Neurosurgery Blog

Neurosurgery 72:646–652, 2013

Subarachnoid hemorrhage (SAH) is found to have no vascular origin by initial catheter angiography in approximately 15% of cases. The most appropriate course for the type and frequency of additional diagnostic workup remains controversial.

OBJECTIVE: To retrospectively assess the diagnostic yield of short-term and long-term repeat catheter angiography in the era of advanced imaging.

METHODS: Between 2003 and 2011, 254 consecutive patients diagnosed with SAH had negative initial angiography. SAH was perimesencephalic (PM) in 46.5% and nonperimesencephalic (NPM) in 53.5%. Angiography was repeated at 1-week (short-term) and 6-week (long-term) intervals from the initial negative angiogram.

RESULTS: Ten of 254 patients had a vascular source of hemorrhage on short-term follow-up angiography with a diagnostic yield of 3.9%. One hundred seventy-four patients with negative findings on the first 2 angiograms received a third angiogram, and 7 of these patients were found to have a vascular abnormality. The estimated yield of this third angiogram was 4.0%. The overall diagnostic yield of repeat angiography was 0% in the PM group and 12.5% in the NPM group. The diagnostic yield of shortterm and long-term follow-up angiography in patients with NPM SAH was 7.3% and 7.8%, respectively. NPM patients were more likely to experience vasospasm and hydrocephalus requiring external ventricular drainage or cerebrospinal fluid diversion than PM patients.

CONCLUSION: Our results support a protocol of short-term and long-term angiographic follow-up in patients with NPM SAH and negative initial angiography. Aggressive protocols of follow-up angiography may not be necessary in patients with PM SAH.

Neurosurgery 72:492–496, 2013

High-resolution magnetic resonance vessel wall imaging (MR-VWI) is increasingly used to study steno-occlusive cerebrovascular disease, but has not yet been applied to patients with aneurysmal subarachnoid hemorrhage (SAH).

OBJECTIVE: To study the ability of high-resolution MR-VWI to determine the site of rupture in patients with aneurysmal SAH.

METHODS: Medical records of patients admitted with aneurysmal SAH between December 2011 and May 2012 were reviewed. MR-VWI was routinely performed for patients treated in the IMRIS Neurovascular Suite immediately before definitive treatment of the ruptured aneurysm.

RESULTS: We report for the first time high-resolution MR-VWI in 5 patients with aneurysmal SAH. Three patients harbored multiple intracranial aneurysms. The ruptured aneurysms demonstrated thick vessel wall enhancement in all cases. None of the associated unruptured aneurysms demonstrated this MR imaging finding.

CONCLUSION: High-resolution MR-VWI identified the site of rupture in patients with aneurysmal SAH, including those patients harboring multiple intracranial aneurysms. It may represent a useful tool in the investigation of aneurysmal SAH.

J Neurosurg 117:913–919, 2012

Management of unruptured intracranial aneurysms remains controversial in neurosurgery. The contribution of morphological parameters has not been included in the treatment paradigm in a systematic manner or for any particular aneurysm location. The authors present a large sample of middle cerebral artery (MCA) aneurysms that were assessed using morphological variables to determine the parameters associated with aneurysm rupture.

Methods. Preoperative CT angiography (CTA) studies were evaluated using Slicer software to generate 3D models of the aneurysms and their surrounding vascular architecture. Morphological parameters examined in each model included 5 variables already defined in the literature (aneurysm size, aspect ratio, aneurysm angle, vessel angle, and size ratio) and 3 novel variables (flow angle, distance to the genu, and parent-daughter angle). Univariate and multivariate statistical analyses were performed to determine statistical significance.

Results. Between 2005 and 2008, 132 MCA aneurysms were treated at a single institution, and CTA studies of 79 aneurysms (40 ruptured and 39 unruptured) were analyzed. Fifty-three aneurysms were excluded because of reoperation (4), associated AVM (2), or lack of preoperative CTA studies (47). Ruptured aneurysms were associated with larger size, greater aspect ratio, larger aneurysm and flow angles, and smaller parent-daughter angle. Multivariate logistic regression revealed that aspect ratio, flow angle, and parent-daughter angle were the strongest factors associated with ruptured aneurysms.

Conclusions. Aspect ratio, flow angle, and parent-daughter angle are more strongly associated with ruptured MCA aneurysms than size. The association of parameters independent of aneurysm morphology with ruptured aneurysms suggests that these parameters may be associated with an increased risk of aneurysm rupture. These factors are readily applied in clinical practice and should be considered in addition to aneurysm size when assessing the risk of aneurysm rupture specific to the MCA location.

Neurosurgery 71:994–1002, 2012

Recognizing an aneurysmal basal rupture using angiographic evaluation is crucial for optimal treatment.

OBJECTIVE: To evaluate the incidence of a small basal outpouching (the most common angiographic configuration suggesting a basal rupture), the incidence of a ruptured basal outpouching, and the results of surgical and endovascular treatments.

METHODS: The occurrence of small basal outpouchings was determined in the initial angiographic examinations of 471 patients with a ruptured aneurysm. Information was also obtained from patient charts, surgical and interventional reports, operative video records, and reviews of radiological investigations.

RESULTS: A small basal outpouching was identified in 41 (8.7%) of the 471 ruptured aneurysms. In the surgical series (n = 286), a basal rupture was identified in 8 (30.8%) of the 26 cases of a basal outpouching and successfully treated by aneurysm clip placement. In the endovascular series (n = 185), intraprocedural aneurysm rebleeding developed in 5 of the 15 patients (33.3%) with a basal outpouching, which was most commonly observed with anterior communicating artery aneurysms.

CONCLUSION: The current surgical series included a 9% incidence of ruptured intracranial aneurysms with a small basal outpouching, and a 31% incidence of these basal outpouchings being identified as the rupture point. The results also suggested that endovascular coiling of a basal outpouching carries a high risk of intraprocedural aneurysm rebleeding, whereas surgical clipping is safer and provides more protection against rebleeding of aneurysms with a basal rupture.

Neurosurg Rev (2012) 35:497–504

Aneurysms located at the distal portion of the anterior inferior cerebellar artery (AICA) are rare, and their clinical features are not fully understood. We report the clinical features and management of nine distal AICA aneurysms in nine patients treated during the past decade at Kagoshima University Hospital and affiliated hospitals.

Our series includes seven women and two men. Of their nine aneurysms, eight were ruptured and one was unruptured; six were saccular and three were dissecting aneurysms. The most prevalent location was the meatal loop (n=5) followed by the postmeatal (n=3) and premeatal segment (n=1) of the AICA, suggesting hemodynamic stress as an etiology of these distal AICA aneurysms. Of the nine patients, five presented with angiographic features suggestive of increased hemodynamic stress to the AICA and the common trunk of the posterior inferior cerebellar artery, with vertebral artery stenosis, marked laterality, and a primitive hypoglossal artery.

We addressed eight aneurysms (eight patients) surgically; one aneurysm in one patient disappeared in the course of 3 months without surgical treatment. Of the eight surgically treated aneurysms, seven were ruptured and one was unruptured, five were clipped via lateral suboccipital craniotomy, two were trapped via lateral suboccipital craniotomy, and one was embolized. Good outcomes were obtained in six of the eight patients who underwent operation (75 %).

We consider increased hemodynamic stress attributable to anatomic variations in the AICA and related posterior circulation to be the predominant contributor to the development of distal AICA aneurysms. Direct clipping and trapping yielded favorable outcomes in our series.

J Neurosurg 117:309–315, 2012

The yield of CT angiography (CTA) and MR angiography (MRA) in patients with subarachnoid hemorrhage (SAH) who have a negative initial catheter angiogram is currently not well understood. This study aims to determine the yield of CTA and MRA in a prospective cohort of patients with SAH and a negative initial catheter angiogram.

Methods. From January 1, 2005, until September 1, 2010, the authors instituted a prospective protocol in which patients with SAH—as documented by noncontrast CT or CSF xanthochromia and a negative initial catheter angiogram— were evaluated using CTA and MRA to assess for causative cerebral aneurysms. Two neuroradiologists independently evaluated the noncontrast CT scans to determine the SAH pattern (perimesencephalic or not) and the CT and MR angiograms to assess for causative cerebral aneurysms.

Results. Seventy-seven patients were included, with a mean age of 52.8 years (median 54 years, range 19–88 years). Fifty patients were female (64.9%) and 27 male (35.1%). Forty-three patients had nonperimesencephalic SAH (55.8%), 29 patients had perimesencephalic SAH (37.7%), and 5 patients had CSF xanthochromia (6.5%). Computed tomography angiography demonstrated a causative cerebral aneurysm in 4 patients (5.2% yield), all of whom had nonperimesencephalic SAH (9.3% yield). Mean aneurysm size was 2.6 mm (range 2.1–3.3 mm). Magnetic resonance angiography demonstrated only 1 of these aneurysms. No causative cerebral aneurysms were found in patients with perimesencephalic SAH or CSF xanthochromia.

Conclusions. Computed tomography angiography is a valuable adjunct in the evaluation of patients with nonperimesencephalic SAH who have a negative initial catheter angiogram, demonstrating a causative cerebral aneurysm in 9.3% of patients.

Neurosurgery 71:239–244, 2012 DOI: 10.1227/NEU.0b013e3182571953

The Enterprise Vascular Reconstruction Device and Delivery System (Cordis; the Enterprise stent) was approved for use in conjunction with coiling of wide-necked aneurysms in 2007. No published long-term aneurysm occlusion or complication data exist for the Enterprise system.

OBJECTIVE: We compiled data on consecutive patients treated with Enterprise stent-assisted coiling of aneurysms from 9 high-volume neurointerventional centers.

METHODS: A 9 center registry was created to evaluate large volume data on the delayed safety and efficacy of the Enterprise stent system. Pooled data were compiled for consecutive patients undergoing Enterprise stent-assisted coiling at each institution prior to May 2009.

RESULTS: Two-hundred twenty-nine patients with 229 aneurysms, 32 of which were ruptured aneurysms, were included in the study. Mean clinical and angiographic follow-up was 619.6 ± 26.4 days and 655.7 ± 25.2 days, respectively. Mean aneurysm size was 9.2 ± 0.4 mm. Fifty-nine percent of patients demonstrated 100% coil obliteration and 81% had 90% or higher occlusion at last follow-up angiography. A total of 19 patients (8.3%) underwent retreatment of their aneurysms during the follow-up period. Angiographic in-stent stenosis was seen in 3.4% and thromboembolic events occurred in 4.4%. Overall, 90% of patients who underwent Enterprise-assisted coiling had a modified Rankin Scale score of 2 or less at last follow-up. A poor modified Rankin Scale score was strongly associated with rupture status (P < .001).

CONCLUSION: Although this study is limited by its retrospective nature, the Enterprise stent system appears to be an effective, safe, and durable treatment for intracranial aneurysms when used in conjunction with coiling.

Neuroradiology (2012) 54:597–606. DOI 10.1007/s00234-011-0945-0

Endovascular treatment of cerebral aneurysms includes follow-up imaging to identify aneurysms that may need retreatment. The aim of this study was to determine predictors of incomplete aneurysm occlusion at 1 year after endovascular coiling for ruptured cerebral aneurysms.
Methods In 129 patients of the Prospective Registry of Subarachnoid Aneurysms Treatment cohort, ruptured aneurysms were coiled within 14 days of onset and both initial post-coiling and 1-year follow-up digital subtraction angiography or magnetic resonance angiography were obtained. Factors predicting 1-year incomplete aneurysm occlusion (retreatment within 1-year or residual aneurysms at 1 year) were determined using multivariate logistic regression analyses.
Results One-year incomplete aneurysm occlusion was identified in 59 patients, including ten patients who were retreated within 1-year post-coiling. Dome size ≥7.5 mm (P=0.007, odds ratio (OR)=5.00, 95% confidence interval (CI)=1.55– 16.15), pre-treatment aneurysm re-rupture (P=0.023, OR= 3.50, 95% CI=1.19–10.31), non-small size/small neck aneurysm (dome size, ≥10 mm or neck size, ≥4 mm; P= 0.022, OR=3.26, 95% CI=1.19–8.96), and residual aneurysms on immediate post-coiling angiograms (P=0.017, OR= 1.43, 95% CI=1.07–1.93) significantly predicted incomplete aneurysm occlusion at 1-year post-coiling.
Conclusions In addition to the characteristics of aneurysm and initially incomplete aneurysm occlusion, this study showed pre-treatment aneurysm re-rupture to be a predictor that favors closer imaging follow-ups for coiled aneurysms.

J Neurosurg 116:871–881, 2012. http://thejns.org/doi/abs/10.3171/2011.11.JNS11311

Prediction of aneurysm rupture likelihood is clinically valuable, given that more unruptured aneurysms are being discovered incidentally with the increased use of imaging. The authors set out to evaluate the relative performance of morphological features for rupture status discrimination in the context of the divergent geometrical and hemodynamic characteristics of sidewall- and bifurcation-type aneurysms.

Methods. Catheter 3D rotational angiographic images of 271 consecutive aneurysms (101 ruptured, 135 bifurcation type) were used to assess the following parameters in 3D: maximum diameter (Dmax), height, height/width ratio, aspect ratio, size ratio, nonsphericity index, and inflow angle. Univariate statistics applied to the bifurcation, sidewall, and combined (bifurcation + sidewall) sets identified significant features for inclusion in multivariate analysis yielding area under the curve (AUC) and optimal thresholds in the receiver-operating characteristic. Furthermore, a computational fluid dynamics analysis was performed to evaluate the flow and wall shear stress conditions inside sidewall and bifurcation aneurysms at different inflow angles.

Results. The mean Dmax, height, and inflow angle were significantly greater in ruptured sidewall aneurysms than in unruptured sidewall aneurysms, but showed no difference between ruptured and unruptured bifurcation lesions. There was a statistically significant difference between ruptured and unruptured aneurysms for all measured features in the combined set. Multivariate analysis identified the following: 1) nonsphericity index as the only rupture status discriminator in bifurcation lesions (AUC = 0.67); 2) height/width ratio, size ratio, and inflow angle as strong discriminators in sidewall lesions (AUC = 0.87); and 3) height/width ratio, inflow angle, and size ratio as intermediate discriminators in the combined group (AUC = 0.76). Computational fluid dynamics analysis showed that although increasing inflow angle in a sidewall model led to deeper penetration of flow, higher velocities, and higher wall shear stress inside the aneurysm dome, it produced the exact opposite results in a bifurcation model.

Conclusions. Retrospective morphological and hemodynamic analysis point to a dichotomy between sidewall and bifurcation aneurysms with respect to performance of shape and size parameters in identifying rupture status, suggesting the need for aneurysm type–based analyses in future studies. The current most commonly used clinical risk assessment metric, Dmax, was found to be of no value in differentiating between ruptured and unruptured bifurcation aneurysms.

J Neurosurg 116:157–163, 2012. DOI: 10.3171/2011.8.JNS11324

The authors sought to identify the presence of a “July effect,” a transient increase in adverse outcomes during July, among a cohort of spontaneous subarachnoid hemorrhage (SAH) admissions recorded in the National Inpatient Sample (NIS).

Methods. The discharge status, admission month, patient demographics, treatment parameters, and hospital characteristics among spontaneous SAH admissions were extracted from the 2001–2008 NIS. Multivariate regression was used to determine whether an unfavorable discharge status and/or in-hospital mortality significantly increased in summer months in a pattern suggestive of a July effect. Additional models were generated to assess the impact of hospital teaching status on these outcomes.

Results. Among 57,663,486 hospital admissions from the 2001–2008 NIS, 52,879 cases of spontaneous SAH (ICD-9-CM 430) were treated at teaching (36,914 cases [70%]) and nonteaching (15,965 cases [30%]) facilities. Regression models failed to reveal a July effect for in-hospital mortality (c2 = 0.75, p = 1.000) or unfavorable discharges (c2 = 1.69, p = 0.999) among monthly SAH admissions, although they did suggest a significant reduction in these outcomes (in-hospital mortality, OR = 0.89, p < 0.001; unfavorable discharges, OR = 0.88, p < 0.001) among teaching hospitals as compared with nonteaching hospitals after adjustment for disparities in demographic, treatment, and hospital characteristics.

Conclusions. The discharge disposition among SAH admissions within the NIS was not suggestive of a July effect but did reveal that teaching institutions have significantly lower rates of adverse outcomes when compared with nonteaching hospitals. Note, however, that the origins of this difference related to teaching status remain unclear.

J Neurosurg 116:135–144, 2012.DOI: 10.3171/2011.8.JNS101767

The purpose of this ongoing study is to compare the safety and efficacy of microsurgical clipping and endovascular coil embolization for the treatment of acutely ruptured cerebral aneurysms and to determine if one treatment is superior to the other by examining clinical and angiographic outcomes. The authors examined the null hypothesis that no difference exists between the 2 treatment modalities in the setting of subarachnoid hemorrhage (SAH). The current report is limited to the clinical results at 1 year after treatment.

Methods. The authors screened 725 patients with SAH, resulting in 500 eligible patients who were enrolled prospectively in the study after giving their informed consent. Patients were assigned in an alternating fashion to surgical aneurysm clipping or endovascular coil therapy. Intake evaluations and outcome measurements were collected by nurse practitioners independent of the treating surgeons. Ultimately, 238 patients were assigned to aneurysm clipping and 233 to coil embolization. The 2 treatment groups were well matched. There were no anatomical exclusions. Crossing over was allowed, but primary outcome analysis was based on the initial treatment modality assignment. Posttreatment care was standardized for both groups. Patient outcomes at 1 year were independently assessed using the modified Rankin Scale (mRS). A poor outcome was defined as an mRS score > 2 at 1 year. The primary outcome was based on the assigned group; that is, by intent to treat.

Results. One year after treatment, 403 patients were available for evaluation. Of these, 358 patients had actually undergone treatment. The remainder either died before treatment or had no identifiable source of SAH. A poor outcome (mRS score > 2) was observed in 33.7% of the patients assigned to aneurysm clipping and in 23.2% of the patients assigned to coil embolization (OR 1.68, 95% CI 1.08–2.61; p = 0.02). Of treated patients assigned to the coil group, 124 (62.3%) of the 199 who were eligible for any treatment actually received endovascular coil embolization. Patients who crossed over from coil to clip treatment fared worse than patients assigned to coil embolization, but no worse than patients assigned to clip occlusion. No patient treated by coil embolization suffered a recurrent hemorrhage.

Conclusions. One year after treatment, a policy of intent to treat favoring coil embolization resulted in fewer poor outcomes than clip occlusion. Although most aneurysms assigned to the coil treatment group were treated by coil embolization, a substantial number crossed over to surgical clipping. Although a policy of intent to treat favoring coil embolization resulted in fewer poor outcomes at 1 year, it remains important that high-quality surgical clipping be available as an alternative treatment modality.

Neurosurg Focus 31 (6):E4, 2011. DOI: 10.3171/2011.9.FOCUS11237

The management of incidental small unruptured intracranial aneurysms (UIAs) is controversial and many factors need to be considered in the decision-making process. The authors describe a large consecutive series of patients harboring small incidental intracranial aneurysms. Treatment strategy, natural history, complications, and short-term outcomes are presented.

Methods. Between January 2008 and May 2011, the authors prospectively evaluated 212 patients with 272 small (< 10-mm) incidental aneurysms. Treatment recommendations (observation, endovascular treatment, or surgery), complications of treatment, and short-term outcomes were assessed.

Results. Recommended treatment consisted of observation in 125 patients, endovascular embolization in 64, and surgery in 18. Six patients were excluded from further analysis because they underwent treatment elsewhere. In the observation group, at a mean follow-up of 16.7 months, only 1 patient was moved to the embolization group. Seven (6%) of the 125 patients in the observation group died of causes unrelated to aneurysm. Sixty-five patients underwent 69 embolization procedures. The periprocedural permanent morbidity and mortality rates in patients undergoing endovascular treatment were 1.5% and 1.5%, respectively (overall morbidity and mortality rate 3.0%). In the surgery group no periprocedural complications were observed, although 1 patient did not return to her previous occupation. No aneurysmal rupture was documented in any of the 3 treatment groups during the follow-up period.

Conclusions. A cautious and individualized approach to incidental UIAs is of utmost importance for formulation of a safe and effective treatment algorithm. Invasive treatment (either endovascular or surgery) can be considered in selected younger patients, certain “higher-risk” locations, expanding aneurysms, patients with a family history of aneurysmal hemorrhage, and in those who cannot live their lives knowing that they harbor the UIA. Although the complication rate of invasive treatment is very low, it is not negligible. The study confirms that small incidental UIAs deemed to be not in need of treatment have a very benign short-term natural history, which makes observation a reasonable approach in selected patients.

Neurosurgery 69:1105–1115, 2011 DOI: 10.1227/NEU.0b013e318227e0e1

In patients with aneurysmal subarachnoid hemorrhage (SAH), preliminary results indicate that the amplitude of the single intracranial pressure (ICP) wave is a better predictor of the early clinical state and 6-month outcome than the mean ICP.

OBJECTIVE: To perform a randomized and blinded single-center trial comparing the effect of mean ICP vs mean ICP wave amplitude (MWA)-guided intensive care management on early clinical state and outcome in patients with aneurysmal SAH.

METHODS: Patients were randomized to 2 different types of ICP management: maintenance of mean ICP less than 20 mm Hg and MWA less than 5mm Hg. Early clinical state was assessed daily using the Glasgow Coma Scale. The primary efficacy variable was 12-month outcome in terms of the Rankin Stroke Score.

RESULTS: Ninety-seven patients were included in the study. There were no significant differences in treatment between the 2 groups apart from a larger volume of cerebrospinal fluid drained during week 1 in the MWA group. There was a tendency toward higher Glasgow Coma Scale scores in the MWA group during weeks 1 (P = .08) and 2 (P = .07). Outcome in terms of Rankin Stroke Score at 12 months was significantly better in the MWA group (P < .05).

CONCLUSION: This randomized and blinded trial disclosed a significant better primary efficacy variable (Rankin Stroke Score after 12 months) in the MWA patient group. We suggest that proactive intensive care management with MWA-tailored cerebrospinal fluid drainage during the first week improves aneurysmal SAH outcome.

Acta Neurochir (2011) 153:2103–2109. DOI 10.1007/s00701-011-1171-6

The management of complex paraclinoid aneurysms is still challenging. In this article we describe our approach to paraclinoid aneurysms, which has evolved over several years, using an exclusively intradural approach.

Method All procedures are done under continuous electrophysiological monitoring. A standard pterional approach is used to access the paraclinoid region exclusively intraduraly. After optic nerve unroofing and tailored clinoidectomy, the aneurysm neck is visualized and clipped using the tandem clipping technique and suction decompression if necessary. Aneurysm occlusion is verified using intraoperative ICG angiography and postoperative 3D DSA.

Conclusion The exclusively intradural approach to complex paraclinoid aneurysms with tailored clinoidectomy offers an excellent surgical corridor for the treatment of these challenging lesions

Neurosurgery 69:557–565, 2011 DOI: 10.1227/NEU.0b013e31821a86da

Despite increasing acceptance of endovascular coiling for treating intracranial aneurysms, incomplete occlusion remains a limitation. Attempts to reduce recanalization have prompted creation of polyglycolic/polylactic acid–coated (Matrix) coils shown to improve neointima formation; however, previous publications demonstrate conflicting results regarding their efficacy. Few studies account for factors influencing recurrence, and only 4 studies include bare platinum (BP) coil control groups.

OBJECTIVE: To compare initial and short- and mid-term occlusion as well as retreatment rates using Matrix compared with BP coils.

METHODS: Retrospective review of patients undergoing coiling of cerebral aneurysms from 2001 to 2005 was performed. Analysis included a multivariate logistic regression model designed to detect a 35% absolute difference in initial occlusion between coil treatment groups with 80% power.

RESULTS: Complete initial occlusion was achieved in 64% of BP (n = 45) and 63% of Matrix (n = 56) cases (P = 1.0). Follow-up occlusion rates in the short term and mid term were 52% and 60%, respectively, for BP cases and 42% and 67%, respectively, for Matrix cases (P = .24 and P = .38, respectively). After adjusting for size, morphology, volumetric packing density, location, rupture, and balloon remodeling, no difference in initial and subsequent occlusion or retreatment rates for BP coils versus Matrix coils was appreciated.

CONCLUSION: After controlling for factors influencing recanalization, this investigation failed to show a significant difference between coil groups.

Acta Neurochir. DOI 10.1007/s00701-011-1139-6

In recent years the endovascular treatment of intracranial aneurysms (coiling) has progressively gained recognition, particularly after the publication of the International Subarachnoid Aneurysm Trial (ISAT) in 2002. Despite the fact that in ISAT middle cerebral artery (MCA) aneurysms were clearly underrepresented, the study is often used as an argument to favor coiling above surgery in MCA aneurysms. Taken into account that MCA aneurysms are very well accessible for surgery, a contemporary assessment of the benefits of a preferred surgical strategy for MCA aneurysms was performed in a tertiary neurovascular referral center.

Methods A prospectively kept single-center database of 151 consecutive patients with an MCA aneurysm was reviewed over a 6-year period (2001–2006). Long-term follow-up after surgical treatment of a ruptured MCA aneurysm was obtained in 74 out of 77 (96%) patients. The outcome was compared with relevant series in the literature.

Results After a mean follow-up of 4.7 years, 59 out of 74 surgically treated patients (80%) with a ruptured MCA aneurysm had a good outcome (mRankin 0–2). All patients with an unruptured MCA aneurysm also had a good outcome after clipping. This is well-matched with the findings of the literature search, and competitive with the endovascular results.

Conclusion Surgical clipping is recommended as the principal treatment strategy for MCA aneurysms. This is not only ethically defendable in view of the surgical results but also in line with a strategy to maintain surgical experience within centralized neurovascular centers.

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.

Neurosurgery 68:372–378, 2011 DOI: 10.1227/NEU.0b013e3181ffe931

Treatment of Spetzler-Martin Grade IV and V brain arteriovenous malformations (ie, high-grade AVMs) carries a high risk of morbidity and even mortality. However, little is known about the behavior of these lesions if left untreated.

OBJECTIVE: To investigate the natural history of patients with high-grade AVMs.

METHODS: Patients with untreated high-grade AVMs admitted to our center between 1952 and 2005 were followed from admission until death, AVM rupture, or initiation of treatment. Rates of rupture and various risk factors were analyzed using Kaplan-Meier life table analyses and Cox proportional hazards models. Functional outcome was assessed 1 year after possible AVM rupture using the Glasgow Outcome Scale.

RESULTS: Sixty-three patients with a mean follow-up time of 11.0 years (range, 1 month to 39.6 years) were identified. Twenty-three patients (37%) experienced a subsequent rupture. The average annual rate of rupture was 3.3%. In patients with hemorrhagic presentation, the annual rate was 6.0%, compared to 1.1% in patients with unruptured AVMs (P = .001, log-rank test; hazard ratio, 5.09 [1.40-18.5, 95% CI]; P = .013, multivariate Cox regression model). One year after the first subsequent rupture, 6 patients (26%) had died, and 9 (39%) had moderate or severe disability.

CONCLUSION: Untreated high grade AVMs presenting with hemorrhage have a significant risk of subsequent rupture, and their rupture carries a higher risk of case fatality and permanent morbidity than AVMs in general. The risks associated with their treatment should be appraised in light of perilous natural history.

Neurosurgery 68:140–154, 2011 DOI: 10.1227/NEU.0b013e3181fd860e

Residual and recurrent intracranial aneurysms after endovascular treatment with Guglielmi detachable coils may necessitate a microsurgical occlusion.

OBJECTIVE: To analyze the microsurgical technique and describe how the location, morphology, and appearance of the coiled aneurysm affect the technique.

METHODS: We retrospectively analyzed 81 patients with 82 previously coiled aneurysms treated microsurgically at 2 Finnish neurosurgical university hospitals in Helsinki and Kuopio between July 1995 and August 2009. Seven videos were selected to demonstrate the microsurgical strategy in various locations.

RESULTS: Fifty-eight aneurysms (71%) were located at anterior circulation and 24 (29%) at posterior circulation. Fifteen patients were operated on within the first month (early surgery) after coiling, whereas 66 were treated later (late surgery). Complete or partial removal of coils during surgery may facilitate clipping, but is significantly (P, .001) more difficult to accomplish in late surgery. Removal of coils may also increase the chance of poor outcome. Chance of poor outcome also increased with intraoperative aneurysm rupture, size of the aneurysm, and posterior circulation location. Good clinical outcome (same or better clinical condition 3 months after surgery) was achieved in 71 patients (88%). After microsurgery, 4 patients were severely disabled and 6 patients died, 3 of them because of poor clinical condition.

CONCLUSION: Complete microsurgical occlusion of the residual aneurysm is possible. However, in large or giant aneurysms direct microsurgery is a challenging high-risk procedure, and we recommend that these patients be referred to a dedicated neurovascular center to minimize surgical complications. Even in experienced hands, use of different bypass procedures may be the best option for demanding growing lesions, especially those in the posterior circulation.

Neurosurgery 68:132–139, 2011 DOI: 10.1227/NEU.0b013e3181fe23a1

A seasonal and meteorological influence on the incidence of spontaneous subarachnoid hemorrhage (SAH) has been suggested, but a consensus in the literature has yet to emerge.

OBJECTIVE: This study examines the impact of weather patterns on the incidence of SAH using a geographically broad analysis of hospital admissions and represents the largest study of the topic to date.

METHODS: We retrospectively analyzed SAH admissions to 155 US hospitals during the calendar years 2004 to 2008 (N = 7758). Daily weather readings for temperature, pressure, and humidity were obtained for the same period from National Oceanic and Atmospheric Administration weather stations located near each hospital. The daily values of each weather variable were associated with the daily volume of SAH admissions using a combination of correlation and time-series analyses.

RESULTS: No seasonal trends were observed in the monthly volume of SAH admissions during the study period. No significant correlation was detected between the daily SAH admission volume and the day’s weather, the previous day’s weather, or the 24-hour weather change.

CONCLUSION: This study represents the most comprehensive investigation of the association between weather and spontaneous SAH to date. The results suggest that neither season nor weather significantly influences the incidence of SAH.