Neurosurgery Blog

Neurosurgery 69:349–356, 2011 DOI: 10.1227/NEU.0b013e31821661c3

The risk of aneurysm rupture appears to be related to multiple factors such as topology, morphology, size, perianeurysmal environment, and blood flow hemodynamics.

OBJECTIVE: To evaluate aneurysm morphology and to quantitatively compare the volumetric parameters between ruptured and unruptured aneurysms from our clinical database at the UCLA Medical Center.

METHODS: Novel algorithms that automatically compute aneurysm geometry were tested on the basis of voxel data obtained from angiographic images, and measurements of aneurysm morphology were automatically recorded. We studied a total of 50 aneurysms (25 ruptured and 25 unruptured) with sizes ranging from 3 to 26 mm. To compare the geometric characteristics between ruptured and unruptured groups, we examined measurements, including volume and surface area, and the ratios of these measurements to the minimal bounding sphere around each aneurysm.

RESULTS: More than 65% of ruptured aneurysms had a ratio of aneurysm volume to bounding sphere volume (AVSV) of > 0.5. More than 70% of ruptured aneurysms had a ratio of aneurysm surface to bounding sphere surface (AASA) of < 1. A trend differentiating ruptured and unruptured aneurysms was observed in AVSV (P = .07) and AASA (P = .04). Classification and regression trees analysis showed 68% correct classification with rupture for AVSV and 70% for AASA.

CONCLUSION: By comparing aneurysm geometry with the bounding sphere, we found a trend associating the ratios of aneurysm volume and surface area with rupture. These geometric parameters may be useful for understanding the influence of morphology on the risk of aneurysm rupture.

J Neurosurg 115:387–397, 2011.DOI: 10.3171/2011.3.JNS101413

The conceptual division of intracranial arteries into segments provides a better understanding of their courses and a useful working vocabulary. Segmental anatomy of cerebral arteries is commonly cited by a numerical nomenclature, but an analogous nomenclature for cerebellar arteries has not been described. In this report, the microsurgical anatomy of the cerebellar arteries is reviewed, and a numbering system for cerebellar arteries is proposed.

Methods. Cerebellar arteries were designated by the first letter of the artery’s name in lowercase letters, distinguishing them from cerebral arteries with the same first letter of the artery’s name. Segmental anatomy was numbered in ascending order from proximal to distal segments.

Results. The superior cerebellar artery was divided into 4 segments: s1, anterior pontomesencephalic segment; s2, lateral pontomesencephalic segment; s3, cerebellomesencephalic segment; and s4, cortical segment. The anterior inferior cerebellar artery was divided into 4 segments: a1, anterior pontine segment; a2, lateral pontine segment; a3, flocculopeduncular segment; and a4, cortical segment. The posterior inferior cerebellar artery was divided into 5 segments: p1, anterior medullary segment; p2, lateral medullary segment; p3, tonsillomedullary segment; p4, telovelotonsillar segment; and p5, cortical segment.

Conclusions. The proposed nomenclature for segmental anatomy of cerebellar artery complements established nomenclature for segmental anatomy of cerebral arteries. This nomenclature is simple, easy to learn, and practical. The nomenclature localizes distal cerebellar artery aneurysms and also localizes an anastomosis or describes a graft’s connections to donor and recipient arteries. These applications of the proposed nomenclature with cerebellar arteries mimic the applications of the established nomenclature with cerebral arteries.

Neurosurgery 69:344–348, 2011 DOI: 10.1227/NEU.0b013e31821819a0

Recent advances in skull base and microsurgical techniques minimize the need for brain retraction.

OBJECTIVE: We studied the impact of such techniques in 36 patients (51 aneurysms) using magnetic resonance imaging (MRI).

METHODS: Preoperative and 24 hours postoperative MR imaging was performed in patients undergoing microsurgical clipping of intracranial aneurysms. Images were evaluated for parenchymal signal changes. During surgery, use and time of brain retraction were recorded. The degree of cortical injury was quantified using a 0 to 3 scale (grade 0 = normal surface; 1 = pial/arachnoidal damage; 2 = gray matter injury; 3 = contusion/necrosis).

RESULTS: Brain retraction by use of a brain spatula was used in all patients. Retraction times ranged from 14 to 290 minutes (mean, 84.1). Cortical surface changes were grade 0 in 86% and grade 1 in 14%; none showed grade 2 or 3 changes. In the postoperative MRI, 4 patients presented with parenchymal alterations, 4 with edema (11.1%), and 1 patient had additional contusion (2.8%). All lesions were confined to the temporal pole. The grade of cortical surface changes was not related to lesions found on MR imaging. No patients showed retraction-related neurological deficits.

CONCLUSION: The incidence of evident mechanical parenchymal injury (infarction or contusion) is very low when appropriate microsurgical and skull base techniques are used. Minor pia-arachnoid injury should nevertheless continue to be attended through future advances.

Neurosurgery 68[ONS Suppl 2]:ons300–ons309, 2011 DOI: 10.1227/NEU.0b013e3182124810

Neurovascular surgeons have been trying to find a solution to the problem of surgical invasiveness by applying minimally invasive keyhole approaches.

OBJECTIVE: To evaluate the feasibility and surgical outcomes of a superciliary keyhole approach for unruptured intracranial aneurysms (UIAs) as an alternative to a pterional approach.

METHODS: The authors report on a consecutive series of patients who underwent a superciliary approach for clipping UIAs smaller than 15 mm arising at the supraclinoid internal carotid artery (ICA), A1 segment, anterior communicating artery (ACoA), and M1 segment including the middle cerebral artery (MCA) bifurcation. The data were compared with a historical control group (n = 90) who underwent a pterional approach for UIAs.

RESULTS: A total of 120 aneurysms were successfully clipped in 102 patients with a mean age of 58 years. There was no direct mortality related to the surgery, and only 1 (1.0%) patient developed significant morbidity adversely affecting the Glasgow Outcome Scale score. The superciliary approach demonstrated statistically significant advantages over the pterional approach, including a shorter operative duration (mean, 120 min), no intraoperative blood transfusion, and extremely rare postoperative epidural hemorrhages. In addition, temporalis atrophy was rare and palsy of the frontalis persisting more than 6 months only occurred in 6 patients (5.9%) and was resolved within 2 years. The overall cosmetic outcome was excellent.

CONCLUSION: A superciliary approach can be a reasonable alternative to a pterional approach for small (,15 mm) UIAs arising at the supraclinoid ICA, A1, ACoA, and M1 segment including the MCA bifurcation.

J Neurosurg 115:18–23, 2011. DOI: 10.3171/2011.3.JNS10620

The purpose of this paper is to evaluate whether venous indocyanine green (ICG) videoangiography has any potential for predicting the presence of a safe collateral circulation for veins that are at risk for intentional or unintentional damage during surgery.

Methods. The authors performed venous ICG videoangiography during 153 consecutive neurosurgical procedures. On those occasions in which a venous sacrifice occurred during surgery, whether that sacrifice was preplanned (intended) or unintended, venous ICG videoangiography was repeated so as to allow us to study the effect of venous sacrifice. A specific test to predict the presence of venous collateral circulation was also applied in 8 of these cases.

Results. Venous ICG videoangiography allowed for an intraoperative real-time flow assessment of the exposed veins with excellent image quality and resolution in all cases. The veins observed in this study were found to be extremely different with respect to flow dynamics and could be divided in 3 groups: 1) arterialized veins; 2) fast-draining veins with uniform filling and clear flow direction; and 3) slow-draining veins with nonuniform filling. Temporary clipping was found to be a simple and reversible way to test for the presence of potential anastomotic circulation.

Conclusions. Venous ICG videoangiography is able to reveal substantial variability in the venous flow dynamics. “Slow veins,” when they are tributaries of bridging veins, might hide a potential for anastomotic circulation that deserve further investigation.

Acta Neurochir (2011) 153:1361–1366. DOI 10.1007/s00701-011-1063-9

Aneurysms located at the middle cerebral artery bifurcation remain a clear neurosurgical indication. We detail here the steps necessary to enable safe surgery for Sylvian fissure aneurysms.

Methods: An angiogram with 3D reconstruction is obtained and reviewed intraoperatively, just prior to the skin incision. During the exposure, the cistern is kept open by small cottonoids, thereby avoiding brain retraction. Continuous monitoring of MEPs along with ICG microscopic angiofluorescence allows for detection of vascular compromise. Intraoperative angiography with 3D reconstruction allows for immediate correction of less than satisfactory surgical outcome.

Conclusions Careful planning of surgical strategy followed by a minimally invasive technique (with continuous neuro-monitoring) ensures safe surgery. The availability of intra-operative radiological guidance allows for optimal management.

Neurosurg Focus 30 (6):E24, 2011, DOI: 10.3171/2011.3.FOCUS1165

Literature reports on the natural history of cerebral cavernous malformations (CMs) are numerous, with considerable variability in lesion epidemiology, hemorrhage rates, and risk factors for hemorrhage.

In this review, the authors performed a meta-analysis of 11 natural history studies. The overall male-to-female ratio was 1:1, and the mean age at presentation was 30.6 years. Overall, 37% of patients presented with seizures, 36% with hemorrhage, 23% with headaches, 22% with focal neurological deficits, and 10% were asymptomatic. Some patients had more than one symptom. Seizure presentation was most prevalent among supratentorial CMs, while focal neurological deficits were common in patients with infratentorial CMs. By location, CMs were in the cerebral hemispheres (66%), brainstem (18%), basal ganglia or thalamus (8%), cerebellum (6%), and other (2.5% [combined supra- and infratentorial, callosal or insular]). Overall, 19% of patients harbored multiple intracranial CMs, and 9% had radiographically apparent associated developmental venous anomalies. An overall annual hemorrhage rate of 2.4% per patient-year (range 1.6%–3.1%) was identified across 3 studies.

Prior hemorrhage and female sex were risk factors for bleeding, while CM size and multiplicity did not affect hemorrhage rates. Although not impacting the hemorrhage rate itself, deep location was a risk factor for increased clinical aggressiveness.

Neurosurgery 68[ONS Suppl 2]:ons294–ons299, 2011 DOI: 10.1227/NEU.0b013e31821343c6

Intraoperative rupture of an intracranial aneurysm is a potentially devastating but avoidable and manageable complication of aneurysm surgery.

OBJECTIVE: To describe a surgical technique that the authors have used successfully to repair a tear at the neck of an intracranial aneurysm, as well as alternative options for managing this intraoperative complication.

METHODS: The tear on the neck of the aneurysm is covered with a small piece of free cotton and held in place with a suction device to clear the field of blood. The cotton is then clipped onto the tear with an aneurysm clip, using the cotton as a bolster to obliterate the tear. The cotton increases the surface area, allowing the clip to be placed more distally on the neck to preserve patency of the parent artery. Case examples are used to illustrate the technique.

RESULTS: Both authors independently have used this technique on several occasions to successfully repair tears at the neck of an aneurysm.

CONCLUSION: Intraoperative rupture of an intracranial aneurysm is a potentially devastating complication, particularly if a tear occurs at the neck. This simple yet effective method has been very useful in repairing a partial avulsion or tear of the neck of an aneurysm.

Acta Neurochir (2011) 153:1273–1281. DOI 10.1007/s00701-011-0981-x

The role of endovascular interventions in managing dural arteriovenous fistulas (DAVFs) is increasing. Furthermore, in patients with aggressive DAVFs, different surgical interventions are required for complete obliteration or disconnection. Our objective was to evaluate the management of patients with intracranial DAVFs treated in our institution to identify the parameters that may help guide the long-term management of these lesions.

Methods The hospital records of 53 patients with intracranial DAVFs were reviewed. We then conducted a systematic telephone interview to obtain long-term follow-up information.

Results The main presenting symptoms were tinnitus and headache. Nineteen (35%) patients presented with intracranial bleeding, 84% of patients scored between 0 and 2 using a modified Rankin Scale at the last follow-up visit. Twentyfour patients were treated surgically. Overall postoperative complications occurred in seven (29%) surgically treated patients, but only two patients permanently worsened. For patients with Borden type II and III fistulas, the annual incidence of hemorrhage was 30%. Two patients had late recurrences of surgically and endovascularly occluded DAVFs. Long-term follow-up showed that compared with spinal DAVFs, only 50% of intracranial DAVFs showed complete remission of symptoms, 41% partial remission, 6% no remission and 4% deterioration of symptoms that led to treatment of the DAVF.

Conclusion In general, intracranial DAVFs can be successfully surgically managed by simple venous disconnection in many cases. However, half of the patients do not show complete remission of symptoms. Age and the occurrence of perioperative complication were the most important determinants of outcome.

Neurosurgery 68:1427–1433, 2011 DOI: 10.1227/NEU.0b013e31820b4f1c

Fully equipped high-end digital subtraction angiography (DSA) within the operating room (OR) environment has emerged as a new trend in the fields of neurosurgery and vascular surgery.

OBJECTIVE: To describe initial clinical experience with a robotic DSA system in the hybrid OR.

METHODS: A newly designed robotic DSA system (Artis zeego; Siemens AG, Forchheim, Germany) was installed in the hybrid OR. The system consists of a multiaxis robotic C arm and surgical OR table. In addition to conventional neuroendovascular procedures, the system was used as an intraoperative imaging tool for various neurosurgical procedures such as aneurysm clipping and spine instrumentation.

RESULTS: Five hundred one neurosurgical procedures were successfully conducted in the hybrid OR with the robotic DSA. During surgical procedures such as aneurysm clipping and arteriovenous fistula treatment, intraoperative 2-/3-dimensional angiography and C-arm-based computed tomographic images (DynaCT) were easily performed without moving the OR table. Newly developed virtual navigation software (syngo iGuide; Siemens AG) can be used in frameless navigation and in access to deep-seated intracranial lesions or needle placement.

CONCLUSION: This newly developed robotic DSA system provides safe and precise treatment in the fields of endovascular treatment and neurosurgery.

Neurosurgery 68:1164–1171, 2011 DOI: 10.1227/NEU.0b013e31820edbd3

The apparent paradox of natural history data suggesting low rupture risk of small asymptomatic aneurysms and the median size of aneurysm rupture remains unexplained. Aneurysm growth rates and their potential relationship with rupture risk have not been well examined in natural history studies.

OBJECTIVE: To examine the question of whether small asymptomatic aneurysms ≤ 7 mm that are followed up over time rupture and to determine the relationship between aneurysm growth and rupture.

METHODS: We reviewed all publications on unruptured aneurysms published from 1966 to 2009. We then selected all aneurysms ≤ 7 mm for which measurements were reported for at least 2 time points and for which initial asymptomatic status and ultimate outcome (rupture vs unruptured) were reported. Using the Mann-Whitney U test, we compared absolute diameter annual growth rate.

RESULTS: Our search retrieved 64 aneurysms. Thirty aneurysms ruptured during followup, of which 27 were enlarged before rupture (90%). Thirty-four aneurysms did not rupture, of which 24 enlarged during follow-up (71%). There was a statistically significant trend toward larger absolute diameter growth for ruptured aneurysms vs unruptured aneurysms (3.89 ± 2.34 vs 1.79 ± 1.02 mm; P < .001), respectively. Annual growth rates for aneurysms for the 2 groups, however, were not statistically different (27.46 ± 18.76 vs 32.00 ± 29.30; P = .92).

CONCLUSION: Small aneurysms are prone to growth and rupture. Aneurysm rupture is more likely to occur in aneurysms with larger absolute diameter growth, but rupture can also occur in the absence of growth. The annual growth rate in both groups suggests that rate of growth of aneurysms is highly variable and unpredictable, justifying treatment or close diagnostic follow-up.

Neurosurgery 68:966–973, 2011 DOI: 10.1227/NEU.0b013e318208f1ba 

Subarachnoid clot is important in the development of delayed vasospasm after subarachnoid hemorrhage (SAH).

OBJECTIVE: To compare the clearance of subarachnoid clot and the incidence of symptomatic vasospasm in surgical clipping and embolization with Guglielmi detachable coils for aneurysmal SAH.

METHODS: The subjects were 115 patients with Fisher group 3 aneurysmal SAH on computed tomography scan at admission whose aneurysm was treated by surgical clipping (clip group; n = 86) or Guglielmi detachable coil embolization (coil group; n = 29) within 72 hours of ictus. Software-based volumetric quantification of the subarachnoid clot was performed, and the amount of hemoglobin in drained cerebrospinal fluid was measured.

RESULTS: Clearance of the subarachnoid clot on the computed tomography scan was rapid in the clip group until the day after the operation but slow in the coil group (58.9% removed vs 27.8% removed; P = .008). However, postoperative clearance of the clot occurred more rapidly in the coil group. Reduction of the clot until days 3 through 5 did not differ significantly between the 2 groups (72.9% removed vs 75.2% removed). The amount of hemoglobin in the clip group was . 0.8 g/d until day 3 and then gradually decreased (n = 15), but hemoglobin in the coil group remained at . 0.8 g/d until day 5 (n = 17). The incidence of symptomatic vasospasm did not differ between the groups.

CONCLUSION: Subarachnoid clot can be removed directly during surgical clipping, which is not possible with endovascular treatment. However, the percentage reduction of the clot on days 3 through 5 did not differ between the 2 groups.

J Neurosurg 114:1088–1094, 2011. DOI: 10.3171/2010.8.JNS10759

Surgical routes to posterior inferior cerebellar artery (PICA) aneurysms are opened between the vagus (cranial nerve [CN] X), accessory (CN XI), and hypoglossal (CN XII) nerves for safe clipping, but these routes have not been systematically defined. The authors describe 3 anatomical triangles and their relationships with PICA aneurysms, routes for surgical clipping, outcomes, and angiographically demonstrated anatomy.

Methods. The vagoaccesory triangle is defined by CN X superiorly, CN XI laterally, and the medulla medially. It is divided by CN XII into the suprahypoglossal triangle (above CN XII) and the infrahypoglossal triangle (below CN XII). From a consecutive surgical series of 71 PICA aneurysms in 70 patients, 51 aneurysms were analyzed using intraoperative photographs.

Results. Forty-three PICA aneurysms were located inside the vagoaccessory triangle and 8 were outside. Of the aneurysms inside the vagoaccessory triangle, 22 (51%) were exposed through the suprahypoglossal triangle and 19 (44%) through the infrahypoglossal triangle; 2 were between triangles. The lesions were evenly distributed between the anterior medullary (16 aneurysms), lateral medullary (19 aneurysms), and tonsillomedullary zones (16 aneurysms). Neurological and CN morbidity linked to aneurysms in the suprahypoglossal triangle was similar to that associated with aneurysms in the infrahypoglossal triangle, but no morbidity was associated with PICA aneurysms outside the vagoaccessory triangle. A distal PICA origin on angiography localized the aneurysm to the suprahypoglossal triangle in 71% of patients, and distal PICA aneurysms were localized to the infrahypoglossal triangle or outside the vagoaccessory triangle in 78% of patients.

Conclusions. The anatomical triangles and zones clarify the borders of operative corridors to PICA aneurysms and define the depth of dissection through the CNs. Deep dissection to aneurysms in the anterior medullary zone traverses CNs X, XI, and XII, whereas shallow dissection to aneurysms in the lateral medullary zone traverses CNs X and XI. Posterior inferior cerebellar artery aneurysms outside the vagoaccessory triangle are frequently distal and superficial to the lower CNs, and associated surgical morbidity is minimal. Angiography may preoperatively localize a PICA aneurysm’s triangular anatomy based on the distal PICA origin or distal aneurysm location.

J Neurosurg 114:984–993, 2011. DOI: 10.3171/2010.12.JNS101297

Parafalcine arteriovenous malformations (AVMs) have a midline plane in common, but differ in their location (anterior, middle, or posterior) and depth (superficial or deep). Surgical management varies with AVM location and depth in terms of patient position, head position, craniotomy, and surgical approach. This study examined surgical strategies, patient outcomes, and regional factors influencing results.

Methods. Patients with AVMs located on the medial surface of the cerebral hemisphere were identified retrospectively from a consecutive, single-neurosurgeon series that is registered prospectively as part of the UCSF Brain Arteriovenous Malformation Study Project. During a 12-year period, 443 patients with AVMs were treated surgically. Of these 443 patients, 132 (30%) had parafalcine AVMs, which were distributed in zones as follows: superficialanterior, 25 (18.9%); superficial-middle, 26 (19.7%); superficial-posterior, 39 (29.5%); deep-anterior, 25 (18.9%); deep-posterior, 17 (12.9%). Five different surgical strategies were used depending on AVM zone.

Results. Complete AVM resection was achieved in 123 (93.2%) of 132 patients. Overall, neurological condition improved in 74 patients (56.1%) and remained unchanged in 41 patients (31.1%). Neurological condition deteriorated in 12 patients (9.1%), and 5 patients (3.8%) died. Patients with AVMs in the superficial-middle zone had the highest rate of neurological deterioration (26.9%).

Conclusions. Parafalcine AVMs lie on a midline surface that, when exposed with a bilateral craniotomy across the superior sagittal sinus and a wide opening of the interhemispheric fissure, makes them superficial. However, unlike convexity AVMs, which are approached perpendicularly, parafalcine AVMs are approached tangentially. Gravity retraction is useful with deeply located AVMs (those in the deep-anterior and deep-posterior zones), because it widens the interhemispheric fissure and accesses deep arterial feeding vessels from the anterior and posterior cerebral arteries. Surgical risks were increased in the superficial-middle zone, which is likely explained by the proximity of sensorimotor cortex. The authors’ regional classification of parafalcine AVMs may serve as a guide to surgical planning.

Acta Neurochir (2011) 153:869–878. DOI 10.1007/s00701-010-0848-6

Onyx has emerged in recent years for the endovascular treatment of brain arteriovenous malformations (AVMs). However, the role of Onyx embolization is still under discussion. We report our initial experiences in the treatment of brain AVMs with Onyx embolization.

Methods Between January 2004 and December 2007, 86 patients with brain AVMs were embolized with Onyx. Clinical presentation included intracerebral hemorrhage in 32 patients, seizures in 25 patients, headaches in 20 patients, neurologic deficits in 3 patients, and in 6 patients the AVM was an incidental finding. According to the Spetzler–Martin scale, three AVMs were grade I, 13 were grade II, 45 were grade III, 19 were grade IV, and 6 were grade V. Seventy-four AVMs were located in eloquent regions.

Results Initial complete obliteration after final embolization was achieved in 16 patients (18.6%), with an average of 80.5% (range, 30–100%) volume reduction. Partial embolization was followed by surgery in 18 patients, whereas 17 AVMs were cured. In 48 patients treated by embolization and radiosurgery, four patients were lost to follow-up. Three-year follow-up angiography was performed on 30 patients and showed complete obliteration after radiosurgery in 23 patients. The remaining 14 patients are awaiting 3-year postradiosurgery results. Embolization-related permanent morbidity was 3.5%, whereas mortality was 1.2%.

Conclusions Although Onyx allows moderate obliteration rates, combined management, such as adjunctive embolization with microsurgery or radiosurgery, may be effective for selected large AVMs.

Neurosurg Focus 30 (4):E9, 2011. DOI: 10.3171/2011.2.FOCUS10313

Currently, the effectiveness of minimally invasive evacuation of intracerebral hemorrhage (ICH) utilizing the endoscopic method is uncertain and the technique is considered investigational.

The authors analyzed their experience with this method in terms of case selection, surgical technique, and long-term results.

Methods. The authors performed a retrospective analysis of the clinical and radiographic data obtained in 68 patients treated with endoscope-assisted ICH evacuation. Rebleeding, morbidity, and mortality were recorded as primary end points. Hematoma evacuation rate was calculated by comparing the pre- and postoperative CT scans. Glasgow Coma Scale scores and scores on the extended Glasgow Outcome Scale (GOSE) were recorded at the 6-month postoperative follow-up. The technical aspect of this report explains details of the procedure, the instruments that are used, the methods for hemostasis, and the role of hemostatic agents in the management of intraoperative hemorrhage. The pertinent literature was reviewed and summarized.

Results. All surgeries were performed within 12 hours of ictus, and 84% of the surgeries were performed within 4 hours. The mortality rate was 5.9%, and surgery-related morbidity occurred in 3 cases (4.4%). The hematoma evacuation rate was 93% overall—96% in the putaminal group, 86% in the thalamic group, and 98% in the subcortical group. The rebleeding rate was 1.5%. The mean operative time was 85 minutes, and the average blood loss was 56 ml. The mean GOSE score was 4.9 at 6-month follow-up. The authors acknowledge the limitations of these preliminary results in a small number of patients.

Conclusions. The data suggest that early endoscope-assisted ICH evacuation is safe and effective in the management of supratentorial ICH. The rebleeding, morbidity, and mortality rates are low compared with rates reported in the literature for the traditional craniotomy method. This study also showed that early and complete evacuation of ICH may lead to improved outcomes in selected patients. However, the safety and efficacy of endoscope-assisted ICH evacuation should be further investigated in a large, prospective, randomized trial.

J Neurosurg 114:944–953, 2011. DOI: 10.3171/2010.3.JNS081131

The purpose of this paper was to present the safety, efficacy, and clinical/angiographic follow-up results of HyperForm balloon-assisted endosaccular coil occlusion of distal anterior circulation bifurcation aneurysms.

Methods. Over a 7-year period, the authors treated 864 middle cerebral artery, distal anterior cerebral artery bifurcation, and anterior communicating artery aneurysms by means of coil embolization with HyperForm balloon assistance in 800 patients. In 37 aneurysms, 2 HyperForm balloons were used simultaneously for remodeling.

Results. The overall mortality rate was 7.1%, including 1.4% procedural mortality. Various neurological deficits were present at discharge in 8.9% of the patients, and 4.4% had permanent disabling morbidity 6 months posttreatment (modified Rankin Scale score ≥ 2). Thromboembolic complications developed during the treatment of 15 aneurysms (1.7%) causing morbidity or mortality in 10 cases (1.3%). There were 14 intraoperative perforations (1.6%). In all 14 cases, the HyperForm balloon saved patients from severe bleeding. The perforation led to morbidity or mortality in 3 cases (0.4%); there were no negative consequences in 11. There were 726 patients with 757 aneurysms (87.6%) available for follow-up. Control angiograms were obtained at 6 months in 386 patients, at 1 year in 267, and at 2 years in 104, revealing an 82% complete obliteration rate according to the most recent follow-up angiograms.

Conclusions. The satisfactory results obtained in this experience demonstrate that HyperForm balloon remodeling provides strong benefits for the endovascular management of middle cerebral, anterior cerebral, and anterior communicating artery aneurysms without increasing the risk of treatment. Not only does this technique allow for the safe treatment of these aneurysms, but it also expands the indications of endovascular treatment to include aneurysms that otherwise cannot be treated with simple coil embolization.

J Neurosurg 114:842–849, 2011.DOI: 10.3171/2010.8.JNS10663

The authors propose a 3-tier classification for cerebral arteriovenous malformations (AVMs). The classification is based on the original 5-tier Spetzler-Martin grading system, and reflects the treatment paradigm for these lesions. The implications of this modification in the literature are explored.

Methods. Class A combines Grades I and II AVMs, Class B are Grade III AVMs, and Class C combines Grades IV and V AVMs. Recommended management is surgery for Class A AVMs, multimodality treatment for Class B, and observation for Class C, with exceptions to the latter including recurrent hemorrhages and progressive neurological deficits. To evaluate whether combining grades is warranted from the perspective of surgical outcomes, the 3-tier system was applied to 1476 patients from 7 surgical series in which results were stratified according to Spetzler- Martin grades.

Results. Pairwise comparisons of individual Spetzler-Martin grades in the series analyzed showed the fewest significant differences (p < 0.05) in outcomes between Grades I and II AVMs and between Grades IV and V AVMs. In the pooled data analysis, significant differences in outcomes were found between all grades except IV and V (p = 0.38), and the lowest relative risks were found between Grades I and II (1.066) and between Grades IV and V (1.095). Using the pooled data, the predictive accuracies for surgical outcomes of the 5-tier and 3-tier systems were equivalent (receiver operating characteristic curve area 0.711 and 0.713, respectively).

Conclusions. Combining Grades I and II AVMs and combining Grades IV and V AVMs is justified in part because the differences in surgical results between these respective pairs are small. The proposed 3-tier classification of AVMs offers simplification of the Spetzler-Martin system, provides a guide to treatment, and is predictive of outcome. The revised classification not only simplifies treatment recommendations; by placing patients into 3 as opposed to 5 groups, statistical power is markedly increased for series comparisons.

Neurosurgery 68:731–737, 2011 DOI: 10.1227/NEU.0b013e3182077373

Intraprocedural rupture is a dangerous complication of endovascular treatment. Small ruptured anterior communicating artery (ACoA) aneurysms and microaneurysms present a challenge for both surgical and endovascular therapies to achieve obliteration. An understanding of the complication rates of treating ruptured ACoA microaneurysms may help guide therapeutic options.

OBJECTIVE: To report the largest cohort of ACoA microaneurysms treated with endovascular therapy over the course of the past 10 years.

METHODS: We performed a retrospective review of 347 ACoA aneurysms treated in 347 patients at Cleveland Clinic and Emory University over a 10-year period. Patient demographics, aneurysmal rupture, size, use of balloon remodeling, patient outcomes, intraprocedural rupture, and rerupture were reviewed.

RESULTS: Rupture rates were examined by size for all patients and subgroups and dichotomized to evaluate for size ranges associated with increased rupture rates. The highest risk of rupture was noted in aneurysms less than 4 mm. Of 347 aneurysms, 74 (21%) were less than 4 mm. The intraprocedural rupture rate was 5% (18/347) for ACoA aneurysms of any size. There was an intraprocedural rupture rate of 2.9% (8/273) among ACoA aneurysms greater than 4 mm compared with 13.5% (10/74) in less than 4-mm aneurysms. Procedural rupture was a statistically significant predictor of modified Rankin score after adjusting for Hunt and Hess grades (HH).

CONCLUSION: ACoA aneurysms less than 4 mm have a 5-fold higher incidence of intraprocedural rerupture during coil embolization. Outcome is negatively affected by intraprocedural rerupture after adjusting for HH grade.

Neurosurgery 68:403–415, 2011 DOI: 10.1227/NEU.0b013e3181ff9cde

Brainstem cavernous malformations (BSCMs) are relatively uncommon, low-flow vascular lesions. Because of their relative rarity, relatively little data on their natural history and on the efficacy and durability of their treatment.

OBJECTIVE: To evaluate the long-term durability of surgical treatment of BSCMs and to document patient outcomes and clinical complications.

METHODS: The charts of all patients undergoing surgical treatment of BSCM between 1985 and 2009 were reviewed retrospectively. The study population consisted of 300 patients who had surgery for BSCM. Forty patients were under 19 years of age at surgery; pediatric BSCMs have been reported separately. Patient demographics, lesion characteristics, surgical approaches, and patient outcomes were examined.

RESULTS: The study population consisted of 260 adult patients with a female-to-male ratio of 1.5 and mean age of 41.8 years. Of the 260 patients, 252 presented with a clinical or radiographic history of hemorrhage. The mean follow-up in 240 patients was 51 months. The mean Glasgow Outcome Scale on admission, at discharge, and at last follow-up was 4.4, 4.2, and 4.6. Postoperatively, 137 patients (53%) developed new or worsening neurological symptoms. Permanent new deficits remained in 93 patients 3(36%). There were perioperative complications in 74 patients (28%); tracheostomy, feeding tube placement, and cerebrospinal fluid leakage were most common. Eighteen patients (6.9%) experienced 20 rehemorrhages. Twelve patients required reoperation for residual/recurrent BSCM. The overall annual risk of postoperative rehemorrhage was 2%/patient.

CONCLUSION: Although BSCM surgery has significant associated risks, including perioperative complications, new neurological deficits, and death, most patients have favorable outcomes. Overall, surgery markedly improved the risk of rehemorrhage and related symptoms and should be considered in patients with accessible lesions.