Patient functional outcomes and quality of life after surgery for unruptured brain arteriovenous malformation

BACKGROUND

Studies have questioned the effectiveness of surgery for the management of unruptured brain arteriovenous malformation (ubAVM). Few studies have examined functional outcomes and quality of life (QOL) prior and 12 months after surgical repair of ubAVM.

OBJECTIVE

This study examined the effectiveness of surgical management of ubAVM by measuring patients' perceived QOL and their ability to perform everyday activities.

METHODS

Between 2011 and 2016, patients diagnosed with an unbAVM were assessed using the Quality Metric Short Form 36 (SF36), the DriveSafe component of the off-road driver screening tool DriveSafeDriveAware (DSDA), the modified Barthel Index (mBI) and the modified Rankin Scale (mRS). Reassessments were conducted at the 6-week post-operative follow-up for surgical patients and at 12-month follow-up for surgical and conservatively managed patients.

RESULTS

Forty-five patients enrolled in the study, of which 35 (78%) had their ubAVM surgically treated. Patients undergoing surgery had a significantly lower ubAVM Spetzler-Ponce Class (SPC). There was no significant difference 12 months after presentation in function or QOL for either the conservative or surgical group. The surgical group had significantly higher QOL of life scores from pre-surgery to 12 months post-surgery (PCS p < 0.01; MCS p = 0.02). Higher SP grade ubAVM was significantly related to poorer function in the surgical group (SP C compared with SP A; p = 0.04, mean difference - 12.4, 95%CI - 24.3 to - 0.4).

CONCLUSION

Function and QOL are not diminished after surgical treatment of low Spetzler-Ponce Class unruptured brain arteriovenous malformations. QOL is higher 12 months after surgery for ubAVM than for those who do not have treatment for their ubAVM.

Risk of First Hemorrhage of Brain Arteriovenous Malformations During Pregnancy: A Systematic Review of the Literature

BACKGROUND

Recommendations on the management of brain arteriovenous malformations (bAVM) with respect to pregnancy are based upon conflicting literature.

OBJECTIVE

To systematically review the reported risk and annualized rate of first intracranial hemorrhage (ICH) from bAVM during pregnancy and puerperium.

METHODS

MEDLINE, EMBASE, and Scopus databases were searched for relevant articles in English published before April 2018. Studies providing a quantitative risk of ICH in bAVM during pregnancy were eligible.

RESULTS

From 7 initially eligible studies, 3 studies met the criteria for providing quantitative risk of first ICH bAVM during pregnancy. Data from 47 bAVM ICH during pregnancy across 4 cohorts were extracted for analysis. Due to differences in methodology and definitions of exposure period, it was not appropriate to combine the cases. The annualized risk of first ICH during pregnancy for these 4 cohorts was 3.0% (95% confidence interval [CI]: 1.7-5.2%); 3.5% (95% CI: 2.4-4.5%); 8.6% (95% CI: 1.8-25%); and 30% (95% CI: 18-49%). Only the last result from the last cohort could be considered significantly increased in comparison with the nonpregnant period (relative rate 6.8, 95% CI: 3.6-13). The limited number of eligible studies and variability in results highlighted the need for enhanced rigor of future research.

CONCLUSION

There is no conclusive evidence of an increased risk of first hemorrhage during pregnancy from bAVM. Because advice to women with bAVM may influence the management of pregnancy or bAVM with significant consequences, we believe that a retrospective multicenter, case crossover study is urgently required.

Results of Surgery for Low-Grade Brain Arteriovenous Malformation Resection by Early Career Neurosurgeons: An Observational Study

BACKGROUND

For sustainability of arteriovenous malformation (AVM) surgery, results from early career cerebrovascular neurosurgeons (ECCNs) must be acceptably safe.

OBJECTIVE

To determine whether ECCNs performance of Spetzler-Ponce Class A AVM (SPC A) resection can be acceptably safe.

METHODS

ECCNs completing a cerebrovascular fellowship (2004-2015) with the last author were included. Inclusion of the ECCN cases occurred if they: had a prospective database of all AVM cases since commencing independent practice; were the primary surgeon on SPC A; and had made the significant management decisions. All SPC A surgical cases from the beginning of the ECCN's independent surgical practice to a maximum of 8 yr were included. An adverse outcome was considered a complication of surgery leading to a new permanent neurological deficit with a last modified Rankin Scale score >1. A cumulative summation (Cusum) plot examined the performance of each surgery. The highest acceptable level of adverse outcomes for the Cusum was 3.3%, derived from the upper 95% confidence interval of the last author's reported series.

RESULTS

Six ECCNs contributed 110 cases for analysis. The median number of SPC A cases operated by each ECCN was 16.5 (range 4-40). Preoperative embolization was performed in 5 (4.5%). The incidence of adverse outcomes was 1.8% (95% confidence interval: <0.01%-6.8%). At no point during the accumulated series did the combined cohort become unacceptable by the Cusum plot.

CONCLUSION

ECCNs with appropriate training appointed to large-volume cerebrovascular centers can achieve results for surgery for SPC A that are not appreciably worse than those published from high-volume neurosurgeons.

Variability of pyrethroid concentrations on hard surface kitchen flooring in occupied housing

Pyrethroids are a class of neurotoxic insecticides, and some studies have used single-time wiping of hard surface flooring to estimate indoor pyrethroid concentrations. Considering that human activities may affect concentrations, knowledge of temporal variability is needed to reduce the uncertainty of exposure estimates that are calculated using wipe sampling of pyrethroids in occupied housing. During weeks one, two, and six of a 6-week study, two wipe samples of hard surface kitchen flooring were collected in each of 50 occupied residences and used to estimate the temporal variability of eight pyrethroids and six pyrethroid degradation products. Beginning 1 month prior to sample collection, the participants kept pesticide use diaries. All pyrethroids were widely distributed among the houses, and co-occurrence of multiple pyrethroids was common structured. Application diaries and detection frequencies appeared unconnected, but the applications were correlated with measurable changes in pyrethroid concentrations. In general, degradation products were detected less frequently and at lower concentrations than their parent pyrethroids. Estimates of the intraclass correlation coefficient (ICC) for individual pyrethroids ranged from 0.55 (bifenthrin) to 0.80 (deltamethrin), and two sampling events at each residence would have been sufficient to estimate the mean concentration of most pyrethroids with an ICC of 0.80.

Functional outcomes and quality of life after microsurgical clipping of unruptured intracranial aneurysms: a prospective cohort study

OBJECTIVE

Few studies have examined patients’ ability to drive and quality of life (QOL) after microsurgical repair for unruptured intracranial aneurysms (uIAs). However, without a strong evidentiary basis, jurisdictional road transport authorities have recommended driving restrictions following brain surgery. In the present study, authors examined the outcomes of the microsurgical repair of uIAs by measuring patients’ perceived QOL and cognitive abilities related to driving.

METHODS

Between January 2011 and January 2016, patients with a new diagnosis of uIA were prospectively enrolled in this study. Assessments were performed at referral, before surgery, and at 6 weeks and 12 months after surgery in those undergoing microsurgical repair and at referral and at 12 months in conservatively managed patients. Assessments included the Physical Component Summary (PCS) and Mental Component Summary (MCS) of the SF-36, the off-road driver-screening instrument DriveSafe (DS), the modified Barthel Index (mBI), and the modified Rankin Scale (mRS).

RESULTS

One hundred sixty-nine patients were enrolled in and completed the study, and 112 (66%) of them had microsurgical repair of their aneurysm. In the microsurgical group, there was a trend for improved DS scores: from a mean (± standard deviation) score of 108 ± 10.7 before surgery to 111 ± 9.7 at 6 weeks after surgery to 112 ± 10.2 at 12 months after surgery (p = 0.05). Two percent of the microsurgical repair group and 4% of the conservatively managed group whose initial scores indicated competency to drive according to the DS test subsequently had 12-month scores deemed as not competent to drive; the difference between these 2 groups was not statistically significant (p > 0.99). Factors associated with a decline in the DS score among those who had a license at the time of initial assessment were an increasing age (p < 0.01) and mRS score > 0 at one of the assessments (initial, 6 weeks, or 12 months; p < 0.01).

Mean PCS scores in the microsurgical repair group were 52 ± 8.1, 46 ± 6.8, and 52 ± 7.1 at the initial, 6-week, and 12-month assessments, respectively (p < 0.01). These values represented a significant decline in the mean PCS score at 6 weeks that recovered by 12 months (p < 0.01). There were no significant changes in the MCS, mBI, or mRS scores in the surgical group.

CONCLUSIONS

Overall, QOL at 12 months for the microsurgical repair group had not decreased and was comparable to that in the conservatively managed group. Furthermore, as assessed by the DS test, the majority of patients were not affected in their ability to drive.

Deliberate employment of postoperative hypotension for brain arteriovenous malformation surgery and the incidence of delayed postoperative hemorrhage: a prospective cohort study

OBJECTIVE

The aim of this study was to examine the impact of deliberate employment of postoperative hypotension on delayed postoperative hemorrhage (DPH) for all Spetzler-Ponce Class (SPC) C brain arteriovenous malformations (bAVMs) and SPC B bAVMs ≥ 3.5 cm in diameter (SPC B 3.5+).

METHODS

A protocol of deliberate employment of postoperative hypotension was introduced in June 1997 for all SPC C and SPC B 3.5+ bAVMs. The aim was to achieve a maximum mean arterial blood pressure (BP) ≤ 70 mm Hg (with cerebral perfusion pressure > 50 mm Hg) for a minimum of 7 days after resection of bAVMs (BP protocol). The authors compared patients who experienced DPH (defined as brain hemorrhage into the resection bed that resulted in a new neurological deficit or that resulted in reoperation during the hospitalization for microsurgical bAVM resection) between 2 periods (prior to adopting the BP protocol and after introduction of the BP protocol) and 4 bAVM categories (SPC A, SPC B 3.5− [that is, SPC B < 3.5 cm maximum diameter], SPC B 3.5+, and SPC C). Patients excluded from treatment by the BP protocol were managed in the intensive care unit to avoid moderate hypertensive episodes. The pooled cases of all bAVM treated by surgery were analyzed to identify characteristics associated with the risk of DPH. These identified characteristics were then examined by multiple logistic regression analysis in both SPC B 3.5+ and SPC C cases.

RESULTS

From a cohort of 641 bAVMs treated by microsurgery, 32 patients with DPH were identified. Of those, 66% (95% CI 48–80) had a permanent new neurological deficit with a modified Rankin Scale score of 2–6. This included a mortality rate of 13% (95% CI 4.4–29). The BP protocol was used to treat 162 patients with either SPC B 3.5+ or SPC C. For SPC B 3.5+, there was no significant reduction in DPH with the introduction of the BP protocol (p = 0.77). For SPC C, there was a significant (p = 0.035) reduction of DPH from 29% (95% CI 13%–53%) to 8.2% (95% CI 3.2%–18%) associated with the introduction of the BP protocol. Multiple logistic regression analysis found that the absence of the BP protocol (p = 0.011, odds ratio 7.5, 95% CI 1.6–36) remained significant for the development of DPH in patients with SPC C bAVMs.

CONCLUSIONS

Treating patients with SPC C bAVMs with a protocol that lowers BP immediately after resection seems to reduce the risk of DPH. For SPC A and SPC B 3.5− bAVMs, there is unlikely to be a need to do more than avoid postoperative hypertension. For SPC B 3.5+ bAVMs, a larger number of patients would be required to test the absence of benefit of the BP protocol.

The Risk of Seizure Following Surgery for Brain Arteriovenous Malformation: A Prospective Cohort Study

BACKGROUND

The evidence for the risk of seizures following surgery for brain arteriovenous malformations (bAVM) is limited.

OBJECTIVE

To determine the risk of seizures after discharge from surgery for supratentorial bAVM.

METHODS

A prospectively collected cohort database of 559 supratentorial bAVM patients (excluding patients where surgery was not performed with the primary intention of treating the bAVM) was analyzed. Cox proportional hazards regression models (Cox regression) were generated assessing risk factors, a Receiver Operator Characteristic curve was generated to identify a cut-point for size and Kaplan–Meier life table curves created to identify the cumulative freedom from postoperative seizure.

RESULTS

Preoperative histories of more than 2 seizures and increasing maximum diameter (size, cm) of bAVM were found to be significantly (P &lt; .01) associated with the development of postoperative seizures and remained significant in the Cox regression (size as continuous variable: P = .01; hazard ratio: 1.2; 95% confidence interval: 1.0-1.3; more than 2 seizures: P = .02; hazard ratio: 2.1; 95% confidence interval: 1.1-3.8). The cumulative risk of first seizure after discharge from hospital following resection surgery for all patients with bAVM was 5.8% and 18% at 12 mo and 7 yr, respectively. The 7-yr risk of developing postoperative seizures ranged from 11% for patients with bAVM ≤4 cm and with 0 to 2 preoperative seizures, to 59% for patients with bAVM &gt;4 cm and with &gt;2 preoperative.

CONCLUSION

The risk of seizures after discharge from hospital following surgery for bAVM increases with the maximum diameter of the bAVM and a patient history of more than 2 preoperative seizures.

Complication-Effectiveness Analysis for Unruptured Intracranial Aneurysm Surgery: A Prospective Cohort Study

BACKGROUND

The aim of intervention for unruptured intracranial aneurysms (UIAs) is safe, effective treatment.

OBJECTIVE

To analyze a prospective database for variables influencing the risk of surgery to produce a risk model adjusting this risk for effectively treated aneurysms.

METHODS

First, we identified variables to create a model from multiple logistic regression for complications of surgery leading to a 12-month modified Rankin Scale score >1. Second, we established the long-term cumulative incidence of freedom from retreatment or rupture (treated aneurysm) from Kaplan-Meier analysis. Third, we combined these analyses to establish a model of risk of surgery per effective treatment.

RESULTS

One thousand twelve patients with 1440 UIA underwent 1080 craniotomies. We found that 10.1% (95% confidence interval [CI], 8.4-12.0) of craniotomies resulted in a complication leading to a modified Rankin Scale score >1 at 12 months. Logistic regression found age (odds ratio, 1.04; 95% CI, 1.02-1.06), size (odds ratio, 1.12; 95% CI, 1.09-1.15), and posterior circulation location (odds ratio, 2.95; 95% CI, 1.82-4.78) to be significant. Cumulative 10-year risk of retreatment or rupture was 3.0% (95% CI, 1.3-7.0). The complication-effectiveness model was derived by dividing the complication risk by the 10-year cumulative freedom from retreatment or rupture proportion. Risk per effective treatment ranged from 1% for a 5-mm anterior circulation UIA in a 20-year-old patient to 70% for a giant posterior circulation UIA in a 70-year-old patient.

CONCLUSION

Complication-effectiveness analyses increase the information available with regard to outcome for the management of UIAs.

Transdural arterial recruitment to brain arteriovenous malformation: clinical and management implications in a prospective cohort series

OBJECTIVE The occurrence of transdural arterial recruitment (TDAR) in association with brain arteriovenous malformation (bAVM) is uncommon, and the reason for TDAR is not understood. The aim of this cohort study was to examine patient and bAVM characteristics associated with TDAR and the implications of TDAR on management. METHODS A prospective surgical database of bAVMs was examined. Cases previously treated elsewhere or incompletely examined by digital subtraction angiography (DSA) assessment were excluded. Three studies of this cohort were performed, as follows: characteristics associated with TDAR, the relationship between TDAR and neurological deficits unassociated with hemorrhage (NDUH), and the impact of TDAR on outcome from surgery. Regression models were performed. RESULTS Of 769 patients with complete DSA who had no previous treatment, 51 (6.6%) were found to have TDAR. The presence of TDAR was associated with increasing age (p < 0.01; OR 1.05; 95% CI 1.02-1.07); presentation with NDUH (p < 0.01; OR 2.71; 95% CI 1.29-5.71); increasing size of the bAVM (p < 0.01; OR 1.57; 95% CI 1.29-1.91); and combined supply from both anterior and posterior circulations (p = 0.02; OR 2.37; 95% CI 1.17-4.78). Further analysis of TDAR cases comparing those with and without NDUH found an association of larger size (6.6 cm [2.9 SD] compared with 4.7 cm [1.8 SD]; p < 0.01) and combined supply from both anterior and posterior circulations (relative risk 2.5; 95% CI 1.0-6.2; p = 0.04) to be associated with an NDUH presentation. For the 632 patients undergoing surgery there was an increased risk of complications (where this produced a new permanent neurological deficit at 12 months represented by a modified Rankin Scale score of > 1) with the following variables: size; location in eloquent brain; deep venous drainage; increasing age; and no presentation with hemorrhage. The presence of TDAR was not associated with an increased risk of complications from surgery. CONCLUSIONS The authors found that TDAR occurs in older patients with larger bAVMs, and that TDAR is also more likely to be associated with bAVMs presenting with NDUH. The likely explanation for the presence of TDAR is a secondary recruitment arising as a consequence of shear stress, rather than a primary vascular supply present from the earliest development of the bAVM.

The Risk of Seizure After Surgery for Unruptured Intracranial Aneurysms

BACKGROUND:

We aimed to identify a group of patients with a low risk of seizure after surgery for unruptured intracranial aneurysms (UIA).

OBJECTIVE:

To determine the risk of seizure after discharge from surgery for UIA.

METHODS:

A consecutive prospectively collected cohort database was interrogated for all surgical UIA cases. There were 726 cases of UIA (excluding cases proximal to the superior cerebellar artery on the vertebrobasilar system) identified and analyzed. Cox proportional hazards regression models and Kaplan-Meier life table analyses were generated assessing risk factors.

RESULTS:

Preoperative seizure history and complication of aneurysm repair were the only risk factors found to be significant. The risk of first seizure after discharge from hospital following surgery for patients with neither preoperative seizure, treated middle cerebral artery aneurysm, nor postoperative complications (leading to a modified Rankin Scale score &gt;1) was &lt;0.1% and 1.1% at 12 months and 7 years, respectively. The risk for those with preoperative seizures was 17.3% and 66% at 12 months and 7 years, respectively. The risk for seizures with either complications (leading to a modified Rankin Scale score &gt;1) from surgery or treated middle cerebral artery aneurysm was 1.4% and 6.8% at 12 months and 7 years, respectively. These differences in the 3 Kaplan-Meier curves were significant (log-rank P &lt;.001).

CONCLUSION:

The risk of seizures after discharge from hospital following surgery for UIA is very low when there is no preexisting history of seizures. If this result can be supported by other series, guidelines that restrict returning to driving because of the risk of postoperative seizures should be reconsidered.

Complication-Effectiveness Analysis for Brain Arteriovenous Malformation Surgery

BACKGROUND:

Intervention for brain arteriovenous malformations (bAVMs) should aim at treatment that is safe and effective.

OBJECTIVE:

To analyze a prospective database to derive the probability of neurological deficit and adjust this risk for effectively treated bAVMs (complication-effectiveness analysis [CEA]).

METHODS:

First, we calculated the percentage of surgical complications leading to a modified Rankin Scale &gt;1 at 12 months after surgery for each Spetzler-Ponce class (SPC). Second, we performed a sensitivity analysis of these results by including bAVMs not undergoing surgery, to correct for bias. Third, we established the long-term cumulative incidence of freedom from recurrence from Kaplan-Meier analysis. Finally, we combined the results to calculate the risk of surgery per effective treatment in a complication-effectiveness analysis.

RESULTS:

Seven hundred seventy-nine patients underwent 641 microsurgical resections. Complications of surgery leading to a modified Rankin Scale &gt;1 at 12 months occurred in 1.4% (95% confidence interval [CI]: 0.5-3.3), 20% (95% CI: 15-26), and 41% (95% CI: 30-52) of SPC A, SPC B, and SPC C, respectively. The cumulative 9-year freedom from recurrence was 97% for SPC A and 92% for other bAVMs. The 9-year CEA risk was 1.4% (credible range: 0.5%-3.4%) for SPC A, 22% to 24% (credible range: 16%-31%) for SPC B, and 45% to 63% (credible range: 33%-73%) for SPC C bAVM.

CONCLUSION:

CEA presents the treatment outcome in the context of efficacy and provides a basis for comparing outcomes from techniques with different times to elimination of the bAVM.

Factors Associated With Proximal Intracranial Aneurysms to Brain Arteriovenous Malformations

BACKGROUND:

The risk of hemorrhage from a brain arteriovenous malformation (bAVM) is increased when an associated proximal intracranial aneurysm (APIA) is present. Identifying factors that are associated with APIA may influence the prediction of hemorrhage in patients with bAVM.

OBJECTIVE:

To identify patient- and bAVM-specific factors associated with APIA.

METHODS:

We analyzed a prospective database of bAVMs for factors associated with the presence of APIA. Factors analyzed included age, sex, bAVM size, aneurysm size, circulation contributing to the bAVM, location of the aneurysm, deep venous drainage, and Spetzler-Ponce categories. Multiple logistic regression was performed to identify an association with APIA.

RESULTS:

Of 753 cases of bAVM with complete angiographic surveillance, 67 (9%) were found to have APIA. Older age (continuous variable; odds ratio, 1.04; 95% confidence interval, 1.02-1.05) and posterior circulation supply to the bAVM (odds ratio, 2.29; 95% confidence interval, 1.32-3.99) were factors associated with increased detection of APIA. The association of posterior circulation–supplied bAVM was not due to infratentorial bAVM location because 72% of posterior circulation APIAs were supplying supratentorial bAVM.

CONCLUSION:

APIAs appear to develop with time, as evident from the increased age for those with APIAs. Furthermore, they were more likely present in bAVMs supplied by the posterior circulation. This may be due to a difference in hemodynamic stress.

Surgery for Unruptured Spetzler-Martin Grade 3 Brain Arteriovenous Malformations

BACKGROUND:

There is uncertainty regarding the management of unruptured Spetzler-Martin grade 3 brain arteriovenous malformations (SMG3 ubAVM).

OBJECTIVE:

To analyze our series of patients treated by surgery.

METHODS:

A single-surgeon database of consecutively enrolled bAVMs (between 1989 and 2014) was analyzed. Adverse outcomes due to surgery were assigned within the first 6 weeks following surgery and outcome was prospectively recorded and assigned at the last follow-up visit by using modified Rankin Scale (mRS) score.

RESULTS:

Of the 137 reviewed patients, 112 (82%) were treated by surgery, 15 (11%) were treated elsewhere or by radiosurgery, and 10 (7%) were recommended for conservative management. Surgery for SMG3 ubAVM was associated with adverse outcomes with a new permanent neurological deficit of mRS &gt;1 in 23 of 112 (21%) patients. Permanent neurological deficit leading to a mRS &gt;2 from surgery was 3.6% (95% confidence interval, 1.1%-9.1%). Late recurrence of a bAVM occurred in 3 of 103 (2.9%) patients who had complete obliteration of bAVM confirmed immediately after surgery and who were subsequently later followed with radiological studies during the mean follow-up period of 3.0 years (range, 6 days to 18.8 years).

CONCLUSION:

When discussing surgical options for SMG3 ubAVM, a thorough understanding of the significance and incidence of adverse events and outcomes is required to fully inform patients. For our series, the additional subclassification of SMG ubAVM (based on variables contributing to the SMG or age) would not have been of use.

Role of surgery in the management of brain arteriovenous malformations: prospective cohort study

BACKGROUND AND PURPOSE

Management of brain arteriovenous malformation (bAVM) is controversial. We have analyzed the largest surgical bAVM cohort for outcome.

METHODS

Both operated and nonoperated cases were included for analysis. A total of 779 patients with bAVMs were consecutively enrolled between 1989 and 2014. Initial management recommendations were recorded before commencement of treatment. Surgical outcome was prospectively recorded and outcomes assigned at the last follow-up visit using modified Rankin Scale. First, a sensitivity analyses was performed to select a subset of the entire cohort for which the results of surgery could be generalized. Second, from this subset, variables were analyzed for risk of deficit or near miss (intraoperative hemorrhage requiring blood transfusion of ≥2.5 L, hemorrhage in resection bed requiring reoperation, and hemorrhage associated with either digital subtraction angiography or embolization).

RESULTS

A total of 7.7% of patients with Spetzler-Ponce classes A and B bAVM had an adverse outcome from surgery leading to a modified Rankin Scale >1. Sensitivity analyses that demonstrated outcome results were not subject to selection bias for Spetzler-Ponce classes A and B bAVMs. Risk factors for adverse outcomes from surgery for these bAVMs include size, presence of deep venous drainage, and eloquent location. Preoperative embolization did not affect the risk of perioperative hemorrhage.

CONCLUSIONS

Most of the ruptured and unruptured low and middle-grade bAVMs (Spetzler-Ponce A and B) can be surgically treated with a low risk of permanent morbidity and a high likelihood of preventing future hemorrhage. Our results do not apply to Spetzler-Ponce C bAVMs.

Surgery for unruptured arteriovenous malformations of the brain is better than conservative management for selected cases: a prospective cohort study

Object

The aim of this study was to identify patients who are likely to benefit from surgery for unruptured brain arteriovenous malformations (ubAVMs).

Methods

The authors' database was interrogated for the risk and outcome of hemorrhage after referral and the outcome from surgery. Furthermore, the outcome from surgery incorporated those cases excluded from surgery because of perceived greater risk (sensitivity analysis). Finally, a comparison was made for the authors' patients between the natural history and surgery. Data were collected for 427 consecutively enrolled patients with ubAVMs in a database that included patients who were conservatively managed. Kaplan-Meier analysis was performed on patients observed for more than 1 day to determine the risk of hemorrhage. Variables that may influence the risk of first hemorrhage were assessed using Cox proportional hazard regression models and Kaplan-Meier life table analyses from referral until the first occurrence of the following: hemorrhage, treatment, or last review. The outcome from surgery (leading to a new permanent neurological deficit with last review modified Rankin Scale [mRS] score > 1) was determined. Further sensitivity analysis was made to predict risk from surgery for the total ubAVM cohort by incorporating outcomes of surgical cases as well as cases excluded from surgery because of perceived risk, and assuming an adverse outcome for these excluded cases.

Results

A total of 377 patients with a ubAVM were included in the analysis of the risk of hemorrhage. The 5-year risk of hemorrhage for ubAVM was 11.5%. Hemorrhage resulted in an mRS score > 1 in 14 cases (88% [95% CI 63%–98%]). Patients with Spetzler-Ponce Class A ubAVMs treated by surgery (n = 190) had a risk from surgery of 1.6% (95% CI 0.3%–4.8%) for a permanent neurological deficit leading to an mRS score > 1 and 0.5% (95% CI < 0.1%–3.2%) for a permanent neurological deficit leading to an mRS score > 2. Patients with Spetzler-Ponce Class B ubAVMs treated by surgery (n = 107) had a risk from surgery of 14.0% (95% CI 8.6%–22.0%) for a permanent neurological deficit leading to an mRS score > 1. Sensitivity analysis of Spetzler-Ponce Class B ubAVMs, including those in patients excluded from surgery, showed that the true risk for surgically eligible patients may have been as high as 15.6% (95% CI 9.9%–23.7%) for mRS score > 1, had all patients who were perceived to have a greater risk experienced an adverse outcome. Patients with Spetzler-Ponce Class C ubAVMs treated by surgery (n = 44) had a risk from surgery of 38.6% (95% CI 25.7%–53.4%) for a permanent neurological deficit leading to an mRS score > 1. Sensitivity analysis of Class C ubAVMs, including those harbored by patients excluded from surgery, showed that the true risk for surgically eligible patients may have been as high as 60.9% (95% CI 49.2%–71.5%) for mRS score > 1, had all patients who were perceived to have a greater risk experienced an adverse outcome.

Conclusions

Surgical outcomes for Spetzler-Ponce Class A ubAVMs are better than those for conservative management.

Haemodynamic analysis of vessel remodelling in STA-MCA bypass for Moyamoya disease and its impact on bypass patency

The purpose of this study is to estimate the remodelling characteristics of STA-MCA bypass and its influence on patency via the use of computational fluid dynamic (CFD) technology. The reconstructed three-dimensional geometries from MRA were segmented to create computational domains for CFD simulations. Eleven patients, who underwent regular MRA both immediately following surgery and at the six months follow-up, were studied. The flow velocities at STA were measured via the use of quantitative MRA (QMRA) to validate simulation results. STA-MCA bypass patency was confirmed for each patient immediately following surgery. The simulation indicated that the remodelling of the arterial pedicle in nine patients was associated with a reduction in the resistance to flow through the bypass. For these cases, the modelling of a driving pressure of 10mmHg through the bypass at 6 months post-surgery resulted in a 50% greater blood flow than those found immediately following surgery. However, two patients were found to exhibit contradictory patterns of remodelling, in which a highly curved bending at the bypass immediately post-surgery underwent progression, with increased resistance to flow through the bypass at 6 months follow-up, thereby resulting in a modelled flow rate reduction of 50% and 25%, respectively. This study revealed that STA-MCA bypass has a characteristic remodelling that usually reduces flow resistance. The initial morphology of the bypass may have had a significant effect on the outcome of vessel remodelling.

Smoking increases the risk of de novo intracranial aneurysms

OBJECTIVE

Case series have identified that de novo intracranial aneurysms occur. However, the risk for this occurrence has not been established. We examined the risk for the de novo intracranial aneurysm detection in a consecutive surgical case series.

METHODS

A prospectively collected surgical database of intracranial aneurysms was retrospectively examined. Patients were analyzed if they were followed for more than 6 months postoperatively with angiography. Kaplan-Meier curve analysis of de novo aneurysms detection included the comparison of smoking vs. never smoked; those with and without a family history; single vs. multiple aneurysms at initial presentation; and original presentation with rupture vs. nonrupture.

RESULTS

Of the 1366 surgically treated patients (1942 aneurysms), 472 patients (702 aneurysms) were followed with angiography for more than 6 months (average, 54 months). Thirty-three patients (6.99%) were detected to have de novo aneurysms. Multivariate analysis found a smoking history significantly increases the likelihood of de novo aneurysm detection. Kaplan-Meier analysis found the 5- and 10-year de novo aneurysm detection rate to be 4.21% (95% confidence interval [CI] 3.86-12.8) and 15% (95% CI 10-16), respectively. A smoking history increases the 5- and 10-year detection rate to 5.81% and 17% (hazard ratio 2.58; 95% CI 1.13-5.90) respectively. No increased risk was present for an initial presentation that included multiple aneurysms, a family history, or rupture.

CONCLUSION

There is a 10-year de novo aneurysm detection rate of between 10% and 16% after surgery. Smoking increases the risk of de novo aneurysm detection. Consideration needs to be given to surveillance angiography after aneurysm treatment.

Use of indocyanine green videoangiography during intracranial aneurysm surgery reduces the incidence of postoperative ischaemic complications

Microscope-integrated near-infrared indocyanine green videoangiography (ICGVA) has been shown to be a useful adjunct for intracranial aneurysm surgery. That the routine application of this technique reduces the risk of postoperative ischaemic complication, however, has not been reported. We present a retrospective matched-pair comparison of ICGVA guided aneurysm surgery versus historic control surgical cohort treated by the same author. Index patients and controls were matched for aneurysm size, location, patient demographics, risk factors, comorbidities, and surgical treatments. Ninety-one eligible patients with 100 intracranial aneurysms were treated using ICGVA assistance. There were no statistically significant differences between the two groups in terms of patient age, sex, risk factors, comorbidities and aneurysm characteristics. Of the 100 aneurysms in the ICGVA group, 107 investigations of ICGVA were performed. In 79 aneurysms (79.0%), ICGVA was considered useful but did not affect surgical management. In six patients (6.0%), ICGVA led to a crucial change of intraoperative strategies. In nine patients (9.0%), it was considered critical in assuring patency of small perforators. ICGVA was of no benefit in four patients (4.0%) and was misleading in two (2.0%). Postoperative ischaemic complications occurred in three patients (3.3%) in the ICGVA group compared with seven patients (7.7%) in the control group (p<0.001). Our study supports the use of ICGVA in aneurysm surgery as a safe and effective modality of intraoperative blood flow assessment. With all limitations of a retrospective matched-pair comparison, the use of ICGVA during routine aneurysm surgery reduces the incidence of postoperative ischaemic complications.

Surgical management of dural arteriovenous fistulas of the transverse-sigmoid sinus in 42 patients

A retrospective study was performed to analyse a prospectively collected database from a single surgeon (M.K.M.) of transverse-sigmoid sinus dural arteriovenous fistulas (DAVF) between 1991 and August 2011. During the study period, 144 patients with 160 DAVF were managed. Sixty-five of the DAVF were located in the transverse-sigmoid sinus and 42 were treated with surgery, or embolisation and surgery. All patients who underwent surgery were symptomatic with retrograde cortical venous drainage. The average follow-up period was 18months (range, 2-82months). Total elimination of the DAVF was achieved in all instances, including two patients (5%) who required further surgery after postoperative cerebral angiography showed that some venous drainage had persisted after the first operation. There was no new permanent neurological deficit or mortality attributable to surgery. Our institutional experience shows that in selected patients with transverse-sigmoid sinus DAVF, the involved sinus can be surgically resected with a high success rate and it is as safe as many alternative options. We suggest that this definitive treatment option should be offered to patients, and the outcome should be compared to other treatment modalities.

The failure of preoperative ethylene-vinyl alcohol copolymer embolization to improve outcomes in arteriovenous malformation management: case series

OBJECT

Ethylene-vinyl alcohol copolymer embolization is increasingly used preoperatively in the resection of brain arteriovenous malformations (AVMs). However, the case for embolization improving the outcome of resection has not been evaluated. In this paper the authors set out to compare outcomes after surgery for brain AVMs in 2 consecutive periods of practice. In the first period, selective embolization was used without the use of ethylene-vinyl alcohol copolymer. In the second period, selective embolization with ethylene-vinyl alcohol copolymer was performed.

METHODS

A consecutive case series (prospectively collected data) was retrospectively analyzed. Adverse outcomes were considered to be an outcome modified Rankin Scale score greater than 2 due to embolization or surgery.

RESULTS

A total of 538 surgical cases were included. The percentages of adverse outcomes were as follows: 0.34% for Spetzler-Martin AVMs less than Grade III (1 of 297 cases); 5.23% (95% CI 2.64%-9.78%) for Grade III AVMs (9 of 172 cases); and 17% (95% CI 10%-28%) for AVMs greater than Grade III (12 of 69 cases). There was no improvement in outcomes from the first period to the second period. The adverse outcome for Grade III brain AVMs in the first period was 5.2% (7 of 135 cases) and in the second period (after ethylene-vinyl alcohol copolymer was introduced) it was 5.4% (2 of 37 cases). For AVMs greater than Grade III, the adverse outcome was 12% (6 of 49 cases) in the first period and 30% (6 of 20 cases) in the second period.

CONCLUSIONS

Outcomes for brain AVM surgery were not improved by ethylene-vinyl alcohol copolymer embolization. Preoperative embolization of high-grade AVMs with an ethylene-vinyl alcohol copolymer did not prevent those hemorrhagic complications which embolization is hypothesized to prevent based on theoretical speculations but not demonstrated in practice.

Time to rethink the role of the library in educating doctors: driving information literacy in the clinical environment

QUESTION

Can information literacy (IL) be embedded into the curriculum and clinical environment to facilitate patient care and lifelong learning?

SETTING

The Australian School of Advanced Medicine (ASAM) provides competence-based programs incorporating patient-centred care and lifelong learning. ASAM librarians use outcomes-based educational theory to embed and assess IL into ASAM's educational and clinical environments.

METHODS

A competence-based IL program was developed where learning outcomes were linked to current patients and assessed with checklists. Weekly case presentations included clinicians' literature search strategies, results, and conclusions. Librarians provided support to clinicians' literature searches and assessed their presentations using a checklist.

MAIN RESULTS

Outcome data showed clinicians' searching skills improved over time; however, advanced MEDLINE searching remained challenging for some. Recommendations are provided.

CONCLUSION

IL learning that takes place in context using measurable outcomes is more meaningful, is enduring, and likely contributes to patient care. Competence-based assessment drives learning in this environment.

Role of inhibition in chronic cerebral hypoperfusion

Chronic reductions in cerebral blood flow (CBF) of between 25 and 50% maintained for 26 weeks impair neuronal function, through a mechanism which is not known, but which is now explored. Increased GABAergic synaptic inhibition may play a role, as inhibitory interneurons are known to be relatively resistant to acute ischaemic insults. The phenomenon of tetanus-induced longterm potentiation (LTP) was previously found to be impaired in this setting, and was thus examined in the in vitro rat hippocampus in the presence of bicuculline, a specific GABA(A) antagonist, to evaluate the role of inhibition in the impairment of LTP in chronic cerebral hypoperfusion (CCH). Nine Sprague-Dawley rats aged 8-10 weeks had arteriovenous fistulae (AVF) surgically constructed to reduce CBF to between 25 and 50%. Ten animals were used as age-matched controls. After a further 26 weeks, 400 mum hippocampal slices were prepared. Tetanic stimulation was used in order to attempt to induce LTP. In vitro extracellular field potentials from control and AVF slices with 5 x 10(-)6 M bicuculline exposure and subsequent tetanic stimulation were compared. There was no statistical difference between the responses of the two groups in either scenario (P > 0.05), although LTP was in general more difficult to induce (only occurring in 60% of control animals). Possible causes of this are discussed. It is concluded that increased GABAergic synaptic inhibition does not play a role in impairment of neuronal function seen after 26 weeks of non-infarctional CCH.

Herniation of an enlarged middle cerebral artery through a temporal bone defect in association with an arteriovenous malformation

We present a previously undescribed variant of the middle cerebral artery (MCA) protruding through a defect in the temporal bone, associated with a large arteriovenous malformation (AVM). The patient, a 59-year-old male, presented with a large right frontoparietal AVM with feeding aneurysms and a recent haemorrhage. Preoperative imaging demonstrated a tortuous right MCA feeder abutting the anterosuperior temporal bone in the region of the pterion. An associated temporal bone defect was visible. The patient underwent a pterional craniotomy for surgical clipping of aneurysms associated with the AVM. On reflection of the temporalis muscle, the MCA branch was transected as it coursed through a defect in the temporal bone. This patient demonstrates that the MCA may deviate from its usual anatomy and herniate through a defect in the skull. Because a pterional craniotomy is such a common surgical approach, knowledge and anticipation of such anatomic variants are essential to avoid catastrophic vascular injury during surgery.

Influence of the combination of patient age and deep venous drainage on brain arteriovenous malformation recurrence after surgery

OBJECT

Case reports suggest that young age is a critical factor in determining recurrence of brain arteriovenous malformations (AVMs) after surgery. However, other factors that may contribute to the increased risk of recurrence have not been considered. In this study, the authors' goal was to ascertain the risk and risk factors of recurrence after resection of AVMs of the brain.

METHODS

A consecutive case series (prospectively collected data) of 600 cases of resection of brain AVMs was retrospectively analyzed. Radiological evidence of recurrence or nonrecurrence, as well as clinical evidence of recurrence, could be established in 427 of these cases that underwent follow-up for more than 350 days after initial surgery. These cases were analyzed using Kaplan-Meier curves and Cox regression with respect to age and the presence of deep venous drainage.

RESULTS

Nine recurrent AVMs were found in 8 patients. By analysis of the Kaplan-Meier curves, the 10-year recurrence rate was 14% for those with deep venous drainage, compared with 4% for those without deep venous drainage. Stratifying by age, in the 0- to 20-year age group, the 10-year recurrence rates were 63% and 13% for those with and without deep venous drainage, respectively. In the 20- to 39-year age group, the rates were 5% and 0% respectively, and in the 40-year and older age group they were 0% and 3%, respectively. The hazard ratio for deep venous drainage, adjusted for age, was 5.97 (95% CI 1.20-29.69, p = 0.029).

CONCLUSIONS

The risk of recurrence after AVM resection is significant for young patients with deep venous drainage.

Mean Arterial Pressure Required for Maintaining Patency of Extracranial-to-Intracranial Bypass Grafts

BACKGROUND:

Maintaining flow in a newly established high-flow bypass into the intracranial circulation may be threatened by low blood pressure.

OBJECTIVE:

To identify mean arterial blood pressure below which early graft failure may ensue.

METHODS:

Computational fluid dynamic blood flow simulation and Doppler ultrasound–derived velocities were combined to study 12 patients with common carotid–to–intracranial (internal carotid artery in 9 and middle cerebral artery in 3) arterial brain bypass with interposition of the saphenous vein. Patients underwent carotid duplex and high-resolution computed tomography angiography to obtain the necessary data. A mean time-averaged pressure gradient across both anastomoses of the graft was then calculated.

RESULTS:

The bypass graft mean blood flow ± SD was 180.3 ± 76.2 mL/min (95% confidence interval: 132–229). The mean time-averaged pressure gradient ± SD across the bypass graft was 10.2 ± 8.7 mm Hg (95% confidence interval: 4.6-15.7). This compared with a mean pressure gradient ± SD on the contralateral carotid of 21.7 ± 13.8 mm Hg. From these data, the minimum mean ± SD systemic pressure necessary to maintain graft flow of at least 40 mL/min was 61.6 ± 2.31 mm Hg, and the mean peak wall shear stress ± SD at the proximal anastomosis was 0.8 ± 0.7 Pa (95% confidence interval: 0.3-1.2).

CONCLUSION:

Early postoperative mean arterial pressure less than approximately 60 mm Hg may induce blood flow in the bypass to decrease to less than 40 mL/min, a flow below which low shear stress may lead to early graft occlusion.

Incidence of subarachnoid haemorrhage: an Australian national hospital morbidity database analysis

Incidences of subarachnoid haemorrhage (SAH) in Australia have been reported in regional studies with variable rates. We investigated the national SAH rate and evaluated the trend over the 10 years from 1998 to 2008. The crude SAH incidence, not related to trauma or arteriovenous malformation, was estimated at 10.3 cases per 100,000 person-years (95% confidence interval [CI]: 10.2-10.4). Females have a higher incidence of SAH (12.5 cases per 100,000; 95% CI: 12.3-12.8) compared to males (8.0 cases per 100,000; 95% CI: 7.8-8.3), with age-adjusted incidence increases with increasing age for both sexes. Less than 10% of SAH occurred in the first three decades of life. The peak age group for patients to experience SAH was between 45 years and 64 years, accounting for almost 45% of the overall annual SAH admissions. Aneurysms located in the anterior circulation were a more common source of rupture compared to those located in the posterior circulation (rate ratio 3.9; 95% CI: 3.6-4.2). Contrary to contemporary observations in the literature, we did not observe a decline in the incidence of SAH during this specified study period.

Comparative Patency Between Intracranial Arterial Pedicle and Vein Bypass Surgery

BACKGROUND:

Long-term patency of extracranial-to-intracranial (EC-IC) vein bypass is poorly understood.

OBJECTIVE:

We report our experience of patency of arterial pedicle grafts and interposition vein grafts for the purpose of EC-IC bypass.

METHODS:

We analyzed 294 consecutive patients who underwent 178 intracranial arterial pedicle bypass procedures and 152 intracranial vein bypass procedures. Bypass patency was assessed by digital subtraction angiography, computed tomographic angiography, and/or Doppler ultrasound. The modified Rankin Scale (mRS) was assigned for clinical grading at the last follow-up consultation.

RESULTS:

The main indication for arterial pedicle bypass surgery was internal carotid artery occlusion (79 cases); for vein bypass surgery, it was giant aneurysms (61 cases). Procedure-related complications due to surgery occurred in 3 cases (1.7%; 95% CI: 0.4-5.1%) of arterial pedicle bypass surgery and 12 cases (7.9%; 95% CI: 4.5-13.4%) of vein bypass surgery. The patency rate at 6 weeks was 98% (95% CI: 95.0-99.7%) for arterial pedicle bypass and 93% (95% CI: 87.4-96%) for vein bypass, with almost all graft failures occurring within the first week following surgery. Beyond the first week, bypass patency was similar for both groups, with both arterial pedicle grafts and vein bypass grafts that were patent at 1 week having a long-term patency of 99%. There was no statistically significant difference in early, late, and overall patency between the 2 bypass groups.

CONCLUSION:

The surgical complication rate was greater for vein bypass. Both arterial pedicle and vein bypass have good long-term patency.

The embryologic basis for the anatomy of the cerebral vasculature related to arteriovenous malformations

A detailed understanding of vascular anatomy is essential to facilitate appropriate decision-making by clinicians responsible for treating arteriovenous malformations (AVM) of the brain and dura. This work reviews the embryologic development of the cerebral vasculature, including the dural venous sinuses, with a focus on the relevant angioarchitecture. There is little doubt that dural AVM are acquired lesions; however, conflicting evidence exists regarding the pathophysiology of brain AVM. Patients described in this review provide support for both of the proposed mechanisms for the development of brain AVM (post-natal development compared to embryologic origin). Further work is required to improve our understanding of the pathophysiology of these lesions.

How assessment drives learning in neurosurgical higher training

Certifying the competence of neurosurgeons is a process of critical importance to the people of Australia and New Zealand. This process of certification occurs largely through the summative assessment of trainees involved in higher neurosurgical training. Assessment methods in higher training in neurosurgery vary widely between nations. However, there are no data about the 'utility' (validity, reliability, educational impact) of any national (or bi-national) neurosurgical training system. The utility of this process in Australia and New Zealand is difficult to study directly because of the small number of trainees and examiners involved in the certifying assessments. This study is aimed at providing indirect evidence of utility by studying a greater number of trainees and examiners during a formative assessment conducted at a training seminar in Neurosurgery in April 2005.

AIM

To evaluate an essay examination for neurosurgical trainees for its validity, reliability and educational impact.

METHODS

A short answer essay examination was undertaken by 59 trainees and corrected by up to nine examiners per part of question. The marking data were analysed. An evaluation questionnaire was answered by 48 trainees. Eight trainees who successfully passed the Fellowship examination who had also taken the short essay examination underwent a semi-structured interview.

RESULTS

The essay examination was found to be neither reliable (generalisability coefficient of 0.56 if the essay paper had comprised 6 questions) nor valid. Furthermore, evidence suggests that such an examination may encourage a pursuit of declarative knowledge at the expense of competence in performing neurosurgery.

CONCLUSION

This analysis is not directly applicable to the Fellowship examination itself. However, this study does suggest that the effect of assessment instruments upon neurosurgical trainees' learning strategies should be carefully considered.

The neurosurgical training curriculum in Australia and New Zealand is changing. Why?

The Neurosurgical Advanced Training curriculum of the Royal Australasian College of Surgeons (RACS) is currently undergoing change. Given the high standard of neurosurgery in Australia and New Zealand, it may be questioned why such change is necessary. However, the curriculum has not kept pace with developments in professional practice, educational practice or educational theory, particularly in the assessment of medical competence and performance. The curriculum must also adapt to the changing training environment, particularly the effects of reduced working hours, reducing caseloads due to shorter inpatient hospital stays and restricted access to public hospital beds and operating theatres, and the effects of sub-specialisation. A formal review of the curriculum is timely.

Surgery for unruptured intracranial aneurysms in a low-volume neurosurgical unit

OBJECTIVES

To evaluate outcomes after surgical treatment for unruptured intracranial aneurysms in a low-volume neurosurgical unit.

MATERIAL AND METHODS

Consecutive patients operated during the years 1988-98 at the Department of Neurosurgery, University Hospital of North Norway, were studied retrospectively. Procedure-related complications were registered. The modified Rankin Scale and the Glasgow Outcome Scale, Extended version (GOS-E), were used for assessment of outcome.

RESULTS

Thirty-six aneurysms were repaired in 32 patients during 34 surgical procedures. Surgery-related central nervous system complications occurred in eight (25%) patients. The complication rate was 35% for the first 17 procedures, and 12% for the last 17. The latter group of procedures were performed during a period of 3 years, whereas the former group was spread over a period of 8 years. A favourable outcome (GOS-E score 6-8) was reached in 27 (84%) patients.

CONCLUSION

Decision-making in patients with unruptured intracranial aneurysms must be based on knowledge about institution-specific complication rates, preferably followed on a prospective basis.

Surgical Risks Associated with the Management of Grade I and II Brain Arteriovenous Malformations

OBJECTIVE

Grade I and II arteriovenous malformations (AVMs) have been considered safe to resect. However, unoperated low-grade AVMs have not been considered in previously reported series. The aim of this study was to examine all cases, both operated and unoperated, to identify any characteristics of low-grade AVMs that comprise a subgroup that might pose a relatively higher risk.

METHODS

A prospectively enrolled AVM database included 237 patients in Spetzler-Martin Grade I or II. These patients were analyzed on the basis of demographic characteristics, angiographic and magnetic resonance imaging features, clinical presentation, method of treatment, and outcome.

RESULTS

Surgery was performed in 220 patients in Spetzler-Martin Grade I or II. Seventeen patients did not undergo treatment because of poor neurological condition (six patients), patient refusal (nine patients), and perceived surgical difficulty (AVM size approaching 3 cm adjacent to Broca's area) (two patients). The overall surgical morbidity rate was 0.9%, and the mortality rate was 0.5%. Adverse outcomes occurred in 1 (0.6%) of 180 patients with AVMs located away from eloquent cortex and in 2 (5%) of 40 patients with AVMs adjacent to eloquent cortex. None of 28 surgical patients with deep venous drainage had an adverse outcome. All 219 patients who survived surgery underwent postoperative angiography that confirmed cure. No postoperative hemorrhage has occurred in 1143 patient-years of follow-up (mean follow-up, 5.3 yr).

CONCLUSION

When considering adverse outcome in the surgical series of Grade I and II AVMs alone, no statistical difference between non-eloquently located AVMs (0.6%) and eloquently located AVMs (5% adverse outcome) can be detected. However, consideration of all Grade I and II AVMs, both surgical and nonsurgical, may prove that a difference in outcome exists between these two groups masked by case selection. Generalization of the chances of adverse outcomes to all Grade I and II AVMs (both operated and unoperated) suggests that the risk of performing surgery on noneloquent brain in our series was 0.6% and that in eloquent brain could have been as high as 9.5%, had all such patients undergone surgery.

Magnesium: a useful adjunct in the prevention of cerebral vasospasm following aneurysmal subarachnoid haemorrhage

Despite recent advances in the management of aneurysmal subarachnoid haemorrhage delayed ischaemic deficits from cerebral vasospasm remains a major cause of morbidity and mortality. As magnesium is a potent cerebral vasodilator we have introduced routine supplementation in patients presented with subarachnoid haemorrhage to determine whether there has been a reduction in the incidence of cerebral vasospasm.

METHOD

All patients presented with aneurysmal subarachnoid haemorrhage from February 1997 were included except those who presented after day 5 following bleed. Identical management protocol was used except intravenous magnesium supplementation which was introduced to all patients from May 1999. Incidence of cerebral vasospasm on angiograms among the two groups was analysed.

RESULTS

Seven out of 10 patients who did not receive magnesium supplement developed vasospasm requiring intra-arterial papaverine compared with 2 of 13 patients among the treated group (P<0.008).

CONCLUSIONS

From our pilot study it appears that magnesium supplement has a beneficial role in the prevention of cerebral vasospasm following aneurysmal subarachnoid haemorrhage. Further studies would seem justified.

Angioplasty and stenting in the posterior cerebral circulation

PURPOSE

To report initial experience with intracranial vertebral artery (VA) and basilar artery (BA) percutaneous transluminal angioplasty (PTA) and stenting.

METHODS

Eleven patients (10 men; mean age 66 years, range 56-75) with intracranial 14 VA and 3 BA stenoses were managed from December 1997 through November 1999. All patients presented with vertebrobasilar ischemia (VBI) despite antiplatelet and anticoagulant therapy. Clinical presentations included visual disturbance (n = 8), dysarthria/dysphasia (n = 5), and vertigo (n = 5).

RESULTS

Five patients underwent PTA only of 7 lesions with a mean preprocedural stenosis of 80% (range 50%-90%) that was reduced to 54% (range 30%-70%) after dilation. Six patients received 9 stents, 2 for VA dissections, 3 for tandem lesions, and 1 for a BA lesion. There were no embolic strokes. Patients were followed by clinical evaluation and personal or telephone interviews. Over a mean 18-month follow-up (range 12-35), 8 (73%) patients remained asymptomatic, while 3 (27%) had permanent deficits, 2 related to the procedure and 1 owing to distal disease

CONCLUSIONS

Intracranial VA or BA angioplasty and stenting alleviated symptoms in patients with vertebrobasilar ischemia despite best medical management and may prevent stroke.

Prolonged thiopentone infusion for neurosurgical emergencies: usefulness of therapeutic drug monitoring

Serial serum thiopentone concentrations were measured during and following completion of an intravenous infusion of thiopentone in 20 patients with neurosurgical emergencies. The concentration data from a further 55 patients who had had some such measurements were reviewed retrospectively. The patients received an infusion for longer than 24 hours at a rate adjusted to maintain EEG burst suppression. The data were interpreted in terms of thiopentone pharmacokinetics and used to produce statistical models relating to clinical outcomes. In these patients, the one-month mortality rate following commencement of thiopentone treatment was 20%; the mean durations of pupillary and motor unresponsiveness following cessation of an infusion were 22 and 91 hours, respectively. Predictors of a prolonged duration of motor unresponsiveness included a prolonged duration of pupillary unresponsiveness, a low thiopentone clearance and a high maximum serum concentration of thiopentone. From pooled logistic regression, median effective serum thiopentone concentrations (EC50) were found to be 50 mg x l(-1) for recovery of pupillary responsiveness and 12 mg x l(-1) for the recovery of motor responsiveness. Because prolonged high-dose thiopentone leads to prolonged residual serum concentrations, it is difficult to distinguish the residual pharmacological effects of thiopentone from the clinical condition. This study suggests that, based on EC50 values for responses, monitoring of post-infusion serum thiopentone concentrations may help determine whether a patient's clinical state is due to residual thiopentone pharmacological effects.

The surgical management of contralateral anterior circulation intracranial aneurysms

This study reviews the surgical management of contralateral anterior circulation aneurysms in patients with bilateral intracranial aneurysms repaired following a unilateral craniotomy. Between 1993 and 1999, 27 patients had 88 intracranial aneurysms repaired. Eleven patients presented following subarachnoid haemorrhage. Excluding midline aneurysms, 31 anterior circulation aneurysms were contralateral to the craniotomy and all were repaired at the same time that ipsilateral or midline aneurysms were repaired. Morbidity included one death and one case of loss of unilateral vision directly attributable to surgery and two cases of cerebral infarction due to vasospasm. No new neurological deficit or mortality could be directly attributed to the repair of a contralateral aneurysm. The repair of all accessible aneurysms, including those contralateral to the craniotomy, during one session avoids the risk of haemorrhage from incidental or unrecognised ruptured aneurysms (particularly during the aggressive treatment of vasospasm), avoids a second craniotomy, decreases overall hospitalisation and can improve visualisation of carotid-ophthalmic aneurysms.

Spinal arteriovenous malformations: a review with case illustrations

Spinal arteriovenous malformations are united by the existence of arteriovenous shunting but are quite heterogeneous in terms of pathology. Until recently, the pathological confusion has been such that management has been poorly understood and this is magnified by the rarity of the lesions. Type 1 AVMs, where the fistula is located in the dura, usually present with a venous hypertensive myelopathy and are relatively easily dealt with surgically. Type 2 AVMs, most closely mimicking the parenchymal AVMs of the brain, usually present with haemorrhage and may be surgically remediable but with much greater risk than the type 1 lesions. Type 3 AVMs, with a diffuse location through both the cord and extra-CNS tissue, usually present early in life with a myelopathy and are often untreatable. Type 4 AVMs, with a fistula located on the pial surface of the cord, usually present with a venous hypertensive myelopathy or subarachnoid haemorrhage, can be treated relatively easily by surgery when small but may be better treated endovascularly when the fistula is large. The purpose of this review is to summarise the current pathological, clinical and management literature with illustrative cases underscoring the important features of this heterogeneous disorder.