Implementation and preliminary clinical experience with the use of ceiling mounted mobile high field intraoperative magnetic resonance imaging between two operating rooms

OBJECTIVE

Intraoperative magnetic resonance imaging (ioMRI) provides immediate feedback and quality assurance enabling the neurosurgeon to improve the quality of a range of neurosurgical procedures. Implementation of ioMRI is a complex and costly process. We describe our preliminary 16 months experience with the integration of an IMRIS movable ceiling mounted high field (1.5 T) ioMRI setup with two operating rooms.

METHODS

Aspects of implementation of our ioMRI and our initial 16 months of clinical experience in 180 consecutive patients were reviewed.

RESULTS

The installation of a ceiling mounted movable ioMRI between two operating rooms was completed in April 2008 at Barnes-Jewish Hospital in St. Louis. Experience with 180 neurosurgical cases (M:F-100:80, age range 1-79 years, 71 gliomas, 57 pituitary adenomas, 9 metastases, 11 other tumor cases, 4 Chiari decompressions, 6 epilepsy resections and 22 other miscellaneous procedures) demonstrated that this device effectively provided high quality real-time intraoperative imaging. In 74 of all 180 cases (41%) and in 54% of glioma resections, the surgeon modified the procedure based upon the ioMRI. Ninety-three percent of ioMRI glioma cases achieved gross/near total resection compared to 65% of non ioMRI glioma cases in this time frame.

CONCLUSION

A movable high field strength ioMRI can be safely integrated between two neurosurgical operating rooms. This strategy leads to modification of the surgical procedure in a significant number of cases, particularly for glioma surgery. Long-term follow up is needed to evaluate the clinical and financial impact of this technology in the field of neurosurgery.

Clinical features and outcome in North American adults with idiopathic basal arterial occlusive disease without moyamoya collaterals

OBJECTIVE

To define the clinical characteristics and outcome of patients with idiopathic stenosis or occlusion of the basal arteries, without moyamoya collateral vessel formation.

METHODS

We identified patients who presented to our institution from 1996 to 2005 with occlusive disease of the distal internal carotid artery or the proximal middle or anterior cerebral arteries demonstrated by digital subtraction cerebral angiography. We excluded those with evidence of atherosclerotic disease, systemic vasculitis, moyamoya phenomenon, or any other condition that could otherwise explain their arterial occlusive disease. Medical records were reviewed for presenting symptoms and clinical characteristics. Outcome was determined from chart review and phone interviews.

RESULTS

Twelve patients were identified. All presented with transient ischemic attack or stroke. Eleven were women. Age at presentation ranged from 34 to 71 years. Nine had a history of hypertension; 5 had unilateral intracranial disease. Recurrent stroke on medical therapy occurred in none of the 5 during an average follow-up of 29 months. Seven had bilateral disease. Ischemic stroke occurred between 2 and 107 months after the initial event in 5 of 8 medically treated hemispheres. Moyamoya collateral vessels developed in 1 patient as shown on follow-up angiography.

CONCLUSION

The clinical features and outcome of these patients are similar to those reported in large case series of North American patients with moyamoya phenomenon. These data suggest a common etiology for the basal arterial occlusive process and a variable ability to form moyamoya collateral vessels.

Cranial dural arteriovenous fistulas: modification of angiographic classification scales based on new natural history data

This article presents a modification to the existing classification scales of intracranial dural arteriovenous fistulas based on newly published research regarding the relationship of clinical symptoms and outcome. The 2 commonly used scales, the Borden-Shucart and Cognard scales, rely entirely on angiographic features for categorization. The most critical anatomical feature is the identification of cortical venous drainage (CVD; Borden-Shucart Types II and III and Cognard Types IIb, IIa + b, III, IV, and V), as this feature identifies lesions at high risk for future hemorrhage or ischemic neurological injury. Yet recent data has emerged indicating that within these high-risk groups, most of the risk for future injury is in the subgroup presenting with intracerebral hemorrhage or nonhemorrhagic neurological deficits. The authors have defined this subgroup as symptomatic CVD. Patients who present incidentally or with symptoms of pulsatile tinnitus or ophthalmological phenomena have a less aggressive clinical course. The authors have defined this subgroup as asymptomatic CVD. Based on recent data the annual rate of intracerebral hemorrhage is 7.4-7.6% for patients with symptomatic CVD compared with 1.4-1.5% for those with asymptomatic CVD. The addition of asymptomatic CVD or symptomatic CVD as modifiers to the Borden-Shucart and Cognard systems improves their accuracy for risk stratification of patients with high-grade dural arteriovenous fistulas.

Cerebral hemodynamics as a predictor of stroke in adult patients with moyamoya disease: a prospective observational study

Moyamoya disease is an obliterative vasculopathy of the large arteries at the base of the brain. In the US, it most commonly affects women in their 3rd and 4th decades of life, frequently causing ischemic stroke. The natural history of this disorder is not well described. It is very likely that hemodynamic factors play an important role in the risk of future stroke, as has been established in atherosclerotic carotid occlusive disease. The authors describe an ongoing, prospective observational study designed to test the hypothesis that increased oxygen extraction in the cerebral hemisphere beyond the occlusive lesion is a predictor of subsequent risk of ipsilateral stroke in medically treated patients with moyamoya phenomenon. On enrollment, all patients undergo regional measurements of cerebral oxygen extraction fraction (OEF) with PET. Information on baseline clinical, laboratory, epidemiological, and angiographic risk factors are obtained at the time of the PET study. Decisions regarding surgery are made by the treating physicians based on clinical information while being blinded to PET data. Patients undergo follow-up at 6-month intervals to determine the subsequent risk of ipsilateral stroke. All patients will return at 1 and 3 years for repeat PET studies. Secondary, exploratory, aims of this longitudinal and blinded study are to determine other predictive factors for stroke in this population; to determine preliminary estimates of the effects of different medical treatment regimens in this population; to determine the temporal changes in hemodynamic impairment in medically treated patients; to determine the effects of surgery on hemodynamic impairment in the subset of patients who undergo surgical revascularization; and to obtain estimates of surgical complication rates for patients with and without hemodynamic impairment.

Resident duty hour regulation and patient safety: establishing a balance between concerns about resident fatigue and adequate training in neurosurgery

Postgraduate training in medicine has been under scrutiny over the past 10 years with a major focus on physician personal health and patient safety. The culmination of a series of events led to the 80-hour work week instituted by the Accreditation Council on Graduate Medical Education in 2003. The effect this mandate has had on surgical education, and specifically training in neurological surgery, has been incompletely evaluated. Nevertheless, external pressure has prompted the Institute of Medicine to issue a new report on resident work hours and patient safety. In this report, the authors focus on the unique aspects of neurosurgical training in which physicians are trained to safely and effectively carry out complex high-risk tasks, the experience from abroad where work hours are reduced to well below 80 hours/week, and the risk that further reduction in work hours poses to the public. The authors conclude that there must be an adequate balance between the risks associated with resident fatigue and those associated with an inexperienced neurosurgical work force for public health.

Transport characteristics of nanoparticle-based ferrofluids in a gel model of the brain

A current advance in nanotechnology is the selective targeting of therapeutics by external magnetic field-guided delivery. This is an important area of research in medicine. The use of magnetic forces results in the formation of agglomerated structures in the field region. The transport characteristics of these agglomerated structures are explored. A nonintrusive method based on in situ light-scattering techniques is used to characterize the velocity of such particles in a magnetic field gradient. A transport model for the chain-like agglomerates is developed based on these experimental observations. The transport characteristics of magnetic nanoparticle drug carriers are then explored in gel-based simulated models of the brain. Results of such measurements demonstrate decreased diffusion of magnetic nanoparticles when placed in a high magnetic field gradient.

CRANIAL DURAL ARTERIOVENOUS FISTULAE

OBJECTIVE

Cranial dural arteriovenous fistulae (dAVF) with cortical venous drainage (CVD) (Borden Types 2 and 3) are reported to carry a 15% annual risk of intracranial hemorrhage (ICH) or nonhemorrhagic neurological deficit (NHND). The purpose of this study was to compare the clinical course of Type 2 and 3 dAVFs that present with ICH or NHND with those that do not.

METHODS

Twenty-eight patients with Type 2 or 3 dAVFs were retrospectively evaluated. CVD was classified as asymptomatic (aCVD) if patients presented incidentally or with pulsatile tinnitus or orbital phenomena. CVD was classified as symptomatic (sCVD) if patients presented with ICH or NHND. Occurrence of new ICH or new or worsening NHND between diagnosis and disconnection of CVD or last follow-up (if not disconnected) was noted. Overall frequency of events was compared using Fisher's exact test. Cumulative, event-free survival was compared using Kaplan-Meier analysis with log-rank testing.

RESULTS

Of 17 patients with aCVD, 1 (5.9%) developed ICH and none experienced NHND or death during the median 31.4-month follow-up period. Of 11 patients with sCVD, 2 (18.2%) developed ICH and 3 (27.3%) experienced new or worsened NHND over the median 9.7-month follow-up period. One of these patients subsequently died. Overall frequency of ICH or NHND was significantly lower in patients with aCVD versus sCVD (P = 0.022). Respective annual event rates were 1.4 versus 19.0%. aCVD patients had significantly higher cumulative event-free survival (P = 0.0016).

CONCLUSION

Cranial dAVFs with aCVD may have a less aggressive clinical course than those with sCVD.

ANEURYSMAL SUBARACHNOID HEMORRHAGE, HYDROCEPHALUS, AND ACUTE PARAPARESIS

OBJECTIVE

The triad of acute spontaneous intracranial subarachnoid hemorrhage (SAH), hydrocephalus, and profound paraparesis in the absence of anterior cerebral artery vasospasm or ischemia has not been described previously. In this report, we present 6 patients presenting with this triad and provide a critical analysis of the clinical characteristics, radiographic workup, and long-term outcome for such patients.

CLINICAL PRESENTATION

Six (0.9%) of 695 patients with nontraumatic SAH managed at Barnes-Jewish Hospital between January 2003 and January 2008 presented with profound paraparesis or paraplegia. All were Hunt and Hess Grade III or higher, and all had extensive SAH and ventriculomegaly on initial head computed tomography. Five patients underwent extensive spinal imaging, but no abnormality was identified.

INTERVENTION

Five patients underwent surgical aneurysm obliteration, whereas 1 patient had no underlying aneurysm identified on multiple angiograms. All of the patients required urgent ventriculostomy for hydrocephalus, and 5 patients went on to require permanent shunt placement. Five of the 6 patients had gradual resolution of their presenting paraparesis over the course of 3 to 6 months.

CONCLUSION

The clinical triad of SAH, hydrocephalus, and profound paraparesis has not been reported previously. In contrast to previous reports, these patients had aneurysms at varying sites, without evidence of vasospasm or ischemia. Interestingly, all required acute cerebrospinal fluid diversion, 5 of 6 patients required permanent shunting, and almost all demonstrated gradual and often complete resolution of their presenting paraparesis. The etiology of this syndrome remains to be defined, but a combined deleterious effect of SAH and acute ventricular distention on cerebral function is suggested.

Mechanism of ATP-induced local and conducted vasomotor responses in isolated rat cerebral penetrating arterioles

BACKGROUND

Adenosine triphosphate (ATP), a potent vascular regulator in the cerebral circulation, initiates conducted vasomotor responses which may be impaired after pathological insults. We analyzed the mechanism of ATP-induced local vasomotor responses and their effect on conducted vasomotor responses in rat cerebral penetrating arterioles.

METHODS

Arterioles were cannulated and their internal diameter monitored. Vasomotor responses to ATP were observed in the presence or absence of inhibitors, or after endothelial impairment. Smooth muscle membrane potentials were measured in some vessels.

RESULTS

Microapplication of ATP produced a biphasic response (constriction followed by dilation), which resulted in conducted dilation preceded by a membrane hyperpolarization. alpha,beta-methylene-ATP or pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) blunted the ATP-mediated constriction and enhanced local and conducted dilation. N(omega)-monomethyl-L-arginine, endothelial impairment and N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanamide (MS-PPOH) reduced the local dilation caused by ATP. The conducted dilation was attenuated by MS-PPOH and endothelial impairment, but not N(omega)-monomethyl-L-arginine or indomethacin.

CONCLUSION

ATP-induced conducted dilation is preceded by membrane hyperpolarization. Local ATP induces initial local constriction via smooth-muscle P(2X1) and subsequent dilation via endothelial P(2Y) receptors. Nitric oxide, cytochrome P450 metabolites, and intermediate and large conductance K(Ca) channels mediate dilation caused by ATP. ATP-induced conducted dilation is dependent upon both the endothelium and cytochrome P450 metabolites.

Automated, compliant, high-flow common carotid to middle cerebral artery bypass

The authors describe the use of the Cardica C-Port xA Distal Anastomosis System to perform an automated, high-flow extracranial–intracranial bypass. The C-Port system has been developed and tested in coronary artery bypass surgery for rapid distal coronary artery anastomoses. Air-powered, it performs an automated end-to-side anastomosis within seconds by nearly simultaneously making an arteriotomy and inserting 13 microclips into the graft and recipient vessel. Intracranial use of the device was first simulated in a cadaver prepared for microsurgical anatomical dissection.

The authors used this system in a 43-year-old man who sustained a subarachnoid hemorrhage after being assaulted and was found to have a traumatic pseudoaneurysm of the proximal intracranial internal carotid artery. The aneurysm appeared to be enlarging on serial imaging studies and it was anticipated that a bypass would probably be needed to treat the lesion. An end-to-side bypass was performed with the C-Port system using a saphenous vein conduit extending from the common carotid artery to the middle cerebral artery. The bypass was demonstrated to be patent on intraoperative and postoperative arteriography. The patient had a temporary hyperperfusion syndrome and subsequently made a good neurological recovery.

The C-Port system facilitates the performance of a high-flow extracranial–intracranial bypass with short periods of temporary arterial occlusion. Because of the size and configuration of the device, its use is not feasible in all anatomical situations that require a high-flow bypass; however it is a useful addition to the armamentarium of the neurovascular surgeon.

Combined surgical resection and stereotactic radiosurgery for treatment of cerebral metastases

BACKGROUND

Patients with limited intracranial metastatic disease traditionally have been treated with surgery followed by WBRT. However, there is growing concern for the debilitating cognitive effects after WBRT in long-term survivors. We present a series of patients treated with surgery followed by SRS, while reserving WBRT as a salvage therapy for disease progression.

METHODS

Medical records from 15 patients with 1 to 2 cerebral metastases who underwent both resection and SRS were reviewed. Outcome measures included overall survival, survival by RPA class, EOR, local tumor control, progression of intracranial disease, need for WBRT salvage therapy, and COD.

RESULTS

Fifteen patients with cerebral metastases were treated with the combined surgery-SRS paradigm. Eight of the 15 patients (53.3%) were designated RPA class 1, with 6 of 15 (40.0%) in class 2 and 1 of 15 (6.7%) in class 3. Gross total resection was achieved in 12 cases (80.0%). Overall median survival was 20.0 months, with values of 22.0 and 13.0 months for RPA classes 1 and 2, respectively. Local recurrence occurred in 16.7% of those patients with GTR. Six patients (40.0%) went on to receive WBRT at a median of 8.0 months from initial presentation. Twelve patients (80.0%) had died at the completion of the study, and the COD was CNS progression in 33.3%.

CONCLUSIONS

Surgical resection combined with SRS is an effective treatment for selected patients with limited cerebral metastatic disease. Survival using this combined treatment was equivalent to or greater than that reported by other studies using surgery + WBRT or SRS + WBRT.

Effect of antiplatelet therapy on thromboembolic complications of elective coil embolization of cerebral aneurysms

BACKGROUND AND PURPOSE

Thromboembolic events are the most common complications of elective coil embolization of cerebral aneurysms. Administration of oral clopidogrel and/or aspirin could lower the thromboembolic complication rate.

MATERIALS AND METHODS

Records over a 10-year period were reviewed in a retrospective cohort study. For 369 consecutive elective coil embolization procedures, 25 patients received no antiplatelet drugs, 86 received antiplatelet drugs only after embolization, and 258 received antiplatelet drugs before and after embolization.

RESULTS

Symptomatic thromboembolic complications (transient ischemic attack or stroke within 60 days) occurred in 4 (16%) of 25 when no antiplatelet drugs were given, in 2 (2.3%) of 86 when antiplatelet drugs were administered only after embolization, and in 5 (1.9%) of 258 when antiplatelet drugs were administered before and after embolization. The lower symptomatic thromboembolic complication rate in the patients who received any antiplatelet therapy was statistically significant (P = .004). Clots were visible intraprocedurally in 5 (4.5%) of 111 when no antiplatelet drugs were administered before procedures and in 4 (1.6%) of 258 when they were (P value not significant). None of the 9 was symptomatic postprocedurally, but 7 were lysed or mechanically disrupted. Extracerebral hemorrhagic complications occurred in 0 (0%) of 25 when no antiplatelet drugs were given and in 11 (3.2%) of 344 when they were (P value not significant).

CONCLUSION

Oral clopidogrel and/or aspirin significantly lowered the symptomatic thromboembolic complication rate of elective coil embolization of unruptured cerebral aneurysms. There were trends toward a lower rate of intraprocedural clot formation in patients given antiplatelet drugs before procedures and a higher hemorrhagic complication rate in patients given antiplatelet drugs. Benefits of antiplatelet therapy appear to outweigh risks.

Current Status of Manpower Needs for Management of Cerebrovascular Disease

THE CEREBROVASCULAR DISCIPLINE has undergone dramatic changes in recent years. The advent, development, and now widespread application of endovascular therapy for various cerebrovascular diseases has been the predominant influence behind many of these changes, but other factors (some scientific, others less so) have also contributed significantly. As our discipline evolves, it is critical to periodically examine how such changes have altered our manner of practice and to determine what impact such changes might have on manpower allocation and training for the future. This article is our attempt at providing such an assessment. First, we will critically review recent trends within the fields of intracranial aneurysms, arteriovenous malformations, carotid atherosclerotic occlusive disease, and ischemic stroke and how these trends have impacted our profession. Thereafter, we will provide a perspective on what the cerebrovascular manpower needs of the future might be and by whom these needs will be met. Finally, we will examine how the new generation of cerebrovascular specialists, including neurosurgeons, neuroradiologists, and some neurologists, will attain their requisite surgical or endovascular training and attempt to determine which careers, pathways, and opportunities will be available to these individuals in the future.

Effect of intraarterial papaverine and/or angioplasty on the cerebral veins in patients with vasospasm after subarachnoid hemorrhage due to ruptured intracranial aneurysms

Object

The goal in this study was to determine if there was a change in intracranial venous diameters after endo-vascular treatment of carotid distribution vasospasm caused by subarachnoid hemorrhage.

Methods

The venous diameters were measured in all patients who received intraarterial papaverine and/or balloon angioplasty for treatment of vasospasm during the study period of 3 years. To evaluate the veins of Labbé and Trolard, the straight sinus, and the superior sagittal sinus (SSS), measurements were performed in a blinded manner with the aid of a magnification loupe. Predetermined sites were evaluated on angiograms obtained before and after endovascular treatment. Forty-three treatments in 26 patients were included: 18 patients (33 territories) were treated with intraarterial papaverine alone, four (four territories) were treated with balloon angioplasty alone, and four (six territories) were treated with both papaverine infusion and angioplasty.

The mean measured venous diameters increased significantly after addition of papaverine (10.9%), and also after combined papaverine and angioplasty (4.2%). There was no statistically significant increase in the mean venous diameters after angioplasty alone. If the initial intracranial pressure (ICP) was less than 15 mm Hg before treatment, the veins showed a greater tendency to dilate than if the initial ICP measurements were greater than 15 mm Hg. The straight sinus and the SSS increased more in diameter than the veins of Labbé and Trolard. There was no statistically significant correlation between the change in venous diameters with treatment and ICP.

Conclusions

Endovascular treatment produces measurable increases in intracranial venous diameters. However, these changes do not correlate with changes in ICP.

Safety and technical efficacy of over-the-wire balloons for the treatment of subarachnoid hemorrhage–induced cerebral vasospasm

Object

Over the past decade, low-pressure, flow-directed balloons have been replaced by over-the-wire balloons in the treatment of vasospasm induced by subarachnoid hemorrhage (SAH). The authors assess the procedural safety and technical efficacy of these newer devices.

Methods

Seventy-five patients who underwent 85 balloon angioplasty procedures for the treatment of SAH-induced vasospasm were identified from a prospective quality-assurance database. Medical records and angiographic reports were reviewed for evidence of procedural complications and technical efficacy.

No vessel rupture or perforation occurred, but thromboembolic complications were noted in four (4.7%) of the 85 procedures. Balloon angioplasty was frequently attempted and successfully accomplished in the distal internal carotid (100%), proximal middle cerebral (94%), vertebral (73%), and basilar (88%) arteries. Severe narrowing was present in 89 proximal anterior cerebral arteries. Angioplasty was attempted in 41 of these vessels and was successful in only 14 (34%). In 19 of the 27 unsuccessful attempts, the balloon could not be advanced over the wire due to severe vasospasm or unfavorable vessel angle. Follow-up angiography in a subset of patients demonstrated that severe recurrent vasospasm occurred in 15 (13%) of 116 vessels studied after angioplasty.

Conclusions

Over-the-wire balloons involve a low risk for vessel rupture. The anterior cerebral artery remains difficult to access and successfully treat with current devices. Further improvements in balloon design, such as smaller inflated diameters and better tracking, are necessary. Finally, thromboembolic complications remain an important concern, and severe vasospasm may recur after balloon angioplasty.

Clinical Features and Outcome in North American Adults With Moyamoya Phenomenon

Background and Purpose— To describe baseline clinical features and outcomes of adults with moyamoya phenomenon treated at a single North American institution.

Methods— We identified 34 adults with moyamoya phenomenon by review of angiographic records. Clinical presentation and baseline stroke risk factors were obtained by chart review. Follow-up was obtained prospectively. A 5-year Kaplan-Meier stroke risk was calculated.

Results— The median age was 42 (range 20 to 79) years. Twenty-five were women. The initial symptom was ischemia, hemorrhage, or asymptomatic in 24, 7, and 3 patients, respectively. Twenty-two had bilateral involvement and 12 had unilateral moyamoya vessels. Baseline stroke risk factors were similar between groups. The median follow-up in 31 living patients was 5.1 (range 0.2 to 19.6) years. Fourteen patients were treated with surgical revascularization (20 total hemispheres). In medically treated symptomatic hemispheres, the 5-year risk of recurrent ipsilateral stroke was 65% after the initial symptom and 27% after angiographic diagnosis. Patients with bilateral involvement presenting with ischemic symptoms were at the highest risk of subsequent stroke (n=17, 5-year risk of stroke with medical treatment after first symptom of 82%). In surgically treated hemispheres, the 5-year risk of perioperative or subsequent ipsilateral stroke or death was 17%. This was significantly different compared with medical treatment after first symptom ( P =0.02) but not after angiographic diagnosis.

Conclusion— Moyamoya phenomenon in North American adults is associated with a high risk of recurrent stroke, particularly those with bilateral involvement and ischemic symptoms. These data suggest a potential benefit with surgery if diagnosis could be made earlier.

Use of side branch in saphenous vein interposition graft for high-flow EC/IC bypass procedures

✓ Saphenous vein (SV) interposition grafts are often used for high-flow extracranial—intracranial bypass procedures. During these procedures, it is essential to remove air and debris from the graft and to evaluate blood flow through the graft after it has been anastomosed to other cortical vessels.

In this paper, the authors describe the preservation of a large side branch on the proximal end of the SV. This side branch can be used to flush out air and debris from the graft and to evaluate blood flow during revascularization.

Histologic and hemodynamic effects of endosaccular platinum coils for intracranial aneurysms

Over the past 15 years, endosaccular platinum coil therapy for intracranial aneurysms has evolved from clinical pilot studies of investigational devices to common clinical practice. The mechanism by which these coils reduce the risk of aneurysm rupture-the primary goal of intracranial aneurysm treatment-is the focus of this review. Both histological mechanisms of scar formation and hemodynamic mechanisms of flow diversion may be involved. We will first review aneurysm epidemiology to provide the context and rationale for therapy for patients harboring intracranial aneurysms. Next, we will review the data for and theories of the pathophysiology of aneurysm formation, growth, and rupture, particularly as they relate to endovascular coil therapy. Histological and hemodynamic studies of coiled aneurysms in animals and humans will be reviewed. Finally, we will discuss emerging coil-based therapies, such as bioactive polymer coatings for platinum coils and the adjunctive use of stents.

Update on the management of unruptured intracranial aneurysms

Over the past decade, several factors have led to a dramatic change in the manner in which patients with unruptured intracranial aneurysms are diagnosed and treated. These factors include the increased use of noninvasive imaging modalities for the diagnosis of intracranial aneurysms, publication of new natural history data detailing the hemorrhage risks associated with unruptured intracranial aneurysms, and the broad application of endovascular therapy for their treatment. With these new technologies and new natural history data has come considerable uncertainty about the optimal treatment strategy for patients with unruptured intracranial aneurysms. In this light, it seems prudent to review periodically and examine critically all recent data pertaining to the natural history and treatment of unruptured intracranial aneurysms, in an effort to provide a scientific update on which management recommendations can be based. This review article represents the authors' attempt at such an update, and it is their hope that members of the community of neurovascular surgeons might find this information helpful during their continuing efforts to provide optimal care for their patients with unruptured intracranial aneurysms.