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.

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.

Brain tissue response to CO2 in patients with arteriovenous malformation.

We tested whether cerebral arteriovenous malformations (AVM) alter brain tissue oxygen pressure, PO2, carbon dioxide pressure PCO2, and pH before, during, and after hypercapnia. A craniotomy was performed and a sensor inserted into normal brain tissue (control) (n = 7) or into tissue adjacent to an AVM (n = 9). Under baseline conditions, tissue PO2 was 80% lower in AVM compared to control patients, but PCO2 and pH were normal. During a 10 mm Hg increase in PaCO2, tissue PO2 increased only in AVM patients, PCO2 increased in both groups, and pH decreased only in controls. When hypercapnia was reversed, tissue PCO2 decreased below baseline and pH increased in AVM patients. Results suggest that tissue CO2 washout and elevated pH result from increases in blood flow during hypercapnia. This response may be related to symptoms of hyperperfusion during AVM resection.

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.

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.

Juxtaorbital en plaque meningiomas. Report of four cases and review of literature.

Juxtaorbital spheroid wing or ridge meningiomas are the most common of the basal meningiomas. These are at times meningiomas en plaque, which in most patients do not have significant intracranial component. This article reviews the literature on en-plaque meningiomas and discusses the role of MR imaging and CT in the diagnosis of en-plaque meningiomas of the paraorbital region. The role of fat-suppression, gadolinium-enhanced, T1-weighted MR imaging is emphasized.

Brain tissue gases and pH during arteriovenous malformation resection.

OBJECTIVE: The purpose of this study was to determine whether baseline partial pressure of oxygen (PO2), partial carbon dioxide pressure (PCO2), and pH in brain tissue adjacent to arteriovenous malformations (AVMs) are different from those in control patients. In addition, PO2, PCO2, and pH changes were measured during resection of the AVMs. METHODS: Two groups were studied. Group 1 (n = 8) was composed of nonischemic patients scheduled for cerebral aneurysm clipping. Group 2 (n = 13) was composed of patients undergoing neurosurgery for resection of AVMs. After the craniotomy, the dura was retracted and a combined PO2, PCO2, and pH sensor was inserted into nonischemic brain tissue in Group 1. In Group 2, the sensor was inserted into tissue 2 to 3 cm from the margin of the AVMs, within the same arterial blood supply. After equilibration of the sensor, tissue gases and pH were measured during steady-state anesthetic conditions in Group 1 and during resection of AVMs in Group 2. RESULTS: Under baseline conditions before the start of surgery, tissue PO2 was decreased in patients with AVMs compared with control patients, but PCO2 and pH were not changed. During resection of the AVMs, PO2 and pH increased and PCO2 decreased compared with baseline measurements. These parameters did not change in control patients during a similar time period. CONCLUSION: The results suggest that cerebrovascular or metabolic adaptation occurs in patients with AVMs with decreased tissue perfusion pressure as an adjustment for decreased oxygen delivery. During resection of AVMs, this adaptation produces a relative hyperemic environment with tissue hyperoxia, hypocapnia, and alkalosis that is not corrected by the end of surgery.

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.

Thiopental and desflurane treatment for brain protection.

OBJECTIVE: Thiopental produces cerebral metabolic depression and cerebral vasoconstriction. However, the effect of thiopental on brain tissue oxygen pressure (PO2), carbon dioxide pressure, and pH is not known. In a prospective study, we measured brain tissue gases and pH during thiopental or desflurane treatment that was administered for brain protection during brain artery occlusion. METHODS: After institutional review board approval, 20 patients undergoing craniotomies for cerebrovascular surgery were tested; 10 were randomized to receive thiopental and 10 to receive desflurane. After each craniotomy, a Neurotrend probe (Diametrics Medical, Minneapolis, MN) was inserted to measure tissue PO2, carbon dioxide pressure, and pH in a tissue region at risk to develop ischemia during temporary brain artery occlusion. Thiopental or desflurane was administered to produce burst suppression of electroencephalography, and then temporary artery occlusion was performed during aneurysm or extracerebral-to-intracerebral bypass surgery. RESULTS: Thiopental produced no change in tissue gases or pH, but temporary artery clipping in thiopental-treated patients decreased PO2 30% (P < 0.05). Desflurane increased PO2 70% (P < 0.05), and tissue oxygenation remained elevated during temporary artery occlusion. Tissue pH did not decrease in either group during temporary brain artery occlusion. CONCLUSION: Thiopental has a metabolically neutral effect on brain tissue gases and pH, even though it is known to decrease cerebral oxygen consumption. The metabolic depressant and vasodilator effects of desflurane enhance tissue oxygenation and attenuate tissue PO2 reductions produced by artery occlusion. Both thiopental and desflurane inhibit ischemic lactic acidosis and decreases in pH.

Distal internal carotid artery pseudoaneurysms: technique and pitfalls of surgical management: two technical case reports.

OBJECTIVE AND IMPORTANCE: Small, irregular aneurysms of the internal carotid artery (ICA) that are not related to arterial divisions are rare and have characteristics similar to pseudoaneurysms: they do not appear to have well-formed sacs, they are surrounded by clot, and they avulse readily. We report two patients whose treatment demonstrates the surgical technique and important points concerning the management of distal ICA pseudoaneurysms. CLINICAL PRESENTATION: Both patients presented with diffuse subarachnoid hemorrhage. The initial angiographic results were unremarkable in each case. A week after presentation, however, a growing outpouching in the distal ICA was seen. INTERVENTION: At surgery, the aneurysms were found to be on the medial wall of the ICA and were not related to arterial divisions. Quantitative blood flow measurements of the efferent vessels at risk (ICA, M1 and A1 segments) were obtained using a perivascular microflowprobe before and after clipping. In each patient, the aneurysm avulsed entirely during clip application, despite careful placement of the clip parallel to the parent vessel. An encircling clip was then used. Pathological sectioning of the aneurysms revealed loose connective tissue and/or clot with no defined aneurysmal sac. CONCLUSION: Aneurysms of the distal ICA that are not related to arterial divisions are difficult to visualize on angiograms immediately after subarachnoid hemorrhage. They are frail, avulse easily, and may be pseudoaneurysms, necessitating the use of encircling clips. The base of the aneurysm or clot must be trimmed to prevent it from buckling inside the clip sleeve and compromising the ICA lumen. Measuring distal blood flow quantitatively provides valuable information about the patency of the ICA inside the metallic sleeve, since this segment cannot be demonstrated with angiography.

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.

Access to the cavernous sinus through the vertebral artery: technical case report.

The cavernous sinus in 3 of a series of 147 fast-flow direct carotid-cavernous fistulae was best reached through the vertebral artery. All three patients were anatomically cured without morbidity.

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.

Cerebral blood flow and metabolic response to etomidate and ischemia.

The purpose of this study was to measure the cerebrovascular and metabolic effects of etomidate during cerebral aneurysm surgery. Flow probes were placed on brain arteries to measure regional tissue perfusion. Cerebral oxygen consumption (CMRO2) was determined from blood flow measures and arterial-jugular bulb oxygen content differences. CBF and CMRO2 decreased 40% during etomidate infusion to suppress the electroencephalogram. During temporary brain artery occlusion, measurement of arterial blood flow in the circle of Willis provides an indication of collateral blood flow to potentially ischemic territory. The use of multiple flow probes can provide information on the effect of anesthetic drugs and surgical manipulation on cerebral circulation.

Brain tissue acid-base response to hypercapnia in neurosurgical patients.

These studies were conducted in neurosurgical patients to determine brain tissue nonbicarbonate buffering of pH changes during hypercapnia. Following a craniotomy, a sensor which continuously measures oxygen pressure, carbon dioxide pressure, pH and temperature was inserted into cortex tissue of nine subjects. Bicarbonate concentration was calculated from the Henderson-Hasselbach equation. Following baseline measures, PaCO2 was increased 10mmHg for 10 min. Tissue pCO2 increased 9 mmHg (p < 0.05) without a change in tissue pO2. In six patients, tissue bicarbonate concentration increased from 18 to 20 meq L-1 (p < 0.05), indicating a 40-50% attenuation of the increase in hydrogen ion (H+) by nonbicarbonate buffering mechanisms. Three patients showed no increase in tissue bicarbonate during hypercapnia; 2 had baseline tissue pH less than 6.5 and one displayed signs of tissue hypoxia during the CO2 challenge. In all patients, increases in tissue H+ during hypercapnia were related to baseline tissue bicarbonate concentration. Marked increases in H+ were seen when baseline bicarbonate decreased below 10 meq L-1. These results suggest that when tissue bicarbonate is depleted, the risk of H+ induced injury during hypercapnia is increased.

Ultrasonic perivascular flow probe: technique and application in neurosurgery.

Documentation and measurement of intraoperative cerebral blood flow during various neurosurgical procedures is not only valuable but also very informative. There are various methods by which qualitative and quantitative measurement of blood flow have been developed over the years. The use of perivascular ultrasonic flow more recently is fast gaining popularity. We describe the technique, principle and application of ultrasonic perivascular micro-flow probe quantitative measurement of selective vessel flow in neurosurgery.

Dominant A1: angiographic and clinical correlations with anterior communicating artery aneurysms.

It has been observed but never proven that anomalies of the anterior communicating artery complex are associated with anterior communicating artery aneurysms (ACAA). Therefore, in an effort to understand the significance of haemodynamic factors in the genesis, as well as the clinical course of ACAA, we evaluated the correlation between certain angiographic patterns of flow in the anterior circulation and the clinical findings of 51 patients with ACAA compared with 50 matched controls. Four significant associations which have never been validated were identified: 1) a dominant A1 (filling both A2's) was found in 57% of ACAA patients versus 14% of controls (p less than 0.001). 2) Unilateral hypoplasia of the opposite A1 was present in 24% of ACAA patients versus 6% of controls (p = 0.01). 3) Exclusive filling of the ACAA from one A1 occurred in 78%. 4) No statistically significant relationship was found between the anatomic flow patterns studied and the patients clinical presentation including age, sex, or grade. We conclude that anterior communicating artery aneurysms are significantly related in a majority of patients with the presence of a dominant A1, probably as the result of enhanced haemodynamic stress caused by this anatomic abnormality in the circulation. However, this association is not constant, and a dominant pattern of flow did not correlate with the clinical course. This is probably a reflection of the differences between factors initiating aneurysm formation and those influencing its growth, as well as of the relative limitations of angiography when pathophysiological extrapolations are attempted.

Brain tissue oxygen pressure, carbon dioxide pressure and pH during ischemia.

In this case we evaluated brain tissue pO2, pCO2 and pH during ischemia and arterial oxygen desaturation (hypoxia). In both situations brain pO2 decreased. During ischemia, tissue pCO2 increased while pH decreased; but both pCO2 and pH were stable during hypoxia. These results suggest that brain tissue pO2, pCO2 and pH measures provide information on tissue perfusion and oxygen availability during ischemia and hypoxia.

Regional tissue pO2, pCO2, pH and temperature measurement.

We compared the difference in brain tissue oxygen pressure (pO2), carbon dioxide pressure (pCO2), pH and temperature with 2 probes inserted 1 cm apart, in 7 patients. Following a craniotomy for cerebrovascular surgery, two Neurotrend probes which measure pO2, pCO2, pH and temperature were inserted into the brain 1 cm apart. Measures were compared between the probes under baseline anesthetic conditions and during the course of surgery. Under baseline conditions, tissue pO2, pCO2, pH and temperature were not different between the 2 probes. A significant correlation was seen between the probes in pH and temperature. During the course of surgery, variation in tissue gases and pH occurred with changes in ventilation and blood pressure but the difference between the probes remained stable. Ischemic changes in pO2, pCO2 and pH were seen in one of the 2 probes during brain artery occlusion or retractor placement. These results show that tissue pO2, pCO2 and pH are consistent in local brain regions during steady state conditions. The relationship between local measures is disrupted by regional ischemia.

Head registration techniques for image-guided surgery.

Localization of the pathological structures in relation to the surrounding anatomy and understanding of the surgical anatomy are probably the most important keys to successful neurosurgery. Image-guided surgery is an important tool for understanding an individual's anatomy and for precisely locating the lesion. Head registration is the most important step in image-guided surgery, required by every system in use today, although these systems show great differences. In this study, head registration techniques and user algorithms in 83 image-guided surgery cases were analyzed. Several types of fiducials including skin markers, bone fiducials, and the stereotactic frame were used for registration. Clinical applications, ease of use, and computer-calculated accuracy values for each type were compared. The average accuracy was 1.50 mm. X-spot skin markers are the fiducials most commonly used with CT scan. The stereotactic frame was the most accurate method, with an accuracy of 0.69 mm. Disc-shaped fiducials were used when MRI was the imaging modality; they provided an average accuracy of 2.62 mm. Head registration is an important part of image-guided surgery; the procedure used for registration should be based on the requirements of each individual case. Our results indicated that the stereotactic frame is the most accurate method of registration; however, skin markers provide reasonable accuracy with significant ease of use and patient comfort.