Age-Related Changes in the Temperature of the Lumbar Spine Measured by Passive Microwave Radiometry (MWR).

A study was conducted to determine the age dependence of the temperature of the low back in the region of the five lumbar vertebrae by using passive microwave radiometry (MWR). The rationale for the study is that the infrared brightness on which the temperature measurement is based will be dependent upon blood circulation and thus on metabolic, vascular, and other regulatory factors. The brightness and infrared temperatures were determined in five zones above each of the medial, left, and right lateral projections of the vertebrae. A total of 115 healthy subjects were recruited, aged between 18 and 84 years. No significant differences in infrared temperature were detected. As predicted, brightness temperature increased until 25 years old and then gradually decreased. In subjects over 70 years of age, compared with those aged 60-70 years, there is a significant increase in brightness temperature at the level of 3-5 lumbar vertebrae by 0.3-0.7 °C. This is interpreted as indicating that individuals who have lived to an advanced age successfully maintain metabolic and regenerative processes. The benchmark data that has been obtained can be usefully employed in future studies of the aetiology of low back pain. In particular, the prospect exists for the technology to be used to provide a non-invasive biomarker to evaluate the effectiveness of antiaging therapies.

Impact of a Perioperative Protocol on Length of ICU and Hospital Stay in Complex Spine Surgery.

BACKGROUND: In an attempt to improve patient care, a perioperative complex spine surgery management protocol was developed through collaboration between spine surgeons and neuroanesthesiologists. The aim of this study was to investigate whether implementation of the protocol in 2015 decreased total hospital and intensive care unit (ICU) length of stay (LOS) and complication rates after elective complex spine surgery. MATERIALS AND METHODS: A retrospective cohort study was conducted by review of the medical charts of patients who underwent elective complex spine surgery at an academic medical center between 2012 and 2017. Patients were divided into 2 groups based on the date of their spine surgery in relation to implementation of the spine surgery protocol; before-protocol (January 2012 to March 2015) and protocol (April 2015 to March 2017) groups. Outcomes in the 2 groups were compared, focusing on hospital and ICU LOS, and complication rates. RESULTS: A total of 201 patients were included in the study; 107 and 94 in the before-protocol and protocol groups, respectively. Mean (SD) hospital LOS was 14.8±10.8 days in the before-protocol group compared with 10±10.7 days in the protocol group (P<0.001). The spine surgery protocol was the primary factor decreasing hospital LOS; incidence rate ratio 0.78 (P<0.001). Similarly, mean ICU LOS was lower in the protocol compared with before-protocol group (4.2±6.3 vs. 6.3±7.3 d, respectively; P=0.011). There were no significant differences in the rate of postoperative complications between the 2 groups (P=0.231). CONCLUSION: Implementation of a spine protocol reduced ICU and total hospital LOS stay in high-risk spine surgery patients.

Implementing an infection control and prevention program decreases the incidence of healthcare-associated infections and antibiotic resistance in a Russian neuro-ICU.

Background: The impact of infection prevention and control (IPC) programs in limited resource countries such as Russia are largely unknown due to a lack of reliable data. The aim of this study is to evaluate the effect of an IPC program with respect to healthcare associated infection (HAI) prevention and to define the incidence of HAIs in a Russian ICU. Methods: A pioneering IPC program was implemented in a neuro-ICU at Burdenko Neurosurgery Institute in 2010 and included hand hygiene, surveillance, contact precautions, patient isolation, and environmental cleaning measures. This prospective observational cohort study lasted from 2011 to 2016, included high-risk ICU patients, and evaluated the dynamics of incidence, etiological spectrum, and resistance profile of four types of HAIs, including subgroup analysis of device-associated infections. Survival analysis compared patients with and without HAIs. Results: We included 2038 high-risk patients. By 2016, HAI cumulative incidence decreased significantly for respiratory HAIs (36.1% vs. 24.5%, p-value = 0.0003), urinary-tract HAIs (29.1% vs. 21.3%, p-value = 0.0006), and healthcare-associated ventriculitis and meningitis (HAVM) (16% vs. 7.8%, p-value = 0.004). The incidence rate of EVD-related HAVM dropped from 22.2 to 13.5 cases per 1000 EVD-days. The proportion of invasive isolates of Klebsiella pneumoniae and Acinetobacter baumannii resistant to carbapenems decreased 1.7 and 2 fold, respectively. HAVM significantly impaired survival and independently increasing the probability of death by 1.43. Conclusions: The implementation of an evidence-based IPC program in a middle-income country (Russia) was highly effective in HAI prevention with meaningful reductions in antibiotic resistance.

Healthcare-associated ventriculitis and meningitis in a neuro-ICU: Incidence and risk factors selected by machine learning approach.

PURPOSE: To define the incidence of healthcare-associated ventriculitis and meningitis (HAVM) in the neuro-ICU and to identify HAVM risk factors using tree-based machine learning (ML) algorithms. METHODS: An observational cohort study was conducted in Russia from 2010 to 2017, and included high-risk neuro-ICU patients. We utilized relative risk analysis, regressions, and ML to identify factors associated with HAVM development. RESULTS: 2286 patients of all ages were included, 216 of them had HAVM. The cumulative incidence of HAVM was 9.45% [95% CI 8.25-10.65]. The incidence of EVD-associated HAVM was 17.2 per 1000 EVD-days or 4.3% [95% CI 3.47-5.13] per 100 patients. Combining all three methods, we selected four important factors contributing to HAVM development: EVD, craniotomy, superficial surgical site infections after neurosurgery, and CSF leakage. The ML models performed better than regressions. CONCLUSION: We first reported HAVM incidence in a neuro-ICU in Russia. We showed that tree-based ML is an effective approach to study risk factors because it enables the identification of nonlinear interaction across factors. We suggest that the number of found risk factors and the duration of their presence in patients should be reduced to prevent HAVM.

Effects of Anesthetic Management on Early Postoperative Recovery, Hemodynamics and Pain After Supratentorial Craniotomy.

Various clinical trials have assessed how intraoperative anesthetics can affect early recovery, hemodynamics and nociception after supratentorial craniotomy. Whether or not the difference in recovery pattern differs in a meaningful way with anesthetic choice is controversial. This review examines and compares different anesthetics with respect to wake-up time, hemodynamics, respiration, cognitive recovery, pain, nausea and vomiting, and shivering. When comparing inhalational anesthetics to intravenous anesthetics, either regimen produces similar recovery results. Newer shorter acting agents accelerate the process of emergence and extubation. A balanced inhalational/intravenous anesthetic could be desirable for patients with normal intracranial pressure, while total intravenous anesthesia could be beneficial for patients with elevated intracranial pressure. Comparison of inhalational anesthetics shows all appropriate for rapid emergence, decreasing time to extubation, and cognitive recovery. Comparison of opioids demonstrates similar awakening and extubation time if the infusion of longer acting opioids was ended at the appropriate time. Administration of local anesthetics into the skin, and addition of corticosteroids, NSAIDs, COX-2 inhibitors, and PCA therapy postoperatively provided superior analgesia. It is also important to emphasize the possibility of long-term effects of anesthetics on cognitive function. More research is warranted to develop best practices strategies for the future that are evidence-based.

Neurosurgery in Siberia.

There is archaeological evidence that the first neurosurgical procedure in what is now known as Siberia was performed in 8005 ± 100 B.C. According to signs of bone growth, perhaps more than half of the individuals who received the ancient trepanations survived. In Siberia, the first operations on the human brain and spinal cord were performed in 1909 at Tomsk University Hospital by the outstanding Russian surgeon and professor Vladimir M. Mysh. Professor Mysh initially moved from Saint Petersburg to Tomsk and later to Novosibirsk. Nicolay N. Burdenko, the founder of Russian neurosurgery and the Moscow Neurosurgical Institution, began his medical education at the Tomsk Imperial University. In the 1950s, Professor Ksenia I. Kharitonova exerted her great influence upon the development of neurosurgery in Siberia. Since 1955, and for 30 years thereafter, Professor Kharitonova was recognized as a principal leader of Siberian neurosurgery. She applied every effort to spread neurosurgical knowledge, and she popularized best practices around Siberia and the Far East. Perestroika deconstructed and ultimately eliminated the orderly system of neurosurgical service in the Soviet Union. From another perspective, the process opened the window to the world. Fully equipped centers and clinics with state-of-the-art techniques for neuro-oncology, cerebrovascular diseases, neurotrauma, and spinal pathology management in Novosibirsk, Barnaul, Kemerovo, and Irkutsk were enabled.

Early postoperative cognitive dysfunction and postoperative delirium after anaesthesia with various hypnotics: study protocol for a randomised controlled trial--the PINOCCHIO trial.

BACKGROUND: Postoperative delirium can result in increased postoperative morbidity and mortality, major demand for postoperative care and higher hospital costs. Hypnotics serve to induce and maintain anaesthesia and to abolish patients' consciousness. Their persisting clinical action can delay postoperative cognitive recovery and favour postoperative delirium. Some evidence suggests that these unwanted effects vary according to each hypnotic's specific pharmacodynamic and pharmacokinetic characteristics and its interaction with the individual patient.We designed this study to evaluate postoperative delirium rate after general anaesthesia with various hypnotics in patients undergoing surgical procedures other than cardiac or brain surgery. We also aimed to test whether delayed postoperative cognitive recovery increases the risk of postoperative delirium. METHODS/DESIGN: After local ethics committee approval, enrolled patients will be randomly assigned to one of three treatment groups. In all patients anaesthesia will be induced with propofol and fentanyl, and maintained with the anaesthetics desflurane, or sevoflurane, or propofol and the analgesic opioid fentanyl.The onset of postoperative delirium will be monitored with the Nursing Delirium Scale every three hours up to 72 hours post anaesthesia. Cognitive function will be evaluated with two cognitive test batteries (the Short Memory Orientation Memory Concentration Test and the Rancho Los Amigos Scale) preoperatively, at baseline, and postoperatively at 20, 40 and 60 min after extubation.Statistical analysis will investigate differences in the hypnotics used to maintain anaesthesia and the odds ratios for postoperative delirium, the relation of early postoperative cognitive recovery and postoperative delirium rate. A subgroup analysis will be used to categorize patients according to demographic variables relevant to the risk of postoperative delirium (age, sex, body weight) and to the preoperative score index for delirium. DISCUSSION: The results of this comparative anaesthesiological trial should whether each the three hypnotics tested is related to a significantly different postoperative delirium rate. This information could ultimately allow us to select the most appropriate hypnotic to maintain anaesthesia for specific subgroups of patients and especially for those at high risk of postoperative delirium. REGISTERED AT TRIAL.GOV NUMBER: ClinicalTrials.gov: NCT00507195.

Early decreased tumor volume following fractionated Gamma Knife Radiosurgery for metastatic melanoma and the role of "adaptive radiosurgery": case report.

OBJECTIVE: We report a case in which fractionated gamma knife radiosurgery was used to treat a metastatic melanoma lesion. The tumor demonstrated a rapid response to radiosurgery with an observable reduction in tumor volume between the second and third treatments, requiring a favorable modification in the third fractionated treatment. CLINICAL PRESENTATION: A 61-year-old woman presented with a frontal floor metastatic melanoma lesion that was located adjacent to the optic apparatus. INTERVENTION: Gamma knife radiosurgery was administered in three fractionated treatments of 6.5 Gy to the 50% isodose line in each case. Repeat imaging for the purpose of planning demonstrated that tumor volume at the time of the third treatment, 9 days following the first treatment, had decreased by 31%, resulting in a 21% decrease in the dose administered to the optic chiasm. CONCLUSION: A case of metastatic melanoma treated with fractionated GKRS is presented, in which a significant reduction in tumor volume was noted 9 days following the initial treatment. This case provides insight into the rate with which malignant neoplasms may respond to intermediate-dose hypofractionated GKRS, and lends support to the concept of "adaptive radiosurgery" as a means of optimizing radiation to an evolving target while minimizing collateral radiation to surrounding structures.

Long-term outcomes and patterns of tumor progression after gamma knife radiosurgery for benign meningiomas.

OBJECT: To characterize the timing and patterns of long-term treatment failure after Gamma Knife radiosurgery (GKRS) for benign meningiomas. METHODS: Data were retrospectively reviewed in 116 patients who underwent 136 GKRS treatments for benign intracranial meningiomas from 1996 to 2004. Patients with atypical or malignant meningiomas were excluded. Surgical resection preceded GKRS in 72 patients (62%). The median tumor volume was 3.4 cm, and the median prescription dose to the 50% isodose line was 16 Gy. RESULTS: The median follow-up time was 75 months (range, 4-146 months). Overall tumor control was achieved in 128 of 136 lesions (94%), of which tumor size was stable in 68% and decreased in 26%. Seven patients experienced disease progression in 8 tumors, occurring at a mean time of 90 months. The overall 5-year and 10-year actuarial tumor control rate was 98.9% and 84%, respectively. Characteristics corresponding to tumor progression included insufficient tumor coverage (98% vs 93%, P = .007), cavernous sinus lesions, and meningiomatosis. Complications after GKRS developed in 8% of patients, in whom the mean tumor volume was nearly double that in patients with no adverse effects (11 vs 5.7 cm3, P = .003). CONCLUSIONS: GKRS demonstrates excellent long-term tumor control in the management of benign meningiomas. Tumor progression occurred at a mean time of 7.5 years after GKRS, reinforcing the need for long-term surveillance despite initial tumor control. Treatment failure was related to undercoverage of lesions in the majority of cases, with the remainder demonstrating evidence of abnormal tumor biology.

Neurosurgical center in Astana, capital of Kazakhstan.

Formation of the Republican Scientific Center of Neurosurgery (RSCN) in Astana, the new capital of Kazakhstan, has allowed improvements in neurosurgery in this country on a qualitatively new level. The latest achievements in neuro-oncologic, spine, pediatric, and vascular neurosurgery are available in the RSCN. The center has come into being as a result of dynamic economic development in Kazakhstan. The RSCN is ready to become a leading neurosurgical center in the central Asia region.

Delayed toxicity from gamma knife radiosurgery to lesions in and adjacent to the brainstem.

The aims of this study were to assess the incidence of, and risk factors for, delayed toxicity following gamma knife stereotactic radiosurgery (GKRS) to lesions in and adjacent to the brainstem. We retrospectively evaluated the delayed toxicity of GKRS following the treatment of 114 lesions in and adjacent to the brainstem in 107 patients. The median tumor volume was 6.2 cm(3) and the median dose to the tumor margin was 16Gy. The mean follow-up was 40 months. Thirteen patients (12%) demonstrated clinical evidence of delayed toxicity, with a median latency to the development of toxicity of 6 months. The actuarial incidence of toxicity at 1 year and 5 years was 10.2% and 13.8%. Larger tumor volume (p=0.02) and larger treatment volume (p=0.04) were associated with an increased incidence of delayed toxicity. Large lesions adjacent to the brainstem have a higher than previously suspected rate of delayed toxicity.

Alexander N. Konovalov: neurosurgeon, leader, mentor.

Alexander N. Konovalov, M.D., Ph.D., has been the director of the esteemed Burdenko Neurosurgery Institute for 32 years and is the foremost figure in Russian neurosurgery. He brought neurosurgery in the former Soviet Union onto the world stage despite the isolationist policies of its former totalitarian regime. After the fall of the Soviet Union, he maintained the unity of the Eastern European neurosurgeons. We present the activity and achievements of Alexander N. Konovalov.

Hemodynamic and oxygen transport patterns after head trauma and brain death: implications for management of the organ donor.

OBJECTIVES: The aims of the present study were to describe the temporal hemodynamic and oxygen transport patterns of patients with head injuries as well as the patterns of those who became brain dead to better understand the role of underlying central regulatory hemodynamic mechanisms and ultimately to improve rates of organ donation. METHODS: We studied 388 consecutive noninvasively monitored patients with severe head trauma; 79 of these became brain dead. Monitoring was started shortly after admission to the emergency department and was designed to describe the sequence of cardiac, pulmonary, and tissue perfusion functions by cardiac index (CI), mean arterial pressure, heart rate, arterial saturation by pulse oximetry (Sapo2), and transcutaneous oxygen and carbon dioxide (Ptco2/Fio2 and Ptcco2) patterns. The latter were used as markers of tissue perfusion or oxygenation. RESULTS: Patients with head injuries who subsequently became brain dead initially had low CI with poor tissue perfusion beginning shortly after emergency department admission. This was followed by a prolonged period characterized by high CI (4.43 +/- 1.3 L x min(-1) x m2) and enhanced tissue oxygenation (Ptco2/Fio2 238 +/- 186). In the late or end stage of brain death, hemodynamic deterioration and collapse led rapidly to arrest. In attempts to maintain hemodynamic stability for organ donation, the effects of various therapies on the hemodynamic patterns were preliminarily described. CONCLUSIONS: The hyperdynamic state with exaggerated peripheral tissue perfusion or oxygenation in brain-dead patients associated with loss of central vasoconstrictive mechanisms of the stress response resulted in unopposed peripheral metabolic vasodilatation producing high CI and tissue perfusion.

Postoperative Gamma Knife surgery for benign meningiomas of the cranial base.

OBJECT: The standard treatment for meningiomas is complete resection, but the proximity of skull base meningiomas to important neurovascular structures makes complete excision of the lesion difficult or impossible. The authors analyzed the mid- and long-term results obtained in patients treated with postresection Gamma Knife surgery (GKS) for residual or recurrent benign meningiomas of the cranial base. METHODS: Thirty-six patients with residual or recurrent benign meningiomas of the skull base following one or more surgical procedures underwent GKS. There were 31 women and five men, ranging in age from 22 to 73 years. The median tumor volume was 4.1 ml (range 0.8-20 ml) and the median radiation dose to the tumor margin was 16 Gy (range 15-16 Gy). RESULTS: Patients were followed for a median of 81 months (range 30-141 months) after GKS. At the end of the follow-up period, overall neurological improvement was observed in 16 patients (44.4%), whereas the condition in 20 patients (55.6%) was unchanged. One patient suffered transient cerebral edema 6 months after GKS. Based on imaging documentation, a partial response was seen in five patients (13.9%), the disease remained stable in 30 patients (83.3%), and in one patient (2.8%) there was an increase in tumor size. The actuarial progression-free survival rate was 100% at 5 years and 94.7% at 10 years. CONCLUSIONS: Gamma Knife surgery was shown to be an excellent adjunct to resection because of its durable rate of tumor control and low toxicity. It should be initially considered along with surgery for the treatment of complex skull base meningiomas.

Surgical outcomes in 118 patients with Rathke cleft cysts.

OBJECT: Microscopic Rathke cleft cysts are a common incidental autopsy finding, but some Rathke cleft cysts can become sufficiently large to cause visual impairment, hypothalamic-pituitary dysfunction, and headaches. In this study patients were evaluated pre- and postoperatively to ascertain the clinical significance of surgical intervention on endocrine and visual improvement. Factors correlated with cyst recurrence were also evaluated. METHODS: A retrospective analysis was conducted in 160 patients with Rathke cleft cysts who were treated between 1984 and 1995 and completed at least a 5-year follow-up period. Of these 160 patients, 118 initially exhibited symptoms of visual impairment or endocrine dysfunction, became symptomatic during the follow-up period, or were found to have cyst enlargement. These 118 patients underwent transsphenoidal surgery. Forty-two patients with incidental lesions that demonstrated no growth on magnetic resonance (MR) images were followed up without an operation. Complete resection, as observed on MR images 3 months postoperatively, was obtained in 114 (97%) of 118 patients. Vision improved postoperatively in 57 (98%) of 58 patients. Hypogonadism improved in 11 (18%) of 62 patients, growth hormone deficiency resolved in 14 (18%) of 78 patients, and hypocortisolemia resolved in one (14%) of seven patients. Twenty-two patients (19%) began to exhibit symptoms of diabetes insipidus, which had not been present preoperatively. The total 5-year recurrence rate was 18% (21 of 118 patients), with 12 patients requiring a repeated operation. Surgical and pathological factors that were found to be statistically associated with recurrence were the use of a fat and/or fascial graft for closure (p < 0.01) and the presence of squamous metaplasia in the cyst wall (p < 0.01). The extent of resection of the cyst wall was not associated with an increased rate of recurrence. In 42 (69%) of 61 patients the incidental cysts did not progress on imaging studies or clinically. CONCLUSIONS: This is the largest series of patients with symptomatic Rathke cleft cysts who received operative intervention and participated in the longest postoperative follow up reported in the literature. The high recurrence rate (18%) supports the theory that a relationship exists between a symptomatic Rathke cleft cyst and craniopharyngioma. Improvements in visual and endocrine dysfunction can be expected after surgical decompression of the optic apparatus and the hypothalamic-pituitary axis.

Gamma knife radiosurgery for benign cavernous sinus tumors: quantitative analysis of treatment outcomes.

OBJECTIVE: We review our 8-year experience with gamma knife radiosurgery (GKRS) for the treatment of patients with benign cavernous sinus tumors and present a quantitative analysis of factors relevant to treatment outcomes. METHODS: From 1994 to 2002, a total of 139 patients with benign cavernous sinus tumors were treated in 145 sessions. Their median age was 53 years, and the median follow-up was 3.5 years. The tumors included 57 meningiomas, 76 pituitary tumors (49 nonfunctional adenomas, 15 prolactinomas, 5 adrenocorticotropic hormone-secreting tumors, 6 growth hormone-secreting tumors, and 1 plurihormone-secreting tumor), 4 schwannomas, 1 hemangioma, and 1 paraganglioma. Sekhar tumor grades were as follows: I, n = 28 (20%); II, n = 42 (30%); III, n = 42 (30%); IV, n = 19 (14%); and V, n = 8 (6%). The median tumor volume was 3.4 cm(3), and the median prescribed dose was 15 Gy defined to the 50% isodose line. RESULTS: A total of 136 treated tumors (97.8%) were well controlled by GKRS, with low morbidity. For meningiomas, 29 tumors (51%) were unchanged and 26 (46%) were smaller at a median of 15.2 months. For pituitary tumors, 50 (66%) were unchanged and 25 (33%) were smaller at a median of 20.6 months. Improvement in cranial nerve (CN) function was seen in 19 (36.5%) of 52 patients with pre-GKRS deficits, and 3 patients (2.2%) developed new stable CN deficits after GKRS: 1 patient developed IVth CN palsy at 9 months, and 2 developed persistent VIth CN palsies at 43 and 45 months, respectively, that required surgical correction. Two patients developed transient VIth CN palsies at 48 months that self-resolved after another year. Endocrine function normalized for all 6 treated patients with a growth hormone-secreting tumor at a median of 18 months. One of the 5 adrenocorticotropic hormone-secreting tumors required retreatment after 17 months because of continued cortisol elevation. Thirteen (87%) of 15 prolactinoma patients had normalized prolactin levels within 2 years of the procedure; 2 patients relapsed by endocrine criteria at 18 and 22 months after GKRS. Two patients with normalized prolactin levels completed three normal pregnancies within 3 years of treatment. Six patients (4.3%) with a median tumor volume of 8 cm(3) developed radiation-induced injury at a median of 36 months after GKRS. Five of these patients also underwent external beam radiotherapy and received a median dose of 52.2 Gy in 30 fractions. Quantitative analysis revealed that the radiation dose to critical structures (optic apparatus and pons) is correlated with their distance from tumor margins. Underdosed tumor volume, tumor volume, and total treated volume are correlated with treatment outcomes. CONCLUSION: GKRS is a safe and effective treatment for selected patients with benign cavernous sinus tumors and is an important adjunct for treating postoperative tumor residual and/or recurrent tumor. Continued analysis of treated patients over an extended time is needed to evaluate long-term disease control and potential late GKRS complications.

Study of magnetic resonance imaging-based arteriovenous malformation delineation without conventional angiography.

OBJECTIVE: In this study, we aimed to assess the feasibility of arteriovenous malformation (AVM) delineation for gamma knife radiosurgery without conventional angiography and to correlate factors that may affect AVM delineation. METHODS: A series of 57 consecutive patients with AVMs treated with gamma knife radiosurgery from August 1994 to December 2000 were reviewed. All patients in the study had undergone pretreatment angiography. The mean AVM volume was 2.8 cm(3), with a median of 2.0 cm(3) (range, 0.04-22 cm(3)). All AVMs were delineated on the original frame-based magnetic resonance imaging (MRI) scans by a vascular neurosurgeon without the assistance of angiography and then compared with the actual AVM delineation on the basis of previously performed angiography and MRI. Univariate correlation analysis was used to determine the relationship of AVM coverage, size, diffuseness, previous embolization, and hemorrhage parameters. RESULTS: The study volume or MRI-based volume alone coincided with the actual treatment volume by a mean of 58% for diffuse and 87% for nondiffuse AVMs (P = 0.0005). At AVM volume greater than 2 cm(3), the median percentage of coinciding volume was 63% for embolized AVMs and 82% for nonembolized AVMs (P = 0.0315). Conversely, the study volume overestimated the actual treatment volume by a mean of 57% for AVMs larger than 2 cm(3) versus 25% for AVMs smaller than 2 cm(3) (P = 0.0012). In general, the percentage of the coinciding volume was inversely related to that of the excess volume, whereas both the study volume and the coinciding volume were proportionate to AVM volume at treatment. CONCLUSION: MRI-based AVM delineation without conventional angiography may be feasible only for selected patients, such as those with nondiffuse and large nonembolized AVMs.