Biomedical subjects
Publications and source records attributed to F Vinuela.
The development of techniques of radiologic intravascular navigation with particles and balloons has created new therapeutic alternatives to neurologic diseases such as intracranial arteriovenous malformations and fistulas. The authors discuss the applications of these therapeutic tools.
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Forty-six patients with cerebral arteriovenous malformations (AVM's) were selected for embolization with bucrylate. These patients were assigned to three different groups. Group I consisted of 22 patients with nonresectable AVM's who were selected for embolization with a Silastic calibrated-leak ballon. In 16 or these patients, embolization was achieved, with partial obliteration of the AVM in 14 and complete obliteration in two. Five patients had subarachnoid hemorrhage caused by the balloon bursting and concomitant dissection of the feeding vessel. Four of these patients recovered completely and one died of a brain-stem hemorrhage. A permanent field defect was noted in five cases, and two patients had a transient mild neurological deficit. Group II consisted of 13 patients treated by intraoperative embolization. Complete obliteration by embolization was obtained in four cases, and complete surgical resection after embolization in five. Partial embolization with no surgical resection was achieved in five cases. Three of these patients had a permanent mild neurological deficit and two had transient deficits. There was no mortality in this group. Group III consisted of 11 patients treated by embolization with bucrylate using a new latex calibrated-leak balloon. This balloon has a higher malleability, and takes on the exact configuration of the feeder, with no risk of dissection. This balloon also permits delivery of the faster and larger injection of bucrylate to the arterial feeders of the AVM. Two AVM's were completely obliterated, and embolization was only partially successful in the other cases. Neurological complications consisted of incomplete field defects in two cases, slight memory loss in one case, and transient clumsiness of the arm and face in one case. Two patients have a catheter permanently glued in the malformation, with no neurological complication. There was no mortality in this group.
Severe intractable epistaxis remains a therapeutic challenge for the otolaryngologist. Embolization would appear to add a valuable treatment modality in dealing with particular cases refractory to conventional management. In selective cases it may prove superior to surgical intervention because of repeated accessibility and circumvention of the problem of collateral internal maxillary artery flow. This paper presents three cases of epistaxis of unusual causes which were initially uncontrolled by conventional management. Each patient received preliminary selective carotid angiography followed by one of two different intra-arterial embolization methods. The results were effective and illustrate the potential adjunctive or primary role embolizing procedures have in dealing with uncontrolled epistaxis.
A series of 54 traumatic carotid-cavernous fistulas has been treated with detachable balloon catheters. The balloon was introduced through one of three different approaches: the endarterial route; the venous route through the jugular vein, the inferior petrosal sinus, and the cavernous sinus; or surgical exposure of the cavernous sinus; with occlusion of the fistula by a detachable balloon directly positioned in the cavernous sinus. Full follow-up review demonstrated that the carotid blood flow was preserved in 59% of cases. The most frequent complication was a transient oculomotor nerve palsy, which occurred in 20% of cases. In three cases where both the fistula and the carotid artery were originally occluded by the balloon, the superior portion of the fistula was later found not to be completely occluded, and these patients had intracranial ligation of the supraclinoid portion of the carotid artery. Three patients had hemiparesis, transient in two cases and permanent in the other. The results show that the fistula was totally occluded in 53 cases; in the one exception the patient became asymptomatic but had a minimal angiographic leak.
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The subarachnoid space continues into the orbit as part of the optic nerve sheath. This space varies in size but is usually tiny. Occasionally, prominent (one case in our experience) enhancement of the optic nerve as part of metrizamide computed tomography (CT) cisternography is seen on transverse and coronal scans presumably because of a patulous optic subarachnoid space. In five cases, we have appreciated minimal enhancement of optic nerves with metrizamide only by close comparison of CT numbers with base-line scans. One of these patients had a tiny meningioma removed successfully from the optic sheath, with return to normal vision of a previously blind eye.
Magnetic resonance imaging has become the study of choice for the majority of abnormalities of the craniocervical junction as well as for demonstration of primary pathology of the spinal cord, and brain stem. Although the applications of MR are currently limited by its high cost, relatively long scan time, and low sensitivity to calcification, new pulse sequences, faster scan strategies, and lower cost MR scanner are changing this situation. MR contrast agents and the use of 3-D imaging techniques combined with gradient echoes promise to play a role in MR of the craniocervical junction in the near future.
A spectrum of embolic agents including PVA, avitene, gelfoam, ethanol, IBCA, silicone microspheres, metal and platinum coils, and balloons containing contrast of HEMA were imaged in vitro at 0.3 Tesla using spin echo, gradient echo, and inversion recovery sequences. Signal intensities associated with these agents and changes created by addition of blood are presented. The in vitro model is also correlated with clinical MR material. Recognition of embolic materials is important to avoid confusion with persistent flow void, hemorrhage, or thrombus.
The MR appearance of acute subarachnoid hemorrhage experimentally produced in Macaca monkeys and observed in patients with clinically documented acute subarachnoid hemorrhage is presented. Subarachnoid hemorrhages were produced in two Macaca Nemestrema monkeys using the technique of Frazee. CT and MR imaging were performed immediately after the procedure and at frequent intervals up to two week post hemorrhage. MR including T1 and T2 weighted multiplanar spin echo images were obtained. The imaging studies were compared with clinical evaluations and pathological specimens of all animals. Findings in the experimental animals are correlated with those observed in patients with clinically documented subarachnoid hemorrhage. The results show that acute subarachnoid hemorrhage (SAH) can be detected with MRI as isointense signal replacing normally black CSF spaces on T1 weighted images. Signal changes most likely relate to protein water binding associated with the clotting mechanism rather than oxidative denaturation of hemoglobin. Imaging performed experimentally and clinically beyond four days, however, showed a marked increase in signal intensity on T1 weighted images which probably does result from methemoglobin formation within the clot matrix. Although CT remains the gold standard in detecting acute SAH, MR does provide some sensitivity to its presence.
Eight cases of presumed acute occlusion of intracranial arteries, 7 middle cerebral and 1 posterior cerebral, demonstrated the occluded artery as an abnormal high density structure on non-enhanced computed tomography. Three cases underwent subsequent angiography which confirmed the diagnosis. CT scanning is therefore able to visualize acute thromboembolism in the intracranial arteries. In the appropriate clinical setting of acute stroke, an artery visualized on non-contrast CT scan as diffuse high density and higher in density than other visualized vessels should be suspected as acutely occluded by clot.
Occlusion of the anterior cerebral artery is a rare condition. A review of CT scans from 413 patients with ischemic infarction confirmed this low relative incidence: only 3% of CT scans evidencing infarction involved the territory of the anterior cerebral artery. Four major mechanisms of anterior cerebral artery occlusion have been identified in this series: Emboli in unusual hemodynamic circumstances such as patients presumed to have increased flow through the anterior communicating artery because of unilateral internal carotid artery occlusion. Propagation of thrombotic material from an occluded internal artery into the intracranial branches. Spasm, emboli or propagating thrombosis associated with anterior communicating aneurysm.
The applications of digital subtraction angiography (DSA) in neurologic diagnosis have been evolving as clinical experience with this technology accumulates. Initial enthusiasm with the intravenous contrast material injections has been tempered by often equivocal results. Intravenous DSA (IV-DSA) is still an accurate screening technique for extracranial carotid atherosclerosis, comparable to duplex ultrasound. Intracranial imaging is less satisfying with intravenous injections but reliable information is available in the assessment of the venous sinuses and parasellar internal arteries. The future of DSA lies with intraarterial contrast injections, as this technique substantially decreases the risks and costs of definitive cerebrovascular investigation.
A 46-year-old woman under investigation for three episodes of amaurosis fugax in the left eye proved to have a left anterior-middle fossa dural arteriovenous malformation with pial venous drainage. The malformation received its main supply from the left middle meningeal artery, but its anterior part was fed by the recurrent meningeal branch of the left ophthalmic artery. Transient episodic lowering of retinal arterial pressure due to shunting of blood from the ophthalmic artery to the malformation is the most likely explanation for the occurrence of amaurosis fugax, indicating that this symptom occurs in some patients on a hemodynamic basis.
PURPOSE: To describe our experience with the use of Amytal injected through a superselective catheter prior to planned embolization of cerebral arteriovenous malformations. MATERIALS AND METHODS: 109 superselective tests were performed with 30-mg injections of Amytal. All patients were evaluated by both clinical examination and EEG. RESULTS: Twenty-three of these tests were positive. There were no prolonged neurologic complications of the Amytal test. We also examined the value of EEG monitoring compared to clinical monitoring during the Amytal test. Of the 23 positive Amytal tests, only 12 showed a change on clinical exam (52%). This meant that almost half of the positive Amytal tests would have been falsely called negative (false negative rate of 10%). There were also three positive Amytal tests with changes on clinical examination without any change on EEG. CONCLUSION: The superselective Amytal test can be done safely as part of the interventional neuroradiologic procedure. Clinical and EEG monitoring of the patient are essential.
PURPOSE: To describe the incidence of neurologic dysfunction following embolization of supratentorial AVMs, and to correlate findings with results of preembolization Amytal tests. MATERIALS AND METHODS: Data from 147 embolizations of supratentorial AVMs following Amytal tests in 30 awake patients were analyzed retrospectively. RESULTS: Of five embolizations done after a positive Amytal test, two were followed by neurologic complications. Eighty-two embolizations done as single embolizations immediately after a negative Amytal test were associated with no neurologic complications. The remaining embolizations were parts of multiple series of embolizations, each beginning with an Amytal test and followed by a number of embolizations without catheter movement or repeat Amytal testing. Since any prior embolization in the series might reduce the sump effect of the AVM, embolic agent delivered later in the series could potentially reach functional brain tissue not fully tested by the Amytal test. Therefore, repeat embolizations (not immediately preceded by an Amytal test) were considered separately. In 60 repeat embolizations, six (10%) were associated with some neurologic complication. CONCLUSIONS: Repeat Amytal testing might detect the loss of sump effect as the AVM is embolized. We conclude that use of data from superselective Amytal tests adds to the safety of AVM embolizations and that repeat Amytal testing potentially could be valuable when serial embolization of a vessel is planned.
BACKGROUND AND PURPOSE: Our aim was to describe an expanded experience with endovascular mechanical embolectomy in a broad group of patients, including those not meeting entry criteria for the MERCI multicenter trials. METHODS: We performed an analysis of all patients with ischemic stroke treated with the Merci Clot Retrieval Device at a single academic center outside of the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) trials. RESULTS: Twenty-four patients were treated with the device. Nine were MERCI trial ineligible: 4 received intravenous (IV) tissue plasminogen activator (tPA), 1 received IV tPA and was younger than 18 years of age, and 4 had time-to-treatment of longer than 8 hours. Mean age was 64 years (range, 14-89 years; 42% women). Median National Institutes of Health Stroke Scale (NIHSS) score was 21 (range, 11-30). Median symptoms-to-procedure-start time was 303 minutes (range, 85-2385 minutes). Recanalization (Thrombolysis in Myocardial Infarction, 2-3) was achieved in 15/24 (63%). In device-only patients, recanalization occurred in 10/16. In patients who failed IV tPA undergoing rescue embolectomy, recanalization was achieved in 4/5. Three patients unresponsive to device therapy received rescue intra-arterial tPA/abciximab; recanalization was achieved in 2/3. Recanalization was achieved in 3/4 patients in whom treatment was started longer than 8 hours after symptom onset. Asymptomatic hemorrhage occurred in 38%; symptomatic hemorrhage, in 8%. Three device fractures occurred; none worsened clinical outcome. In-hospital mortality was 17%; 90-day mortality, 29%. Good 90-day functional outcome (modified Rankin Scale, <or=2) was achieved by 25% (6/24). CONCLUSIONS: Endovascular mechanical embolectomy is an effective means of achieving revascularization in patients with acute ischemic stroke, including patients with late treatment start and intravenous tPA failure. Device-based therapy achieved recanalization in nearly two thirds of patients and good clinical outcomes in one fourth, with symptomatic hemorrhage in less than one tenth.
With the use of Tracker and Balt microcatheter systems, intravascular pressure measurements were obtained in an experimental animal model, establishing the reliability of mean blood pressure measurements from these microcatheter systems. In the experimental model, selective occlusion of branches of the external carotid artery with simultaneous pressure measurements showed significant and reproducible changes in intravascular pressures. Also, pharmacologic manipulation of the blood pressure with simultaneous microcatheter and 6-French catheter recordings demonstrated an accurate and linear response of the microcatheter systems to mean blood pressure as it varied from 30 to 130 mm Hg. Preliminary results in humans with vascular malformations yielded similar results. We studied two cases of brain arteriovenous malformations (AVMs), one sigmoid-transverse sinus dural AVM, and one brain arteriovenous fistula (AVF). In these four cases the pressure dropped substantially, approaching the level of the shunt. In the case of the brain AVF, pressures rose in the same vessel after embolization. In the case of the dural AVM, correlation of the venous pouch pressures and the angiographic appearance indicated that shunting was no longer present when the venous and arterial pressures equalized. This system can be of substantial benefit in the evaluation and therapy of these lesions, and may increase our understanding of the physiology of vascular malformations.