Comparison of Blood Oxygenation Level-Dependent fMRI and Provocative DSC Perfusion MR Imaging for Monitoring Cerebrovascular Reserve in Intracranial Chronic Cerebrovascular Disease.

BACKGROUND AND PURPOSE: Loss of hemodynamic reserve in intracranial cerebrovascular disease reduces blood oxygenation level-dependent activation by fMRI and increases asymmetry in MTT measured by provocative DSC perfusion MR imaging before and after vasodilation with intravenous acetazolamide. The concordance for detecting hemodynamic reserve integrity has been compared. MATERIALS AND METHODS: Patients (n = 40) with intracranial cerebrovascular disease and technically adequate DSA, fMRI and provocative DSC perfusion studies were retrospectively grouped into single vessels proximal to and distal from the circle of Willis, multiple vessels, and Moyamoya disease. The vascular territories were classified as having compromised hemodynamic reserve if the expected fMRI blood oxygenation level-dependent activation was absent or if MTT showed increased asymmetry following vasodilation. Concordance was examined in compromised and uncompromised vascular territories of each group with the Fischer exact test and proportions of agreement. RESULTS: Extensive leptomeningeal collateral circulation was present in all cases. Decreased concordance between the methods was found in vascular territories with stenosis distal to but not proximal to the circle of Willis. Multivessel and Moyamoya diseases also showed low concordance. A model of multiple temporally displaced arterial inputs from leptomeningeal collateral flow demonstrated that the resultant lengthening MTT mimicked compromised hemodynamic reserve despite being sufficient to support blood oxygenation level-dependent contrast. CONCLUSIONS: Decreased concordance between the 2 methods for assessment of hemodynamic reserve for vascular disease distal to the circle of Willis is posited to be due to well-developed leptomeningeal collateral circulation providing multiple temporally displaced arterial input functions that bias the perfusion analysis toward hemodynamic reserve compromise while blood oxygenation level-dependent activation remains detectable.

In vivo evaluation of quantitative MR angiography in a canine carotid artery stenosis model.

BACKGROUND AND PURPOSE: Large-vessel cerebral blood flow quantification has emerged as a potential predictor of stroke risk. QMRA uses phase-contrast techniques to noninvasively measure vessel flows. To evaluate the in vivo accuracy of QMRA for measuring the effects of progressive arterial stenosis, we compared this technique with invasive flow measurements from a sonographic transit-time flow probe in a canine model. MATERIALS AND METHODS: A sonographic flow probe was implanted around the CCA of hound dogs (n = 4) under general anesthesia. Pulsatile blood flow and arterial pressure were continuously recorded during CCA flow measurements with QMRA. A vascular tourniquet was applied around the CCA to produce progressive stenosis and varying flow rates. Statistical comparisons were made by using the Pearson product moment correlation coefficient. RESULTS: A total of 60 paired CCA flow measurements were compared. Mean blood flows ranged between 21 and 691 mL/min during QMRA acquisition as measured by the flow probe. The correlation coefficients between flow probe and QMRA measurements for mean, maximum, and minimum volume flow rates were 0.99 (P < .0001), 0.98 (P < .0001), and 0.96 (P < .0001), respectively. The overall proportional difference between the 2 techniques was 7.8 ± 1%. Measurements at higher flow rates and in the absence of arterial stenosis had the lowest PD. CONCLUSIONS: Noninvasive CCA flow measurements by using QMRA are accurate compared with invasive flow-probe measurements in a canine arterial flow model with stenosis and may be useful for the evaluation of the hemodynamic effects of stenosis caused by cerebrovascular atherosclerosis.

Use of cervical spinal cord stimulation in treatment and prevention of arterial vasospasm after aneurysmal subarachnoid hemorrhage. Technical details.

Based on past laboratory and anecdotal clinical experience, we hypothesized that prolonged cervical spinal cord stimulation (SCS) in the acute settings of aneurysmal subarachnoid hemorrhage (aSAH) would be both safe and feasible, and that 2-week stimulation will reduce incidence of cerebral arterial vasospasm. The goal of our clinical study was to establish feasibility and safety of cervical SCS in a small group of selected aSAH patients. Single-arm non-randomized prospective study of cSCS in aSAH patients involved percutaneous implantation of 8-contact electrode in 12 consecutive aSAH patients that satisfied strict inclusion criteria. The electrode insertion was performed immediately upon surgical or endovascular securing of the ruptured aneurysm while the patient was still under general anesthesia. Patients were stimulated for 14 consecutive days or until discharge. There were no complications related to the electrode insertion or to SCS during the study and no long-term side effects of SCS during 1-year follow-up. There was 1 unrelated death and two electrode pullouts. This article summarizes technical details of SCS electrode insertion and the stimulation parameters used in the research study. Our study of SCS for prevention of vasospasm after aSAH conclusively shows both safety and feasibility of this promising treatment approach. Despite high level of acuity in aSAH patients, impaired level of consciousness, frequent patient re-positioning, need in multiple tests and variety of monitors, SCS electrodes may be safely implanted and maintained for the two-week period. Long-term follow up shows no adverse effects of cervical SCS in this patient category.

Regional cerebral blood flow using quantitative MR angiography.

BACKGROUND AND PURPOSE: We sought to derive regional cerebral blood flow using vessel flows from quantitative MR angiography (qMRA). MATERIALS AND METHODS: Flow rates in the 15 major cerebral arteries were measured on retrospectively gated fast 2D phase-contrast MR angiography obtained in 83 healthy adult volunteers (age range, 24-74 years; mean, 42 years). The arterial network of the brain was partitioned into 12 different regions, in which flows were calculated from the measured flows of the 15 cerebral arteries. RESULTS: The mean flows of the 15 arteries and the 12 regions were calculated. The mean total cranial flow and the mean total cerebral blood flow were 949 +/- 158 mL/min and 695 +/- 113 mL/min, respectively. The mean regional flows for the anterior and posterior circulation were 483 +/- 87 mL/min and 212 +/- 34 mL/min, respectively. The relative contributions of the flows in the 11 regions to their parent regions were obtained. The mean flows in the individual arteries and the regions with age were also calculated. The mean flows for the female group were significantly lower than those for the male group (P < .001) for the 2 common carotids and the cranial circulation and left/right extracranial circulation. However, the intracranial circulation was not different between sexes. CONCLUSIONS: The 12 regions in the cerebral circulation were identified and formed into a partition tree, and the mean regional flow for each region was determined using vessel flows from qMRA.

Increased brain oxygenation during intubation-related stress.

BACKGROUND AND OBJECTIVES: The purpose of this study was to determine whether brain oxyhaemoglobin-deoxyhaemoglobin coupling was altered by anaesthesia or intubation-induced stress. METHODS: This was a prospective observational study in the operating room. Thirteen patients (ASA I and II) undergoing spinal or peripheral nerve procedures were recruited. They were stabilized before surgery with mask ventilation of 100% oxygen. Anaesthesia was induced with 2 microg kg(-1) fentanyl and 3 mg kg(-1) thiopental. Laryngoscopy and intubation were performed 4 min later. After intubation, desflurane anaesthesia (FiO2=1.0) was adjusted to maintain response entropy of the electroencephalogram at 40-45 for 20 min. Prefrontal cortex oxyhaemoglobin and deoxyhaemoglobin were determined every 2 s using frequency domain near-infrared spectroscopy. Blood pressure, heart rate and response entropy were collected every 10 s. RESULTS: Awake oxyhaemoglobin and deoxyhaemoglobin were 18.9 +/- 2.3 micromol (mean +/- SD) and 12.7 +/- 0.8 micromol, respectively, and neither changed significantly during induction. Intubation increased oxyhaemoglobin by 37% (P < 0.05) and decreased deoxyhaemoglobin by 16% (P < 0.05), and both measures returned to baseline within 20 min of desflurane anaesthesia. Blood pressure, heart rate and electroencephalogram response entropy increased during intubation, and the increase in heart rate correlated with the increase in brain oxygen saturation (r = 0.48, P < 0.05). CONCLUSIONS: Intubation-related stress increased oxyhaemoglobin related to electroencephalogram and autonomic activation. Stress-induced brain stimulation may be monitored during anaesthesia using frequency domain near-infrared spectroscopy.

Spontaneous disappearance of vein of galen malformation and posterior fossa venous pouch.

Cerebrovascular anomalies remain an issue of controversy regarding diagnosis, classification, and treatment. We report the first case of total and asymptomatic regression and disappearance of a vein of Galen malformation associated with a posterior fossa venous pouch. Different aspects of the vein of Galen are discussed together with emphasis on the underlying mechanisms of spontaneous thrombosis and regression.A 4-month-old boy presented with macrocrania and signs of intracranial hypertension. Computerized tomography disclosed two masses, the first was a giant aneurysmal dilatation in the posterior fossa, and the second was a gigantic pouch at the level of the vein of Galen. Hydrocephalus was treated by ventriculo-peritoneal shunting. Two months later, the shunt was revised, and posterior fossa was explored without active treatment. Both abnormalities regressed spontaneously. No recurrence occurred, and the child remained neurologically intact. Total disappearance of the masses as well as normal brain and cerebrovascular anatomy were confirmed by angiography, MRI, and MRA. Over a follow-up period of 17 years, the patient did not develop complications. He had perfect clinical tolerance and resumed a normal life.

Bedside external ventricular drain placement for the treatment of acute hydrocephalus.

The purpose of this retrospective study was to evaluate the results of external ventricular drain (EVD) placement for the management of hydrocephalus. We present our experience with 103 consecutive cases over one year, 56 of which had subarachnoid hemorrhage (SAH). Short tunnel ventriculostomy was performed at the bedside in the neurosurgical intensive care unit (NSICU), using sterile technique. Long-term care included meticulous site care by a dedicated NSICU nurse, daily cultures and prophylactic antibiotics. The average duration of EVD was 10.7 days (range 1-28 days). There was one case of positive cerebrospinal fluid (CSF) culture. Additional complications included one small intraparenchymal hematoma and two cases of EVD disconnection. No patient died form EVD-associated complications. No rebleed from aneurysmal SAH was seen. There was no correlation between the duration of EVD and infection. We conclude that placement of short EVD in the NSICU is safe and can be maintained for the required duration of treatment with minimum infection rate.

Closed chest hypothermic circulatory arrest for complex intracranial aneurysms.

BACKGROUND: Recent advances in techniques of cardiopulmonary bypass permitted hypothermic circulatory arrest (HCA) using groin cannulation with the chest closed (CC-HCA) and without direct access to the heart. Herein we describe our experience with this technique for complex intracranial aneurysms. METHODS: Between 1992 and 1999, 16 patients (4 men and 12 women) with a mean age of 52 years (range 32 to 61 years) with complex intracranial aneurysms underwent resection or clipping of their aneurysms at our institution using the technique of CC-HCA and groin cannulation. Groin access was obtained with 16F to 19F arterial and 18F to 20F venous cannulas placing the tips at the aortoiliac and atriocaval junctions, respectively. Patients were cooled to a nasopharyngeal temperature of 16 degrees C. RESULTS: Mean circulatory arrest time was 32 minutes. No patient required conversion to standard sternotomy and central cannulation. There were no intraoperative deaths. The 30-day hospital mortality was 2 of 16 patients (12%). Of the 14 surviving patients (88%), 1 developed bilateral third nerve palsy and another left hemiparesis that improved on follow-up. Both were discharged to an extended care facility and continued to do well at home after discharge. Two patients developed deep venous thrombosis postoperatively and required anticoagulation. All patients continued to do well at a mean follow-up of 42 months. CONCLUSIONS: The less invasive technique of CC-HCA through groin cannulation avoids complications associated with a sternotomy, is safe and is associated with little morbidity, reduced operative time, and early hospital discharge and rehabilitation.

Computerized hemodynamic evaluation of the cerebral circulation for bypass.

This article describes details of the application of computer modeling of cerebral blood circulation. A brief review of the different computer modeling techniques and the current models used today for predicting surgical options for bypass surgery are presented. The use of phase contrast MR for estimating intracranial flow rates makes these models even more accurate. Two case studies are presented with computer simulation results with verification of predicted outcome both clinically and from actual flow of measurements.

Guglielmi detachable coiling for intracranial aneurysms: the story so far.

Spontaneous rupture of cerebral aneurysms typically results in subarachnoid hemorrhage. The primary goal of treatment of cerebral aneurysms is to prevent future rupture. Surgical clipping had been the mainstay of treatment of both ruptured and unruptured cerebral aneurysms. In 1991, Guglielmi detachable coil (GDC) embolization was introduced as an alternative method for treating selected patients with aneurysm. The goal of the treatment is prevent the flow of blood into the aneurysm sack by filling the aneurysm with coils and thrombus. Theoretically, there are several advantages of GDC over surgery. These procedures are performed under general anesthesia with the standard transfemoral approaches used in diagnostic angiography. Since its inception, GDC embolization has evolved as a result of both clinical experience and the introduction of technological improvements. We are now better at selecting aneurysms appropriate for coiling, which also have wide necks. Advances in GDC technology have also improved this method of treatment. Over the last several years, the number of coil sizes has been increased, multidimensional coils allowing safer initial coil placement have become available, and, more recently, softer coils have been introduced. Our current approach is to have both surgical and endovascular options for patients.

Hemodynamics of in-tandem stenosis of the internal carotid artery: when is carotid endarterectomy indicated?

BACKGROUND: Recent publications have pointed out the importance of evaluating patients with in-tandem stenosis and in particular the association of moderate stenosis of the extracranial internal carotid artery (ICA) with moderate or severe stenosis of the intracranial internal carotid artery. Such evaluations are needed in symptomatic patients before planning carotid endarterectomies because observations have shown that in some cases the removal of an extracranial lesion does not necessarily improve these symptoms. This paper examines the hemodynamic effects of in-tandem stenosis in the internal carotid artery. METHODS: Equations describing flow in arteries are modified to accommodate two regions of stenosis in tandem. An equivalent value of stenosis is derived such that two stenoses in tandem behave as a single stenosis with similar hemodynamic properties. The solution to this problem is solved mathematically and this was used to analyze the observations made in five studies published on in-tandem stenosis of the internal carotid artery. RESULTS: Equivalent stenoses for various values of extracranial and intracranial stenoses are presented. It was found that two stenotic lesions in tandem are not equivalent to a simple summation of both values. A graphical solution is presented to show the hemodynamic effects of both stenoses. CONCLUSIONS: The most critical determinant of hemodynamic compromise when two lesions are in tandem is the larger one. Hence removal of a more proximal lesion may have little effect on a larger distal lesion if the symptoms are due to hypoperfusion. It is important that one distinguish between hypoperfusion and thromboembolic causes of the symptoms. No conclusions about the risk of thromboembolic events after a carotid endarterectomy in the setting of a distal stenosis can be made from this study.

Improved phase-contrast flow quantification by three-dimensional vessel localization.

In this paper, a method of three-dimensional (3D) vessel localization is presented to allow the identification of a vessel of interest, the selection of a vessel segment, and the determination of a slice orientation to improve the accuracy of phase-contrast magnetic resonance (PCMR) angiography. A marching-cube surface-rendering algorithm was used to reconstruct the 3D vasculature. Surface-rendering was obtained using an iso-surface value determined from a maximum intensity projection (MIP) image. This 3D vasculature was used to find a vessel of interest, select a vessel segment, and to determine the slice orientation perpendicular to the vessel axis. Volumetric flow rate (VFR) was obtained in a phantom model and in vivo using 3D localization with double oblique cine PCMR scanning. PCMR flow measurements in the phantom showed 5. 2% maximum error and a standard deviation of 9 mL/min during steady flow, 7.9% maximum error and a standard deviation of 13 mL/min during pulsatile flow compared with measurements using an ultrasonic transit-time flowmeter. PCMR VFR measurement error increased with misalignment at 10, 20, and 30 degrees oblique to the perpendicular slice in vitro and in vivo. The 3D localization technique allowed precise localization of the vessel of interest and optimal placement of the slice orientation for minimum error in flow measurements.

Giant anterior communicating artery aneurysm infiltrated with a primary cerebral lymphoma: case report.

OBJECTIVE AND IMPORTANCE: Central nervous system lymphomas exhibit angiotropic characteristics. Nevertheless, direct association with an intracranial aneurysm is very rarely reported. We present a case of a giant aneurysm infiltrated with a large cell non-Hodgkin's lymphoma. The incidence of primary central nervous system lymphoma is increasing, and similar cases may become more frequent in the future. CLINICAL PRESENTATION: A 65-year-old man had presented with a giant anterior cerebral artery aneurysm, new onset of seizures, aphasia, and hemiparesis. The aneurysm was treated with Guglielmi detachable coils. Six months later, the patient exhibited fever and neurological deterioration. Magnetic resonance images suggested an enhancing lesion posterior to the neck of the aneurysm. Antibiotic treatment given elsewhere was unsuccessful. INTERVENTION: A craniotomy for a suspected abscess was performed, with removal of the aneurysm and clipping of the neck. The aneurysm sac appeared to be filled with thrombus and pus. The results of aerobic, anaerobic, and fungal cultures were negative. Postoperative magnetic resonance images demonstrated a residual mass, posterior to the aneurysm within the striatum and the internal capsule. Histological examination of the aneurysm wall revealed a large B-cell lymphoma. The diagnosis was confirmed by a stereotactic biopsy. Radiation therapy resulted in a transient decrease in the size of the lesion. CONCLUSION: Although the tumor was not apparent on the initial imaging studies, it may have been the cause of the patient's presenting symptoms. Infiltration of the aneurysm wall by the lymphoma also raises the possibility of a causal relationship. As the incidence of primary central nervous system lymphoma is reported to be on the increase, awareness this uncommon association of an aneurysm and malignant lymphoma is of value.

What percentage of surgically clipped intracranial aneurysms have residual necks?

OBJECTIVE: To determine the angiographically proven rate and persistence of occlusion of intracranial aneurysms after surgical clipping as reported in the literature. This should establish a basis for comparing surgery with new endovascular methods of treatment. METHODS: We reviewed the literature published during the period from 1979 through 1999, dividing the articles into two groups. The first group of articles reported patients undergoing surgical treatment with immediate postoperative angiography. The second group of articles documented symptomatic recurrence or regrowth of aneurysms that were surgically treated previously. The data from these articles are presented for analysis. RESULTS: During the period 1979 to 1999, six series of patients undergoing surgical treatment of aneurysms with immediate postoperative angiography were reported. These reported series comprised a total of 1,397 patients, of whom 1,370 underwent postoperative angiography demonstrating 1,569 clipped aneurysms. Residual filling was found in 82 aneurysms (5.2%) on postoperative angiography. Of the 1,370 patients, only 124 patients with 169 aneurysms were reported to have had any long-term angiographic follow-up. The second group consisted of 226 patients representing six reported groups of patients, who either presented up to 24 years after aneurysm clipping with recurrent symptoms of hemorrhage or mass effect, or had important findings on intraoperative and postoperative angiograms. CONCLUSION: The lack of information regarding both the frequency of residual filling or regrowth and long-term angiographic follow-up of patients with surgically treated aneurysms makes meaningful comparison between surgical treatments and new treatment methods for intracranial aneurysms difficult or impossible. Detailed analysis with high-quality angiography should be performed to determine the success of surgical treatment.

Techniques of coiling cerebral aneurysms.

BACKGROUND: More than 200 aneurysms have been coiled at the UIC Medical Center within the last 5 years. We describe in detail the technical factors that increase the chance of complete occlusion of a cerebral aneurysm with coils. Aneurysms selected for coiling have good geometry or are in a location that is difficult to reach surgically. Patients with medical conditions that preclude surgical treatment may also undergo coiling. METHODS: Patients with aneurysms, either ruptured or unruptured, are treated under general anesthesia, fully anticoagulated and deeply paralyzed. Coiling is done under simultaneous biplane roadmapping. After the first coil has created a mesh, the aneurysm is densely packed with soft coils of decreasing diameter, until no more coils can be deployed into the aneurysm. RESULTS: The morbidity and mortality rates associated with the coiling procedure have continuously decreased over the last 5 years. The morphological outcomes have improved, due to extensive use of the remodeling technique and to advancements in materials, such as refinements in the coils themselves or the availability of over-the-wire balloon catheters in different sizes and hydrophilic wires with complex tip configurations. Twenty-one percent of the aneurysms were considered to be incompletely occluded immediately after coiling. Of this group, one-third of the aneurysms were found to be completely occluded on follow-up angiograms by 6 months; these have remained occluded. One-third were more than 95% occluded after the coiling procedure; in these patients, the dome was completely occluded, but there was a small neck remnant, which has remained stable in all patients on control angiograms obtained at 6 months and 1, 2, and 4 years; none have rebled. These patients are followed medically. The remaining one-third of the aneurysms in this subgroup were less than 95% occluded, although the dome was completely thrombosed. None of them have rebled, but the neck remnant in most has regrown over a period ranging from 6 months to 2 years. These patients have undergone a second treatment-either surgical clipping, permanent occlusion of the parent vessel, or repeat coiling using the remodeling technique. The overall rebleeding rate of incompletely occluded aneurysms is extremely low (less than 1%). CONCLUSION: The low morbidity and mortality rates and the good morphological outcome obtained in most cases make coiling a reasonable alternative to surgical clipping in properly selected cases.

Hypoxic brain tissue following subarachnoid hemorrhage.

BACKGROUND: Subarachnoid hemorrhage can lead to cerebral ischemia and irreversible brain injury. The purpose of this study was to determine whether subarachnoid hemorrhage produces changes in brain tissue oxygen pressure, carbon dioxide pressure, or pH during surgery for cerebral aneurysm clipping. METHODS: After institutional review board approval and patient consent, 30 patients undergoing craniotomy for cerebral aneurysm clipping were studied, 15 without and 15 with subarachnoid hemorrhage. Patients with subarachnoid hemorrhage were prospectively separated into groups with modest (Fisher grade 1 or 2; n = 8) and severe bleeds (Fisher grade 3; n = 7). After a craniotomy, a probe was inserted into cortex tissue supplied by the artery associated with the aneurysm. Baseline measures were made in the presence of a 4% end-tidal desflurane level. The end-tidal desflurane level was increased to 9% before clipping of the aneurysm, and a second tissue measurement was made. RESULTS: The median time of surgery after subarachnoid hemorrhage was 2 days, ranging from 1 to 13 days. During baseline anesthesia, brain tissue oxygen pressure was 17+/-9 mm Hg (mean +/- SD) in control patients, 13+/-9 mm Hg in those with Fisher grade 1 or 2 hemorrhage, and 7+/-6 mm Hg in those with Fisher grade 3 hemorrhage (P<0.05 compared with control). Brain tissue pH was 7.10+/-0.10 in control patients, 7.14+/-0.13 in those with Fisher grade 1 or 2 hemorrhage, and 6.95+/-0.18 in those with with Fisher grade 3 hemorrhage (P<0.05). At a 9% end-tidal desflurane level, brain tissue oxygen pressure increased to 19+/-9 mm Hg and brain tissue pH increased to 7.11+/-0.11 in patients with Fisher grade 3 hemorrhage (P<0.05 for both increases). CONCLUSION: These results show that subarachnoid hemorrhage can significantly decrease brain tissue oxygen pressure and pH related to the severity of the bleed. Increasing the desflurane concentration to 9% increased brain tissue oxygen pressure in all patients and brain tissue pH in patients with subarachnoid hemorrhage with baseline acidosis.

Brain tissue PO(2), PCO(2), and pH during cerebral vasospasm.

BACKGROUND: The purpose of the present study was to assess brain tissue monitoring for detection of ischemia due to vasospasm in aneurysmal subarachnoid hemorrhage (SAH) patients. METHODS: After obtaining informed consent, a burr hole was made in 10 patients and a Neurotrend 7 probe was inserted ipsilateral to the region of SAH. In eight patients the probe was inserted during surgery for clipping the aneurysm and in two patients the probe was inserted in the neurosurgery ICU. Brain tissue gases and pH were collected over 6-hour periods for 7 to 10 days until the termination of monitoring. The onset of vasospasm was confirmed by angiography and xenon computed tomography (Xe/CT) cerebral blood flow studies. RESULTS: Seven patients did not develop vasospasm during monitoring and were considered as controls. In this group, brain tissue oxygen pressure (PO(2)) remained above 20 mmHg, carbon dioxide pressure (PCO(2)) stabilized at 40 mmHg and pH remained between 7.1 and 7.2. In three patients who developed vasospasm during monitoring, PO(2) was not different from the control group. However, PCO(2) increased to 60 mmHg and pH decreased to 6.7 (p < 0.001). CONCLUSION: In this study, patients with SAH who developed vasospasm had significantly lower brain tissue pH and higher PCO(2) compared to controls. However, there was no significant change in PO(2) levels associated with vasospasm. Brain tissue monitoring can provide an indication of ischemia during vasospasm.

Surgery following endovascular coiling of intracranial aneurysms.

BACKGROUND: Surgery for intracranial aneurysms that have been treated by endovascular coiling is a new challenge for neurosurgeons and the need for it will undoubtedly continue to increase. The indications for, timing, and technique of surgery in our experience are described. METHODS: We have reviewed our experience with 11 patients who underwent surgery following endovascular coiling with Guglielmi detachable coils (GDCs) of an aneurysm. We analyzed the indications for surgery, surgical techniques used, and patient outcome. RESULTS: There were nine female and two male patients. The mean age was 49 years (range 13 to 67 years). The intervals between coiling and surgery were 1, 2, 3, 4, 7, 7, 10, and 14 days, 6 weeks, 2, 18, and 25 months. The indications for surgery were partial treatment (3), growth of residual neck (2), persistent mass effect of a giant aneurysm (1), mass effect from the coil ball (2), coil migration (2), and coil protrusion with embolic event (1). The coils were removed at the time of surgery from 9 of 11 aneurysms before clipping. In two cases it was possible to place a clip across the neck of the aneurysm without removing the coils, as the coils no longer occupied the neck. There were two permanent deficits directly related to the endovascular procedures. Two other patients who presented with subarachnoid hemorrhage had residual neurological deficits post surgery and one patient with a giant aneurysm had persistent visual loss. CONCLUSION: Surgery remains a viable option at any time for treating aneurysms that have been previously treated by GDC placement. The operative approach is determined by the need for coil removal and the duration since coiling.

Quantitative assessment of vessel flow integrity for aneurysm surgery. Technical note.

Quantitative measurement of blood flow in cerebral vessels during aneurysm surgery can help prevent ischemic injury and improve patient outcome. The authors report a case of a superior cerebellar artery (SCA) aneurysm in which perivascular microflow probes were used to measure blood flow quantitatively in both the SCA and the posterior cerebral artery before and after aneurysm clipping. Following aneurysm clipping, blood flow in the SCA was reduced to less than 25% of its initial baseline value. Prompt detection of compromised blood flow gave the surgeon the opportunity to adjust the clip and restore SCA flow to its preclipping value within 5 minutes of initial clip placement. Quantitative vessel-flow measurements were integral to the safe progression of the operation and may have prevented an adverse neurological outcome in this patient. The recommended surgical technique and the principle of operation are described.