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Leodante B. da Costa, Thorsteinn Gunnarsson and M. Christopher Wallace

Aneurysmal subarachnoid hemorrhage (SAH) carries a grim prognosis, with high mortality and morbidity rates. The mortality rate in the first 30 days postrupture is estimated to be in the range of 40 to 50%, and almost half of the survivors will be left with a neurological deficit. Unlike patients with aneurysmal SAH, those with unruptured intracranial aneurysms usually experience no neurological deficit, and their treatment is prophylactic, aiming to reduce the risk of future bleeding and its consequences. The risk of rupture therefore assumes special importance when making decisions regarding which patient or aneurysm to treat.

In previous reports the risk of bleeding for unruptured aneurysms has been stated as approximately 2% per year. The retrospective part of the International Study of Unruptured Intracranial Aneurysms (ISUIA) reported very low annual bleeding rates (0.05–1%) and high surgical morbidity and mortality rates (8–18%), prompting discussion in which the benefits of prophylactic treatment in the majority of these lesions were questioned. Prospective data from the second part of the ISUIA recently included rupture rates ranging from 0 to 10% per year. The aim of this paper was to review the evidence that is currently available for neurosurgeons to use when making decisions regarding patients who would benefit from treatment of an unruptured intracranial aneurysm.

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J. Marc C. Van Dijk, Karel G. TerBrugge, Robert A. Willinsky and M. Christopher Wallace

Object. Dural arteriovenous fistulas (AVFs) are a well-known pathoanatomical and clinical entity. Excluding bilateral involvement of the cavernous sinus, multiple dural AVFs are rare, with isolated reports in the literature. The additional risk associated with multiplicity is unknown, although it has been claimed that there is a greater risk of hemorrhage at presentation. In a group of 284 patients with dural AVFs consecutively treated at a single center, the occurrence of multiplicity is investigated and its risk factors for hemorrhage are identified.

Methods. Among the 284 patients with both cranial and spinal dural AVFs, 20 patients with multiple fistulas were found. Nineteen (8.1%) of 235 patients with cranial AVFs had multiple cranial fistulas, and one (2%) of 49 patients with spinal AVFs harbored two spinal fistulas. Twelve patients were found to have a lesion at two separate sites, seven patients had them at three locations, and one patient had four fistulas, each at a different site.

In the subgroup with multiple AVFs the percentage of hemorrhage at presentation was three times higher than in the entire group (p = 0.01). Cortical venous drainage in cranial fistulas was present in 84% of patients with multiple lesions compared with 46% of patients with solitary lesions (p < 0.005).

Conclusions. Multiple dural AVFs are not rare. In this group of 284 patients it was found in 8.1% of all patients with cranial dural AVFs. Multiplicity was associated with a higher percentage of cortical venous drainage, a pattern of drainage reportedly yielding a higher risk for hemorrhage.

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J. Marc C. van Dijk, Karel G. TerBrugge, Robert A. Willinsky and M. Christopher Wallace

Object. A single-institution series of 119 consecutive patients with a dural arteriovenous fistula (DAVF) and cortical venous reflux was reviewed to assess the overall clinical outcome of multidisciplinary management after long-term follow up. The selective disconnection of the cortical venous reflux compared with the obliteration of the entire DAVF was evaluated.

Methods. Dural arteriovenous fistulas in patients in this series were diagnosed between 1984 and 2001, and treatment was instituted in 102 of them. The outcome of adequately treated patients was compared with that of a control group consisting of those with persistent cortical venous reflux and with data found in the literature. In cases of combined dural sinus drainage and cortical venous reflux, a novel treatment concept of selective disconnection of the cortical venous reflux that left the sinus drainage intact, and thus converted the aggressive DAVF into a benign lesion, was evaluated.

Endovascular treatment, which was instituted initially in 78 patients, resulted in an obliteration or selective disconnection in 26 (25.5%) of 102 cases. In 70 cases (68.6%) the DAVFs were surgically obliterated or disconnected. In six cases (5.9%), patients were left with persistent cortical venous reflux. No lasting complications were noted in this series. Follow-up angiography confirmed a durable result in 94 (97.9%) of 96 adequately treated cases, at a mean follow up of 27.6 months (range 1.4–138.3 months).

Selective disconnection was performed in 23 DAVFs with combined sinus drainage and cortical venous reflux. These patients' long-term outcomes were equal to those with obliterated DAVFs, and the complication rate was lower.

Conclusions. Considering the ominous course of DAVFs with patent cortical venous reflux, multidisciplinary treatment of these lesions is highly effective and the complication rate is low. Selective disconnection provides a valid treatment option of DAVFs with combined dural sinus drainage and cortical venous reflux, as has been shown in cranial DAVFs with direct cortical venous reflux.

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Christopher E. Wolfla, Dennis J. Maiman, Frank J. Coufal and James R. Wallace

Object. Intertransverse arthrodesis in which instrumentation is placed is associated with an excellent fusion rate; however, treatment of patients with symptomatic nonunion presents a number of difficulties. Revision posterior and traditional anterior procedures are associated with methodological problems. For example, in the latter, manipulation of the major vessels from L-2 to L-4 may be undesirable. The authors describe a method for performing retroperitoneal lumbar interbody fusion (LIF) in which a threaded cage is placed from L-2 through L-5 via a lateral trajectory, and they also detail a novel technique for implanting a cage from L-5 to S-1 via an oblique trajectory. Although they present data obtained over a 2-year period in the study of 15 patients, the focus of this report is primarily on describing the surgical procedure.

Methods. The lateral lumbar spine was exposed via a standard retroperitoneal approach. Using the anterior longitudinal ligament as a landmark, the L2–3 through L4–5 levels were fitted with instrumentation via a true lateral trajectory; the L5—S1 level was fitted with instrumentation via an oblique trajectory. A single cage was placed at each instrumented level.

Fifteen symptomatic patients in whom previous lumbar fusion had failed underwent retroperitoneal LIF. Thirty-eight levels were fitted with instrumentation. There have been no instrumentation-related failures, and fusion has occurred at 37 levels during the 2-year postoperative period.

Conclusions. The use of retroperitoneal LIF in which threaded fusion cages are used avoids the technical difficulties associated with repeated posterior procedures. In addition, it allows L2—S1 instrumentation to be placed anteriorly via a single surgical approach. This construct has been shown to be biomechanically sound in animal models, and it appears to be a useful alternative for the management of failed multilevel intertransverse arthrodesis.

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Farhad Pirouzmand, M. Christopher Wallace and Robert Willinsky

✓ A spinal epidural arteriovenous fistula with secondary reflux into the perimedullary veins is a rare entity. The authors present such a case with a discussion of its pathophysiology and treatment. The mechanism for formation of a spinal dural arteriovenous fistula is outlined based on the anatomical substrates in this region.

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Cian J. O'Kelly, Abhaya V. Kulkarni, Peter C. Austin, David Urbach and M. Christopher Wallace

Object

Chronic shunt-dependent hydrocephalus is a recognized complication of aneurysmal subarachnoid hemorrhage. While its incidence and risk factors have been well described, the long-term performance of shunts in this setting has not been not widely reported.

Methods

Using administrative databases, the authors derived a retrospective cohort of patients undergoing treatment of a ruptured aneurysm in Ontario, Canada, between 1995 and 2005. The authors determined the incidence of shunt-dependent hydrocephalus and analyzed putative risk factors. Mortality rates and indicators of morbidity were recorded. Patients were followed up for the occurrence of shunt failure over time.

Results

Of 3120 patients in the cohort, 585 (18.75%) developed shunt-dependent hydrocephalus. On multivariate analysis, age, acute hydrocephalus, ventilation on admission, aneurysms in the posterior circulation and giant aneurysms were all significant predictors of shunt-dependent hydrocephalus. The mortality rate was not increased in patients with chronic hydrocephalus (hazard ratio 1.04, p = 0.63); however, indicators of morbidity were increased in these patients. Of the 585 patients with shunt-dependent hydrocephalus, only 173 (29.6%) underwent a subsequent revision procedure. Ninety-eight percent of these revisions were completed within 6 months. Subsequent revisions occurred more frequently. On multivariate analysis, significant predictors of shunt revision included aneurysm location in the posterior circulation and endovascular treatment of the initial ruptured aneurysm.

Conclusions

Shunt-dependent hydrocephalus affects a significant proportion of subarachnoid hemorrhage survivors, contributing to additional morbidity among these patients. Shunt failures occur less frequently in patients who underwent treatment for a ruptured aneurysm than with other forms of hydrocephalus. Most failures occur within 6 months, suggesting that shunt dependency may be transient in the majority of patients.

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Roberto C. Heros

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Cian J. O'Kelly, Abhaya V. Kulkarni, Peter C. Austin, M. Christopher Wallace and David Urbach

Object

Enrolling a selected sample of ruptured intracranial aneurysms, the International Subarachnoid Aneurysm Trial (ISAT) found endovascular coiling to be superior to microsurgical clipping. The performance of coiling in a more general population of ruptured aneurysms has not been adequately studied.

Methods

Using provincial administrative data from Ontario, the authors conducted a retrospective cohort study of adult patients with subarachnoid hemorrhage (SAH) who underwent aneurysm repair. The exposure was defined as endovascular versus surgical aneurysm repair. The prespecified primary outcome was time to death or readmission for SAH. Data from the entire cohort were analyzed using a multivariable adjusted Cox proportional hazards model. Propensity scores were used to compare a matched subgroup of patients with aneurysms who had similar baseline characteristics. The potential impact of unmeasured confounding was assessed using sensitivity analysis.

Results

Between 1995 and 2004, 2342 aneurysms were clipped and 778 were coiled in Ontario. The proportion of aneurysms treated by coiling increased steadily over time. In the adjusted analysis of the entire cohort, endovascular coiling was associated with a significantly increased hazard of death or SAH readmission (hazard ratio 1.25 [95% CI 1.00–1.55], p = 0.04). Similar results were obtained from the propensity score matched analysis (hazard ratio 1.25 [95% CI 1.04–1.50], p = 0.02). Measures of procedural morbidity and mortality were not significantly different between groups.

Conclusions

The results of the current analysis call into question the generalizability of the ISAT to all ruptured aneurysms. Given the limitations inherent in this form of analysis, further clinical studies—rigorously assessing the performance of endovascular therapy in patients with non-ISAT-like aneurysms—are indicated.