Seizures and Brain Arterovenous Malformation: A Surgical Series.

Seizures are common symptoms of supratentorial arteriovenous malformations (AVMs). The potential risk factors for epilepsy in patients with AVMs are still controversial. The reported long-term outcome of seizures after surgical treatment of AVMs is variable and the data available are mainly from small retrospective case series.We identified all consecutive patients between 1990 and 2006 who underwent microsurgical resection of supratentorial AVMs at our institute. Pre-operative risk factors for seizures, intra-operative characteristics, long-term neurological disability, and seizure outcome (Engel's classification) were recorded and analyzed.During the study period, 110 patients underwent surgical resection of supratentorial AVM. Sixty of them (55 %) were symptomatic for seizures preoperatively. In our series, the absence of preoperative neurological deficits (p = 0.005), a large AVM size (p = 0.005), and no history of preoperative AVM hemorrhage (p < 0.001) were identified as risk factors for preoperative seizures. Following surgical resection, 77 % of patients with preoperative seizures had a modified Engel class I outcome. Among patients without a history of preoperative epilepsy, 56 % had new-onset seizures after surgical resection. None of the risk factors associated with preoperative seizures was associated with post-operative seizures. As there are no reliable factors predicting patients who may benefit from surgical treatment, epilepsy control should not be considered as the primary goal of AVMs surgery.

Surgical exclusion of unruptured middle cerebral artery aneurysms: experience of 126 cases.

A group of 126 surgical patients with 143 unruptured MCA aneurysms was evaluated in order to determine the risks of treatment and possible adjuncts for safer surgery. The precise location and size of the aneurysms were determined in each case; 21 aneurysms were located on the M1 tract, 109 on the main division - which consisted of more than two branches in 10 cases and was proximally located in 12 cases - and 13 were distal; 36 aneurysms were small (<7 mm), 90 standard, and 17 large or giant (>15 mm); 45 patients harbored multiple aneurysms (12 on the ipsilateral MCA). The aneurysms were excluded by clip in most cases, with the assistance of intraoperative flowmetry in 78 patients. Temporary proximal vessel occlusion was used in 57 patients (>10 min in 8 cases), without significant effects on radiological or clinical outcome. After surgery, newly occurring minor deficits were observed in 5 patients and significant deficits in 4; one patient died from an intractable coagulopathy. The low rate (3.9 %) of unfavorable results (modified Rankin Score > 2) linked to surgery justifies serious consideration for treatment in these patients, especially when facing the high disability rate after the rupture of aneurysms in this anatomical location.

Surgery after embolization of cerebral arterio-venous malformation: experience of 123 cases.

A group of 123 patients with large or critically located arterio-venous malformations (AVMs), operated on between 1990 and 2011 and who underwent preoperative embolization, was assessed in order to clarify the risks of this combined treatment. AVM location, volume, and Spetzler's grade were assessed in each case; AVM volume was over 20 cm(3) in 49 % of the cases; Spetzler's grade was 3 or above in 76 % of the cases (with 34 cases in grades 4-5). A mean of 2.3 embolization procedures per patient were carried out, using bucrylate and, more recently, Onyx and/or Glubran; a 4.5 % procedure-related complication rate was observed. Complications occurring after surgery were classified as hemorrhagic (16 cases, 8 requiring surgical evacuation) or ischemic (4 cases); hemorrhagic complications were more common for AVMs with volumes >20 cm(3) and/or deep feeders. Surgery-related unfavorable results (modified Rankin Score > 2) were observed in 6 % of patients in Spetzler's grade 3, and in 20-25 % of patients in grades 4-5. More recently, a triple treatment (radiosurgery + embolization + surgery) allowed for obtaining favorable results (mRS 0-2) in all patients. It has been concluded that a combined treatment with embolization and surgery constitutes a reasonable choice for complex cerebral AVMs; the association of radiosurgery may improve the patients outcome.

Results of surgery for cavernomas in critical supratentorial areas.

A total of 121 patients surgically treated between 1991 and 2011 for cavernomas in critical supratentorial areas were evaluated. Anatomical location, size and the possible association with developmental venous anomalies (DVA) were assessed in each case: 43 cavernomas were in the speech area, 39 were rolandic (or peri-rolandic), 14 insular, 10 nuclear, 9 calcarine and 6 ventricular. In 49 % of the cases, the cavernoma was <1.5 cm; in 6 patients, radiological growth was documented. A method of intraoperative localization was adopted in 78 cases: B-mode echography or a stereotactic guide in 22 cases, and a neuronavigation system in 56 cases; preoperative angiography was done in 22 cases. Early postoperative epilepsy (within 7 days of surgery) was observed in 15 cases. As for clinical outcome, 14 patients presented with mild symptoms (modified Rankin Scale 1-2); significant deficits occurred ex-novo in 5 patients. The presence of epilepsy at follow-up was assessed through the Maraire Scale: 44 % of patients presenting with epilepsy were free of seizures and without therapy at a mean follow-up of 4.6 years, and an additional 55 % had complete control of seizures with therapy. It is concluded that surgery is indicated in the management of cavernomas in critical supratentorial locations, with a caveat for insula and especially basal ganglia.

Operative classification of brain arteriovenous malformation. Part two: validation.

SUMMARY: The most important issue when dealing with a patient with a brain AVM is the decision whether to treat or not. Only after this decision has been made, taking into consideration a number of factors depending on both the patient and the specific type of AVM, can the best option for treatment be chosen. An operative classification of brain AVMs, previously adopted in the Department of Neuroradiology and Neurosurgery of Verona (Italy) and published in this journal, was subjected to validation in a consecutive group of 104 patients clinically followed for at least three years after completion of treatment. This classification, slightly modified from the original version concerning the importance of some specific items, allowed us to assess the indication to treat in each case, whatever type of treatment was offered to the patient.

The role of constitutive and inducible nitric oxide synthase in the human brain after subarachnoid hemorrhage.

AIM: Results of prior experimental studies show that nitric oxide (NO) plays an important role in the pathogenesis of vasospasm. In the present study, the expression of endothelial NO synthase (eNOS), neuronal NO synthase (nNOS) and of inducible NO synthase (iNOS) in the human brain after subarachnoid haemorrhage were studied. METHODS: Twenty-three samples of gyrus rectus or temporal operculum that were obtained during a surgical approach to anterior circulation aneurysms were used for this study. Seven samples were obtained during surgery from patients who underwent operation for unruptured aneurysms (control group). eNOS-mRNA, nNOS-mRNA and iNOS-mRNA were extracted and amplified by RT-PCR. Patients were subdivided for intergroup comparison by: age < 60 / > 60 years; source of sample; clinical grading; extent of subarachnoid clot; presence of intracerebral/intraventricular hematoma; surgical timing; vasospasm; outcome. RESULTS: There was a significant increase in the expression of eNOS between SAH and control groups (P=0.046); eNOS hyperexpression was higher in the patients in poor clinical conditions (P=0.002) and lasted until the late phase of haemorrhage. nNOS overall expression was unchanged but hyperexpression was observed in the patients in poor clinical conditions (P=0.008). There was a significant hyperexpression of iNOS in SAH group (P=0.026), and in patients with vasospasm (P=0.0024); the expression was significantly reduced in the late phase of haemorrhage (P=0.0038). CONCLUSIONS: The acute decrease of NO after SAH is not determined by reduced constitutive NOS expression and iNOS induction is a consequence of SAH and plays a major role in the pathogenesis of vasospasm.

Dural arteriovenous fistulas with aggressive course: clinical and angiographic correlations in two patients.

Cranial dural arteriovenous fistulas (DAVFs) usually present with non-aggressive symptoms. We here report two patients who presented a peculiar clinical picture related to DAVFs, with focal neurological signs and haemorrhagic (case 1) or ischaemic lesions (case 2) respectively. The clinical and angiographic findings and putative pathophysiological mechanisms are discussed.

Surgical management of ruptured aneurysms in the eighth and ninth decades.

BACKGROUND: The surgical management of elderly patients with aneurysmal subarachnoid haemorrhage (SAH) is controversial. The present study was performed to more clearly define issues facing elderly SAH patients undergoing surgical repair of their aneurysms. METHOD: Between 1990 and 2000, 100 patients, aged 70 years or older, were managed consecutively with aneurysmal surgical repair at Verona City Hospital. Ninety-seven of these were analysed with regard to age, clinical grade on admission, radiological features, and specific management components (3 patients were excluded from further analysis because of inadequate follow up data). Surviving patients were followed up for a minimum of 6 months and clinical outcome was assessed. FINDINGS: Hydrocephalus requiring permanent CSF diversion occurred in 44% of cases surviving beyond 10 days from their SAH. The development of hydrocephalus requiring shunting was delayed more than 6 weeks in 7% of these cases. Medical complications occurred in 22% of cases. Clinical grade of haemorrhage (p<0.001), early hydrocephalus requiring ventriculostomy (p=0.003) and the development of medical complications (p=0.03) were significantly associated with poor outcome. Clinical vasospasm was not a major determinant of outcome in this group. The need for permanent CSF diversion was significantly associated with increasing age (p=0.03), intraventricular haemorrhage (p<0.001), early hydrocephalus requiring ventriculostomy (p=0.003) and the development of medical complications (p=0.05). INTERPRETATION: Elderly patients experience a different range of complications following aneurysmal subarachnoid haemorrhage than their younger counterparts. Clinicians should remain alert to the development of hydrocephalus, especially of delayed onset.

Double-blind, randomized, vehicle-controlled study of high-dose tirilazad mesylate in women with aneurysmal subarachnoid hemorrhage. Part I. A cooperative study in Europe, Australia, New Zealand, and South Africa.

OBJECT: Findings from previous multicenter clinical trials have suggested that tirilazad mesylate, a synthetic nonhormonal 21-aminosteroid, might be effective in preventing delayed cerebral ischemia following subarachnoid hemorrhage (SAH). This beneficial effect, however, was greater in males than females, possibly because of gender-related pharmacokinetic differences. The authors sought to assess the effects of administering a larger dose of tirilazad in women with SAH. METHODS: To test the efficacy of a higher tirilazad mesylate dose in female patients, a prospective randomized, double-blind, vehicle-controlled trial was conducted at 56 neurosurgical centers in Europe, Australia, New Zealand, and South Africa. Eight hundred nineteen patients were randomly assigned to receive either 15 mg/kg/day of tirilazad mesylate or a placebo containing the citrate vehicle. The two groups were similar in prognostic factors for delayed cerebral ischemia and overall outcome. High-dose tirilazad appeared to be well tolerated because no differences in the incidence of untoward medical events were noted between the two groups. Medical and surgical interventions were no different in the two treatment groups except for hyperdynamic therapy (intentional hypervolemia, induced hypertension, and/or hemodilution), which was more often used in the placebo-treated group to counteract symptomatic vasospasm (24% of patients given placebo compared with 18% of patients given tirilazad, p = 0.02). Mortality rates and overall outcome, assessed using the Glasgow Outcome Scale at 3 months post-SAH, were not different between the two groups, despite a significantly lower incidence of delayed cerebral ischemia in patients given tirilazad. Post hoc subgroup analysis by neurological grade also did not reveal significant differences in outcome, although a trend toward a lower mortality rate favoring the study drug was present in patients with neurological Grade IV and V at admission (32% compared with 37%). Symptomatic vasospasm occurred in 33.7% of the placebo-treated patients as opposed to 24.8% of the patients who were given tirilazad (p = 0.005). The severity of symptomatic vasospasm was also attenuated by administration of the study drug (severe symptomatic vasospasm was reported in 11% of the placebo-treated patients compared with 6% of patients in the tirilazad-treated group (p = 0.008). Clinical cerebral infarction from vasospasm was also reduced from 13% in the vehicle-treated group to 8% in the tirilazad-treated group (p < 0.04). CONCLUSIONS: The authors conclude that high-dose tirilazad mesylate is well tolerated in women with aneurysmal SAH. Although a significant reduction in the incidence of symptomatic vasospasm was observed in the treatment group, the primary end point (mortality rate at 3 months post-SAH) was not affected by the study drug. The use of other potentially effective rescue therapies (that is, hypervolemia, hemodilution, and induced hypertension) to counteract vasospasm may have been responsible for these contrasting observations between the two groups.

Infraoptic course of the anterior cerebral artery associated with an anterior communicating artery aneurysm: anatomic case report and embryological considerations

OBJECTIVE AND IMPORTANCE: An infraoptic course of the proximal anterior cerebral artery is a rare anomaly that has been reported in 32 cases to date, often in association with cerebral aneurysms. This anomaly represents a maldevelopment in the embryogenesis of the anterior circle of Willis, resulting from the persistence of the primitive prechiasmal arterial anastomosis or an error in the development of the definitive ophthalmic artery (OphA). The case of a patient with a ruptured middle cerebral artery aneurysm and an anterior communicating artery aneurysm associated with this anomaly is described, and the anatomic features are outlined. CLINICAL PRESENTATION: A 30-year-old male patient with a right temporal hematoma and subarachnoid hemorrhage was admitted to our department 4 days after the hemorrhaging episode, with normal neurological examination results. Angiography revealed a right middle cerebral artery aneurysm and an anterior communicating artery aneurysm with an anomalous precommunicating tract. INTERVENTION: The patient was surgically treated 14 days after the hemorrhaging episode, through a right frontopterional craniotomy; both aneurysms were excluded by clipping. The anomalous infraoptic proximal tract of the anterior cerebral artery was well documented, with its origin adjacent to the OphA. The patient remained neurologically intact after surgery and was discharged 8 days later. CONCLUSION: The anomalous infraoptic course of the proximal anterior cerebral artery was associated with a low bifurcation of the ipsilateral internal carotid artery and the absence of the contralateral precommunicating tract in this patient. The strict anatomic relationship with the origin of the OphA suggests an error in the development of the definitive OphA, with persistence of an anastomotic loop between the primitive dorsal and ventral OphAs. It is concluded that, for aneurysm surgery, careful angiographic evaluation and an understanding of the neurovascular relationships in the circle of Willis are essential for a successful postoperative course, especially when very rare vascular anomalies are treated.

Epidemiology and pathophysiology of cerebral vasospasm following subarachnoid hemorrhage.

Cerebral vasospasm still accounts for a significant percent of morbidity and mortality after subarachnoid hemorrhage (SAH). There is a clear-cut temporal course for this phenomenon, with a peak of incidence at the end of the first week after SAH. The occurrence of vasospasm is significantly related to the amount of blood deposited in the subarachnoid cisterns. Non-invasive diagnosis and monitoring of vasospasm is now possible with transcranial Doppler, recording the flow velocity on the middle cerebral artery. Under the current knowledge, the pathophysiology of vasospasm is quite complex: the main biological mechanisms are constituted by the direct contraction of the cerebral arteries, and the impairment of the vasodilatory activity elicited by the endothelium, although other mechanisms cannot be excluded. Some of the observed biological changes are induced by the cisternal clot, with formation of oxyhemoglobin, activation of lipid peroxidation and consequent endothelial injury, impaired nourishment of the arterial wall (encased by the clot). Other biological changes occur in the cerebral arteries, with decreased synthesis of prostacyclin, reduced availability of high energy phosphates, impairment of EDRF-induced vasodilatation and production of the powerful vasoconstrictor endothelin. The final result is arterial contraction, due to phosphorylation of the contractile proteins of the smooth muscle cell. Two mechanisms concur to contraction: a) activation of calcium-calmodulin-dependent protein kinases, and b) elevation of protein kinase C (PKC). While the first mechanism leads to a transient contraction, PKC-induced contraction is lasting for longer time. An additional influence on arterial contraction is played by the protease calpain.

Oxidative stress in the human brain after subarachnoid hemorrhage.

OBJECT: The aim of this study was to verify the patterns of antioxidant enzymatic activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the human brain after subarachnoid hemorrhage (SAH) to verify whether an "oxidative stress situation" characterizes the brain response to subarachnoid bleeding. METHODS: Forty samples of gyrus rectus or temporal operculum that were obtained during a surgical approach to anterior circulation aneurysms were used for this study. The activity of total SOD, GSH-Px, and the SOD/GSH/Px ratio (which expresses the balance between the production of hydrogen peroxides by dismutation of superoxide radicals and the scavenging potential) were calculated in each case. Twelve samples were obtained from patients who underwent surgery for unruptured aneurysms (control group); 13 samples were obtained during surgical procedures performed within 72 hours of SAH; and 15 samples were obtained during delayed surgical procedures (> 10 days post-SAH). Ten patients presented with clinical deterioration caused by arterial vasospasm. In both SAH groups, the mean total SOD activity was significantly higher than in the control group (p=0.029). The mean activity of GSH-Px did not differ significantly between the SAH and control groups (p=0.731). There was a significant increase in the SOD/GSH-Px ratio in both SAH groups, as compared with controls (p < 0.05). There was a significant correlation between the enzymatic activity and the clinical severity of the hemorrhage, with findings of lower values of SOD and, mainly, of the SOD/GSH-Px ratio in the poor-grade patients. The SOD/GSH-Px ratio was 2.14+/-0.44 in patients who presented with clinical vasospasm and 1.24+/-0.2 in cases without vasospasm. CONCLUSIONS: The results of this study show an imbalance of the antioxidant enzymatic activities in the human brain after SAH. which is linked to the severity of the initial bleeding and possibly modified by the development of arterial vasospasm.

Shape recovery and volume calculation from biplane angiography in the stereotactic radiosurgical treatment of arteriovenous malformations.

PURPOSE: A model for calculating the three-dimensional volume of arteriovenous malformations from biplane angiography. METHODS AND MATERIAL: Three-dimensional (3D) volume reconstruction is easily feasible with axial, coronal, or sagittal computer tomography (CT) and nuclear magnetic resonance (NMR) scans. On the other hand, radiosurgical treatment of arteriovenous malformations (AVM) is exclusively based on two orthogonal stereotactic projections, obtained with angiographic procedures. Most commonly, AVM volumes have been calculated by assimilating the nidus volume to a prolate ellipsoid. We present an algorithm dedicated to 3D structure reconstruction starting from two orthogonal stereotactic projections. This has been achieved using a heuristic approach, which has been widely adopted in the artificial intelligence domain. RESULTS: Tests on phantom of different complexity have shown excellent results. CONCLUSION: The importance of the algorithm is considerable. As a matter of fact: (a) it allows calculations of complex structures far away from regular ellipsoid; (b) it permits shape recovery; (c) it provides AVM visualization on axial planes.

Gamma Knife radiosurgery in skull base meningiomas. Preliminary experience with 50 cases.

Gamma Knife radiosurgery was performed on 50 patients (10 males and 40 females) with skull base meningiomas (SBMs) between February 1993 and September 1995. The patients ranged in age from 25 to 78 years (mean age 56 years). The location of the tumors was anterior fossa (n = 4), sphenoorbital (n = 2), sellar region (n = 5), cavernous sinus (n = 26), petroclival (n = 12), and occipital foramen (n = 1). The tumor volume ranged from 0.6 to 20 cm3 (mean 8.6 cm3). The mean values for dose planning were edge isodose (EI) 46.7%, edge dose (ED) 18.0 Gy, maximum dose 39.8 Gy, average dose (AD) 25.4 Gy, and average number of isocentres 5.7. The patients were analyzed for five parameters: tumor volume (< 7.5 vs. > or = 7.5 cm3); EI (< 50 vs. > or = 50%); ED (< 18 vs. > or = 18 Gy); AD (< 25 vs. > or = 25 Gy), and primary versus residual or recurrent tumors. The overall frequency of tumor growth control (TGC) was 98%, with 1- and 2-year TGC rates of 97% and 100%, respectively. The most favorable neurological results were obtained with a tumor volume < 7.5 cm3 (p < 0.05), EI > or = 50% (NS), ED > or = 18 Gy (NS) and with primary SBMs (p < 0.01). A favorable TGC was demonstrated at follow-up imaging examinations when the tumor volume was > or = 7.5 cm3 (100% TGC rate), EI < 50% (100%), ED > or = 18 Gy (100%), AD > 25 Gy (100%), in both primary SBMs (100%) and residual or recurrent SBMs (96.5%). To date, only 3 (6%) of the 50 patients have presented signs of neurological worsening related to the Gamma Knife radiosurgery. While no early complications were noted, neuroradiological follow-up did show delayed transient imaging complications (3 edema and 1 radionecrosis; 8% of all patients). In conclusion, our preliminary results seem to confirm that Gamma Knife radiosurgery is an effective and safe adjuvant or a feasible alternative primary treatment in controlling or preventing SBM progression.

A euristic approach to the volume reconstruction of arteriovenous malformations from biplane angiography.

Three-dimensional (3D) volume reconstruction is easily feasible with axial, coronal or sagittal CT and MRI scans. On the other hand, radiosurgical treatment of arteriovenous malformations (AVMs) is exclusively based on two orthogonal stereotactic projections, obtained with angiographic procedures. Most commonly AVM volumes have been calculated by assimilating the nidus volume to a prolate ellipsoid. We present an algorithm dedicated to 3D volume reconstruction starting from two stereotactic orthogonal projections. This has been achieved using a euristic approach which has been widely adopted in the artificial intelligence domain. Tests on phantoms of different complexity have shown excellent results. The importance of the algorithm is considerable. Firstly, it allows calculations of complex structures far removed from a regular ellipsoid. Secondly, it permits shape recovery. Thirdly, it provides AVM visualization on axial planes.

Hemodynamic effects of preoperative embolization in cerebral arteriovenous malformations: evaluation with transcranial Doppler sonography.

A series of 83 patients with cerebral arteriovenous malformations is presented. All patients were evaluated with transcranial Doppler sonography. Thirty-two patients were treated with staged embolization and surgery: 19 of these patients were operated on within 4 weeks of the last embolization, and the remaining 13 patients underwent surgery 6 months or more from embolization. Transcranial Doppler sonography performed 1 day after embolization showed a significant (> 60%) reduction of main feeder flow velocity in 72% of patients after the first embolization and in 45% of patients after the second embolization. In no case did such a significant reduction occur after the third embolization. A flow redistribution in the basal vessels (defined as an increase in flow velocity of at least 30% of the initial value) occurred only in patients after the first embolization (64%). On delayed post-embolization studies, complete recovery of flow velocity in the embolized vessel occurred in 46% of patients, and sonographic recruitment of new feeders occurred in the remaining 54%. When main feeder flow velocity (mean) was higher than 120 cm/s after embolization and before surgery, the incidence of postoperative hyperemic complications (cerebral edema and/or intracerebral hematoma) was significantly higher than in patients with a mean flow velocity under 120 cm/s. It is concluded that transcranial Doppler sonography is a valuable method for a noninvasive hemodynamic assessment of shunt flow in arteriovenous malformations, and it permits a physiological monitoring of hemodynamic changes after embolization and allows more precise indications regarding further stages of embolization and timing of surgery after embolization.

Effect of nicardipine on basilar artery vasoactive responses after subarachnoid hemorrhage.

The effect of the dihydropyridine calcium antagonist, nicardipine, on the vasoactive responses of the basilar artery was investigated after subarachnoid hemorrhage (SAH). Forty-five rabbits were separated into one control group and four groups receiving SAH (nine animals each). The SAH was induced by injecting 5 ml of autologous arterial blood into the cisterna magna. SAH animals were subjected to one of the following: 1) no treatment; 2) intravenous (i.v.) saline infusion (vehicle); 3) i.v. infusion of low-dose nicardipine (0.01 mg/kg/hr), or 4) i.v. infusion of high-dose nicardipine (0.15 mg/kg/hr). The i.v. infusions were started immediately after SAH and continued for 48 hours. Serotonin (5-HT) (10(-8) to 10(-5) mol/L) was used to evoke dose-dependent vasoconstriction of isolated rings of the basilar artery 2 days after SAH. Acetylcholine (ACh) (10(-8) to 10(-4)) and adenosine-triphosphate (ATP) (10(-8) to 10(-4) mol/L) were applied after maximal contraction with 5-HT, evoke a dose-dependent vasodilatation. Compared with controls, in animals subjected to SAH serotonin caused similar or slightly larger contractions; nicardipine infusion did not decrease the amount of contraction observed after SAH. ACh and ATP caused significantly less dilatation in animals submitted to SAH than in controls. After high-dose nicardipine, ACh- and ATP-induced dilatations were significantly more pronounced (57% and 68% of initial contractile tone) than in the other animals receiving SAH (36%-39% and 45%-55%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

[Intra- and postoperative anesthesiologic management in cerebral arteriovenous malformations]. / Management anestesiologico intra- e post-operatorio nelle malformazioni artero-venose cerebrali.

The authors analyze the anesthetic management of 59 cases of "large" arteriovenous malformation (more than 20 cm3), all completely removed by microsurgical technique. The discussion is focused on immediate pre-operative, intra-operative and post-operative pharmacological treatments in order to reduce the hemodynamic effects in the surrounding brain after excision of angiomas.