical patients at the University of Florida., Results: Hyponatremia should be further investigated and treated when the serum sodium level is less than 131 mmol/L (class II). Evaluation of hyponatremia should include a combination of physical examination findings, basic laboratory studies, and invasive monitoring when available (class III). Obtaining levels of hormones such as antidiuretic hormone and natriuretic peptides is not supported by the literature (class III). Treatment of hyponatremia should be based on severity of symptoms (class III). The serum sodium level should not be corrected by more than 10 mmol/L/d (class III). Cerebral salt wasting should be treated with replacement of serum sodium and intravenous fluids (class III). Fludrocortisone may be considered in the treatment of hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm (class I). Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients (class I). Hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm should not be treated with fluid restriction (class II). Syndrome of inappropriate antidiuretic hormone may be treated with urea, diuretics, lithium, demeclocycline, and/or fluid restriction (class III)., Conclusion: The summarized literature on the evaluation and treatment of hyponatremia was used to develop practice management recommendations for hyponatremia in the neurosurgical population. However, the practice management recommendations relied heavily on expert opinion because of a paucity of class I evidence literature on hyponatremia.

Object: The radiosurgery-based arteriovenous malformation (AVM) score (RBAS) is a grading system designed to predict patient outcomes after Gamma Knife surgery for AVMs. This study seeks to validate independently the predictive nature of the RBAS, not only after single treatment but for retreatment, and to assess the overall outcome regardless of number of radiosurgeries., Methods: The authors analyzed 403 patients treated with linear accelerator (LINAC) radiosurgery for AVMs between May 1988 and June 2008. The AVM scores were determined by the following equation: AVM score = (0.1 x volume in cm(3)) + (0.02 x age in years) + (0.3 x location). The location values are as follows: frontal/temporal = 0, parietal/occipital/corpus callosum/cerebellar = 1, and basal ganglia/thalamus/brainstem = 2., Results: Testing demonstrated that the RBAS correlated with excellent outcomes after single or repeat radiosurgery (p < 0.001 for both variables). One hundred sixty-two (49%) of 330 patients had excellent outcomes (obliteration without deficit) after a single treatment. Excellent outcomes were achieved in 74, 64, 50, and 11% of patients with AVM scores of < 1.0 (Group 1), between 1.0 and < 1.8 (Group 2), between 1.8 and < 2.5 (Group 3), and >or= 2.5 (Group 4), respectively. Fifty-one patients (70%) obtained radiosurgical cure and 46 (63%) achieved excellent outcomes after repeat radiosurgery. Of these, 100% achieved excellent outcomes in Group 1, 70% did so in Group 2, 47% in Group 3, and 14% in Group 4. The RBAS correlated with excellent outcomes after overall treatment (p < 0.001). Two hundred seventy-seven patients (69%) obtained AVM obliteration, and 62% achieved excellent outcomes. In Group 1, 87% achieved excellent outcomes, 75% did so in Group 2, 61% in Group 3, and 24% in Group 4., Conclusions: The RBAS is a good predictor of patient outcomes after LINAC radiosurgery.

Image guided surgery is currently performed using frame-based as well as frameless approaches. In order to reduce the invasive nature of stereotactic guidance as well as to reduce the cost in both equipment and time required within the operating room we investigated the use of rapid prototyping (RP) technology. In our approach we fabricated custom patient specific face-masks and guides that can be applied to the patient during surgery. These guides provide a stereotactic reference for the accurate placement of surgical tools to a pre-planned target along a pre-planned trajectory. While the use of RP machines has previously been shown to be satisfactory for the accuracy standpoint, one of our design criteria, completing the entire built and introduction into the sterile field in less than 120 minutes, was unobtainable. Our primary problems were the fabrication time and the non-resistance of the built material to high-temperature sterilization. In the current study, we have investigated the use of subtractive rapid prototyping (SRP) machines to perform the same quality of surgical guidance while improving the fabrication time and allowing for choosing materials suitable for sterilization. Because SRP technology does not offer the same flexibility as RP in term of prototype shape and complexity, our software program was adapted to provide new guide designs suitable for SRP fabrication. The biopsy guide was subdivided for a more efficient built with the parts being uniquely assembled to form the final guide. The accuracy of the assembly was then assessed using a modified Brown-Roberts-Wells phantom base that allows measuring the position of a biopsy needle introduced into the guide and comparing it with the actual planned target. These tests showed that 1) SRP machines provide an average accuracy of 0.77 mm with a standard deviation of 0.05 mm (plus or minus one image pixel) and 2) SRP allows for fabrication and sterilization within three and a half hours after diagnostic image acquisition and we are confident that that further improvements can reduce this time to less than two hours. Further tests will determine the accuracy of the positioning of the face mask on the patient's head under an IRB-approved trial judged against actual frame-based and frameless systems.

The search for efficacious, minimally invasive neurosurgical treatment has led to the development of the operating microscope, endovascular treatment, and endoscopic surgery. One of the most minimally invasive and exciting discoveries is the use of targeted, high-dose radiation for neurosurgical disorders. Radiosurgery is truly minimally invasive, delivering therapeutic energy to an accurately defined target without an incision, and has been used to treat a wide variety of pathological conditions, including benign and malignant brain tumors, vascular lesions such as arteriovenous malformations, and pain syndromes such as trigeminal neuralgia. Over the last 50 years, a tremendous amount of knowledge has been garnered, both about target volume and radiation delivery. This review covers the intense study of these concepts and the development of linear accelerators to deliver stereotactic radiosurgery. The fascinating history of stereotactic neurosurgery is reviewed, and a detailed account is given of the development of linear accelerators and their subsequent modification for radiosurgery.

Trigeminal neuralgia, also called tic douloureux, is a commonly misdiagnosed disorder characterized by intense facial pain. It is a chronic pain disorder that affects the fifth cranial nerve, usually in the fifth to seventh decade of life. Medication is the first line of treatment but frequently fails over time. At that point, many patients seek surgical intervention. This study reviews 108 patients treated over a 1-year period at the University of Florida with one of two surgical procedures: radiofrequency lesioning and microvascular decompression. The short-term results of this experience are reviewed and discussed.

Objective: In this paper, the authors review the results of a single-center experience using linear accelerator (LINAC) radiosurgery for the treatment of cavernous sinus meningiomas., Methods: This is a retrospective analysis with a median follow-up of 50 months. All patients were treated on an outpatient basis. Fifty-five patients were treated and 6 patients were lost to follow-up. Changes in preradiosurgery cranial nerve deficits and symptoms as well as actuarial local tumor control were evaluated., Results: The actuarial local tumor control was 100% at 5 years and 98% at 10 years. One patient had enlargement of tumor. Sixty-five percent had improvement in preradiosurgery cranial nerve deficits, 31% were unchanged and 1 patient (3.5%) was worse. Only 1 patient developed a new neurologic deficit., Conclusions: This is the largest LINAC radiosurgery experience for cavernous sinus meningiomas reported to date. Radiosurgery appears to offer greatly superior tumor control and much lower morbidity than surgical resection of cavernous sinus meningiomas., ((c) 2009 S. Karger AG, Basel.)

Objective: The purpose of this paper is to report on a case of a successful dorsal root entry zone procedure done for the treatment of postherpetic neuralgia and to provide unique MRI documentation outlining the precise location of the surgical lesion., Clinical Presentation: A 79-year-old female presented with postherpetic neuralgia in the left V1 distribution following a herpes zoster infection in that area 7 weeks earlier. She described the pain as constant, burning, aching, and throbbing, rating it as a 10 on a scale from 1 to 10. Prior to surgery, the patient was on large doses of narcotics, which were causing her to be severely somnolent. INTERVENTION OR TECHNIQUE: A dorsal root entry zone electrode with 2 mm of exposed tip was sequentially inserted into the dorsal root entry zone where 30-second, 80-degree lesions were made. The lesions were superficially continuous over the entire dorsal root entry zone from the upper cervical region to the obex. The postherpetic pain completely resolved immediately after surgery and the patient continued to have total pain relief 1 year later. An MRI performed 2 weeks after surgery clearly showed the location of the lesions., Conclusion: This unique clinical radiographic correlation shows that a nucleus caudalis dorsal root entry zone lesion, performed according to the described procedure, will be largely confined to the nucleus caudalis., (Copyright 2009 S. Karger AG, Basel.)

Objective: Stereotactic radiosurgery is a commonly used treatment method in the management of metastatic brain tumors. When lesions enlarge after radiosurgery, it may represent tumor regrowth, radiation necrosis, or both. The purpose of this study was to determine whether standard magnetic resonance imaging (MRI) sequences could reliably distinguish between these pathological possibilities., Methods: A total of 619 patients, reported in a previous study, were treated with radiosurgery for metastatic brain tumors. Of those patients, 59 underwent subsequent craniotomy for symptomatic lesion enlargement. Of those 59 patients, 32 had complete preoperative MRI studies as well as surgical pathology reports. The following MRI features were analyzed in this subset of patients: arteriovenous shunting, gyriform lesion or edema distribution, perilesional edema, cyst formation, and pattern of enhancement. A novel radiographic feature, called the lesion quotient, which is the ratio of the nodule as seen on T2 imaging to the total enhancing area on T1 imaging, was also analyzed., Results: Sensitivity, specificity, and predictive values were computed for each radiographic characteristic. Lesions containing only radiation necrosis never displayed gyriform lesion/edema distribution, marginal enhancement, or solid enhancement. All lesions exhibited perilesional edema. A lesion quotient of 0.6 or greater was seen in all cases of recurrent tumor, a lesion quotient greater than 0.3 was seen in 19 of 20 cases of combination pathology, and a lesion quotient of 0.3 or less was seen in 4 of 5 cases of radiation necrosis. The lesion quotient correlated with the percentage of tumor identified on pathological specimens., Conclusion: The lesion quotient appears to reliably identify pure radiation necrosis on standard sequence MRI. Other examined radiographic features, including arteriovenous shunting, gyriform lesion/edema distribution, enhancement pattern, and cyst formation, achieved 80% or greater predictive value but had either low sensitivity or low specificity.

Objective: To review one of the largest single-institution experiences treating metastatic brain disease with stereotactic radiosurgery., Methods: We performed a retrospective analysis of 619 patients who underwent linear accelerator-based stereotactic radiosurgery for 1569 brain metastases between May 1989 and February 2006. Patient characteristics and treatment parameters were obtained prospectively. Patients were followed up at regular intervals clinically and with imaging studies to document local control, regional control, and survival. Cox proportional hazards analysis was performed using SAS version 9.1 software (SAS Institute, Cary, NC)., Results: Median actuarial survival was 7.9 months. 1- and 2-year actuarial survival probabilities were 0.36 and 0.14, respectively. Radiation Therapy Oncology Group Recursive Partitioning Analysis Class I or II was associated with improved survival, but the difference between the two was insignificant. Female sex, younger age, higher Karnofsky performance status, controlled primary tumor, absence of systemic metastases, asynchronous presentation of brain metastasis, fewer brain metastases, smaller total volume of brain metastases, surgery prior to radiosurgery, and multiple radiosurgical treatments were also associated with improved survival. Melanoma metastasis was associated with impaired survival. Local control was achieved in 84.3% of all lesions treated. 1- and 2-year actuarial local control probabilities were 0.82 and 0.72, respectively. Whole brain radiation therapy prior to radiosurgery was associated with improved regional control., Conclusions: Linear accelerator-based stereotactic radiosurgery is a safe and effective treatment for patients with metastatic brain tumors. Selection of patients who are likely to benefit most from radiosurgery is complex and treatment decisions should be based on the entire clinical picture.

Linear accelerator (LINAC) radiosurgery was developed in the 1980s. The treatment paradigm uses the rotating high-energy X-ray output of the LINAC to focus many hundreds of 'beam equivalents' on intracranial or spinal targets. At the University of Florida, 450 vestibular schwannomas have been treated. Tumor control has been achieved in 90% (5- year actuarial data). 99% of patients treated have required no further intervention. Since reducing the treatment dose to 1,250 cGy, in 1994, the incidence of facial and trigeminal nerve injury has been <1%. No instance of malignant tumor transformation has been observed. Other institutions using modern LINAC techniques report similar excellent results. We believe that radiosurgery is the treatment of choice for smaller vestibular schwannomas.

Object: The goal in this study was to review the effects of treatment plan quality on outcomes after radiosurgery for vestibular schwannoma (VS)., Methods: Between July 1988 and August 2005, 390 patients were treated. The results of this experience have been published recently. In this study the authors looked at dosimetry variables: conformity of treatment plan and steepness of dose gradient, in the same group of patients. Over the duration of this study, dosimetry evolved from a single isocenter with marginal conformity to multiple isocenters with high conformity. Multivariate statistics were used to determine the effects of these variables on tumor control and on two types of complication, facial weakness and facial numbness., Results: The 5-year actuarial tumor control was 91%. Dosimetry had no effect on tumor control. Eighteen patients (4.6%) reported new-onset facial weakness and 14 (3.6%) reported new-onset facial numbness. Since 1994, when peripheral treatment doses were lowered to 1250 cGy, only three (1%) of 298 patients have experienced facial weakness and two (0.7%) of 298 have experienced facial numbness. Statistical analysis confirms, as in the prior study, that treatment volume and treatment dose are significant predictors of both facial weakness and facial numbness. In this model, prior tumor growth was also significant. Dosimetry, however, is definitely not a significant predictor of either complication., Conclusions: Treatment dose appears to be much more important than treatment plan quality in the prevention of facial numbness or weakness after radiosurgery for VS.

The last decade has seen the introduction of advanced technologies that have enabled much more precise application of therapeutic radiation. These relatively new technologies include multileaf collimators, 3-dimensional conformal radiotherapy planning, and intensity modulated radiotherapy in radiotherapy. Therapeutic dose distributions have become more conformal to volumes of disease, sometimes utilizing sharp dose gradients to deliver high doses to target volumes while sparing nearby radiosensitive structures. Thus, accurate patient positioning has become even more important, so that the treatment delivered to the patient matches the virtual treatment plan in the computer treatment planning system. Optical and image-guided radiation therapy systems offer the potential to improve the precision of patient treatment by providing a more robust fiducial system than is typically used in conventional radiotherapy. The ability to accurately position internal targets relative to the linac isocenter and to provide real-time patient tracking theoretically enables significant reductions in the amount of normal tissue irradiated. This report reviews the concepts, technology, and clinical applications of optical tracking systems currently in use for stereotactic radiation therapy. Applications of radiotherapy optical tracking technology to respiratory gating and the monitoring of implanted fiducial markers are also discussed.

Objective: Hyperbaric oxygenation is a rarely used method of treatment for steroid-refractory radiation-induced edema after stereotactic radiosurgery. We present its successful implementation for a radiosurgical complication after the treatment of a deep, large arteriovenous malformation. We also review the literature on hyperbaric oxygenation for radiation-induced complications., Clinical Presentation: A 25-year-old man underwent radiosurgical treatment for a large arteriovenous malformation. Three years later, substantially smaller remaining nidus was retreated. Five months after that treatment, the patient developed edema around the nidus and hemiparesis. This problem was refractory to high-dose steroids., Intervention: The patient underwent a course of 25 hyperbaric oxygenation treatments. Within 1 month, the edema and hemiparesis had improved, allowing steroids to be tapered. A follow-up examination 1 year later revealed complete thrombosis of the arteriovenous malformation and minimal neurological deficit., Conclusion: This technical case report adds to the few studies in the literature suggesting that hyperbaric oxygenation therapy, in conjunction with a slow steroid taper, is a reasonable addition to the treatment armamentarium for radiation-induced cerebral edema associated with clinically evident neurological deficits.

Background: Patients with bilateral vestibular schwannomas offer a unique opportunity to determine the effectiveness of radiosurgery. By using the untreated tumor as an internal control, one can determine whether radiosurgery was able to interrupt the natural history of the treated tumor., Methods: From September 1998 to November 2004, 13 patients with neurofibromatosis type 2 had 14 tumors treated with radiosurgery at the University of Florida. A retrospective analysis was performed on these patients. Actuarial statistics were used to analyze local control in both the treated and untreated tumor., Results: The average follow-up length was 38 months. One patient failed to send a follow-up MRI. Actuarial local control in the treated tumors was 100% at 1 year and 92% at 2 and 5 years. Only 1 of the treated tumors continued to grow. In the untreated tumors, actuarial local control was 100% at 1 year, 78% at 2 years and 21% at 5 years. None of the untreated tumors decreased in size., Conclusion: In all but 1 patient with follow-up data, radiosurgery successfully prevented or reversed tumor growth. Additionally, half of the untreated tumors continued to grow. This study shows that radiosurgery alters the natural history of vestibular schwannomas., ((c) 2007 S. Karger AG, Basel.)

Image-guided surgery can be broken down into two broad categories: frame-based guidance and frameless guidance. In order to reduce both the invasive nature of stereotactic guidance and the cost in equipment and time, we have developed a new guidance technique based on rapid prototyping (RP) technology. This new system first builds a computer model of the patient anatomy and then fabricates a physical reference frame that provides a precise and unique fit to the patient anatomy. This frame incorporates a means of guiding the surgeon along a preplanned surgical trajectory. This process involves (1) obtaining a high-resolution CT or MR scan, (2) building a computer model of the region of interest, (3) developing a surgical plan and physical guide, (4) designing a frame with a unique fit to the patient's anatomy with a physical linkage to the surgical guide, and (5) fabricating the frame using an RP unit. Software was developed to support these processes. To test the accuracy of this process, we first scanned and reproduced a plastic phantom fabricated to validate the system's ability to build an accurate virtual model. A target on the phantom was then identified, a surgical approach planned, a surgical guide designed, and the accuracy and precision of guiding a probe to that target were determined. Steps 1 through 5 were also evaluated using a head phantom. The results show that the RP technology can replicate an object from CT scans with submillimeter resolution. The fabricated reference frames, when positioned on the surface of the phantom and used to guide a surgical probe, can position the probe tip with an accuracy of 1.7 mm at the probe tip. These results demonstrate that the RP technology can be used for the fabrication of customized positioning frames for use in image-guided surgery.